稗草生防菌NX2A的鉴定、安全性及对稗草的致病条件

【目的】明确分离自感病稗草叶片的菌株NX2A的分类学属性、对农田常见作物的安全性及对稗草的致病条件，为菌株NX2A的田间应用提供理论依据。【方法】结合形态学观察和ITS序列分析确定菌株NX2A的分类学属性；通过作物安全性评价明确菌株NX2A对农田常见作物水稻、油菜、辣椒、番茄和茄的安全性；选用L₉（34）正交表，以湿度、稗草叶龄、光照时间和孢子浓度为考察因素，以病情指数和鲜重防效为考察指标，进行菌株NX2A致病条件试验。【结果】结合菌株NX2A的形态学鉴定和分子生物学鉴定结果，将菌株NX2A鉴定为新月弯孢菌（Curvularia lunata）；作物安全性评估试验结果表明，菌株NX2A孢子悬浮液对水稻、油菜、辣椒、番茄和茄的生长无明显影响，植株叶片未见与稗草相同或类似的病斑；菌株NX2A对稗草的致病条件测定结果表明，各因素影响菌株NX2A对稗草病情指数的顺序为光照时间>孢子浓度>湿度>稗草叶龄，影响菌株NX2A对稗草鲜重抑制率的顺序为孢子浓度>光照时间>湿度>稗草叶龄。菌株NX2A防控稗草的最优组合为A3B1C3D2，即以浓度为5.0×106个/mL的孢子悬浮液喷施于1叶期稗草，12 h光照、85%湿度保湿培养。【结论】新月弯孢菌菌株NX2A对稗草有较好的防控效果，且对水稻、油菜、辣椒、茄和番茄等作物安全，具有作为水田稗草生物防控的潜力。

The identification,safety,and efficacy of the biocontrol fungi NX2A for Echinochloa crusgalli

【Objective】The strain NX2A was isolated from the leaves of susceptible Echinochloa crusgalli. Its taxonomic properties,safety for common farm crops,and pathogenic conditions for barnyard grass were studied to provide a theoretical basis for biological control of E. crusgalli.【Method】The strain was identified by morphological charaterization combined with ITS sequence analysis. The safety of NX2A on common crops like rice,rape,pepper,tomato and eggplant was determined via safety evaluation. L₉(34) orthogonal experiment was used in the pathogenicity experiment of NX2A. Humidity,leaf stage,light and inoculation concentration was chosen as factors,disease index and the inhibition rate of fresh weight were as evaluation indexes.【Result】The pathogenic strain NX2A was identified as Curvularia lunata according to morphological identification and molecular identification. The spore suspension of NX2A had no obvious effects on rice,rape,pepper,eggplant and tomato. Plant leaves did not show the same or similar disease spots as barnyard grass. The results of pathogenicity experiment showed that the degree of the influence on disease index were in the order:light > inoculation concentration > humidity > leaf stage;the degree of the influence on fresh weight were in the order:inoculation concentration > light > humidity > leaf stage. The optimum treatment was A₃B₁C₃D₂,namely, 85% humidity, the 1-leaf stage, 12 h light, inoculation concentration was 5.0×106 spores/mL.【Conclusion】C. lunata strain NX2A has a good prevention and control effect on barnyard grass,and is safe for rice,rape,pepper,eggplant,tomato,and has the potential of biological prevention and control of barnyard grass in paddy field.