Archivio Journal of Plant Pathology

Abstract:

Among 26 isolates of Phytophthora capsici from pepper and zucchini plants collected mainly in Piedmont (northern Italy) 19 belonged to A1, 3 to A2 mating type and 4 were homothallic. All the isolates grew between 10 and 38°C showing significant differences in mycelial growth and optimal growth temperature in the range of 25-32°C. 65.4% of the isolates were sensitive to metalaxyl and the others moderately sensitive; nevertheless 50% of them had MIC values ³ 500 µg ml-1. All the isolates were highly sensitive to dimethomorph, showing mean EC50, EC90 and MIC values of 0.48, 0.90, and 1.02 µg ml-1. A differential set of 9 plant species (pepper, tomato, eggplant, Solanum nigrum, melon, squash, pea, French bean and Lima bean) allowed the isolates to be grouped in 13 pathogenicity classes depending on their ability to infect different plant species; all were pathogenic on pepper, 79% on tomato, 58% on S. nigrum, 38% on eggplant; 95% were pathogenic on squash and 20% on melon; 33% caused a root rot on pea and 8% on French bean, but none on Lima bean. Moreover, the isolates belonging to the same pathogenicity group differed in virulence on two differential sets of pepper.