四川稻瘟病菌致病性变异与病害流行的关系

VARIATIONS IN PATHOGENICITY OF RICE BLAST FUNGUS AS RELATED TO ITS EPIDEMICS IN SICHUAN

文根据１９７９～１９９５年利用１９５３个稻瘟病菌株，先后对鉴别品种及主栽品种进行抗谱测定，分析品种田间抗性变化，揭示了稻瘟病菌生理小种变化动态，预示品种抗性丧失时限，是稻瘟病发生流行的前兆；探明了品种抗性丧失的主要原因，是来自品种自身病菌新致病小种数量的增殖和毒力强化，由潜在致病种群上升为优势种群，从而导致该品种抗性的丧失。

In 1979～1995, 1953 strains of rice blast (Piricularia oryzae Cav.) were used to determine the resistance spectrum of the widely cultivated rice varieties and the varieties to be evaluated. Based on the results of the work mentioned, the variations in field resistance were analysed and the dynamics of changes in the races of the pathogen was revealed. The loss of resistance of the predominant cultivar may be taken as a forewarning of an epidemic of the disease. The cause of the loss of resistance was found to be the increase in number of the potential pathogenic races and the strengthening of their toxicity in the variety and, as a result, they become dominant races, thus leading to an outbreak of the disease.