西葫芦根腐和茎基腐病新病原-露湿拟漆斑菌Paramyrothecium roridum

Paramyrothecium roridum,a new pathogen of zucchini root and stem basal rot disease

2013年12月,甘肃省白银市水川镇日光温室中的西葫芦发生了严重的根腐和茎基腐,部分棚室病株率达50%,从病根和病茎上分离得到拟漆斑菌属真菌3株,病株分出率27.3%。采用胚根和茎基部接种法测定了菌株FG-62对西葫芦的致病性:茎基部接种后27 d,植株开始出现凋萎;接种后40 d,两种接种法的西葫芦苗均呈现严重根腐和茎基腐症状,茎基部接种的西葫芦凋萎株率达30%;从病根和病茎上均可再分离出原接种菌。菌株FG-62在PDA平板上25℃培养14 d,产生大量墨绿色至黑色分生孢子座,分生孢子无色至淡榄黑色,单胞,杆状或腰鼓状,两端钝圆,大小为(7.04~9.15)μm×(1.97~2.46)μm,聚集的分生孢子呈黑色。BLASTn分析结果显示,菌株FG-62(GenBank登录号MK252098)的rDNA-ITS序列与露湿拟漆斑菌Paramyrothecium roridum分离物E-469(GenBank登录号KY582183.1)和CBS 357.89(源自模式材料,GenBank登录号NR_145077.1)的序列相似性分别达99.65%和96.83%。依据病原菌形态学和rDNA-ITS序列,将其鉴定为露湿拟漆斑菌P.roridum(Basionym:Myrothecium roridum)。这是露湿拟漆斑菌引起西葫芦根腐和茎基腐的首次报道。

In December 2013,root and stem basal rot of zucchini occurred seriously in several greenhouses in Shuichuan Town,Baiyin City,Gansu Province,China.In some greenhouses,the disease incidence reached up to 50%.Three strains of Paramyrothecium sp.were isolated from the diseased zucchini root and basal stem,the detection rate was 27.3%in diseased plants.The pathogenicity of strain FG-62 was determined by radicle and stem base inoculation.Wilting on zucchini plants appeared at 27 days post inoculation(dpi)at the stem base,inducing serious root rot and stem basal rot of zucchini at 40 dpi after inoculation by the two methods.The wilting rate reached up to 30%after inoculation at the base of stem and the same fungus was re-isolated from diseased root and stem.Strain FG-62 produced a large amount of dark green to black sporodochia on potato dextrose agar(PDA)plate for 14 d at 25℃,conidia were colorless to pale olive black,unicellular,rod-shaped or drum type,and obtuse at both ends,(7.04-9.15)μm×(1.97-2.46)μm,conidia were black in mass.BLASTn analysis showed that the rDNA-ITS sequence of strain FG-62(GenBank accession No.MK252098)had a 99.65%and 96.83%similarity with P.roridum isolate E-469(GenBank accession No.KY582183.1)and CBS 357.89(from TYPE material,GenBank accession No.NR_145077.1),respectively.Strain FG-62 was identified as P.roridum(Basionym:Myrothecium roridum)by morphological and molecular biological characters.This is the first report of root rot and stem basal rot of zucchini caused by P.roridum.