烟草野火病重要流行环节的初步定量研究 Ⅱ.病原菌侵染、潜育显症和病斑扩展

Preliminary Quantative Studies on Important Epidemic Stages of Tobacco Wildfire Ⅱ.Infection of Bacteria,Incubation and Sympotomatic Appearance,and Expansion of Lesion

应用系统分析及定量流行学方法对烟草野火病的重要流行环节进行了初步定量研究。结果表明 :野火病菌只要一接触伤口 ,就完成侵入过程。野火病发病数量与接种体数量的 2 / 3次方成正比。野火病菌的侵染概率 (Y)与露温 (x)的关系为一单峰曲线 ,其回归式为Y =sin(- 2 1x +0 32x2 - 0 0 36x3 )。侵染概率 (Y)与叶表湿润时间 (t)、风速 (v)、空气相对湿度 (h)的关系 ,均为直线关系 ,其回归方程式分别为Y =1 6 4+0 .19t ,Y =1.0 5 8+0 .0 46v ,Y =- 3.8481+0 .0 86 9h。在吉林省生态条件下野火病潜育期为 3～ 5d ,其逐日显症率 (Y)与显症后顺序日数 (d)的关系为“S”型曲线 ,其回归方程为Y =1/ (1+0 .414e-1.3 1d)。野火病斑日龄(d)与野火病斑面积 (S)之间的关系为一倒“J”型曲线 ,其回归方程为S =sin(6 5 3d - 0 2 0d2 +0 0 0 12 6d3 )。

The studies on tobacco wildfire were made by applying systematic analysis and quantitative epidemiology. The results showed that:the process of infection will be finished as soon as the bacteria of P.syringae pv.tabaci get in touch tobacco leaf wounds. Diseased quantity has direct ratio with the 2/3 power of inoculated bacteria quantity; the relationship between infection probability (Y) of the bacteria and dew temperature(X)is an unimodal curve with the regression equation:Y=sin(-2.1x+0.32x 2-0.036x 3).All the relationships between infection probability and leaf wetness period (t),infection probability and wind speed (v),infection probability and air relative humidity(h) present linear patterns with the regression equations respectively:Y=1.64+0.19t,Y=1.058+0.046v,and Y=-3.8481+0.0869h.The incubation period of tobacco wildfire disease is 3～5 d under the ecological conditions in Jilin province. The relationship between the daily accumulated ratio of symptomatic appearance(Y)and the sequence of dates of symptomatic appearance(d)is a 'S'-shape curve with the regression equation:Y=1/(1+0.414e -1.31d ). The relationship between the appearance dates of wildfire lesion(d)and its lesion area(S)is an inverted 'J'-shape curve with the regression equation:S=sin(6.53d-0.20d 2+0.00126d 3).