Doctor of Philosophy (PhD)
Plant, Enviromental and Soil Sciences
Developing improved cotton cultivars depends on how cotton cultivars perform the best when under stresses. Reniform nematode is a major plant pathogen, causing 4-6% yield loss in southern United States. A variation in reproduction and pathogenicity across reniform isolates collected from Louisiana on susceptible cotton was reported. This study was conducted to determine the response of resistant/tolerant cotton genotypes to multiple reniform isolates by inoculating 10,000 juveniles into seven days old seedlings. Across genotypes, the Evan and Avoyelles isolates had significantly higher vermiform nematodes (33,793 and 27,800/250 g soil, respectively) than other isolates. Across isolates, the number of juveniles on A2-190 and Lonren-2 (5,573 and 6,013, respectively) were significantly lower than that on other genotypes. There was a significant interaction between the genotypes and isolates suggesting that the response of genotypes to reniform isolates was different. Salt stress is a major abiotic stress, affecting cotton production in the Macon Ridge and Red River regions in Louisiana. In a preliminary study, 150 day neutral primitive cotton accessions were screened at 0, 125, 250 mM NaCl under hydroponics. A promising subset was rescreened for salt tolerance in pot culture. MT11 had the lowest reduction in plant height and dry shoot weight (32% and 47%), significantly less than FM958 (43% and 66%) across salt concentrations. MT1219 had the lowest accumulation of Na+ (1,026.37 mM) at 250 mM NaCl, and significantly lower than FM958 (2,135.39 mM). Based on reduction in plant parameters, MT11, MT1219, MT45, and MT245 performed better than other genotypes. This study also showed that both hydroponics and pot culture are effective in the screening of a large number of cotton genotypes against elevated salt concentrations. In addition to stresses, cotton breeders are interested to develop a selection index, which aids in an efficient selection of multiple fibers traits. Using the data mining techniques, all developed models agreed that fiber length and strength are the most important fiber properties in determining the spinning consistency index (SCI). This study showed that SCI can be used as alternative selection index for combining the multiple fiber traits to enhance yarn spinning.
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Bhandari, Bikash, "The Response of Gossypium spp. to Biotic and Abiotic Stresses in Louisiana and the Modeling of Yarn Performance" (2015). LSU Doctoral Dissertations. 1674.