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从1956年以来在北京和山西阳高进行的晚疫病初侵染来源的试验没有发现病薯以外的其他可能来源。在北京条件下,病菌冬季在残株上只能存活一个半月,在山西病地连茬种植不能引起早期严重发病。病叶的检查和培养基的诱发培养都未见到卵孢子。病菌从病薯侵染到病苗的三种途径,经过大量调查和试验,结果如下:薯块上的病斑扩展到幼苗基部皮层的最多;其次是由病薯或病苗地下部,长出孢子囊,再侵染到同穴相邻幼苗地下茎引起的。病菌由茎基髓部长上来的最少。后两种只占出土病苗的4%左右。不同途径得病的幼苗,形成中心病株的可能性也有所不同。幼苗得病后有三种情况:一种是病菌很快长到幼苗的生长点,或横向环绕茎基,使幼苗早期死亡,病菌亦同归于尽。第二种是病菌侵染茎基时,茎部有足够的抵抗力,使病斑愈合,病菌死去。第三种情况是幼苗得病时其抗病力与病菌的致病力处于相持状态,病菌缓慢地向上生长,出土后,遇到适宜的条件,产生孢子囊,成为中心病株。通常中心病株形成率只占病薯总数的%1左右。病苗与中心病株的形成受下列因素的制约,病薯的染病程度:种薯的切块、土壤微生物的活动、品种的差异与幼苗抗病力变化的速度。病苗出土后的气象条件影响中心病株和发病中心形成至普遍和严重流行的速度。
No sources of disease other than disease were found from the initial sources of late blight infection in Beijing and Shanxi Yanggao since 1956. Under the conditions of Beijing, the germs can only survive for one and a half months on the stubble in winter, and the stubble planting in the diseased areas of Shanxi Province can not cause the early severe disease. Sick leaves of the culture medium and induced culture have not seen oospores. Bacteria from the pathogen infected potato disease to the three ways, after a lot of investigation and testing, the results are as follows: Lesions on the tubers extend to the base of the seedling cortex up; followed by the bottom of the disease or disease vaccine seedlings grow Sporangium, which in turn infects the underground stems of adjacent seedlings in the same cave. Germs by the stem of the ministerial up to the least. The latter two accounted for only 4% of the diseased seedlings. Different ways to get sick seedlings, the possibility of forming the center diseased strains are also different. Seedlings get sick after three situations: one is the growth of germs quickly grow to the point of seedlings, or transversely around the stem base, the early death of seedlings, germs are also exhausted. The second is the pathogen infection stem base, the stem has sufficient resistance, the lesion healing, bacteria die. The third case is disease resistance of seedlings disease resistance and pathogenicity of bacteria in a stalemate, the bacteria grow slowly upward, after unearthed, met the appropriate conditions, resulting in sporangia, become the center diseased. Usually the center of the rate of diseased plants accounted for only about% of the total number of pathogenic bacteria. The formation of diseased plants and central diseased plants is restricted by the following factors: the degree of disease of diseased plants: the dicing of seed tubers, the activity of soil microorganisms, the difference of cultivars and the rate of disease resistance change of seedlings. Meteorological conditions after the excision of diseased plants affect the prevalence and prevalence of diseased and diseased centers in the center.