Evaluation of the resistance against Phytophthora infestans of wild populations of Solanum lycopersicum var. cerasiforme

Abstract

Late blight caused by Phytophthora infestans (Mont.) de Bary has caused severe losses in the production of tomato (Solanum lycopersicum) in growing areas such as Sinaloa, where losses of up to 100% have been reported. Wild species are a source of disease resistance. Wild populations of Solanum lycopersicum var. cerasiformis were collected in different regions of Mexico, such as the Gulf and Pacific coastal plains, and in intermountain valleys at altitudes around 2000 masl. During the growing seasons of 2008, 2009 and 2010, 19 populations of this variety were evaluated to determine if they have resistance against the pathogen. The Rio Grande variety was used as susceptible control and the LA2533 accession (S. pimpinellifolium) as resistant. We estimated the severity of the disease through the variables: area under the disease progress curve (AUDPC), relative AUDPC, time of onset of symptoms (TAS), rate of disease development (bi) and final evaluation of damage (FE). The results showed variation in the wild populations, from susceptibility to disease resistance. The pathogen resistance response was consistent across the assessment years in which the populations V115, 319, 327 and 330 were noteworthy for presenting the lowest values of AUDPC, AUDPCr, bi and FE, similar to those of LA2533; also, the symptoms appeared 10 days later than in all other populations (longer TAS). The Río Grande control showed considerable damage in all evaluations, up to 100% damage to the plant. These four populations are established as sources of late blight resistance in breeding programs.