云南烤烟腐霉菌种类、分布及致病性研究

 1994～1995年分别从云南省楚雄市、玉溪市、昭通市、晋宁县、永胜县等11个主要烟区,采集根茎病害标样226份,土壤标样60份,分离纯化到42个菌株,鉴定了其中的35个菌株,得到Pythium ap hanidermatum,P.debaryanum,P.ultimum,P.irregulare 4种腐霉菌;其中,P.aphanidermatum出现频率达48.6%,是优势种群。4种腐霉菌在不同烟区,不同类型烟田,不同生育期烤烟和烟田不同位置土壤中的种类和数量分布有一定差异;在水肥条件好的烟区及烤烟苗床和烤烟的根际土壤中腐霉菌的出现频率高,种类多。致病性测定表明,4种腐霉菌都能侵染烤烟,是腐霉致病种;其中P.aphanidermatum发病率最高,达28%,且出现猝倒现象,是对烤烟致病力最强的种。

Distributions and Pathogenicity of Pythium spp Infecting Tobacco in Yunnan Province

During 1994～1995, 226 diseased root neck specimens of tobacco and 60 soil samples were respectively collected from 11 main tobacco planting areas, Chuxiong, Yuxi Zhaotong,Jinling,Yongsheng etc municipalities or counties of Yunnan province. Thirty five strains among 42 Pythium strains which isolated and purified from the specimens were identified as 4 species; Pythium aphanidermatum,P.debaryanum, P.ultimum, P.irregulare. The other strains were unknown, due to the absence of scxual organs P.aphanidermatum is the dominant population, whose freguency in the specimens is 48.6%. There are certain distributiom difference among this 4 species in different tobacco planting areas, different tobacco field types, different growth periods of tobacco, and different positions of soil. The freguencies of Pythium are high and species of it are various in the planting areas with good soil condition and in nursery of tobacoo and soil around the plant root neck. Soil and in vitro inoculation tests indicate that 4 species are all pathogenic species P.aphanidermatum is the most harmful, which infected 28% of plant in the test and were able to cause damping-off.