一种新的棉花苗期黄萎病病情指标

 在丛枝菌根菌(AMF)诱导棉花抗/耐黄萎病的研究过程中发现植株叶柄带菌(Verticillium dahliae,VD)量和木质部变色指数的指标与棉株的发病率和病情指数无相关关系。无症健株带苗率达10%以上;从茎基部测定的木质部变色指数不能反映其抗/耐黄萎病的差异。作者提出了"棉株茎木质部非变色高度"的概念,并发现只有当不质部非变色高度≤株高的50%时,叶片才显黄萎症状。与此相应所提出的木质部非变色级与病级、木质部非变色指数与病情指数则具有一定相关关系。木质部非变色指数可作为棉花苗期黄萎病的病情指标。

A NEW PARAMETER RELATED TO VERTICILLIUM WILT OF COTTON SEEDLINGS

It has been found that there were no correlation between the number of propagules of Verticillium dahliae in petioles(NPP) of cotton plants (seedlings) and some of the disease criteria including the discoloration of the xylem part in stem, the percentage of disease infection and also the disease index there from calculated. It was found that about 10% of the symptomless plants usually were hibernated by the fungus. The discoloration index estimated from the xylem at the basal part of stem did not reflect the severity of the Verticillium wilt of cotton. It is therefore ggested that the height of the non-discoloring part of the xylem is feasible to reflect the severity of the infection. When the non-discolored part of xylem reached 50% of the whole height of the observed plant (seedlings) , the plants began to become yellow and wilt. The present suggestion to use classes of non-discoloring part of xylem as criteria for estimating the severity of infection is more rational. Therefore the suggested parameters based on the non-discoloring height of xylem in cotton plants (seedlings) are feasible to be adopted in estimating the cotton resistance/tolerance to the Verticillium wilt.