2018 ASHS Annual Conference

Target spot, caused by Corynespora cassiicola (Berk. & Curt) Wei, has become a significant threat to tomato production in Florida in recent years. The disease infects tomato foliage and fruits and can result in dramatic yield losses under conditions favorable for disease development. Recent studies have demonstrated increased aggressiveness and fungicide resistance in C. cassiicola populations in the state. In an effort to identify potential sources of host resistance, 83 tomato accessions representing nine different Solanum spp. were screened for resistance to C. cassiicola using a newly developed seedling assay. Initial results identified seven of these accessions as resistant and 22 as moderately-resistant. Assays were subsequently repeated for 12 of the better accessions, and resistance relative to susceptible S. lycopersicum controls was confirmed in each of the 12 accessions. Resistance was identified among S. lycopersicum, S. habrochaites, S. cheesmaniae, and S. pimpinellifolium species. Two S. cheesmaniae accessions (LA1042 and LA0932) and two S. pimpinellifolium accessions (LA1043 and LA2093) demonstrated the highest levels of resistance among the 12 accessions. Ongoing research efforts seek to further validate resistance levels among these accessions using seedling disease screens and field trialing of mature plants. Crosses between resistant accessions and elite germplasm are also underway and will be used to characterize gene action and to begin introgression of resistance into cultivated tomato.