Teliospore Survival and Plant Quarantine Significance of Tilletia Indies (causal agent of Karnal bunt) Particularly in Relation to China

The influence of temperature, light and soil conditions on teliospore germination of Tilletia (Neovossia) Indica was investigated. The teliospores were germinated by incubation in an aqueous suspension in a concavity on a water agar surface and the germination percentage was scored directly under low magnification of the compound microscope. The optimal temperature range for germination was found to be 15 to 22°C. Germination was extremely low at 2°C, but total inhibition was only observed after prolonged exposure to 35®C (in darkness) or to - 18°C under dry conditions. Light was shown to have a stimulating effect on germination (artificial daylight was found to be better that near ultraviolet light). No stimulation was achieved by prolonging the illumination from 12 to 24 h. Teliospores from 5-year-old wheat samples were shown to be viable. The weather conditions of the various wheat- growing areas of China were compared with the results obtained for the survival of teliospores of T. indica. It is concluded that a considerable risk exists for establishment and spread of the Karnal bunt disease if first accidentally introduced into China. Strict quarantine precautions, and policies can minimize or even eliminate this risk.