pH及盐分对大丽轮枝菌微菌核形成的影响

Effect of pH and Salinity on Microsclerotia Formation of Verticillium dahliae

微菌核是棉花黄萎病原大丽轮枝菌(Verticillium dahliae Kleb.)在土壤中的主要存活形式及该病的侵染源,研究土壤pH及盐分对大丽轮枝菌微菌核形成的影响对明确黄萎病发生具有重要意义。采用菌丝生长速率法研究培养基pH及盐分质量浓度与种类对病原菌生长及微菌核形成的影响。供试大丽轮枝菌菌丝生长最适pH为7.0,偏酸或偏碱会抑制菌丝生长,但培养基偏碱可显著促进微菌核形成。当pH为8.0时,大丽轮枝菌菌丝生长受抑制较小,同时微菌核区面积较pH为7.0时增加22.6%。盐分质量浓度影响大丽轮枝菌菌丝生长及微菌核形成。随培养基NaCl质量浓度增加,供试大丽轮枝菌生长受到抑制,菌落面积和菌丝面积均逐渐减小,但微菌核形成量却显著增加;当NaCl质量浓度为10g·L^(-1)时,微菌核区面积较无NaCl时增加40.7%。盐分种类影响供试大丽轮枝菌生长。随盐分质量浓度增加,氯化物(NaCl和KCl)和硫酸盐(Na_2SO_4和MgSO_4)均可促进大丽轮枝菌微菌核形成,而CaCl_2则显著促进菌丝生长,并在质量浓度大于7g·L^(-1)时抑制微菌核形成。在培养环境偏碱性或氯化物和硫酸盐含盐量较高时,均可促进棉花黄萎病原大丽轮枝菌微菌核形成量增加。

Microsclerotia produced by Verticillium dahliae are the source of Verticillium wilt disease in cotton and are persisted in the soil as the resting structure of this pathogenic fungus. We determined the effect of pH and salinity on V.dahliae microsclerotia formation, which is important for preventing the occurrence of Verticillium wilt disease. In this study, the effects of salinity （mass concentration and type） and pH on V.dahliae microsclerotia formation were studied by measuring mycelium growth in altered culture mediums. Colony growth of V.dahliae was inhibited atacidic and alkaline pH 5.5-9.5 levels and optimal at pH 7.0. Verticillium dahliae microsclerotia formation was enhanced at alkaline pH, and the area of microsclerotia was 22.6% larger under pH 8.0 than pH 7.0. Mycelium growth and microsclerotia formation of V.dahliae were also affected by salinity concentration. With a higher mass concentration of NaCl in the culture medium, V.dahliae colony growth and mycelium area were inhibited and decreased, respectively, whereas microsclerotia formation was enhanced. The area of microsclerotia in the culture medium with 10 g·L-1 of NaCl was 40.7% larger than that in the medium without NaCl. Verticillium dahliae growth was also affected by salt type. With the increasing concentration of chloride （i.e., NaCl, KCl） or sulfate （i.e., Na2SO4, MgSO4） salts in the culture medium, V.dahliae microsclerotia formation was increased. In contrast, mycelium growth was enhanced in the presence of CaCl2. Additionally, V.dahlia microsclerotia formation was inhibited at mass concentrations of CaCl2 greater than 7 g·L-1.The results indicated that microsclerotia formation of V.dahlia was enhanced under alkaline pH or high salinity.