QTL mapping for early-maturing traits in upland cotton (Gossypium hirsutum L.)

Henan Institute of higher Learning, Cotton Research Institute, Xinxiang 453003, Henan, China）

Henan Institute of higher Learning, Cotton Research Institute, Xinxiang 453003, Henan, China）

Abstract. F2:3 families from the two upland cotton (Gossypium hirsutum L.) crosses, Baimian2 × TM-1 and Baimian2 × CIR12, were used to detect quantitative trait loci (QTLs) for early-maturing traits. A total of 54 QTLs were identified, of which 14 significant QTLs had the LOD score not only greater than 3 but also greater than the threshold calculated by the permutation test. Five common QTLs were detected in the two crosses, including qBP-17 for bud period, qGP-17a/qGP-17b for the growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs might exist stably in the cotton genome, and could be useful for marker-assisted selection (MAS). It was encouraging to note that the two common QTLs qBP-17 and qYPBF-12/26, had the LOD score not only greater than 3 but also greater than the threshold calculated by permutation test, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation. These two stable QTLs should be considered preferentially in MAS for early-maturing traits. Our research might provide a theoretical basis for marker-assisted selection breeding in short-season cotton.

Abstract. F2:3 families from the two upland cotton (Gossypium hirsutum L.) crosses, Baimian2 × TM-1 and Baimian2 × CIR12, were used to detect quantitative trait loci (QTLs) for early-maturing traits. A total of 54 QTLs were identified, of which 14 significant QTLs had the LOD score not only greater than 3 but also greater than the threshold calculated by the permutation test. Five common QTLs were detected in the two crosses, including qBP-17 for bud period, qGP-17a/qGP-17b for the growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs might exist stably in the cotton genome, and could be useful for marker-assisted selection (MAS). It was encouraging to note that the two common QTLs qBP-17 and qYPBF-12/26, had the LOD score not only greater than 3 but also greater than the threshold calculated by permutation test, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation. These two stable QTLs should be considered preferentially in MAS for early-maturing traits. Our research might provide a theoretical basis for marker-assisted selection breeding in short-season cotton.

Key words: Short-season cotton ,Early-maturing traits ,QTL, Common QTL ,MAS.

Key words: Short-season cotton ,Early-maturing traits ,QTL, Common QTL ,MAS.

1.Introduction

1.Introduction

Short-season cotton, which is also called early-maturing cotton, mainly possesses a dwarf and compact plant type with fewer leaves, shorter internodes and fruit branches, and shorter growth period than normal middle-late-maturing cotton (Yu et al. 1990). The selection and popularization of short-season cotton has significant value in alleviating the contradiction for land between cotton and cereals, and in optimizing agricultural structure. Early maturity traits of cotton are controlled by both quantitative trait loci (QTLs) and the environment, and manifest a variety of genetic modes in different combinations (Song et al. 2005; Dong et al. 2010). Identification of QTLs for early-maturing traits in short-season cotton and making use of the markers linked closely to target genes for MAS are effective methods for simultaneous improvement of earliness and other properties. Fan et al. (2006b) constructed the first genetic linkage map in short-season cotton using a F2 population and 12 QTLs for early-maturing traits were detected on the map. In the study of Guo et al. (2008), a F2 population from the cross of a day-neutral cultivar, Deltapine 61, and a photoperiod-sensitive accession, Twxas 701, was used to construct a genetic map and five QTLs for node of first fruiting branch were detected.

Short-season cotton, which is also called early-maturing cotton, mainly possesses a dwarf and compact plant type with fewer leaves, shorter internodes and fruit branches, and shorter growth period than normal middle-late-maturing cotton (Yu et al. 1990). The selection and popularization of short-season cotton has significant value in alleviating the contradiction for land between cotton and cereals, and in optimizing agricultural structure. Early maturity traits of cotton are controlled by both quantitative trait loci (QTLs) and the environment, and manifest a variety of genetic modes in different combinations (Song et al. 2005; Dong et al. 2010). Identification of QTLs for early-maturing traits in short-season cotton and making use of the markers linked closely to target genes for MAS are effective methods for simultaneous improvement of earliness and other properties. Fan et al. (2006b) constructed the first genetic linkage map in short-season cotton using a F2 population and 12 QTLs for early-maturing traits were detected on the map. In the study of Guo et al. (2008), a F2 population from the cross of a day-neutral cultivar, Deltapine 61, and a photoperiod-sensitive accession, Twxas 701, was used to construct a genetic map and five QTLs for node of first fruiting branch were detected.

From the above studies, it can be concluded that few QTLs for early maturity have been identified and their stability is yet to receive further verification. In our research, the short-season cotton cultivar Baimian2 was used as the central parent to generate two F2 and F2: 3 family lines from the two crosses, Baimian2 × TM-1 and Baimian2 × CIR12. QTLs for early-maturing traits were identified using the two individual maps constructed by SSR markers.

From the above studies, it can be concluded that few QTLs for early maturity have been identified and their stability is yet to receive further verification. In our research, the short-season cotton cultivar Baimian2 was used as the central parent to generate two F2 and F2: 3 family lines from the two crosses, Baimian2 × TM-1 and Baimian2 × CIR12. QTLs for early-maturing traits were identified using the two individual maps constructed by SSR markers.

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2.Materials And Methods

2.Materials And Methods

2.1.Mapping population and Phenotypic data collection

2.1.Mapping population and Phenotypic data collection

Baimian2 is a short-season cotton bred by Henan Institute of Science and Technology. TM-1 is a genetic standard line of upland cotton and exhibits late-maturing in China. CIR12 is a multiple-hybrid line bred by Cotton Research Institute of Chinese Agricultural Academy and exhibits middle-late-maturing in China. In the summer of 2010, the parents and F2:3 family lines for each of the crosses (220 for Baimian2 × TM-1, 208 for Baimian2 × CIR12) were planted in a single-row plot (0.8 m wide, 5 m long) with two replications. For convenience, Baimian2 × TM-1 and Baimian2 × CIR12 are designated as Cross I and Cross II, respectively. Seven early-maturing traits of the two F2:3 family lines were investigated. These traits comprised: seedling period (SP); bud period (BP); flower and boll period (FBP); growth period (GP); yield percentage before frost (YPBF); node of first fruiting branch (NFFB); and height of the node of first fruiting branch (HNFFB). The average of two replications was recorded as the last phenotypic value for each trait..

