CORRELATIONS OF WHITE MOLD RESISTANCE IN SNAP BEAN (PHASEOLUS VULGARIS L.) AMONG FIELD EVALUATIONS, OXALIC ACID TEST, AND STRAW TEST

摘要

White mold is an important constraint of dry and snap bean production in the United States (Park et al., 2001). In snap bean, yield reductions due to white mold infection result in weakened stems which break along with attached pods during harvest andalso due to discolored pods infected with fluffy mycelial growth (Kull et al., 2003). The objective of the research was to compare two types of greenhouse tests and field based methods to screen for resistance to white mold in snap bean. Correlations between field and greenhouse evaluations were measured using two populations that share a common white mold resistant donor parent, G122. A recombinant inbred line (RIL) population, GA, was derived from a cross between G122 and Astrel, a small sieve snap bean cultivar. An independent inbred backcross population (IBC), GPP, was derived from a cross between G122 and PLS8088, a large sieve processing snap bean cultivar. Field evaluations were performed at the Arlington, WI Agricultural Research Station (ARS)in 2004 and 2005 using a blocks within replication design with three replications. Disease severity (DS) was calculated as the mean number of diseased branches per plant using eight plants sampled at random from each plot. Disease incidence (DI) was calculated as the percentage of plants with at least one infected branch using all plants within each plot. Greenhouse evaluations using a randomized complete block design were done using the oxalic acid test (OX) (Kolkman and Kelly, 2000) in 2005 and using a modified straw test (ST) (Petzoldt and Dickson, 1996) in 2005 and 2006.