Elevated CO₂and Temperature Effects on the Incidence of Four Major Chili Pepper Diseases

Abstract

Four major diseases of chili pepper including two fungal diseases, anthracnose (Colletotrichum acutatum) and Phytophthora blight (Phytophthora capsici), and two bacterial diseases, bacterial wilt (Ralstonia solanacearum) and bacterial spot (Xanthomonas campestris pv. vesicatoria), were investigated under future climate-change condition treatments in growth chambers. Treatments with elevated <TEX>$CO_2$</TEX> and temperature were maintained at <TEX>$720ppm{\pm}20ppm$</TEX> <TEX>$CO_2$</TEX> and <TEX>$30^{\circ}C{\pm}0.5^{\circ}C$</TEX>, whereas ambient conditions were maintained at <TEX>$420ppm{\pm}20ppm$</TEX> <TEX>$CO_2$</TEX> and <TEX>$25^{\circ}C{\pm}0.5^{\circ}C$</TEX>. Pepper seedlings or fruits were infected with each pathogen, and then the disease progress was evaluated in the growth chambers. According to paired t-test analyses, bacterial wilt and spot diseases significantly increased by 24% (p=0.008) and 25% (p=0.016), respectively, with elevated <TEX>$CO_2$</TEX> and temperature conditions. On the other hand, neither Phytophthora blight (p=0.906) nor anthracnose (p=0.125) was statistically significant. The elevated <TEX>$CO_2$</TEX> and temperature accelerated the progress of bacterial wilt by two days and bacterial spot by one day compared to the ambient treatment. Temperature regime studies of the diseases without changes in <TEX>$CO_2$</TEX> confirmed that the accelerated bacterial disease progress was mainly due to the increased temperature rather than the elevated <TEX>$CO_2$</TEX> conditions.