Effect of temperature and pH on the growth and sporulation of Phytophthoraclandestina

The effects of temperature and pH on the growth and sporangial production o f isolates from each of the four known races of Phytophthora clandestina Ta ylor, Pascoe & Greenhalgh were investigated. Mycelial growth occurred at te mperatures from 10 to 30 degreesC and pH 3.5 to 9.0 with highest growth rat es of all isolates being at 25 degreesC with a pH of 6.0-6.5. Sporangial pr oduction was greatest between 20 and 25 degreesC and pH 5.0-7.0 with all ra ces. However, sporulation occurred over a temperature range from 10 to 30 d egreesC and from pH 4.0 to 9.0 with all isolates. There were no consistent differences between the four pathogenic races of P. clandestina in their re lative growth rate or extent of sporangial production over a range of tempe ratures and pH values.