Resistance of lettuce and related species to anthracnose (Microdochium panattonianum) in Australia



All 35 commercial lettuce cultivars available in Australia, two cultivars of chicory, one cultivar of endive and single accessions of Lactuca saligna, L. serriola and Sonchus oleraceus were tested for susceptibility to Microdochium panattonianum under glasshouse and field conditions. Under controlled environmental conditions log lesion density on cv. Cos Verdi was linearly related to log inoculum concentration. Inocula from L. saliva and L. serriola were cross-infective but did not infect the single accessions of L. saligna and S. oleraceus tested. All lettuce cultivars were susceptible. Some cultivars showed a relatively greater increase in susceptibility than others at an increased inoculum concentration. Latent periods for different cultivars ranged from 3 to 7 days under glasshouse conditions and from 8 to more than 17 days in a field trial. There was poor correlation between glasshouse and field trials for the disease rating of cultivars. Chicory, endive and the L. saligna accession were immune (symptomless) and the L. serriola accession was highly resistant. The results indicate that L. saligna, L. serriola. endive and chicory are possible sources of genes for resistance to M. panattonianum.