Reaction of Lettuce Germ Plasm to Artificial Inoculation with Sclerotinia minor Under Greenhouse Conditions. G. S. Abawi, Associate Professor, Departments of Plant Pathology and Seeds and Vegetable Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456. R. W. Robinson, Professor, A. C. Cobb, Laboratory Assistant, and J. W. Shail, Research Support Specialist, Departments of Plant Pathology and Seeds and Vegetable Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456. Plant Dis. 64:668-671. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-668.

More than 100 Lactuca accessions were evaluated for resistance to Sclerotinia minor under greenhouse conditions. Plants 5–6 wk old were inoculated with rye seeds colonized by S. minor placed in contact with the taproot 1–2 cm below the soil surface. Surviving plants were reinoculated 3 wk later. All accessions of L. sativa, including introductions from 28 countries, were susceptible. However, several selections of wild Lactuca spp., including L. dentata, L. perennis, L. serriola, L. virosa, and unidentified species, were intermediately to highly resistant to S. minor. Some plants that survived the Sclerotinia test evidently were not genetically resistant, since their selfed progeny were highly susceptible. Although not all testing has been completed, the selfed or sibbed progenies of selections of L. dentata, L. serriola, and an unidentified Lactuca sp. have remained highly resistant. No correlation was found between the area of origin or horticultural type and resistance to S. minor.

Keyword(s): lettuce drop.