Project Summaries

03-412  Project Manager: D. C. Jones

POPULATION DEVELOPMENT AND GENETIC MAPPING OF QTLS FOR FIBER QUALITY

Jinfa Zhang, New Mexico State University

To introduce desirable traits and genes from Pima to Upland and Acala cotton, extensive interspecific breeding has been practiced in the program. As a result numerous introgression lines have been developed and tested. In 2012, 150 promising lines for high yield, fiber quality or stress tolerance were divided into five replicated field tests; 32 lines including three checks were tested under normal and reduced irrigation regimes, while 1700 progeny rows were tested for field performance and fiber quality. One breeding line developed from one interspecific cross between Acala and Pima was tested in New Mexico and 15 other locations across the Cotton Belt. Based on the results received from 7 locations, it yielded over 30% more lint than Acala 1517-08 released by New Mexico in 2010 and it was also the highest yielder among 30 breeding lines and 3 commercial non-transgenic checks. This represents a breakthrough for the first time in cotton in further improving Upland cotton yield by introducing germplasm from Pima cotton. Three new breeding lines displayed high levels of drought tolerant based on replicated field tests under normal and reduced irrigation regimes. The lint yield was 18-28% higher than the recurrent parent (Acala 1517-99) under normal irrigation conditions and 35-85% higher under drought conditions.

A major dominant resistance gene to thrips was identified in 8 of 14 F2 populations of four resistant Pima x four susceptible Upland crosses and a number of thrips resistant breeding lines have been developed by introducing resistance from Pima to Upland cotton. In 7 of the same 14 F2 crosses, segregation in Verticillium wilt resistance fitted to the ratio of 3:1, indicating that the VW resistance is controlled by a major gene. To identify markers based on resistance gene analogs (RGAs) which will provide candidate genes for marker-assisted selection (MAS) for VW resistance and cloning of VW resistance genes, RGA-targeted amplified fragment polymorphic (AFLP) analysis (RGA-AFLP) was performed for the conversion into sequence tagged site (STS) markers. A total of 54 RGA-AFLP markers were cloned and sequenced, resulting in 16 polymorphic STS markers developed for VW resistance.

To develop molecular markers for salt tolerance, polymorphisms in salt responsive genes were surveyed based using the single strand conformation polymorphism (SSCP) technique. Of the 118 SSCP markers for salt response genes, 47 were mapped onto 16 linkage groups and 27 of the mapped SSCP markers were significantly correlated with various phenotypic traits. A total of six QTLs were identified, including three for plant height, one for leaf number, one for root fresh weight, and one for root dry weight.

Cotton fibers are epidermal trichomes on the seed surface which share similarities with leaf trichomes. To identify homologous cotton genes based on known genes involved in the pathway of leaf trichome initiation in Arabidopsis, sequence variations including single nucleotide polymorphisms (SNPs) of the homologous trichome genes were identified in cotton and evaluated using SSCP technique. Of a total of 69 primer pairs, 13 yielded polymorphisms between Upland and Pima cotton and seven markers were mapped to linkage groups. The results will facilitate identification of markers and genes associated with fiber yield and quality traits.

 

Project Year: 2012
 

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