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Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/4/2014 Publication Date: 8/12/2014 Citation: Gillen, A.M., Mengistu, A. 2014. Field evaluation of soybean lines from a new source of resistance to Cercospora kikuchii, 2013. Plant Disease Management Reports. 8:FC275. Interpretive Summary: Purple seed stain, which is caused by the fungus Cercospora kikuchii, is an important seed disease which causes soybean seed quality losses when environmental conditions favor its growth, and harvest is delayed due to wet field conditions. Frogeye leaf spot caused by Cercospora sojina is an important leaf disease which can cause defoliation under favorable conditions. The objective of this research is to develop soybean lines with resistance to purple seed stain and frogeye leaf spot, high yield potential and good agronomics, focusing on breeding lines derived from PI 379559D, a new source of resistance to C. kikuchii. A field trial in Milan, TN, of 26 experimental soybean lines derived from PI 379559D, parental lines, and susceptible and resistant varieties was conducted in 2013 to assess leaf disease during the growing season and disease in seed collected at maturity. Both parental lines were highly resistant to Frogeye leaf spot, and all progeny were highly resistant to Frogeye leaf spot. The environmental conditions in 2013 were unusually favorable to C. kikuchii. Thirteen of the experimental lines had significantly lower seed infestation levels than the susceptible parent and all of the checks. This indicates that PI 379559D may have contributed genes for resistance to these breeding lines. Technical Abstract: Purple seed stain, which is caused by the fungus Cercospora kikuchii, is an important seed disease which causes soybean seed quality losses when environmental conditions favor its growth, and harvest is delayed due to wet field conditions. Frogeye leaf spot caused by the fungus Cercospora sojina is an important leaf disease that can cause defoliation under favorable conditions. The objective of this research is to develop soybean lines with resistance to purple seed stain and frogeye leaf spot, high yield potential and good agronomics, focusing on breeding lines derived from PI 379559D, a new source of resistance to C. kikuchii. Twenty-six experimental soybean lines derived from PI 379559D were evaluated at Milan, TN, in 2013 for Frogeye leaf spot during the growing season and fungal infestation of seed collected at maturity. The primary purpose of the trial was to screen for reaction to Frogeye leaf spot, however the unusually high level of C. kikuchii allowed evaluation of the lines for reaction to this pathogen. The checks included PI 379559D (resistant parent), parental line Freedom (resistant to Frogeye leaf spot and susceptible to purple seed stain), AG4703 maturity group (MG) 4 check (susceptible to Frogeye leaf spot and purple seed stain), DB04-10836 (MG 5 Frogeye leaf spotsusceptible check) and DT98-7553 (MG 5 Frogeye leaf spot susceptible check). Infection of the seed with C. kikuchii was evaluated using a plated seed assay. The Frogeye leaf spot susceptible checks all had high Frogeye leaf spot scores = 7, which was considered highly susceptible. Two elite checks AG4703 and Freedom had C. kikuchii seed infestation scores (25.2 and 24.2%, respectively) which were considered susceptible. All experimental lines and the parents were highly resistant to Frogeye leaf spot, as expected. The resistant parent PI 379559D and thirteen of the experimental lines had significantly lower percentages of C. kikuchii infestation in the seed than the susceptible parent and all of the checks. This indicates that PI 379559D has contributed some resistance genes to these lines. This result needs to be confirmed in a location that regularly has economically damaging levels of purple seed stain to more fully evaluate the utility of these lines. |
