Three Inoculation Methods for Evaluating Sclerotinia Blight Resistance in Peanut

Abstract

Laboratory-based assays for screening germplasm for resistance to Sclerotinia blight in peanuts can be conducted year-round, and thus may accelerate progress in breeding for resistant plants. Three previously proposed inoculation methods (using main stems of intact plants, detached main stems, or detached leaflets) were compared on six peanut genotypes known to represent range of resistance to Sclerotinia blight in the field or laboratory. The intact plant and detached main stem assays identified the most resistant and susceptible genotypes, but different results were obtained from either assay with Red River Runner, a cultivar with intermediate resistance to Sclerotinia blight. No differences among genotypes were observed with the detached leaflet assay. The sensitivity ratio was used to compare the three inoculation methods and identified the intact plant assay as the method with the smallest error variance. These results help identify the most efficient method for assaying physiological resistance to Sclerotinia blight in peanut.

Sclerotinia Blight Resistance in the US Peanut Mini‐Core Collection

“…Nineteen accessions exhibiting the least disease in 2014 were inoculated with S. minor in growth chambers using a previously described protocol for assaying intact plants (Hollowell et al, 2008; Bennett et al, 2016). Thirteen of these accessions are described in the Germplasm Resources Information Network (GRIN) as having erect or bunch growth habits (USDA‐ARS National Genetic Resources Program, 2017; Table 1), so laboratory inoculations were conducted to determine if their resistance might be due to canopy architecture rather than physiological resistance.…”

“…Thirteen of these accessions are described in the Germplasm Resources Information Network (GRIN) as having erect or bunch growth habits (USDA‐ARS National Genetic Resources Program, 2017; Table 1), so laboratory inoculations were conducted to determine if their resistance might be due to canopy architecture rather than physiological resistance. The resistant runner cultivar ‘Georgia‐03L’ and susceptible cultivar ‘Flavor Runner 458’ were used as controls (Woodward and Brenneman, 2008; Bennett and Chamberlin, 2014; Bennett et al, 2016). Plants were grown in the greenhouse using a commercial potting mix (Metro‐Mix 350, Sun Gro Horticulture) in 11‐cm‐diam.…”

Registration of ‘Lariat’ Peanut

“…Lariat was included in intact plant and detached stem laboratory assays to evaluate physiological resistance to Sclerotinia blight of six runner entries (Bennett et al, 2016). Other commercial runner genotypes included Red River Runner, 'Georgia-03L' (Branch, 2004), 'Okrun' (Kirby et al, 1989), 'Tamrun OL 02' (Simpson et al, 2006), and 'Tamrun 96' (Smith et al, 1998).…”

“…1). Lariat and Georgia‐03L were significantly more resistant to Sclerotinia blight than cultivars Tamrun 96, Tamrun OL02, and Okrun in both assays but more resistant than Red River Runner only in the intact plant assay (Bennett et al, 2016).…”

“…Mean lesion length (± SE) over time on runner peanut genotypes Georgia O3L, ARSOK‐R35 (Lariat), Red River Runner, Tamrun 96, Okrun, and Tamrun OL 02 inoculated with Sclerotinia minor using (A) intact plant and (B) detached stem (from Bennett et al, 2016). …”