Identification Of The Pathogens Causing Some Kinds Of Plants Verticillium Wilt, Parasitic Specialization Of Verticillium Wilt And Susceptibility Of Cotton In Different Growth Periods

From 2014 to 2016,14 Verticillium wilt strains were separated from Verticillium wilt samples of 10 kinds of plant including cotton,okra,sunflower,flax,eggplant,elm,piemarker,safflower,mung bean and cabbage,collected from Shihezi University Experimental Station,Shihezi University Experimental Field,Yili Turks County Agricultural Technology Demonstration Park,Boltara Mongolian Autonomous Prefecture,grape station of 121 th farm regiment,133 th farm regiment and 142 th farm regiment of Shihezi City.According to morphological identification,molecular biology identification and pathogenicity determination,14 Verticillium wilt strains were identified as Verticillium dahliae.In addition to okra Verticillium wilt has been reported in China,the safflower Verticillium wilt and flax Verticillium wilt has not been reported in China,they are two kinds of new Verticillium wilt.At present,the occurrence area of cotton Verticillium wilt in Xinjiang is large,and it is suggested that we should not plant safflower,okra and flax in the case of crop rotation,in order to prevent unnecessary loss.12 Verticillium wilt strains from different plant were inoculated on eight kinds of plants.Result showed that strain of okra collected from the Bodhara Mongolian Autonomous Prefecture serious infected okra,not infected cotton,piemarker Safflower and sunflower,and mild infected eggplant and mung bean.The sunflower Verticillium wilt strain collected from Yili Turks County seriously infected sunflowers,but not infected safflower,and mild infected cotton.The strains from Shihezi 121 and 133 farm regiment protected areas seriously infected eggplant,but not infected safflower and flax.The isolate of Verticillium wilt isolated from mung bean of the 142 th farm regiment were highly pathogenic to mung bean but not infected eggplant.The pathogenicity of Verticillium dahliae isolated from different crops in Shihezi University Experimental Station were serious infected cotton,safflower,okra and sunflower.Indicating that there is a certain pathogenicity differentiation in Verticillium dahliae.Microsclerotia is the most important primary infecting source of Verticillium wilt.The experimental results showed that overwintering microsclerotia may have a short dormancy and recovery period after the overwintering.The main results are as follows: the rate of germination of overwintering microsclerotia were slower and lower than unoverwintering microsclertia,the growth rate of colony of overwintering microsclertia is also slower.In addition,overwintering test of hyphae found that most mycelium had fractured after living through the winter,part of the mycelium survived,and the survived hyphae in soil may also be the infecting source,the study about this area have not been detailed reported and need to be researched.Inoculation experiments of cotton in different growth periods indicated that Verticillium wilt of cotton inoculated on 2 leaf to 9 leaf stage of cotton,cotton in different growth periodsall can be infected,but cotton in 4-7 leaf stage were infected more seriously.Cotton buds appears generally in the 6 leaf stage,the results is consistent to that of original Soviet scholar Cyprus(1986)" Verticillium dahliae can infect cotton of different vegetative stage,2-6 leaf stage is the most susceptible";and is not consistent to the conclusions of disease-resistent before the buds and undisease-resistent after the buds of some domestic scholars,which is the most susceptible stage of cotton to Verticillium wilt remains to be studied.The results of inhibition of temperature of different depth soil to the growth of Verticillium dahliae showed that the temperature of surface soils increased continuously from May 11,especially in late May,early June and mid June,when the cotton was in seedling stage and most of the film is exposed and in direct sun.Most of the maximum temperature in the 5-10 cm soil layer was above 30 ℃,even more than 35 ℃ or 40 ℃ and most of the maximum temperature is also at 30 ℃ in the 20 cm soil layer.In particular,May 25-June 18(rainfall),most of the maximum temperature is above 35 ℃ or 40 ℃.In this condition,Verticillium dahliae in 5 cm soil layer did not grow and in 10 cm soil layer grew slowly,the growth rate of Verticillium dahliae in 10 cm soil layer was only 47.4% of the growth rate in30 cm soil layer.The growth of Verticillium dahliae in 20 cm soil layer was also inhibited.According to the literature,Microsclerotia mainly exists in 0~20cm soil layer,the critical air temperature for cotton Verticillium wilt occurrence is 27 ℃-28 ℃(day average temperature),or 35 ℃(day maximum temperature),it seems that the influence of ground temperature to Verticillium wilt occurrence is basically keering with air temperature.Since mid-June,due to the growth of cotton,shading effect of cotton leaves was more and more obvious,the temperature of soil layers began to drop gradually,Verticillium wilt was occurred or more serious gradually.This is consistent with our observations.