Baimian2 is a short-season cotton bred by Henan Institute of Science and Technology. TM-1 is a genetic standard line of upland cotton and exhibits late-maturing in China. CIR12 is a multiple-hybrid line bred by Cotton Research Institute of Chinese Agricultural Academy and exhibits middle-late-maturing in China. In the summer of 2010, the parents and F2:3 family lines for each of the crosses (220 for Baimian2 × TM-1, 208 for Baimian2 × CIR12) were planted in a single-row plot (0.8 m wide, 5 m long) with two replications. For convenience, Baimian2 × TM-1 and Baimian2 × CIR12 are designated as Cross I and Cross II, respectively. Seven early-maturing traits of the two F2:3 family lines were investigated. These traits comprised: seedling period (SP); bud period (BP); flower and boll period (FBP); growth period (GP); yield percentage before frost (YPBF); node of first fruiting branch (NFFB); and height of the node of first fruiting branch (HNFFB). The average of two replications was recorded as the last phenotypic value for each trait..

2.2.Molecular Marker Analysis

2.2.Molecular Marker Analysis

Genomic DNA of the parents and F2 individuals of the two crosses was extracted using a modified CTAB method (Paterson et al. 1993). A total of 4083 SSR primers were chosen to screen for polymorphisms between the parents. All of the primers were mainly selected from the published cotton interspecific or intraspecific maps (Nguyen et al. 2004; Guo et al. 2007; Zhang et al. 2011), and the reported markers linked to QTLs for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). The primer sequences were obtained from the Cotton Microsatellite Database (CMD; 122.72.0.6www.省略/). The protocol for PCR amplification and examination followed that of Zhang et al. (2002). br>

2.3.Map construction and QTL analysisbr>

2.3.Map construction and QTL analysis

Map construction and integration were designed with JionMap 3.0 (Lander 1987). Linkage groups from the two crosses were integrated when they shared at least two common markers. Composite inteval mapping with Windows QTL Cartographer 2.5 (Basten et al. 2001) was used to locate and analyze QTLs. The QTL with a LOD threshold between 2.0 and 3.0 was defined as suggestive QTL (Lander and Kruglyak 1995). The QTL with a LOD threshold greater than or equal to 3.0, or calculated with a permutation test with 1000 times, was defined as significant QTL.

Map construction and integration were designed with JionMap 3.0 (Lander 1987). Linkage groups from the two crosses were integrated when they shared at least two common markers. Composite inteval mapping with Windows QTL Cartographer 2.5 (Basten et al. 2001) was used to locate and analyze QTLs. The QTL with a LOD threshold between 2.0 and 3.0 was defined as suggestive QTL (Lander and Kruglyak 1995). The QTL with a LOD threshold greater than or equal to 3.0, or calculated with a permutation test with 1000 times, was defined as significant QTL.

QTL nomenclature followed the protocol used in rice (Mccouch et al. 1997). MapChart 2.1 was used to draw QTL graphs. Comparing to the allotetraploid intraspecific cotton map constructed by Guo et al. (2007), linkage groups were located to the corresponding chromosome or subgenome. LGX was used to designate uncertain chromosome.

QTL nomenclature followed the protocol used in rice (Mccouch et al. 1997). MapChart 2.1 was used to draw QTL graphs. Comparing to the allotetraploid intraspecific cotton map constructed by Guo et al. (2007), linkage groups were located to the corresponding chromosome or subgenome. LGX was used to designate uncertain chromosome.

3.Results And Analysis

3.Results And Analysis

3.1.Performance of the early-maturing traits of parents

3.1.Performance of the early-maturing traits of parents

Differences in all seven early-maturing traits were significant or highly significant between the parents of the two crosses (Table 1). In Cross I the difference in node of first fruiting branch was significant between Baimian2 and TM-1, and in Cross II differences in seedling period was significant between Baimian2 and CIR12; differences in all other early-maturing traits were highly significant. These results showed that the mapping parents we selected were ideal, and thus the mapping population constructed by them would be beneficial to search for genes responsible for early-maturing traits.

Differences in all seven early-maturing traits were significant or highly significant between the parents of the two crosses (Table 1). In Cross I the difference in node of first fruiting branch was significant between Baimian2 and TM-1, and in Cross II differences in seedling period was significant between Baimian2 and CIR12; differences in all other early-maturing traits were highly significant. These results showed that the mapping parents we selected were ideal, and thus the mapping population constructed by them would be beneficial to search for genes responsible for early-maturing traits.

存入我的阅览室

2.Materials And Methods

2.Materials And Methods

2.1.Mapping population and Phenotypic data collection

2.1.Mapping population and Phenotypic data collection

Baimian2 is a short-season cotton bred by Henan Institute of Science and Technology. TM-1 is a genetic standard line of upland cotton and exhibits late-maturing in China. CIR12 is a multiple-hybrid line bred by Cotton Research Institute of Chinese Agricultural Academy and exhibits middle-late-maturing in China. In the summer of 2010, the parents and F2:3 family lines for each of the crosses (220 for Baimian2 × TM-1, 208 for Baimian2 × CIR12) were planted in a single-row plot (0.8 m wide, 5 m long) with two replications. For convenience, Baimian2 × TM-1 and Baimian2 × CIR12 are designated as Cross I and Cross II, respectively. Seven early-maturing traits of the two F2:3 family lines were investigated. These traits comprised: seedling period (SP); bud period (BP); flower and boll period (FBP); growth period (GP); yield percentage before frost (YPBF); node of first fruiting branch (NFFB); and height of the node of first fruiting branch (HNFFB). The average of two replications was recorded as the last phenotypic value for each trait.. single-row plot (0.8 m wide, 5 m long) with two replications. For convenience, Baimian2 × TM-1 and Baimian2 × CIR12 are designated as Cross I and Cross II, respectively. Seven early-maturing traits of the two F2:3 family lines were investigated. These traits comprised: seedling period (SP); bud period (BP); flower and boll period (FBP); growth period (GP); yield percentage before frost (YPBF); node of first fruiting branch (NFFB); and height of the node of first fruiting branch (HNFFB). The average of two replications was recorded as the last phenotypic value for each trait..

