本文通过分析两种不同交配型球孢白僵菌菌株(MAT1?1?1,I型;MAT1?2?1,II型)在玉米植株中的定殖效率和回收菌株交配型基因序列的变异,拟揭示球孢白僵菌在玉米植株内生定殖过程中玉米对不同交配型菌株的选择规律、不同交配型菌株对环境的适应性能力。试验分为4个接种组,接种菌株为I型交配型菌株(BbOFDH1?5)(处理B5)、II型交配型菌株(BbDPSD2)(处理B2)、两个菌株等量混合(处理B5+B2)、对照组(处理CK),处理组B5、B2、B5+B2接种孢子浓度均为108孢子/mL,对照组接种量为零。结果表明,处理B5、B2、B5+B2三组中均有球孢白僵菌在玉米叶片中定殖,其中,交配型II菌株处理组B2中内生定殖效率高,检测率为33.00%;混合处理组B5+B2中交配型II菌株比I型菌株回收比率高,回收比为12:10。交配型基因序列分析显示,交配型I菌株处理组B5和混合处理组B5+B2的回收菌株中I型交配型基因非编码区序列出现多个位点突变,编码区仅在3个位点出现突变;交配型II菌株处理组B2和混合处理组B5+B2中II型交配型基因序列均没有发生变异。以上结论说明球孢白僵菌在玉米植株定殖过程中,交配型II菌株BbDPSD2定殖率较I型菌株BbOFDH1?5高;玉米植株更倾向于选择II型交配型菌株作为内生菌株;交配型基因MAT1?1?1比MAT1?2?1更易发生突变表明I型菌株对自然环境的适应性更强。
In this study, colonization efficiency of the two mating-type Beauveria bassiana (MAT1?1?1, mating-type I; MAT1?2?1, mating-type II) in maize was assessed and the mating-type gene sequences of recovered B. bassiana strains were analyzed to reveal the host plants selection rules between the two mating-type strains and the environmental adaptability of different mating-type strains during colonization process. Four inoculation trials were applied as follows:BbOFDH1?5 (mating-type I) (treatment B5);BbDPSD2 (mating-type II) (treatment B2); mating-type I/mating-type II mixed equally (treatment B5+B2) and control (CK), spore concentration for treatment B5, B2 and B5+B2 was 108 spores/mL and zero for control. Results showed that endophytes were detected in treatment B5, B2 and B5+B2 in corn leaves. Detection rates showed treatment B2 with mating-type II strain got a higher detecting rate of 33.00%than that of treatment B5 with mating-type I strain. In treatment B5+B2, the recovered endophytes had a higher rate with mating-type II strains than mating-type I strain with ratio 12:10. Among the mating-type I B. bassiana strains recovered from treatment B5 and B5+B2, MAT1?1?1 gene sequence analysis showed that multiple mutation loci in the non-coding region were observed while only three mutation loci in the coding region during the endophytic colonization process. However, no mutation was found about MAT1?2?1 gene from all the strains recovered from treatment B2 and B5+B2. In conclusion, mating-type II strain BbDPSD2 had a higher colonization efficiency than that of mating-type I strain BbOFDH1?5; corn plants prefered mating-type II strain BbDPSD2 to mating-type I strain BbOFDH1?5 as endophytic fungus; the mating-type gene MAT1?1?1 had a higher mutation rates than that of MAT1?2?1 significantly indicated that mating-type I strain had stronger environmental adaptability than that of mating-type II strain.