Comparison of Proanthocyanidin and Phenolic Rich Extracts Derived from Pecan Shell and Husk as Elicitors of Induced Resistance against Phytophthora capsici on Chile Pepper

The use of plant-derived secondary metabolites to induce disease resistance in plants has been well documented. In this study, total phenolics and total proanthocyanidins (PAC) were extracted from shell and husk of pecan (Carya illinoinensis) and quantified. Under greenhouse conditions, the extracts were foliarly applied to chile pepper (Capsicum annuum, cultivar NM 6-4) to compare their ability to induce resistance in plants inoculated with a virulent isolate of Phytophthora capsici. Extractions yielded total phenolic contents of 673 ± 28 mg/g and 293 ± 24 mg/g dry weight (DW) for shell and husk and total PAC contents of 1770.10 ± 158.62 mg/g DW and 901.30 ± 22.84 mg/g DW for shell and husk, respectively. Chile plants treated with total phenolic and PAC extracts from pecan husk or shell or 0.1% salicylic acid, a plant defense hormone, remained asymptomatic throughout the study for three weeks, while plants treated with water, which served as a control, died. Both total phenolic and total PAC extracts derived from pecan byproducts can be used within a greenhouse setting as elicitors to induce resistance response in chile pepper against plant pathogens such as P. capsici.