【摘要】 本文利用２个对水稻抗病基因 Ｐｉ１（ｔ）有致病力的突变菌株和它们的各自原始菌株共同接种高度感病的品种ＣＯ３９。第一轮接种后，采集病叶并收集分生孢子用于下一轮接种，同时分离单孢菌株。经过３ 或４ 轮接种后，共分离９０５个单孢菌株。然后，利用稻瘟病菌的一段倒位重复序列 Ｐｏｔ２所设计的一对引物，Ｐｏｔ２１和Ｐｏｔ２２，直接进行 ＤＮＡ 聚合酶链式反应（ＰＣＲ），检测各菌株在群体中所占比例，结果表明，２个突变体均比各自的原始菌株有更高的适合度，突变体 ＲＣ１（４＋ ５）１４１与原始菌株９２４８６组合中，前者由第１轮接种循环的７１％ 上升到第４轮的１００％ ；突变体 ＭＣ１（３＋ ４）５７９与原始菌株１０１７２１１组合中，前者在各代中均比原始菌多一倍。２个突变体适合度也相差很大，经过３代接种循环后， Ｍ Ｃ１（３＋ ４）５７９则逐渐消失，ＲＣ１（４＋ ５）１４１ 完全占优势，达到１００％ 。突变体 ＲＣ１（４＋ ５）１４１的产孢能力是其它菌株的２～３倍，这表明， 稻瘟病菌菌株在自然条件下成为优势群体，除了致病力发生突变外， 还要在产孢能力上有明显的优势以适应新的抗病基因更多还原

【Abstract】 Two Magnaporthe grisea isolates, MC1(3+4)57 9 and RC1(4+5)141, adapted to C101LAC carrying resistance gene, Pi 1(t) , and their original isolates, 101 7 2 1 1 and 9248 6, were studied in fitness. PCR based fingerprinting by two primers, Pot2 1 and Pot2 2, was employed to overcome the difficulty that the four isolates had no differences in virulence and in lesion morphologically on CO39. A total of 905 single spores were isolated and investigated in fingerprints. The results showed that the adapted isolates had higher fitness than the originals and different fitness from each other. RC1(4+5)141 prevailed over the others if it was co inoculated on CO39. The capacities of sporulation and forming lesion could explain the fitness difference partially though there were other interactions between isolates. RC1(4+5)141 could sporulate much more than the others and form more lesions per 10 000 spores irrespective of its individual and mixtures with other isolates. The micro environment may affect the fitness, but RC1(4+5)141 was not as sensitive as other isolates. That isolate with high capacity of sporulation prevailed easily indicated that if a specific isolate spreads out it must have sporulation advantage and mutate to specific resistance gene.更多还原