Isolation and identification of Phytophthora capsici in Guangdong Province and measurement of their pathogenicity and physiological race differentiation

Abstract

Five isolates collected from different pepper-cropping regions in Guangdong Province, China were determined. Based on their morphological characteristics and symptoms after being re-inoculated to pepper, these isolates were identified as Phytophythora capsici Leonian. The sporangia induced on carrot medium (CA) were morphologically similar and most of their shapes were ovate or elliptic, and obviously papillate. The mean size of the sporangium was 40.8–45.9 (l) μm×23.2–30.9 (b) μm, with l/b ratio 1.4–1.8. There were evident differences in mycelial growth rate, productivity of sporangia and pathogenicity to pepper among the isolates. A test of physiological characteristics showed that one isolate was determined as Race 1, and the other four isolates belonged to Race 3. It is concluded that Race 3 is most likely to be the predominent race in Guangdong Province, China.

Keywords

pepper phytophthora blight, Phytophthora capsici, pathogenicity, physiological race