2019 ASHS Annual Conference

Phytophthora blight caused by Phytophthora capsici is an economically important and yield-reducing disease in chile pepper and other fruiting vegetables. Chemical, cultural, and exclusion methods, have been used as control strategies, but no single method provides complete and satisfactory results. Therefore, additional measures are needed. It has been observed previously that Phytophthora blight develops slower in Jalapeño cultivars than in other chile pepper types. This research aims at identifying the factors associated with the reduction of Phytophthora blight in Jalapeño cultivars. One possible factor could be an increase in the production of phenolic compounds, which are secondary metabolites involved in plant defense mechanisms against plant pathogens. Six Jalapeño genotypes and two non- Jalapeño genotypes were either inoculated or not inoculated with P. capsici. Phenolic compounds were extracted through the Folin-Ciocalteu reagent method and total phenolics were measured spectrophotometrically at two time periods, 12 and 24 hours post-inoculation. Analysis of variance showed no significant 2-way and 3-way interactions among inoculations, genotypes, and time periods. There was a significant difference between inoculation levels and among genotypes, but there was no significant difference between time periods at P-value 0.05. The results showed that the total phenolic content was higher in inoculated plants than non-inoculated plants. Higher phenolic content was observed at 12 hours post-inoculation for all cultivars except for NuMex Pumpkin Spice and NuMex Jalmundo. There was a decline in total phenolic content for Early Jalapeño and NM 6-4 at 24 hours post-inoculation. An increase in phenolic compounds at 12 hours post-inoculation for NM 6-4 was reaction against infection. For NuMex Pumpkin Spice, the lower disease severity may be due to continuous increase in total phenolic content even after 24 hours post-inoculation. However, the lower disease severity in TAM Jalapeño and NuMex Vaquero could be due to the transcription of resistance genes such as CaRGA2 or CaPTI1 because they had similar phenolic content trend as CM-334, which is a resistant genotype to P. capsici. Future work will focus on evaluating the concentration of total phenolic content at earlier stages of post-inoculation (3 and 6 hours) and on analyzing the expression of resistance genes.