Resistance to black root rot among wild clones of strawberry Fragaria virginiana and Fragaria chiloensis (Pratylenchus penetrans, Rhizoctonia, Pythium).

摘要

Black root rot (BRR) is a devastating root disease that affects all strawberry cultivars and is thought to be caused by a complex of pathogens that include the root lesion nematode, Pratylenchus penetrans, and two soil fungi, Rhizoctonia spp. and Pythium spp. Soil fumigation with methyl bromide is the standard practice to combat BRR. However, methyl bromide is a known ozone depletor and its use to be phased out by 2005. To facilitate the breeding of resistant cultivars, native germplasm was screened for their resistance to BRR using field studies and greenhouse screens. The specific goals were to (i) identify pathogens involved in BRR and monitor their levels in strawberry fields across MI, (ii) screen wild genotypes for tolerance and/or resistance to identified pathogens. It was found that the beneficial gains from methyl bromide fumigation are relatively short lived in the perennial matted row system. The main soilborne pathogens responsible for BRR symptoms in Michigan appear to be Rhizoctonia and the root lesion nematode. As a group, the wild genotypes appear to possess more resistance to these pathogens than the cultivars. The F. virginiana genotype, NC 96-35-2, was the most resistant genotype overall, and its resistance appeared to be broad spectrum.