Investigating Reniform Nematode Resistant Genotypes in Combination with Velum Total in Cotton Gossypium hirsutum L.
Type of DegreeMaster's Thesis
Crop Soils and Environmental Sciences
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Cotton, Gossypium hirsutum L., is an important commodity traded in the world market in terms of volume and value. Reniform nematode (Rotylenchulus reniformis) (RN) reduces and limits cotton yields. . At present, nematicides and crop rotations are the most effective management tool for producers. Our study investigates the use of breeding lines that have QTLs for RN resistance and the interaction effect of a nematicide under high RN pressure. The study compared these genotypes in both a non-RN field and a RN-infected field under a Velum Total treatment at two locations: Tennessee Valley Research and Education Center near Belle Mina, AL and in microplots at Auburn University. In 2017 and 2018, the lint yield values of the six lines outperformed commercial controls and the parental lines in RN infested field with Velum and without Velum. This study determined that RN stunts plants, reduces fiber quality, and reduces lint percentage, which all contributes to yield loss. Out of the six composite lines, there were five lines (B148, A202, A4142, B170, and B143) that had reduced egg numbers (P< 0.05) but high yields and can be considered resistant. The line A210 is considered tolerant of RN based on the high egg numbers and good yield. In addition, it is postulated that M713 Ren 4 contains introgression segments of QTLs on chromosome 21 (Renbarb1 and Renbarb2) from GB713 that provides resistance to RN, but this information was never released. In recent studies, Renbarb1 and Renbarb2 are resolved at one locus (Renbarb2), and the marker BNL3729 is strongly associated with the resistant phenotype. To validate this, progenies from these six composite lines were genotyped, and five of the six genotypes contained both Renbarb1 and Renbarb2 (excluding A210) while all six contained Renbarb2. Since involving two markers demonstrated resistance while involving only one marker indicated tolerance, this data confirms that primary resistance is resolved in Renbarb2 since all lines had phenotypic resistance. Further work needs to be done in order to test lines of the 194 population, which were determined to be resistant, and their interaction with a nematicide. Key words; cultivar by management, QTLs, reniform nematode resistance, SSR marker, upland cotton, Velum Total (nematicide)