2.2.Molecular Marker Analysis

2.2.Molecular Marker Analysis

Genomic DNA of the parents and F2 individuals of the two crosses was extracted using a modified CTAB method (Paterson et al. 1993). A total of 4083 SSR primers were chosen to screen for polymorphisms between the parents. All of the primers were mainly selected from the published cotton interspecific or intraspecific maps (Nguyen et al. 2004; Guo et al. 2007; Zhang et al. 2011), and the reported markers linked to QTLs for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). The primer sequences were obtained from the Cotton Microsatellite Database (CMD; 122.72.0.6www.省略/). The protocol for PCR amplification and examination followed that of Zhang et al. (2002). br>

2.3.Map construction and QTL analysisbr>

2.3.Map construction and QTL analysis

Map construction and integration were designed with JionMap 3.0 (Lander 1987). Linkage groups from the two crosses were integrated when they shared at least two common markers. Composite inteval mapping with Windows QTL Cartographer 2.5 (Basten et al. 2001) was used to locate and analyze QTLs. The QTL with a LOD threshold between 2.0 and 3.0 was defined as suggestive QTL (Lander and Kruglyak 1995). The QTL with a LOD threshold greater than or equal to 3.0, or calculated with a permutation test with 1000 times, was defined as significant QTL.

Map construction and integration were designed with JionMap 3.0 (Lander 1987). Linkage groups from the two crosses were integrated when they shared at least two common markers. Composite inteval mapping with Windows QTL Cartographer 2.5 (Basten et al. 2001) was used to locate and analyze QTLs. The QTL with a LOD threshold between 2.0 and 3.0 was defined as suggestive QTL (Lander and Kruglyak 1995). The QTL with a LOD threshold greater than or equal to 3.0, or calculated with a permutation test with 1000 times, was defined as significant QTL.

QTL nomenclature followed the protocol used in rice (Mccouch et al. 1997). MapChart 2.1 was used to draw QTL graphs. Comparing to the allotetraploid intraspecific cotton map constructed by Guo et al. (2007), linkage groups were located to the corresponding chromosome or subgenome. LGX was used to designate uncertain chromosome.

QTL nomenclature followed the protocol used in rice (Mccouch et al. 1997). MapChart 2.1 was used to draw QTL graphs. Comparing to the allotetraploid intraspecific cotton map constructed by Guo et al. (2007), linkage groups were located to the corresponding chromosome or subgenome. LGX was used to designate uncertain chromosome.

3.Results And Analysis

3.Results And Analysis

3.1.Performance of the early-maturing traits of parents

3.1.Performance of the early-maturing traits of parents

Differences in all seven early-maturing traits were significant or highly significant between the parents of the two crosses (Table 1). In Cross I the difference in node of first fruiting branch was significant between Baimian2 and TM-1, and in Cross II differences in seedling period was significant between Baimian2 and CIR12; differences in all other early-maturing traits were highly significant. These results showed that the mapping parents we selected were ideal, and thus the mapping population constructed by them would be beneficial to search for genes responsible for early-maturing traits.

Differences in all seven early-maturing traits were significant or highly significant between the parents of the two crosses (Table 1). In Cross I the difference in node of first fruiting branch was significant between Baimian2 and TM-1, and in Cross II differences in seedling period was significant between Baimian2 and CIR12; differences in all other early-maturing traits were highly significant. These results showed that the mapping parents we selected were ideal, and thus the mapping population constructed by them would be beneficial to search for genes responsible for early-maturing traits.

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Table 1 Performances of early-maturing traits of parents

Table 1 Performances of early-maturing traits of parents

3.2. Map construction

3.2. Map construction

Table 2 shows characteristics of the two maps: Cross I and Cross II (maps not shown) (Fig. 1). A total of 295 and 169 polymorphic loci from the 4083 primers were obtained in Cross I and Cross II, respectively. Chi-square test indicated that eight and 10 loci (5.10% and 5.91%) showed segregation distortion. The map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers. cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers.

Table2Characteristics of two genetic maps: CrossⅠand CrossⅡ

Table2Characteristics of two genetic maps: CrossⅠand CrossⅡ

3.3.QTL analysis

3.3.QTL analysis

A total of 54 QTLs (31 suggestive QTLs and 23 significant QTLs) for the seven early-maturing traits were detected in both crosses. Fourteen out of 23 significant QTLs (13 in Cross I and 10 in Cross II) detected in the two crosses had LOD scores not only greater than 3, but also greater than the threshold calculated by permutation test. Of the14 QTLs, nine were detected in Cross I: qSP-24, qBP-17, qGP-17a, qYPBF-12/26, qFFBN-13, qFFBN-17, qFFBN-12/26, qHFFBN-9 and qHFFBN-17 (Fig. 1); and five QTLs were detected in Cross II: qSP-LG5, qBP-17, qYPBF-12/26, qFFBN-11 and qHFFBN-9 (Fig. 2). These 14 QTLs might truly exist in the cotton genome.

A total of 54 QTLs (31 suggestive QTLs and 23 significant QTLs) for the seven early-maturing traits were detected in both crosses. Fourteen out of 23 significant QTLs (13 in Cross I and 10 in Cross II) detected in the two crosses had LOD scores not only greater than 3, but also greater than the threshold calculated by permutation test. Of the14 QTLs, nine were detected in Cross I: qSP-24, qBP-17, qGP-17a, qYPBF-12/26, qFFBN-13, qFFBN-17, qFFBN-12/26, qHFFBN-9 and qHFFBN-17 (Fig. 1); and five QTLs were detected in Cross II: qSP-LG5, qBP-17, qYPBF-12/26, qFFBN-11 and qHFFBN-9 (Fig. 2). These 14 QTLs might truly exist in the cotton genome.

mon QTLs

mon QTLs

Five QTLs for four early-maturing traits were common in the two crosses (Fig. 3). Of these QTLs, qBP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) for yield percentage before frost, qHFFBN-17 for height of the node of first fruiting branch were always detected close to the common markers DPL0041 and TMB0471 on C17 in the two crosses. qYPBF-12/26 for yield percentage before frost was always detected close to the common markers NAU4926, CGR6772, NAU3291 and NAU2170 on C12/C26 in the two crosses. The favorable genes for these five QTLs were all derived from the same parent Baimian2, so they should be common QTLs.

