Occurrence and inheritance of resistance to powdery mildew (Oidium lycopersici) in Lycopersicon species

Abstract
Among 146 accessions of Lycopersicon pimpinellifolium, 132 of L. esculentum var. cerasiforme and 53 of L. peruvianum screened for resistance to powdery mildew, caused by Oidium lycopersici, a wide variation in reactions was found. Two plants of L. esculentum var. cerasiforme accession LA‐1230 were resistant. One resistant symptomless plant of accession LA‐1230, designated LC‐95, produced homozygous resistant progenies. LC‐95 was crossed with cv. Marmande (susceptible parent) and F1, F2 and backcrosses to the resistant and the susceptible parents were derived. These genotypes were grown in glasshouses at 23°C and 95–100% RH and inoculated with O. lycopersici. The F1 plants were susceptible. F2 and backcross segregations fitted the hypothesis of a single recessive gene which is here designated ol‐2.