Reaction of Solanum (section Lycopersicon) germplasm to Phytophthora capsici

Abstract

The use of resistant cultivars is one of the most efficient strategies for reducing the amount of pesticides in agricultural crops. Several species of the Solanaceae and Cucurbitaceae families are susceptible to diseases caused by Phytophthora capsici isolates. Even though sources of resistance have been identified in other host plants, reports of resistance to P. capsici in cultivated and wild tomato species [genus Solanum (section Lycopersicon)] germplasm are yet scarce. The main objective of the present work was to characterize the reaction of 244 Solanum (Lycopersicon) accessions to P. capsici under controlled greenhouse experiments. In the first set of experiments, tomato seedlings were inoculated at the collar area with a 3 mL of a spore suspension (2 × 104 zoospores mL−1). Disease incidence (dead plants/total plants) was assessed 14 days after inoculation. The accessions were separated in five well-defined reaction groups: highly resistant (HR), resistant (R), moderately susceptible (MR), susceptible (S), and highly susceptible (HS). The reaction of a group of the ten accessions with the highest levels of resistance was then evaluated against a collection of five P. capsici isolates. Differential reaction was observed among accessions and isolates. The resistant response was host species-dependent with susceptibility being more often found in S. peruvianum accessions, whereas sources of resistance were identified more frequently among accessions of the cultivated tomato (S. lycopersicum).