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Abstract
The development of soybean cultivars with disease resistance and abiotic stress tolerance is an important breeding goal. Disease resistance provided by PI 398469 to Southern Soybean Stem Canker (SSC) caused by Diaporthe aspalathi was evaluated in a mapping population. Bulked segregant analysis using Infinium SoySNP50k BeadChips was used to identify putative genomic regions on the soybean chromosomes for SSC resistance. KASP markers were developed for these regions and then used to genotype the recombinant inbred lines (RILs) derived from G81-2057 × PI 398469 and perform quantitative trait locus (QTL) analysis. A single QTL on chromosome (Chr) 14 was identified in the RILs and confirmed in the F2:3 population derived from the same cross between G81-2057 and PI 398469. This QTL was confirmed to be the Rdm3 locus using the RILs derived from a cross of G81-2057 × Crockett and both PI 398469 and Crockett were found to carry resistance alleles at the Rdm3 locus for resistance to SSC.Slow canopy wilting is a drought tolerance mechanism that is critical for developing climate-resilient cultivars. PI 471938, a slow canopy wilting accession, was crossed with Hutcheson to create a RIL mapping population that was evaluated for canopy wilting under rain-fed conditions in seven environments. Three QTLs on Chrs 2, 8, and 9 were identified for slow canopy wilting that accounted for 11, 10, and % of the phenotypic variation, respectively. These QTLs could be exploited by breeders to develop new drought-tolerant cultivars.
Unmanned aerial vehicles (UAVs) can allow plant breeders to collect measurements for traits that are not or cannot be collected in large-scale breeding programs. Canopy coverage (CC) has been studied in early maturity group soybean, but this trait has not been evaluated in elite southern soybean germplasm. In this study, UAVs were used to estimate canopy coverage (CC) in elite southern soybean breeding lines from the University of Georgia Soybean Breeding Program’s Preliminary and Advance yield trials. CC estimates were collected using a UAV at 4, 5, 6, and 7 weeks post-planting between the 2018 and 2021 growing seasons. CC estimates at 5 to 6 weeks after planting were shown to be most informative in elite southern soybean germplasm. Average CC estimates for the three datasets ranged from 23-32%, 36-49%, 49-55 %, and 43-48% for Weeks 4, 5, 6, and 7, respectively. Heritability of estimated CC ranged from 0.05 in 2018-19 for Week 4 to 0.52 in 2020-21 for Week 7. The relationships of CC with yield, 100-seed weight, maturity, lodging, and plant height were investigated, which could be used by breeders to make informed selections in their breeding programs.