CHARACTERIZING SCLEROTINIA SCLEROTIORUM POPULATIONS ACROSS BEAN GROWING REGIONS FOR IMPROVED RESISTANCE SCREENING

摘要

Isolates of Sclerotinia sclerotiorum collected over the past six years from nine bean production regions in the USA, as well as regions in Mexico and France, have been characterized using mycelial compatibility groups (MCGs). A total of 87 MCGs were formed from the USA isolates. The Idaho greenhouse isolate, all the California isolates and, with only one exception, all Mexico and France isolates (data notshown) were unique (Table 1). Clonality varied from 8 clones out of 62 Michigan isolates to 27 clones out of 59 Washington isolates. The data in Table 1 also demonstrates that some clones are found in six or seven states across the USA while seven are limited to only one or two states. These same isolates have also been tested for aggressivenes under greenhouse conditions using a straw test with G122 as the host, and they were found to have varying degrees of aggressiveness (2.8 to 7.9) based on a scale of 1 = no disease, to 9 = death of the plant. Aggressiveness variation of the USA collection ofcharacterized bean isolates is illustrated in Table 2 and Figure 1. Differences in isolate aggressiveness were found among the isolates (P<0.001) but all isolates that are clones had similar aggressiveness. This data provides evidence that pathogen variation can influence resistance screening results. A summary of MCG and aggressiveness characterization of 157 field and greenhouse screening isolates collected across the major USA bean production regions has been published (Otto-Hanson et al., 2011).