桑平疹干枯病的研究

桑平疹干枯病(Massaria mori Miyake)是一种桑树的枝干病害,在浙江省分布较广,为害较重,发病率最高可达100％。经研究发现,本病菌存在无性时期,在PSA培养基中能形成分生孢子器,厚垣孢子以及有性时期的子囊和子囊孢子。明确了本病菌的分类地位应隶属于子囊菌亚门,腔菌纲、格孢腔菌目、格孢腔菌科。本病的发生和寄主、病原的生态环境有关,接种发病率分别为30％,60％。因品种不同,形成愈伤组织有差异,直接影响变色部分的长短。本病菌在越冬后,于次年3月引起初次侵染,均从伤口侵入,一年内有重复感染。完成本病菌的生活史需要35—58天,接种潜育期一般为18天。在12月低温8℃时,子囊孢子萌芽率仅1.5％,故桑树整枝宜在1月份低温时进行。

STUDIES ON MULBERRY BRANCH BLIGHT DISEASE

Mulberry branch blight disease,Massaria mori Miyake,is a disease which harms the mulberry trees and widely distributes in the mulberry areas of Zhejiang Province. It causes more mulberry losses than any other mulberry dieback-like diseases and the highest incidence of this disease may reach 100%. Inoculation test showed that two types of spores of this fungus were freely produced in infected tissues: hyaline small conidia and brown ascospores which were born in pseudothecium. Meanwhile, cultural experiment in PSA medium showed that there were three types of spores : conidia, thick-walled black ascospores and chlamydospores. This pathogenetic fungus ta: nomoically belongs to Ascomycotina, Locu-loascomycetes, Pleosporales, Pleosporaceae. The pathogenicity of this fungus may be varied with variations of the ecotope, varieties of mulberry trees and the callus. Every March this disease begins its primary infection on mulberry trees through their wounded parts of branches. The incubation period of this pathogene is 18 days. The iife cycle ranged from 35 to 58 days. The germination percentage of ascospores is only 1.5% in December. So, it is suggested that dequate time for branch-cutting is in January.