球孢白僵菌对两种植物病原镰孢的拮抗作用

Antagonism of Beauveria bassiana against Two Fusarium spp.Pathogenic to Cotton

体外测定了球孢白僵菌Beauveria bassiana对两种棉花病原镰孢——棉花枯萎病菌Fusarium oxysporium f.sp.vasinfecturn和棉花红腐病菌Fusarium verticillioides的拮抗作用。平板对峙培养时,两种镰孢的生长均受到明显抑制。不同含孢量的球孢白僵菌对两种镰孢的抑制效果不同,且抑制率与孢子浓度成显著的线性量效关系;在接种量为6×107孢子.mL-1时,对两种菌的抑制率均达到90%以上,对红腐病菌的抑制率稍高。白僵菌代谢液对两种植物病原菌也表现出抑菌作用,并且抑制率与代谢液浓度呈显著的线性量效关系。综上述,球孢白僵菌对两种镰孢拮抗作用的机制主要涉及营养和空间竞争以及抗生作用,其中抗生作用对拮抗作用的贡献更大。对抗生性代谢液的初步分析发现,醇沉后的上清液冻干粉经4种有机溶剂浸提后,无明显的抑菌作用;而向培养基中添加球孢白僵菌多糖和蛋白粗提物均能显著抑制两种镰孢菌的菌丝生长。因此,抑菌活性物质主要是大分子的多糖和蛋白。

In vitro antagonism of Beauveria bassiana,an entomopathogenic fungus,was tested against Fusarium oxysporium f.sp.vasinfecturn,pathogen of cotton wilt,and F.verticillioides,pathogen of cotton red rot.On dual culture,B.bassiana showed obvious inhibition on the growth of the two pathogens.Different doses of conidia had different inhibitory effects,with inhibition rate linearly correlated to inoculum,suggesting that the antagonism was associated with competition for nutrition and space.The inhibition on the two pathogens was both over 90% at inoculum of 6×107 spores·mL-1,slightly higher on F.verticillioide.The metabolite in SDY shake culture of B.bassiana also displayed inhibition,with inhibition rate linearly correlated to metabolite concentration,suggesting that the antagonism was also associated with antibiotic substances.Based on the comparison of inhibition rates,antibiosis was considered to contribute more than competition.In the analysis on the antibiotic metabolite,none of the lyophilized supernatant extracted by 4 different organic extractants showed obvious inhibition on the Fusarium spp.,while addition of crude extract of either polysaccharide or protein significantly inhibited mycelium growth of the two Fusarium spp.,suggesting that the main inhibitory substances are polysaccharide and protein with high molecular weight.