作物轮作对土壤中烟草青枯菌数量及发病的影响

为查明春烟换茬后青枯菌在土壤中的消长规律, 采用接种耐药性青枯菌的盆土种植烟草, 烟草枯死后种植不同轮作作物的方法, 研究不同作物对土壤中青枯菌数量及其越冬状况的影响。设茄子、大豆、花生、甘薯、大蒜、玉米、晚稻和双季稻8 个轮作物处理, 后作生长期间定期取样, 用含利福平的选择性培养基检测样品中的青枯菌数量。结果表明, 栽后第4 周起秋茄子和秋大豆根中皆测出青枯菌, 秋茄子根达10⁶ cfu·g^-1;晚稻和秋花生根只第2 周和第8 周测出带菌。秋茄子、秋大豆、秋花生和晚甘薯生长期间土壤皆测出青枯菌,数量先降后升至10⁴~10⁶ cfu·g^-1; 晚稻和秋玉米土壤中青枯菌数量持续下降; 大蒜处理先测出带菌后未测到。冬季对水稻残桩青枯菌数量监测显示, 稻桩根和土壤中青枯菌数量先后出现峰值, 分别达1.00×10⁵ cfu·g^-1 和5.17×10⁴ cfu·g^-1; 发现病菌能在稻根变黑腐烂时增殖。翌年春季从茄子、大豆、花生和甘薯茬口土壤中测出遗留青枯菌数量皆达10⁴ cfu·g^-1, 玉米为10³ cfu·g^-1。烟草移栽后青枯病调查表明, 不同处理发病迟早取决于茬口土壤中菌源数量, 两者相关系数r 为0.908 9。不同茬口土壤发病轻重有显著差异, 茄子茬土发病最重,病情指数100, 大豆和大蒜茬土发病略重于花生、甘薯和玉米茬土; 晚稻茬土发病最轻, 病情指数16.7, 与茄子茬土相比发病期推迟20 d, 病情指数下降83.3%; 双季稻茬土未见发病, 证明烟稻轮作对青枯病有较好的控制效果。

Influence of crop rotation on tobacco bacterial wilt number and pothogenesy

Eggplant,soybean,peanut,sweet potato,late rice,maize,garlic and double cropping rice were respectively planted dur-ing autumn after harvest of spring tobacco in pot experiment with soil inoculated drug-resistant Ralstonia solanacearum.The aim of the experiments was to investigate the number dynamics of R.solanacearum in soils under crop rotations.Throughout the growth season of rotation corps,both root and soil samples were collected at each sampling time.R.solanacearum populations were meas-ured using a se...