DIFFERENCES IN TEMPERATURE REQUIREMENTS BETWEEN POLYMYXA SP. OF INDIAN ORIGIN AND POLYMYXA-GRAMINIS AND POLYMYXA-BETAE FROM TEMPERATE AREAS

The temperature requirements of three single cystosorus strains of Pol ymyxa sp. from India were studied at 15-18, 19-22, 23-26 and 27-30 deg rees C (night-day temperature), and compared with the temperature requ irements of three strains of P. graminis from Belgium, Canada and Fran ce and two strains of P. betae from Belgium and Turkey Sorghum was use d as the host-plant for the Indian strains; the strains of P. graminis and P. betae from temperate areas were cultivated on barley and sugar beet, respectively. The cystosori germination and the development of plasmodia, zoosporangia and cystosori of Polymyxa sp. from India were optimal at 27-30 degrees C. Infection progression was slower at 23-26 degrees C than at 27-30 degrees C. At 19-22 degrees C, infection was i nsignificant. No infection occurred below 19 degrees C. In contrast, t he infection of barley with P. graminis strains from temperate areas w as optimal at 15-18 degrees C, but at 19-22 degrees C the progression appeared inconsistent and infection stayed low. Above 22 degrees C, in fection was insignificant. P. betae strains showed consistent infectio n in the range of 15-18 degrees C to 27-30 degrees C. Plasmodia format ion and cystosori detection of the Belgian strain were slightly advanc ed at 23-26 degrees C compared to 19-22 degrees C but clearly restrain ed at 27-30 degrees C. Fungus development of the P. betae strain from Turkey was almost as high at 27-30 degrees C as at the lower temperatu res. These results strengthen the case for distinguishing between Poly myxa sp. from India and P. graminis or P. betae from temperate areas.