Five QTLs for four early-maturing traits were common in the two crosses (Fig. 3). Of these QTLs, qBP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) for yield percentage before frost, qHFFBN-17 for height of the node of first fruiting branch were always detected close to the common markers DPL0041 and TMB0471 on C17 in the two crosses. qYPBF-12/26 for yield percentage before frost was always detected close to the common markers NAU4926, CGR6772, NAU3291 and NAU2170 on C12/C26 in the two crosses. The favorable genes for these five QTLs were all derived from the same parent Baimian2, so they should be common QTLs.

4.Discussion

4.Discussion

4.1.Primer polymorphism and map construction

4.1.Primer polymorphism and map construction

Construction of a detailed genetic linkage map is necessary for detection of QTLs. However, the low DNA marker polymorphism in intraspecific cotton accessionsmakes it difficult to increase the number of markers (Wendel et al. 1992; Iqbal et al. 2001; Li et al. 2008). In the present study, the total number of 4803 primer pairs appears to be few, but they were mainly selected from the published interspecific and intraspecific genetic maps in tetraploid cotton (Nguyen et al. 2004; Guo et al. 2007;Zhang et al. 2011), and from the reported markers linked to the genes responsible for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). Because the primers from the published maps themselves are polymorphic primers, and the markers linked to the genes responsible for important traits are easy to identify the genotypic differences among different phenotypes, therefore the primer polymorphism among the parents of the two crosses in the present study were always high reached to 7.20% and 4.14% by computation, respectively. This was helpful for the construction of a high-density genetic map. In the study, the map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers. They provides significant information for exploration of agronomically useful genes.

Construction of a detailed genetic linkage map is necessary for detection of QTLs. However, the low DNA marker polymorphism in intraspecific cotton accessionsmakes it difficult to increase the number of markers (Wendel et al. 1992; Iqbal et al. 2001; Li et al. 2008). In the present study, the total number of 4803 primer pairs appears to be few, but they were mainly selected from the published interspecific and intraspecific genetic maps in tetraploid cotton (Nguyen et al. 2004; Guo et al. 2007;Zhang et al. 2011), and from the reported markers linked to the genes responsible for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). Because the primers from the published maps themselves are polymorphic primers, and the markers linked to the genes responsible for important traits are easy to identify the genotypic differences among different phenotypes, therefore the primer polymorphism among the parents of the two crosses in the present study were always high reached to 7.20% and 4.14% by computation, respectively. This was helpful for the construction of a high-density genetic map. In the study, the map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers. They provides significant information for exploration of agronomically useful genes.

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Table 1 Performances of early-maturing traits of parents

Table 1 Performances of early-maturing traits of parents

3.2. Map construction

3.2. Map construction

Table 2 shows characteristics of the two maps: Cross I and Cross II (maps not shown) (Fig. 1). A total of 295 and 169 polymorphic loci from the 4083 primers were obtained in Cross I and Cross II, respectively. Chi-square test indicated that eight and 10 loci (5.10% and 5.91%) showed segregation distortion. The map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers.

Table 2 shows characteristics of the two maps: Cross I and Cross II (maps not shown) (Fig. 1). A total of 295 and 169 polymorphic loci from the 4083 primers were obtained in Cross I and Cross II, respectively. Chi-square test indicated that eight and 10 loci (5.10% and 5.91%) showed segregation distortion. The map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers.

Table2Characteristics of two genetic maps: CrossⅠand CrossⅡ

Table2Characteristics of two genetic maps: CrossⅠand CrossⅡ

3.3.QTL analysis

3.3.QTL analysis

A total of 54 QTLs (31 suggestive QTLs and 23 significant QTLs) for the seven early-maturing traits were detected in both crosses. Fourteen out of 23 significant QTLs (13 in Cross I and 10 in Cross II) detected in the two crosses had LOD scores not only greater than 3, but also greater than the threshold calculated by permutation test. Of the14 QTLs, nine were detected in Cross I: qSP-24, qBP-17, qGP-17a, qYPBF-12/26, qFFBN-13, qFFBN-17, qFFBN-12/26, qHFFBN-9 and qHFFBN-17 (Fig. 1); and five QTLs were detected in Cross II: qSP-LG5, qBP-17, qYPBF-12/26, qFFBN-11 and qHFFBN-9 (Fig. 2). These 14 QTLs might truly exist in the cotton genome.

A total of 54 QTLs (31 suggestive QTLs and 23 significant QTLs) for the seven early-maturing traits were detected in both crosses. Fourteen out of 23 significant QTLs (13 in Cross I and 10 in Cross II) detected in the two crosses had LOD scores not only greater than 3, but also greater than the threshold calculated by permutation test. Of the14 QTLs, nine were detected in Cross I: qSP-24, qBP-17, qGP-17a, qYPBF-12/26, qFFBN-13, qFFBN-17, qFFBN-12/26, qHFFBN-9 and qHFFBN-17 (Fig. 1); and five QTLs were detected in Cross II: qSP-LG5, qBP-17, qYPBF-12/26, qFFBN-11 and qHFFBN-9 (Fig. 2). These 14 QTLs might truly exist in the cotton genome.

mon QTLs

mon QTLs

Five QTLs for four early-maturing traits were common in the two crosses (Fig. 3). Of these QTLs, qBP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) for yield percentage before frost, qHFFBN-17 for height of the node of first fruiting branch were always detected close to the common markers DPL0041 and TMB0471 on C17 in the two crosses. qYPBF-12/26 for yield percentage before frost was always detected close to the common markers NAU4926, CGR6772, NAU3291 and NAU2170 on C12/C26 in the two crosses. The favorable genes for these five QTLs were all derived from the same parent Baimian2, so they should be common QTLs.

Five QTLs for four early-maturing traits were common in the two crosses (Fig. 3). Of these QTLs, qBP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) for yield percentage before frost, qHFFBN-17 for height of the node of first fruiting branch were always detected close to the common markers DPL0041 and TMB0471 on C17 in the two crosses. qYPBF-12/26 for yield percentage before frost was always detected close to the common markers NAU4926, CGR6772, NAU3291 and NAU2170 on C12/C26 in the two crosses. The favorable genes for these five QTLs were all derived from the same parent Baimian2, so they should be common QTLs.

