培养条件及杀菌剂对玉米穗腐病菌可可毛色二孢生长的影响
摘 要 可可毛色二孢（Lasiodiplodia theobromae）穗腐病是近年来发生在玉米上的一种新病害。本文研究了不同培养基、温度、pH、碳源和氮源对该病原菌生长的影响，并评价了8种杀菌剂对该病原菌的抑制效果。结果表明，25 ℃培养1 d后，可可毛色二孢在PDA和MLPA两种培养基上生长速度最快，菌落直径分别为49.88 mm和48.13 mm，显著大于其他处理（p<0.05）；最适合该病原菌生长的温度为30 ℃，培养1 d后菌落直径为61.88 mm，显著大于其他温度处理（p<0.05）；在55 ℃处理10 min后的菌落不能继续生长；最适合该病原菌生长的pH为6，25 ℃培養1 d后菌落直径可达到75.00 mm，显著大于其他处理（p<0.05）；淀粉和硝酸钠分别为可可毛色二孢生长所需的最佳碳源和氮源，在上述两种培养基上培养1 d的菌落直径分别为58.13 mm和37.13 mm，均显著大于其他处理（p<0.05）。咯菌腈、甲基硫菌灵和异菌脲对可可毛色二孢有较好的抑制效果，EC50均小于1 mg/L。本研究结果为深入了解可可毛色二孢玉米穗腐病的发生规律和制定有效防治策略提供依据。
关键词 玉米穗腐病；可可毛色二孢；培养条件；杀菌剂；抑制效果
中图分类号 S435.131 文献标识码 A
Abstract Maize ear rot caused by Lasiodiplodia theobromae is a new disease reported in recent years. In this study， the effects of different media， temperatures， pH value， carbon and nitrogen sources on the growth of L. theobromae were investigated， and the inhibitory activity of 8 fungicides to this pathogen was evaluated. After incubation at 25 ℃ for 1 day， the best growth of L. theobromae was recorded at PDA and MLPA media with the colony diameters of 49.88 mm and 48.13 mm， respectively， which were significant greater than those of the other treatments （p<0.05）. The optimal temperature for L. theobromae growth was 30 ℃ with the colony diameter of 61.88 mm， which was greater than that of the other treatments （p<0.05）， and no mycelial growth was noted at 55 ℃. pH 6 was best for L. theobromae growth at 25 ℃ for 1 day with the colony diameter of 75.00 mm， and there was a significant difference between this treatment and the others （p<0.05）. On the media amended with starch and sodium nitrate， the colony diameter was 58.13 mm and 37.13 mm， respectively， which were significantly higher than that of the other treatments （p<0.05）. The EC50 values of fludioxonil， thiophanate-methyl and iprodione to L. theobromae were less than 1 mg/L， indicating that these three fungicides performed well on inhibiting the growth of this pathogen. The results would provide a basis for further understanding the occurrence regularity of maize ear rot caused by L. theobromae and making effective management strategy.
Keywords maize ear rot； Lasiodiplodia theobromae； culture condition； fungicide； inhibition activity
DOI 10.3969/j.issn.1000-2561.2018.08.021
玉米穗腐病（maize ear rot）发生在玉米生长后期，田间发病率通常为5%～10%，发病严重的年份不低于50%，造成的损失达30%～40%[1]。玉米穗腐病病原菌不仅会造成籽粒霉变或腐烂，导致产量和品质下降，所产毒素也会给食品与饲料生产造成极大安全隐患[2-3]。可可毛色二孢（Lasio¬diplodia theobromae）引起的玉米穗腐病最初发现于海南省乐东县玉米南繁基地[4]，并于次年在三亚市崖城区南滨农场再次被发现。发病果穗籽粒下半部腐烂，籽粒覆盖下的穗轴呈炭黑色，有的果穗整个穗轴尤其是轴心呈灰黑色干腐，症状不易被发现；轻度感染的籽粒顶端表皮呈现白色或放射性白色条纹，重度感染时籽粒发黑霉变，部分籽粒种皮开裂，胚乳呈黑色；湿度大时，在病部表面和籽粒间隙可见灰黑色霉层。该病害连续在不同地点发生，且对果穗的品质造成严重影响，有可能成为玉米生产上的潜在威胁。