The influence of Tilletia spp. inoculum source and environmental conditions on the frequency of infected wheat spikes

Abstract

The influence of inoculum source on the incidence of common bunt, caused by fungi from the genus Tilletia, was estimated based on the frequency of bunt infected wheat spikes in our agroecological conditions. The cultivar Novosadska rana 5 was sown in a random split plot design with four replicates at Rimski Sancevi on three sawing dates in 1999/2000 and 2000/2001. The following variables were evaluated: I - control, II - soilborne inoculum (4 g teliospores/1 l soil), III - seedborne inoculum (2 g teliospores/1 kg seeds), IV - seedborne inoculum + soilborne inoculum (4 g teliospores/1 l soil + 2 g teliospores/1 kg seeds). Correlation and regression analysis were used to evaluate the effect of temperature and precipitation on the frequency of infected spikes. The frequency of bunt infected spikes depended on the source of Tilletia spp. inoculum, and difference in infection frequencies between variables II and III, as well as III and IV, were determined for the assessed infection parameters. When teliospores are the only source of inoculum in soil, 60 days after sawing (r>+0.52) is a critical period in which temperature influences the development of infection. The highest number of plants was infected in the first, while less were infected in the second ten days (decade) after sawing (r>0.41), when temperature was the optimal 5.0-6.0?C. The initial 60 days after sawing were also critical for disease development when teliospores on seeds were the only source of inoculum (r>+0.50). The highest number of plants was infected in the third and fewer in the fifth decade after sawing (r>0.41), when temperature was the optimal 5.0-6.0?C. When infection was caused by teliospores on seeds and in soil, the critical period lasted 120 days after sawing (r>0.42), with a maximum frequency of infection found at the optimal temperatures for the period of 4.0- 5.0?C.