Mapping partial resistance to Fusarium graminearum in ‘Conrad’ soybean
M. L. ELLIS (1), H. Wang (2), P. A. Paul (2), A. E. Dorrance (2)
(1) Ohio State University, Wooster, OH, U.S.A.; (2) Ohio State University, OARDC, Wooster, OH, U.S.A.
Phytopathology 101:S48

Fusarium graminearum has emerged as an important soybean seedling pathogen in Ohio. The objective of this research was to identify the major quantitative trait loci (QTLs) conferring resistance to F. graminearum in a Conrad (Resistant) x Sloan (Susceptible) F_6:8 population. A rolled-towel assay was used to phenotype 262 recombinant inbred lines (RILs). Twenty seeds from each RIL were placed on a germination towel and inoculated with 2.5 × 10⁴ macroconidia/ml, the towels were rolled and placed in a bucket in the dark. The experimental design was a randomized block design, in which blocks and replications of the RILs were set up over time. At seven days after inoculation, the lesion and plant lengths were measured for each seedling, and the proportion of the seedling affected (lesion length/plant length) was calculated as a measure of disease severity. The mean disease severity for each RIL was then analyzed using best linear unbiased predictor. Based on the analysis of the phenotype data, the data fits the model for quantitative resistance. A total of 208 SSR and SNP markers were screened and a map of 172 markers was developed using JoinMap, and QTLs were identified using MapQTL. Conrad is a major source of partial resistance to Phytophthora sojae, this comparison of two root pathogens for overlapping QTLs associated with resistance will provide key clues to both basal resistance and pathogen specific resistance in this cultivar.