大豆灰斑病初侵染来源与病菌侵染条件的研究

STUDIES ON THE SOURCES OF PRIMERY INOCULUM AND THE INFECTIOUS CONDITION OF SOYBEAN FROG EYE LEAF SPOT

本研究采用室内控制培养和室外人工接种的方法较为系统地探讨丁黑龙江省密虎地区大豆灰斑病初侵染来源与病菌侵染条件,试验结果表明病菌在病残体和种子中越冬,为次年初侵染的来源。放置于仓库和地表堆积病残体比埋入地下病残体产孢量多。随着时间的顺延,越冬后病残体产孢量和孢子萌发率也逐渐下降。分生孢子萌发温度范围12～35℃,最适温度20～25℃;在24℃温度条件下,病菌孢子置于相对湿度90％环境中6 h才能萌发,在水滴小萌发率最高;孢子萌发的pH值范围3～9,最适pH6～7;光对孢子萌发无显著影响。在13～30℃范围内病菌均能侵入寄主发病,在最适温度21～25℃范围内保湿6～8 h病菌即可顺利完成侵入寄主过程。在15～20℃温度范围内,病菌在寄主叶片潜育期为4～15d,荚部潜育期17～24d,温度越高潜育期越短,籽粒感病率越高。大豆植株体代谢旺盛的叶片和大于1cm的荚最易感病,而幼嫩和老化组织不易感病。

The conidia and the mycelia of cercospora sojina Hara could survie on diseased plants and seed which were the souces of primery inoculum next year. Seed-trasmited pathogen with soybean frog--eye leaf(SFLS)caused the disease of cotyledon, and the pathogenic fungi father injected the soybean plant with many times. SFLS pathogenic sources of primary inoculum were mainly from the overwinter survivals of indoor storage or stacking the soil surface, and the seed-tansmited pathogen only as the supplements.The experiments showed that the conidia could germinnate among the temperature 12 ℃ to 35 ℃, and the best condition for germination was at 20 ℃ to 25℃, The lowwest relative humidity for germination was 90%, in which the pathogenic fungi have to keep over 6 hours at 24 Cin order to complete the process from germination, and the best condition for germination was in water. The comidia could germinate among the pH3 to 9,and the pH6 to 7 was suftable.During the temperature from 15 ℃ to 30 ℃, the incubational period were shortened as the temperature increased. The incubational period in the soybean aleaves was under or over 17 days at 25 ℃.Results from the studies have shown that both the pods more than 1cm were easily infected, whereas, either the young tissue or old tissue showed a better resistance to the SFLS.