Translating molecular marker discovery to breeding practice: cultivars with resistance to diseases and improved water use efficiency


University of Georgia

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Southeast (GA, FL, AL)

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Genetic materials highly resistant to late leaf spot diseases but agronomically poor are being used to transfer the resistance to lines with improved performance in the southeastern US. The resistant lines contain chromosomal segments from a wild peanut relative. These alien segments have been identified through sequencing and genotyping with the peanut SNP array and this information was used to design molecular markers for marker-assisted selection in breeding. The resistant lines were crossed with TifNV HiO/L, a nematode resistant and high oleic acid line, and progeny were selected for all traits and chromosomal regions with molecular markers. Since the disease resistance is a quantitative trait controlled by multiple genes, the three main introgressed segments were selected in different combinations, then tested in the field and in the laboratory with a detached leaf assay. In all experiments, it was determined that one of the introgressed segments was dispensable while the other two contributed significantly to resistance. These introgression lines were tested along with other sources of leaf spot resistance in a replicated, unsprayed field trial in the 2019 season. Lines for comparison included additional synthetic tetraploid lines and derivatives, elite line resistant and susceptible checks and cultivated x cultivated Cl801 population lines mapped for disease resistance and previously selected. Late leaf spot disease pressure was severe in 2019, and some susceptible checks such as Gregory showed total defoliation. Marker-selected lines showed a range of resistance levels that confirmed the usefulness of markers for selection and selected alleles for resistance. The best lines are being used to make additional backcrosses and screening is being done with marker-assisted selection. Our efforts in the last few months have been focused on advancement, analyzing data, 
preparing/submitting a manuscript on the supported work, and preparing a germplasm release. The latter will allow access to materials by any breeding program and the publications will provide information and protocols for marker-assisted selection. 

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