哈茨木霉Thga1基因敲除突变株对几种植物病原真菌的离体拮抗作用

Antagonism of the Thga1 Gene Knock-out Mutants of Trichoderma harzianum against Three Kinds of Plant Pathogenic Fungi in vitro

Thga1是哈茨木霉Th-33的1种I型G蛋白α亚基基因（GenBank JN874387）。本文针对前期研究获得的2株基因Thga1敲除突变株ΔThga11-1和ΔThga110-1，通过平皿对峙培养分析其对立枯丝核菌、辣椒疫霉菌和尖孢镰刀菌的拮抗作用，研究了突变株产生的挥发性代谢物和非挥发性代谢物对上述3种病原菌生长的影响和对立枯丝核菌的重寄生作用的光学显微镜观察。结果表明，与野生型Th-33相比，基因敲除突变株ΔThga11-1和ΔThga110-1对病原菌的拮抗作用显著下降，不能对3种病原菌菌落进行覆盖和寄生；突变株产生的挥发性代谢产物对病原菌生长的抑制率显著低于野生菌 Th-33，2株突变株对立枯丝核菌、辣椒疫霉和尖孢镰刀菌生长的抑制率分别降低了50%～57%、43%～58%和58%～63%，且突变株之间差异不显著；突变株产生的非挥发性代谢产物对病原菌生长的抑制作用中，除突变株ΔThga11-1对立枯丝核菌的抑制作用与野生菌相比差异不显著外，均显著低于野生菌Th-33，突变株ΔThga11-1和ΔThga110-1对3种病原菌的抑制率分别降低了8%～25%、23%～56%和38%～50%。显微观察发现，野生菌Th-33菌丝能够缠绕、附着、穿透和裂解立枯丝核菌菌丝，但突变株菌丝对立枯丝核菌菌丝没有发现类似作用。上述结果表明，Thga1基因影响了哈茨木霉菌的拮抗、次级代谢和重寄生等作用。

Trichoderma harzianum Th-33 antagonize against a variety of plant pathogenic fungi. Thga1 （GenBank JN874387） of strain Th-33 codes a type I GTP binding protein α subunit. Two Thga1 gene knock-out mutantsΔThgal 1-1 and ΔThgal 10-1 had been constructed in our previous studies. The antagonistic effects of the two mutants against three plant pathogens including Rhizoctonia solani, Phytophthora capsici and Fusarium oxysporum were studied in this paper. The two mutants could not cover and mycoparasitize the colonies of tested pathogens and the antagonisms reduced significantly comparing to wild-type Th-33 when confronted with tested plant pathogens. The inhibitory ratios of volatile metabolites fromΔThgal 1-1 andΔThgal 10-1 to the tested plant pathogens reduced 50%-57%to R. solani, 43%-58%to P. capsici and 58%-63%to F. oxysporum comparing to that of wild-type Th-33 respectively, and there was no significant difference between the two mutants. Inhibition ratios of non-volatile＆amp;nbsp;metabolites fromΔThgal 1-1 andΔThgal 10-1 to the three tested plant pathogens reduced 8%-25%to R. solani, 23%-56%to P. capsici and 38%-50%to F. oxysporum, respectively. The parasitism of wild-type Th-33 against R. solani such as hyphae winding, adhering, penetration and leading to hyphae disruption were observed under microscope, but we have not observed the above phenomena resulting from the two mutants. The results showed that Thga1 influenced antagonism, secondary metabolism and mycoparasitism of T. harzianum.