Establishment of a Composite Evaluation Standard for Tobacco Root Knot Nematode Disease Resistance
Tobacco root knot nematode is an important disease to establish a physiological and pathological resis-tance composite evaluation standard,and screen tobacco germplasm plants with disease resistance.This study con-ducted an investigation in five major tobacco planting counties in Yunnan.During the tobacco harvest period,the pathological and physiological indexes related to the disease,such as the percentage of root knot,the proportion of root browning,the maximum root knot diameter,the withered leaf tip and the stem circumference of foot leaf,were systematically investigated.The data were statistically and correlated,and the evaluation and calculation for-mula of tobacco root knot nematode disease was worked out:Value of resistance=root knot percentagex50+root browning ratiox30+assigned value of maximum root knot diameterx20;The results are as follows immune:0;high resistance:1～15;moderate resistance:16～30;resistance:31～50;susceptibility:51～80;high susceptibility:81～100.On this basis,the resistance of tobacco plants inoculated with root knot nematode in greenhouse for 60 days was e-valuated and identified.The results showed that tobacco plants showed different resistance,of which 40 were sus-ceptible and 20 were resistant.The composite evaluation criteria established in this study can lay a foundation for the selection of tobacco varieties with resistance to tobacco root knot nematode,and compared with the original resistance evaluation criteria,the individual plants with disease resistance potential can be divided more carefully.
万方数据
维普