4.Discussion

4.Discussion

4.1.Primer polymorphism and map construction

4.1.Primer polymorphism and map construction

Construction of a detailed genetic linkage map is necessary for detection of QTLs. However, the low DNA marker polymorphism in intraspecific cotton accessionsmakes it difficult to increase the number of markers (Wendel et al. 1992; Iqbal et al. 2001; Li et al. 2008). In the present study, the total number of 4803 primer pairs appears to be few, but they were mainly selected from the published interspecific and intraspecific genetic maps in tetraploid cotton (Nguyen et al. 2004; Guo et al. 2007;Zhang et al. 2011), and from the reported markers linked to the genes responsible for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). Because the primers from the published maps themselves are polymorphic primers, and the markers linked to the genes responsible for important traits are easy to identify the genotypic differences among different phenotypes, therefore the primer polymorphism among the parents of the two crosses in the present study were always high reached to 7.20% and 4.14% by computation, respectively. This was helpful for the construction of a high-density genetic map. In the study, the map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers. They provides significant information for exploration of agronomically useful genes.

Construction of a detailed genetic linkage map is necessary for detection of QTLs. However, the low DNA marker polymorphism in intraspecific cotton accessionsmakes it difficult to increase the number of markers (Wendel et al. 1992; Iqbal et al. 2001; Li et al. 2008). In the present study, the total number of 4803 primer pairs appears to be few, but they were mainly selected from the published interspecific and intraspecific genetic maps in tetraploid cotton (Nguyen et al. 2004; Guo et al. 2007;Zhang et al. 2011), and from the reported markers linked to the genes responsible for important traits in cotton (Zhang et al. 2003; Mei et al. 2004; Lacape et al. 2005; Jiang et al. 2009). Because the primers from the published maps themselves are polymorphic primers, and the markers linked to the genes responsible for important traits are easy to identify the genotypic differences among different phenotypes, therefore the primer polymorphism among the parents of the two crosses in the present study were always high reached to 7.20% and 4.14% by computation, respectively. This was helpful for the construction of a high-density genetic map. In the study, the map from Cross I harbored 269 loci and 28 linkage groups that spanned 1837.8 cM (approxinately 36.76% of the cotton genome) with an average distance of 6.883 cM between two markers. The map from Cross II harbored 127 loci and 26 linkage groups that spanned 1244.3 cM (approxinately 24.89% of the cotton genome) with an average distance of 9.797 cM between two markers. They provides significant information for exploration of agronomically useful genes.

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4.2.Stable QTLs

4.2.Stable QTLs

Limited by QTL stability, at present only the minority of identified QTLs have been applied to marker-assisted selection in cotton (Guo et al. 2005; Wang et al. 2007), and the majority of QTLs are still unable to be utilized in breeding practice, so it is necessary to search for stable QTLs detected simultaneously in various generations, environments or crosses. Sun et al. (2011) carried out the QTL mapping for ?ber quality traits across multiple generations and environments in upland cotton. They identified nine stable QTLs for ?ber strength ?ber quality in F2, F2:3 and RILs simultaneously, of which two QTLs were detected in all three generations and all four environments. In the present study, five common QTLs for four early-maturing traits were detected in both crosses, comprising q-BP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs could be used for marker-assisted selection. It is encouraging to note that the QTLs qBP-17 for bud period and qYPBF-12/26 for yield percentage before frost had always a high LOD score not only greater than 3, but also greater than the threshold calculated with permutation test in both crosses, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation, respectively. They should be considered preferentially for MAS of early-maturing traits. In addition, QTL qFFBN-9 (cross I) for node of first fruiting branch, and QTLs qFBP-7 (cross II) and qFBP-17 (cross I and II) for flower and boll period were detected on the same chromosomes of the genetic map constructed by Zhang et al. (2008, 2009). Because of lacking common markers, whether these QTLs are common QTLs or not need to be confirmed in future studies. It was also found in the present study that five common QTLs were located on C17 and C12/C26, and in particular four common QTLs for bud period, growth period, yield percentage before frost and height of the node of first fruiting branch were clustered on C17. The result indicated that the genes affecting early-maturing traits might display tight linkage or pleiotropism.

Limited by QTL stability, at present only the minority of identified QTLs have been applied to marker-assisted selection in cotton (Guo et al. 2005; Wang et al. 2007), and the majority of QTLs are still unable to be utilized in breeding practice, so it is necessary to search for stable QTLs detected simultaneously in various generations, environments or crosses. Sun et al. (2011) carried out the QTL mapping for ?ber quality traits across multiple generations and environments in upland cotton. They identified nine stable QTLs for ?ber strength ?ber quality in F2, F2:3 and RILs simultaneously, of which two QTLs were detected in all three generations and all four environments. In the present study, five common QTLs for four early-maturing traits were detected in both crosses, comprising q-BP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs could be used for marker-assisted selection. It is encouraging to note that the QTLs qBP-17 for bud period and qYPBF-12/26 for yield percentage before frost had always a high LOD score not only greater than 3, but also greater than the threshold calculated with permutation test in both crosses, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation, respectively. They should be considered preferentially for MAS of early-maturing traits. In addition, QTL qFFBN-9 (cross I) for node of first fruiting branch, and QTLs qFBP-7 (cross II) and qFBP-17 (cross I and II) for flower and boll period were detected on the same chromosomes of the genetic map constructed by Zhang et al. (2008, 2009). Because of lacking common markers, whether these QTLs are common QTLs or not need to be confirmed in future studies. It was also found in the present study that five common QTLs were located on C17 and C12/C26, and in particular four common QTLs for bud period, growth period, yield percentage before frost and height of the node of first fruiting branch were clustered on C17. The result indicated that the genes affecting early-maturing traits might display tight linkage or pleiotropism.

5.Acknowledgement

5.Acknowledgement

This work was supported by grants from the Research and Establishment of Modern Industrial Technology System for National Cotton (nycytx-06-09) and the Key Scientific Research Project of Henan Province (092102110025, 112102110105).

This work was supported by grants from the Research and Establishment of Modern Industrial Technology System for National Cotton (nycytx-06-09) and the Key Scientific Research Project of Henan Province (092102110025, 112102110105).

