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目的确定引起金钗石斛和铁皮石斛软腐病的病原菌,为制定高效、安全的防治措施提供依据。方法采用普查和定点观察相结合对软腐病发病情况进行田间观察,采集两种石斛典型病株样本,按照柯赫氏法则对其病原菌进行分离、纯化、菌株鉴定及致病性测定。结果在树皮为基质的苗床上软腐病在不同苗龄上均可发生,病原菌主要侵染幼嫩多汁的嫩芽和新枝,引起幼嫩茎叶的腐烂、萎焉和坏死等症状。通过对病原菌形态学观察,以及核糖体rDNA ITS序列分析,侵染石斛植株的2个分离菌株被鉴定为终极腐霉Pythium ultimum。致病性实验证明,这两个菌株为石斛软腐病的致病菌株。结论金钗石斛和铁皮石斛是终极腐霉菌的自然寄主。
Objective To determine the pathogen causing the soft rot of Dendrobium nobile and Dendrobium officinale to provide the basis for developing effective and safe prevention and cure measures. Methods The epidemic situation of soft rot disease was observed by the combination of census and fixed point observation. Two typical diseased specimens of Dendrobium were collected, and their pathogenic bacteria were isolated and purified according to Koch ’s law. Results In the bark-based seedbed, soft rot disease can occur at different seedling ages. The pathogen mainly infects young and juicy shoots and new branches, causing the symptoms of decay, wilting and necrosis of tender stems and leaves. Through morphological observation of pathogens and ribosomal rDNA ITS sequence analysis, two isolates of Dendrobiridae infected plants were identified as Pythium ultimum. Pathogenic experiments show that these two strains of pathogenic strains of soft rot of Dendrobium. Conclusion Dendrobium nobile and Dendrobium candidum are the natural hosts of the ultimate Pythium.