Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2011
Publication Date: July 28, 2012
Citation: Porter, L. 2012. Selection of pea genotypes with partial resistance to Sclerotinia sclerotiorum across a wide range of temperatures and periods of high relative humidity. Euphytica. 186:671-678. Interpretive Summary: White mold, caused by Sclerotinia sclerotiorum, is a damaging disease affecting peas under cool and wet weather conditions. Currently there are no pea cultivars with resistance to this disease, and the use of fungicides is often not economically practical for growers. The present research identified several pea lines that restrict the lesion advancement and/or delay the onset of white mold at various temperatures and periods of high relative humidity based on growth chamber tests. Identifying pea lines with resistance to the white mold pathogen is important because breeders can use these lines as parents in plant crosses to develop mapping populations used to identify the genes associated with the resistance. Once these genes are identified, they can be used as markers to rapidly select pea lines that are resistant to white mold but also posses outstanding cultural characteristics desired by growers. This research was the first step in identifying pea breeding material with potential durable resistance to white mold over a wide temperature range.
Technical Abstract: Pea genotypes from the Pisum Core Collection with potential partial resistance to Sclerotinia sclerotiorum based on lesion expansion, nodal resistance and non-infection period (NIP) were assessed in growth chambers when plants were inoculated with S. sclerotiorum and incubated at five temperatures (15.6, 18.3, 21.1, 23.9, 29.4ºC) and four incubation periods (12, 24, 48, 72 hours) at 90-100% RH. Significant differences in lesion expansion among genotypes were only observed after 48 and 72 hours of incubation. At an incubation period of 48 hours, the following genotypes are recommended to breeders to limit lesion expansion at specific temperatures: genotypes 240515 and 1204-3 at 15.6 and 21.1ºC respectively, and 169603 at 18.3, 23.9 and 29.4ºC. At an incubation period of 72 hours, Bolero is recommended at 15.6, 18.3, 21.1, and 23.9 ºC, and 169603 at 29.4ºC. Based on nodal resistance, the following genotypes at specific combinations of temperature/incubation period are recommended: genotype 164972 at 15.6 and 23.9ºC /12-hour; 166084 at 18.3ºC /12-hour; 171810 at 21.1ºC /24-hour; 169603 at 21.1 and 29.4ºC /12-hour, 23.9 and 29.4ºC /24-hour, 18.3 and 29.4ºC /48-hour and 18.3 and 29.4ºC /72-hour; 240515 at 18.3ºC /12-hour, 18.3ºC /24-hour, 15.6, 21.1 and 23.9ºC /48-hour, and 15.6, 21.1 and 23.9ºC /72-hour; and 270536 at 18.3ºC /24-hour. Pea genotype 169603 demonstrated the greatest ability to extend the NIP at the most temperatures and incubation period combinations. Genotypes 169603 and 240515 were the most promising genotypes for breeders to use as parents to develop partial resistance to S. sclerotiorum across a wide temperature range.