6.References

6.References

[1]Basten CJ, Weir BS, Zeng ZB (2001) QTL cartographer, Version1.15. Department of Statistics, North Carolina State University, Raleigh

[1]Basten CJ, Weir BS, Zeng ZB (2001) QTL cartographer, Version1.15. Department of Statistics, North Carolina State University, Raleigh

[2]Dong Na, Li CQ, Wang QL, Ai NJ, Hu GH, Zhang(2010) Mixed inheritance of earliness and its related traits of short-season cotton under different ecological environments. Cotton Sci 22:304311

[2]Dong Na, Li CQ, Wang QL, Ai NJ, Hu GH, Zhang(2010) Mixed inheritance of earliness and its related traits of short-season cotton under different ecological environments. Cotton Sci 22:304311

[3]Fan SL, Yu SX, Song MZ, Yuan RH (2006b) Construction of molecular linkage map and QTL mapping for earliness in Short-season Cotton.Cotton Sci 18:135139

[3]Fan SL, Yu SX, Song MZ, Yuan RH (2006b) Construction of molecular linkage map and QTL mapping for earliness in Short-season Cotton.Cotton Sci 18:135139

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4.2.Stable QTLs

4.2.Stable QTLs

Limited by QTL stability, at present only the minority of identified QTLs have been applied to marker-assisted selection in cotton (Guo et al. 2005; Wang et al. 2007), and the majority of QTLs are still unable to be utilized in breeding practice, so it is necessary to search for stable QTLs detected simultaneously in various generations, environments or crosses. Sun et al. (2011) carried out the QTL mapping for ?ber quality traits across multiple generations and environments in upland cotton. They identified nine stable QTLs for ?ber strength ?ber quality in F2, F2:3 and RILs simultaneously, of which two QTLs were detected in all three generations and all four environments. In the present study, five common QTLs for four early-maturing traits were detected in both crosses, comprising q-BP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs could be used for marker-assisted selection. It is encouraging to note that the QTLs qBP-17 for bud period and qYPBF-12/26 for yield percentage before frost had always a high LOD score not only greater than 3, but also greater than the threshold calculated with permutation test in both crosses, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation, respectively. They should be considered preferentially for MAS of early-maturing traits. In addition, QTL qFFBN-9 (cross I) for node of first fruiting branch, and QTLs qFBP-7 (cross II) and qFBP-17 (cross I and II) for flower and boll period were detected on the same chromosomes of the genetic map constructed by Zhang et al. (2008, 2009). Because of lacking common markers, whether these QTLs are common QTLs or not need to be confirmed in future studies. It was also found in the present study that five common QTLs were located on C17 and C12/C26, and in particular four common QTLs for bud period, growth period, yield percentage before frost and height of the node of first fruiting branch were clustered on C17. The result indicated that the genes affecting early-maturing traits might display tight linkage or pleiotropism.

Limited by QTL stability, at present only the minority of identified QTLs have been applied to marker-assisted selection in cotton (Guo et al. 2005; Wang et al. 2007), and the majority of QTLs are still unable to be utilized in breeding practice, so it is necessary to search for stable QTLs detected simultaneously in various generations, environments or crosses. Sun et al. (2011) carried out the QTL mapping for ?ber quality traits across multiple generations and environments in upland cotton. They identified nine stable QTLs for ?ber strength ?ber quality in F2, F2:3 and RILs simultaneously, of which two QTLs were detected in all three generations and all four environments. In the present study, five common QTLs for four early-maturing traits were detected in both crosses, comprising q-BP-17 for bud period, qGP-17a/qGP-17b (qGP-17) for growth period, qYPBF-17a/qYPBF-17b (qYPBF-17) and qYPBF-12/26 for yield percentage before frost, and qHFFBN-17 for height of the node of first fruiting branch. These five common QTLs could be used for marker-assisted selection. It is encouraging to note that the QTLs qBP-17 for bud period and qYPBF-12/26 for yield percentage before frost had always a high LOD score not only greater than 3, but also greater than the threshold calculated with permutation test in both crosses, and explained 12.6%～12.6% and 9.0%～12.1% of the phenotypic variation, respectively. They should be considered preferentially for MAS of early-maturing traits. In addition, QTL qFFBN-9 (cross I) for node of first fruiting branch, and QTLs qFBP-7 (cross II) and qFBP-17 (cross I and II) for flower and boll period were detected on the same chromosomes of the genetic map constructed by Zhang et al. (2008, 2009). Because of lacking common markers, whether these QTLs are common QTLs or not need to be confirmed in future studies. It was also found in the present study that five common QTLs were located on C17 and C12/C26, and in particular four common QTLs for bud period, growth period, yield percentage before frost and height of the node of first fruiting branch were clustered on C17. The result indicated that the genes affecting early-maturing traits might display tight linkage or pleiotropism.

5.Acknowledgement

5.Acknowledgement

This work was supported by grants from the Research and Establishment of Modern Industrial Technology System for National Cotton (nycytx-06-09) and the Key Scientific Research Project of Henan Province (092102110025, 112102110105).

This work was supported by grants from the Research and Establishment of Modern Industrial Technology System for National Cotton (nycytx-06-09) and the Key Scientific Research Project of Henan Province (092102110025, 112102110105).

6.References

6.References

[1]Basten CJ, Weir BS, Zeng ZB (2001) QTL cartographer, Version1.15. Department of Statistics, North Carolina State University, Raleigh

[1]Basten CJ, Weir BS, Zeng ZB (2001) QTL cartographer, Version1.15. Department of Statistics, North Carolina State University, Raleigh

[2]Dong Na, Li CQ, Wang QL, Ai NJ, Hu GH, Zhang(2010) Mixed inheritance of earliness and its related traits of short-season cotton under different ecological environments. Cotton Sci 22:304311

[2]Dong Na, Li CQ, Wang QL, Ai NJ, Hu GH, Zhang(2010) Mixed inheritance of earliness and its related traits of short-season cotton under different ecological environments. Cotton Sci 22:304311

[3]Fan SL, Yu SX, Song MZ, Yuan RH (2006b) Construction of molecular linkage map and QTL mapping for earliness in Short-season Cotton.Cotton Sci 18:135139

[3]Fan SL, Yu SX, Song MZ, Yuan RH (2006b) Construction of molecular linkage map and QTL mapping for earliness in Short-season Cotton.Cotton Sci 18:135139

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[4]Guo WZ, Zhang TZ, Ding YZ, Zhu YC, Shen XL, Zhu XF (2005) Molecular marker assisted selection and pyramiding of two QTLs for fiber strength in upland cotton. Acta Genet Sin 32:12751285

