Studies on the causal organism, ecology and control of russet-like disease of potato

Abstract

In recent years, russet-like disease of potato under mulching culture in winter and spring has been causing problems in Saga prefecture. An actinomycete was isolated from potato plants with russet-like disease, which caused identical symptoms in inoculation tests. This actinomycete was found to belong to the genus Streptomyces based on the morphological characteristics and cell wall type. It apparently differed from Streptomyces spp. causing potato common scab in the spore chain morphology, spore surface structure and DNA-DNA homology values. The pathogenic Streptomyces sp. grew well at a temperature of about 37 C but did not grow in a medium at pH 5.0. In the field, the damage was more severe under mulching culture than non-mulching culture and in soil with a neutral pH value compared with acid soil. Fungicide treatment for the control of russet-like disease was not effective. It is considered that if potatoes are cultivated in fields with a soil DH below 5.0. it may be possible to decrease the damage.