Predispositional effect of soil water saturation on infection of chile pepper by Phytophthora capsici

Abstract

Phytophthora capsici is a serious soilborne pathogen in chile pepper [Capsicum annuum L.] in New Mexico, and has been shown to spread under high soil moisture conditions and cause losses in a wide array of crops worldwide. This study was conducted to assess whether soil water saturation predisposes chile pepper to infection by P. capsici. Potted chile pepper plants of 'Criollo de Morelos 334' ('CM334') and 'New Mexico 6-4' ('NM6-4'), resistant and susceptible to P. capsici, respectively, were subjected to soil water saturation conditions (saturated and nonsaturated) for 3 and 6 days at two growth stages (six- to eight-leaf stage and one- to four-flower bud stage) prior to being inoculated or noninoculated with zoospores of P. capsici. Regardless of growth stage, no disease symptoms developed in 'CM334' grown either under saturated or nonsaturated soil conditions at any of the two periods (3 or 6 days) of soil water saturation. In 'NM6-4', disease symptoms consisting of stem necrosis, defoliation, and wilting were expressed. Plant growth stage at inoculation had a significant effect on disease severity (P < 0.0001). However, the response of 'NM6-4' to P. capsici at each growth stage under saturated soil conditions was similar to that under nonsaturated conditions regardless of the period of saturation (P = 0.09). These results indicate that soil water saturation does not exert a significant predispositional effect on infection of chile pepper by P. capsici.