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Node of first fruiting/sympodial branch (NFFB) and its height (HNFFB) are two important indicators to measure cotton ( Gossypium spp.) early maturity. This study performed an association mapping using the mixed linear model (MLM) procedure for NFFB and HNFFB based on 172 Upland cotton ( Gossypium hirsutum L.) cultivars and 331 polymorphic SSR markers. The gene diversity index of 331 markers ranged from 0.0387 to 0.7799 with a mean value of 0.4002 and the polymorphism information content ranged from 0.0379 to 0.7473 with a mean value of 0.3375. A total of 18 markers associated with NFFB were detected in at least two environments, and the range of explained phenotypic variation by markers in different environments was 2.28-11.36 % with a mean value of 5.20 %. A total of 19 markers associated with HNFFB were detected in at least two environments, and the range of explained phenotypic variation by markers in different environments was 2.83-16.96 % with a mean value of 7.92 %. These markers detected in multiple environments are of good stability and can be used for marker-assisted selection (MAS) of target traits. In addition, favorable alleles for NFFB and HNFFB were mined. These favorable alleles and their representative cultivars are expected to be used for breeding practices. This study provides theoretical basis for the further analysis of genetic basis of NFFB and HNFFB, as well as the use of MAS for cotton early maturity. [ABSTRACT FROM AUTHOR]

The selection and popularization of early-maturing cotton is paramount in resolving the conflict between occupying farmlands utilizing grain and cotton while optimizing agricultural structure. Node of first fruiting branch (NFFB) and its height (HNFFB) can be used as the important indicators to measure cotton earliness. In this study, Baimian2, an early-maturing upland cotton ( Gossypium hirsutum L.) variety, was used as the female parent crossed with a late-maturing material (TM-1) and intermediate-maturing variety (CIR12), respectively. Quantitative trait locus (QTL) detection for NFFB and HNFFB was performed within the two F populations, Baimian2 × TM-1 and Baimian2 × CIR12 by composite interval mapping (CIM) and mixed model CIM (MCIM). Eight QTL (three suggestive and five significant) for NFFB and six QTL (three suggestive and three significant) for HNFFB were detected in both populations, located on C1(A1), C5(A5), C6(A6), C9(A9), C11(A11), C13(A13), C17(D3), C25(D6), C12(A12)/C26(D12) and LG1. Results of QTL are consistent with separation analysis to some extent. The two significant major QTL, qNFFB- 17- I for NFFB and qHNFFB- 17- I for HNFFB, were detected simultaneously by CIM and MCIM. They had high reliability and could be used for the marker-assisted breeding to improve cotton earliness. Single marker-analysis showed that 11 molecular markers, such as CGR5222, are linked with NFFB and/or HNFFB. [ABSTRACT FROM AUTHOR]

Improving early maturity in upland cotton (Gossypium hirsutum L.) is an important target in breeding. The node of the first fruiting branch (NFFB) and its height (HNFFB) are two important indexes to measure early maturity in cotton. To facilitate breeding for early maturity traits in upland cotton and reveal the genetic control underlying the two traits, a genome-wide association study was performed using 53,848 high-quality single nucleotide polymorphisms (SNPs) from 77,774 of a recently developed CottonSNP80K array. A total of 55 target trait-associated SNPs were detected, of which 12 SNPs were for NFFB and 43 were for HNFFB. Two SNPs for NFFB and 22 SNPs for HNFFB were repeatedly detected in at least two environments and/or by two models. These 24 SNPs also exhibited high phenotypic contributions of more than 10% and could be used for marker-assisted selection in future breeding programs. Furthermore, 89 candidate genes were identified in the genome sequence of upland cotton. These genes were categorized through Gene Ontology analysis. Gh_A05G1482 might be a potential candidate gene for improving the early maturation of cotton. These findings reveal the genetic control underlying NFFB and HNFFB and provide insight into genetic improvements for early maturity in upland cotton. [ABSTRACT FROM AUTHOR]