Doctor of Philosophy (PhD)
Plant, Enviromental and Soil Sciences
Aflatoxin accumulation in corn continues to be a major problem in all southeastern corn growing states. Development of resistant inbreds and hybrids is a sustainable approach to reduce aflatoxin contamination. Mapping of quantitative trait loci (QTL) for resistance to Aspergillus flavus infection and aflatoxin accumulation in maize and developing markers associated with them can be helpful to speed up the breeding program. An F2:3 mapping population developed from the cross between Mp715 and B73 and a genetic linkage map was constructed using 136 simple sequence repeat (SSR) markers spanning the whole genome. QTL for aflatoxin resistance were identified in both years and were located on chromosomes 3, 4, 5, 8, 9, and 10 with contribution ranging from <1.0 to 9.2% individually toward resistance phenotype. A highly significant correlation was observed between husk cover and aflatoxin content in both years. A few QTL responsible for close husk cover identified in both years overlapped with the QTL region for aflatoxin resistance. Therefore, it should be possible to use markers identified in this study for selection and improvement of both traits simultaneously through MAB. A suppression subtraction hybridization (SSH) library was constructed using tissues from Mp715 and B73 to identify the differentially expressed genes in response to Aspergillus flavus. Three hundred genes related to various functions were identified from the library. Thirty differentially expressed genes were selected to study their expression pattern in seven maize inbreds through RT-PCR and showed differential expression at different time points after fungus inoculation. Higher expression of pathogenesis related protein-4, leucine rich repeat family protein, RNA binding protein, and ubiquitin C-terminal hydrolase in resistant inbreds (Mp715, Mp719, Mp420, and Mp313E) was confirmed by real-time qPCR. These genes may be responsible for resistance in these resistant inbreds. They were integrated into the linkage map generated in this study through in silico mapping. The gene encoding PR4, which was highly expressed in resistant germplasm was located in bin 4.02 where a QTL for aflatoxin resistance was identified. The genes found in the QTL regions and markers linked with them would be helpful to improve resistance to aflatoxin accumulation in corn.
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Dhakal, Ramesh, "Genetics of Resistance to Aflatoxin Accumulation in Corn (Zea mays)" (2015). LSU Doctoral Dissertations. 3736.
Subudhi, Prasanta K.