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ARS Home » Midwest Area » Columbus, Ohio » Soil Drainage Research » Research » Publications at this Location » Publication #138838
Title: QUANTIATIVE TRAIT LOCI FOR PARTIAL RESISTANCE TO PHYTOPHTHORA SOJAE IN SOYBEAN

Author
item BURNHAM, K - OHIO STATE UNIV.
item DORRANCE, A - OHIO STATE UNIV.
item Vantoai, Tara
item ST MARTIN, S - OHIO STATE UNIV.

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2003
Publication Date: 7/25/2003
Citation: BURNHAM, K.D., DORRANCE, A.E., VANTOAI, T.T., ST MARTIN, S.K. QUANTIATIVE TRAIT LOCI FOR PARTIAL RESISTANCE TO PHYTOPHTHORA SOJAE IN SOYBEAN. CROP SCIENCE. 2003. V. 43. P. 1610-1617.

Interpretive Summary: Root and stem rot caused by a fungus (Phytophthora) is a serious disease that reduces soybean yield in the Midwest and the South from 5 to 15% annually. The soybean cultivar 'Conrad' has a unique defense (called partial resistance) to this root rot. The partial resistance allows fungal infection to occur without impacting the soybean growth and grain yield. We conducted a study with three soybean populations, Conrad x Sloan, Conrad x Harosoy, and Conrad x Williams to identify genes associated with this partial resistance to Phytophthora root rot. Following inoculation with the fungus, each of the three populations was evaluated for disease tolerance by measuring lesion size and plant height. Fingerprinting with DNA markers allowed the identification of molecular markers linked to two partial resistance genes. The major gene was associated with 21 to 35% disease reduction while the minor gene was associated with 11 to 21% reduction. The challenge facing soybean breeders is to incorporate partial resistance into high yielding cultivars. The identification of molecular markers linked to genes for partial resistance will facilitate this goal.

Technical Abstract: Partial resistance to Phytophthora sojae Kaufmann and Gerdemann in soybeans [Glycine max (L.) Merr] is expressed as a reduced level of root rot and is effective against all populations of the pathogen. The soybean cultivar `Conrad' has high levels of partial resistance. Three soybean populations, Conrad x `Sloan', Conrad x `Harosoy', and Conrad x `Williams', were evaluated for lesion growth rate and plant height following inoculation with P. sojae and with SSR markers to identify putative quantitative trait loci (QTL). The three populations segregated for lesion growth rate as measured by root inoculations. Family mean heritability estimates for the three populations were 0.62, 0.87 and 0.57 for the F4:6 generation. In total, 70, 45, and 60 SSR markers were polymorphic in each of the three populations, respectively. Two putative QTL's for partial resistance to P. sojae from Conrad were identified in all three populations on soybean major linkage groups (MLG) F and D1b+W, where no single Rps genes have been previously mapped. The QTL on MLG F explained 32.4, 21.4 and 35.0 percent of the phenotypic variation for Conrad x Sloan, Conrad x Harosoy, and Conrad x Williams populations, respectively. For the QTL on MLG D1b + W, the phenotypic variation explained was 10.6, 15.9, and 20.7 percent for the same three populations, respectively. The QTL on major linkage group F was more significant based on the LOD scores. Furthermore, the results indicate that QTLs for partial resistance to P. sojae are different from the mapped Rps genes in soybean. The challenge facing soybean breeders is to incorporate both single gene resistance and partial resistance into a high yielding cultivar. The identification of molecular markers linked to QTLs for partial resistance to P. sojae will facilitate this goal.