[4]Guo WZ, Zhang TZ, Ding YZ, Zhu YC, Shen XL, Zhu XF (2005) Molecular marker assisted selection and pyramiding of two QTLs for fiber strength in upland cotton. Acta Genet Sin 32:12751285

[5]Guo WZ, Cai CP, Wang CB, Han ZG, Song XL, Wang K, Niu XW, Wang C, Lu KY, Shi B, Zhang TZ (2007) A microsatellite-based, gene-rich linkage map reveals genome structure, function, and evolution in Gossypium. Genetics 176:527541

[5]Guo WZ, Cai CP, Wang CB, Han ZG, Song XL, Wang K, Niu XW, Wang C, Lu KY, Shi B, Zhang TZ (2007) A microsatellite-based, gene-rich linkage map reveals genome structure, function, and evolution in Gossypium. Genetics 176:527541

[6]Guo YF, McCarty JC, Jenkins JN, Saha S (2008) QTL for node of first fruiting branch in a cross of an upland cotton, Gossypium hirsutum L., cultivar with primitive accession Texas 701. Euphytica 163:113122

[6]Guo YF, McCarty JC, Jenkins JN, Saha S (2008) QTL for node of first fruiting branch in a cross of an upland cotton, Gossypium hirsutum L., cultivar with primitive accession Texas 701. Euphytica 163:113122

[7]Iqbal MJ, Reddy OUK, El-Zik KM (2001) A genetic bottleneck in the ‘evolution under domestication’ of upland cotton Gossypium hirsutum L. examined using DNA fingerprinting. Theor Appl Genet 103:547-554

[7]Iqbal MJ, Reddy OUK, El-Zik KM (2001) A genetic bottleneck in the ‘evolution under domestication’ of upland cotton Gossypium hirsutum L. examined using DNA fingerprinting. Theor Appl Genet 103:547-554

[8]Jiang F, Zhao J, Zhou L, Guo WZ, Zhang TZ (2009) Molecular mapping of Verticillium wilt resistance QTL clustered on chromosomes D7 and D9 in upland cotton. Sci China, Ser C: Life Sci 52:872884

[8]Jiang F, Zhao J, Zhou L, Guo WZ, Zhang TZ (2009) Molecular mapping of Verticillium wilt resistance QTL clustered on chromosomes D7 and D9 in upland cotton. Sci China, Ser C: Life Sci 52:872884

[9]Lacape JM, Nguyen TB, Courtois B, Belot JL, Giband M, Gourlot JP, Gawryziak G, Roques S, Hau B (2005) QTL analysis of cotton fiber quality using multiple G. hirsutum × G. barbadense backcross generations. Crop Sci 45:123140

[9]Lacape JM, Nguyen TB, Courtois B, Belot JL, Giband M, Gourlot JP, Gawryziak G, Roques S, Hau B (2005) QTL analysis of cotton fiber quality using multiple G. hirsutum × G. barbadense backcross generations. Crop Sci 45:123140

[10]Lander ES, Green P, Abrahamson J, Barlow A, Daly MJ, Lincoln SE, Newburg I (1987) MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics 1: 174181

[10]Lander ES, Green P, Abrahamson J, Barlow A, Daly MJ, Lincoln SE, Newburg I (1987) MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics 1: 174181

[11]Lander ES, Kruglyak L (1995) Gentic dissection of complex traits guidelines for interpreting and reporting linkage results. Nat Genet 11:241247

[11]Lander ES, Kruglyak L (1995) Gentic dissection of complex traits guidelines for interpreting and reporting linkage results. Nat Genet 11:241247

[12]Li CQ, Guo WZ, Ma XL, Zhang TZ (2008) Tagging and mapping of QTL for yield and its components in upland cotton (Gossypium hirsutum L.) population with varied lint percentage. Cotton Sci 20:163169

[12]Li CQ, Guo WZ, Ma XL, Zhang TZ (2008) Tagging and mapping of QTL for yield and its components in upland cotton (Gossypium hirsutum L.) population with varied lint percentage. Cotton Sci 20:163169

[13]Mccouch SR, Cho YG, Yano M, Paul E, Blinstrub M, Morishima H, Kinoshita T (1997) Report on QTL nomenclature. Rice Genet Newsl 14:11213

[13]Mccouch SR, Cho YG, Yano M, Paul E, Blinstrub M, Morishima H, Kinoshita T (1997) Report on QTL nomenclature. Rice Genet Newsl 14:11213

[14]Mei M, Syed NH, Gao W, Thaxton PM, Smith CW, Stelly DM, Chen ZJ (2004) Genetic mapping and QTL analysis of fiber-related traits in cotton (Gossypium L.). Theor Appl Genet 108:280291

[14]Mei M, Syed NH, Gao W, Thaxton PM, Smith CW, Stelly DM, Chen ZJ (2004) Genetic mapping and QTL analysis of fiber-related traits in cotton (Gossypium L.). Theor Appl Genet 108:280291

[15]Nguyen TB, Giband M, Brottier P, Risterucci AM, Lacape JM (2004) Wide coverage of tetraploid cotton genome using newly developed microsatellite markers. Theor Appl Genet 109:167175

[15]Nguyen TB, Giband M, Brottier P, Risterucci AM, Lacape JM (2004) Wide coverage of tetraploid cotton genome using newly developed microsatellite markers. Theor Appl Genet 109:167175

[16]Paterson AH, Brubaker CL, Wendel JF (1993) A rapid method for extraction of cotton (Gossypium spp.) genomic DNA suitable for RFLP and PCR analysis. Plant Mol Biol Rep 11:112127

[16]Paterson AH, Brubaker CL, Wendel JF (1993) A rapid method for extraction of cotton (Gossypium spp.) genomic DNA suitable for RFLP and PCR analysis. Plant Mol Biol Rep 11:112127

[17]Shappley ZW, Jenkins JN, Zhu J, Jack C, McCarty JC (1998) Quantitative trait loci associated with agronomic and fiber traits of upland cotton. J Cotton Sci 2: 153163

[17]Shappley ZW, Jenkins JN, Zhu J, Jack C, McCarty JC (1998) Quantitative trait loci associated with agronomic and fiber traits of upland cotton. J Cotton Sci 2: 153163

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[4]Guo WZ, Zhang TZ, Ding YZ, Zhu YC, Shen XL, Zhu XF (2005) Molecular marker assisted selection and pyramiding of two QTLs for fiber strength in upland cotton. Acta Genet Sin 32:12751285

