小麦叶锈菌相对寄生适合度变异研究

 本研究采用小麦叶锈菌的4个单孢菌株和由这4个单孢菌株组成的1个混合菌株,分别对5个小麦慢锈品种接种,继代繁殖8代和16代后,对所表现的潜伏期、侵染效能和产孢量进行测定,并提出用病害量=1/潜伏期×侵染效能×产孢量作为参数来评价相对寄生适合度。结果表明,继代互作后,潜伏期、侵染效能或产孢量在某些特定的品种:菌株组合中发生了显著变化,并相应地导致病害量也发生了显著变化。说明通过小麦叶锈菌与小麦品种间的继代互作,可以导致叶锈菌的相对寄生适合度发生变异。但这些变异,未能导致慢锈品种变为快锈品种或快锈品种变为慢锈品种。
为了检查寄生适合度属性的变异是否由于锈菌本身的变异,对各组合的第1、8和16代的叶锈菌的夏孢子芽管的核相进行了观察,并进行小种鉴定。结果表明,继代互作后锈菌出现的异核现象仅占0.18-2.00%,不能解释是寄生适合度发生变化的原因。小种鉴定,也没有观察到毒性发生变异。作者认为,在寄主和病原物长期相互作用的过程中,一些微观上的变异未必能在宏观上观察到,当人们检查到明显的变化时,可能是由于突变,也可能是由于渐变造成的。量变质变,质变建立在量变基础上。

ON THE VARIATION OF RELATIVE PARASITIC FITNESS OF PUCCINIA RECONDITA F. SP. TRITICI

Five wheat cultivars with different degree of slow rusting were inoculated respectively with 5 single spore cultures of Puccinia recondita f.sp.tritici and subcultured the rusts on these hosts for 16 generations. The variation of relative parasitic fitness of the pathogen was studied by observing the variation of latent period, infection efficency, and sporulaton shown by the interaction of 5 cultivars of the Ist,8th,and 16th generation.
The results showed that one or more attributes of the parasitic fitness shown by the interaction of certain cultivar x culture varied significantly, indicating the relative parasitic fitness of the pathogen could be enhanced after successive interactions of host and pathogen for generations. Such variations, however, were not due to the variation of the rust itself, because the virulence of the cultures of the 1st, 8th, and 16th generations did not vary as determined by the differentials and the rate of heterokaryosis occurred was not high and could not account for the cause of variation of fitness.
It was concluded that some minor variations occurring in the interaction of host and pathogen during micro-evolution might not be shown out macroscopically.Detectable variation might result from step-by-step mutation. Qualitative variation was based on quantitative variation.