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Title: Reaction of the core collection of peanut germplasm to Sclerotinia blight and pepper spot

Author
item DAMICONE, J - OK AGRIC EXP STATION
item Holbrook, Carl - Corley
item SMITH, D - Oklahoma State University
item Melouk, Hassan
item Chamberlin, Kelly

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2009
Publication Date: 3/15/2010
Citation: Damicone, J.P., Holbrook Jr, C.C., Smith, D.L., Melouk, H.A., Chamberlin, K.D. 2010. Reaction of the core collection of peanut germplasm to Sclerotinia blight and pepper spot. Peanut Science. 37(1):1-11.

Interpretive Summary: Sclerotinia blight on peanut, caused by the fungus Sclerotinia minor Jagger, is endemic to peanut production areas of North Carolina, Virginia, Oklahoma, and Texas where the pathogen persists for extended periods in soil as sclerotia. Yield loss is generally proportional to the percentage of plants affected and results primarily from stem and peg decay that causes pods to become detached from plants during digging. Management of Sclerotinia blight has relied on an integrated program of cultural practices, partially resistant cultivars, and fungicide programs which may add $100-$150/acre to production costs. New sources of resistance to Sclerotinia blight in peanut are desperately needed. Entries from the peanut core collection, a subset of the USDA peanut germplasm collection, were planted in non-replicated plots in a field with a history of Sclerotinia blight. Variability existed among entries for reaction to Sclerotinia blight. Of the 744 entries evaluated, 11% had no disease, nearly 30% had <10% disease incidence, and only 21% had 50% disease incidence or more. Entries were selected for further evaluation in replicated plots based on a nil to low (<10%) incidence of Sclerotinia blight, good entry adaptation and/or vigor, and desirable characteristics including that included an intermediate to prostrate growth habit and pepper spot resistance. Entries 208, 128, 804, 582, and 273 combined resistance to Sclerotinia blight, pepper spot and web blotch; and less than erect growth habits. Entry 103 had good Sclerotinia blight resistance and yield, but an upright growth habit. Entry 92 had an upright growth habit and low yield, but good Sclerotinia blight resistance. Both entries 92 and 103 had unusually good resistance to pepper spot and web blotch compared to other upright entries. Entries 426, 184, and 562 were upright and susceptible to susceptible to pepper spot, but had resistance to web blotch and the best resistance to Sclerotinia blight. These entries appear to be the best new sources of resistance to Sclerotinia blight for local peanut breeding programs and for identifying clusters of related germplasm in entire germplasm collection.

Technical Abstract: In 2001, entries from the peanut core collection, a subset of the USDA peanut germplasm collection, were planted in non-replicated plots in a field with a history of Sclerotinia blight. Variability existed among entries for reaction to Sclerotinia blight. Of the 744 entries evaluated, 11% had no disease, nearly 30% had <10% disease incidence, and only 21% had 50% disease incidence or more. Most of the resistant entries had an upright plant habit and were in early and mid maturity groups. Many of the early maturing entries were susceptible to the foliar disease pepper spot which occurred throughout the study. Entries were selected for further evaluation in replicated plots based on a nil to low (<10%) incidence of Sclerotinia blight, good entry adaptation and/or vigor, and desirable characteristics including that included an intermediate to prostrate growth habit and pepper spot resistance. The selected entries grown in both 2002 and 2003 (n=64) were compared to resistant (Tamspan 90), moderately resistant (Tamrun 96), and susceptible (Okrun) reference cultivars. Most entries (57 in 2001 and 47 in 2003) had disease incidence less than Tamrun 96 and similar to Tamspan 90. In 2003 when disease incidence was highest, all of the 47 entries with resistant reactions that did not differ from Tamspan 90 had erect plant growth habits except for entries 208 and 582 which were prostrate, and entries 273, 128 and 804 which were intermediate. The criteria of resistance to Sclerotinia blight and yield similar to Tamspan 90, plant habit, and/or reactions to pepper spot and web blotch were used to select the best entries. Entries 208, 128, 804, 582, and 273 combined resistance to Sclerotinia blight, pepper spot and web blotch; and less than erect growth habits. Entry 103 had good Sclerotinia blight resistance and yield, but an upright growth habit. Entry 92 had an upright growth habit and low yield, but good Sclerotinia blight resistance. Both entries 92 and 103 had unusually good resistance to pepper spot and web blotch compared to other upright entries. Entries 426, 184, and 562 were upright and susceptible to susceptible to pepper spot, but had resistance to web blotch and the best resistance to Sclerotinia blight. These entries appear to be the best new sources of resistance to Sclerotinia blight for local peanut breeding programs and for identifying clusters of related germplasm in entire germplasm collection.