[4]Guo WZ, Zhang TZ, Ding YZ, Zhu YC, Shen XL, Zhu XF (2005) Molecular marker assisted selection and pyramiding of two QTLs for fiber strength in upland cotton. Acta Genet Sin 32:12751285

[5]Guo WZ, Cai CP, Wang CB, Han ZG, Song XL, Wang K, Niu XW, Wang C, Lu KY, Shi B, Zhang TZ (2007) A microsatellite-based, gene-rich linkage map reveals genome structure, function, and evolution in Gossypium. Genetics 176:527541

[5]Guo WZ, Cai CP, Wang CB, Han ZG, Song XL, Wang K, Niu XW, Wang C, Lu KY, Shi B, Zhang TZ (2007) A microsatellite-based, gene-rich linkage map reveals genome structure, function, and evolution in Gossypium. Genetics 176:527541

[6]Guo YF, McCarty JC, Jenkins JN, Saha S (2008) QTL for node of first fruiting branch in a cross of an upland cotton, Gossypium hirsutum L., cultivar with primitive accession Texas 701. Euphytica 163:113122

[6]Guo YF, McCarty JC, Jenkins JN, Saha S (2008) QTL for node of first fruiting branch in a cross of an upland cotton, Gossypium hirsutum L., cultivar with primitive accession Texas 701. Euphytica 163:113122

[7]Iqbal MJ, Reddy OUK, El-Zik KM (2001) A genetic bottleneck in the ‘evolution under domestication’ of upland cotton Gossypium hirsutum L. examined using DNA fingerprinting. Theor Appl Genet 103:547-554

[7]Iqbal MJ, Reddy OUK, El-Zik KM (2001) A genetic bottleneck in the ‘evolution under domestication’ of upland cotton Gossypium hirsutum L. examined using DNA fingerprinting. Theor Appl Genet 103:547-554

[8]Jiang F, Zhao J, Zhou L, Guo WZ, Zhang TZ (2009) Molecular mapping of Verticillium wilt resistance QTL clustered on chromosomes D7 and D9 in upland cotton. Sci China, Ser C: Life Sci 52:872884

[8]Jiang F, Zhao J, Zhou L, Guo WZ, Zhang TZ (2009) Molecular mapping of Verticillium wilt resistance QTL clustered on chromosomes D7 and D9 in upland cotton. Sci China, Ser C: Life Sci 52:872884

[9]Lacape JM, Nguyen TB, Courtois B, Belot JL, Giband M, Gourlot JP, Gawryziak G, Roques S, Hau B (2005) QTL analysis of cotton fiber quality using multiple G. hirsutum × G. barbadense backcross generations. Crop Sci 45:123140

[9]Lacape JM, Nguyen TB, Courtois B, Belot JL, Giband M, Gourlot JP, Gawryziak G, Roques S, Hau B (2005) QTL analysis of cotton fiber quality using multiple G. hirsutum × G. barbadense backcross generations. Crop Sci 45:123140

[10]Lander ES, Green P, Abrahamson J, Barlow A, Daly MJ, Lincoln SE, Newburg I (1987) MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics 1: 174181

[10]Lander ES, Green P, Abrahamson J, Barlow A, Daly MJ, Lincoln SE, Newburg I (1987) MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics 1: 174181

[11]Lander ES, Kruglyak L (1995) Gentic dissection of complex traits guidelines for interpreting and reporting linkage results. Nat Genet 11:241247

[11]Lander ES, Kruglyak L (1995) Gentic dissection of complex traits guidelines for interpreting and reporting linkage results. Nat Genet 11:241247

[12]Li CQ, Guo WZ, Ma XL, Zhang TZ (2008) Tagging and mapping of QTL for yield and its components in upland cotton (Gossypium hirsutum L.) population with varied lint percentage. Cotton Sci 20:163169

[12]Li CQ, Guo WZ, Ma XL, Zhang TZ (2008) Tagging and mapping of QTL for yield and its components in upland cotton (Gossypium hirsutum L.) population with varied lint percentage. Cotton Sci 20:163169

[13]Mccouch SR, Cho YG, Yano M, Paul E, Blinstrub M, Morishima H, Kinoshita T (1997) Report on QTL nomenclature. Rice Genet Newsl 14:11213

[13]Mccouch SR, Cho YG, Yano M, Paul E, Blinstrub M, Morishima H, Kinoshita T (1997) Report on QTL nomenclature. Rice Genet Newsl 14:11213

[14]Mei M, Syed NH, Gao W, Thaxton PM, Smith CW, Stelly DM, Chen ZJ (2004) Genetic mapping and QTL analysis of fiber-related traits in cotton (Gossypium L.). Theor Appl Genet 108:280291

[14]Mei M, Syed NH, Gao W, Thaxton PM, Smith CW, Stelly DM, Chen ZJ (2004) Genetic mapping and QTL analysis of fiber-related traits in cotton (Gossypium L.). Theor Appl Genet 108:280291

[15]Nguyen TB, Giband M, Brottier P, Risterucci AM, Lacape JM (2004) Wide coverage of tetraploid cotton genome using newly developed microsatellite markers. Theor Appl Genet 109:167175

[15]Nguyen TB, Giband M, Brottier P, Risterucci AM, Lacape JM (2004) Wide coverage of tetraploid cotton genome using newly developed microsatellite markers. Theor Appl Genet 109:167175

[16]Paterson AH, Brubaker CL, Wendel JF (1993) A rapid method for extraction of cotton (Gossypium spp.) genomic DNA suitable for RFLP and PCR analysis. Plant Mol Biol Rep 11:112127

[16]Paterson AH, Brubaker CL, Wendel JF (1993) A rapid method for extraction of cotton (Gossypium spp.) genomic DNA suitable for RFLP and PCR analysis. Plant Mol Biol Rep 11:112127

[17]Shappley ZW, Jenkins JN, Zhu J, Jack C, McCarty JC (1998) Quantitative trait loci associated with agronomic and fiber traits of upland cotton. J Cotton Sci 2: 153163

[17]Shappley ZW, Jenkins JN, Zhu J, Jack C, McCarty JC (1998) Quantitative trait loci associated with agronomic and fiber traits of upland cotton. J Cotton Sci 2: 153163

存入我的阅览室