Progress in Molecular Breeding of Cottton for Drought Resistance and Fiber Quality Traits

Working group session: 
Germplasm and Genetic Stocks
Presentation type: 
oral
Authors: 
Boopathi, N. Manikanda; Ravikesavan, R; Sathish, S
Presenter: 
Boopathi, N. Manikanda
Correspondent: 
Boopathi, N. Manikanda
Abstract: 
The cotton germplasm maintained at TNAU were evaluated for drought tolerance in two different pot experiments using physio-morphological and biochemical traits. The selected cotton entries were further evaluated under field conditions and six germplasm lines were selected from these studies that have shown contrasting drought tolerance and superior fiber quality traits for mapping population development. Genetic linkage maps were constructed using different mapping population types such as F2, BC1 and RILs derived from Gossypium hirsutum cv. KC3 (drought tolerant) and G. barbadense cv. Suvin (drought susceptible). QTL analysis identified several QTLs including two major QTLs on chromosome 19 and 25 for fiber quality traits under drought stress and such QTLs were also reported across the world using different types of mapping populations and genetic backgrounds. Consistent major QTLs linked to fiber quality traits under water limited environments are being fine mapped with the new set of markers. Further, the mapping populations were evaluated under rainfed and controlled irrigation at different cotton growing regions and seasons to validate the QTLs and confirm the potential of these QTLs in MAS. To this end, hybrids are being developed to produce backcross progenies through MAS. Simultaneously, an attempt was also made to understand molecular response of cotton to water stress through gene expression studies. Negative regulations of gene expression by endogenous, non-coding microRNAs (miRNAs) have been shown to play important role in abiotic stress responses in plants. Though miRNAs with their targets have been widely studied in cotton, limited knowledge is available on the miRNA population of cotton in response to water stress. Differentially expressed miRNAs and their targets were identified in response to drought under natural field conditions through high-throughput small RNA sequencing by comparing leaf samples of KC3 and Suvin. Comparison of miRNAs expressed under water stressed conditions between KC3 and Suvin, have resulted 7494 miRNA reads with at least two folds of differential expression and interestingly, almost all of the miRNAs identified in this study were up regulated at least by two folds. Our results reveal the presence of numerous conserved and unidentified, novel miRNAs in cotton in response to drought under the field conditions and first time we have demonstrated that there are huge numbers of water stress related miRNAs in cotton that sequentially and complexly involved in gene regulation that ultimately lead to drought resistance in cotton. Further, this is the first report on experimentally identifying and validating miRNAs in G. barbadense. Characterization of these miRNAs might have enormous potential in elucidating the molecular mechanism and more importantly genetic improvement of drought tolerance in cotton.