Pea Germplasm with Partial Resistance to Sclerotinia sclerotiorum Extends the Time Required by the Pathogen to Infect Host Tissue

摘要

White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) de Bary, can be a serious disease in pea (Pisum sativum L.). Currently there are no pea genotypes with complete resistance to this pathogen. The objective of this research was to identify pea germplasm with partial resistance to S. sclerotiorum, focusing on initial infection and severity as influenced by environment. Selected pea genotypes from the USDA-ARS Pisum core collection and two cultivars were assessed for the time required by S. sclerotiorum to severely infect these genotypes at all combinations of five temperatures (15.6, 18.3, 21.1, 23.9, and 29.4 degrees C) and four periods of high relative humidity (PHRH) (12, 24, 48, and 72 h) under controlled environmental conditions. Severe infection is defined as the death of all plant tissue above a stem inoculation point, preventing reproduction. The commercial genotypes 'Bolero' and '1204-3' did not prevent severe infection at any temperature x PHRH combination. However, pea genotypes PI 164972, PI 169603, PI 197044, PI 240515, PI 270536, and PI 280611 prevented severe infection at 15.6, 18.3, 29.4, and either 21.1 or 23.9 degrees C following a 12 h PHRH in repeated trials. Plant Introduction 164972, PI 169603, and PI 280611 also prevented severe infection following a 24 h PHRH but only at 29.4 degrees C. Severe infection occurred for all genotypes after a 48 or 72 h PHRH at all temperatures tested. Plant Introduction 169603 and PI 240515 are recommended to pea breeders as the best germplasm to extend the time required for serious infection by S. sclerotiorum.