Abstract:

In order to screen out the Trichoderma spp.with strong biocontrol effect on rice sheath blight， 20 strains were isolated and purified from different plant rhizosphere soil samples by the dilution coating plate method. It was found that D1 strain and the fermentation concentrated had strong inhibitory effects on rice sheath blight， through the indoor plate confrontation culture test， and the inhibitory rates reached 80.82% and 69.55%， respectively. From the pot disease prevention test of the D1 strain against rice sheath blight， it was concluded that the D1 strain was against rice plants. D1 strain was safe and increased the yield of rice by 27.41% compared with sterile water treatment； the control effect of D1 strain on rice sheath blight was between 51.09% and 70.64%. The control effect of germs was the highest when strain D1 was first treated for 24 h and then followed by simultaneous inoculation treatment， and the treatment had the lowest control effect with D1 strain after inoculation with the germs for 24 h. It showed that the D1 strain had preventive and therapeutic effects on rice sheath blight， and the preventive effect was better than the curative effect. The D1 strain was initially identified as Trichoderma brevicompactum through morphology and molecular studies. A confrontation experiment between D1 and 8 plant pathogens showed that the inhibitory rate of D1 strain against them was between 63.03% and 95.18%； at 20~30 ℃ and pH 4~5， strain D1 was effective against rice sheath blight， with the best antibacterial effect. the tested 5 fungicides had different virulence to the mycelial growth of the D1 strain， and their EC₅₀ value was 0.042~384.24 mg·L^-1， but they had strong antibacterial effect at the common concentration in the field with the inhibitory rate from75.8% to 100%. This study provided theoretical basis for the pollution-free control of rice sheath blight.

Key words: rice sheath blight, Trichoderma spp., bacteriostasis, biological control, adaptability

摘要：

为筛选对水稻纹枯病具有生防潜力的木霉菌，采用稀释涂布平板法从不同植物根际土样中分离纯化出20株木霉菌菌株。通过室内平板对峙培养试验，发现D1菌株及其发酵浓缩液对水稻纹枯病菌的抑制作用较强，抑菌率达分别达到了80.82%和69.55%。D1菌株对水稻安全，比对照增产27.41%；D1菌株对水稻纹枯病的防效范围为51.09%~70.64%。先用D1菌株处理24 h后接种纹枯病菌的防效最高，其次是纹枯病菌和D1菌株同时处理，先接病菌24 h后再用D1菌株处理的防效最低。说明D1菌株对纹枯病有预防和治疗作用，预防效果优于治疗。经形态学和分子生物学初步鉴定D1菌株为短密木霉（Trichoderma brevicompactum）。D1菌株与辣椒炭疽病菌等8种作物病原菌真菌对峙培养，对它们的生长抑菌率在63.03%~95.18%。在20~30 ℃和pH 4~5时D1菌株对纹枯病菌的抑菌效果最好。5种杀菌剂对D1菌株的菌丝生长毒力不同，EC₅₀值为0.042~384.24 mg·L^-1，在田间常用水平下均有较强的抑菌作用，抑菌率为75.8%~100%。研究结果为水稻纹枯病的无公害防治提供了理论依据。

关键词: 水稻纹枯病, 木霉菌, 抑菌作用, 生物防治, 适应性