Bioassaying To Toxin Of Verticillium Dahliae And Effect Of The Toxin On Biochemistry Metabolism Of Cotton Seedlings

Verticillium dahliae is a important disease that affect cotton production in our country, it has resulted in a serious disaster to much of cotton areas since 30s of last century when it introduced in China, and it is one of the key restricting factors to limit the cotton production in China. In recent years, many reports gradually pay attention to toxin of Verticillium dahliae, and consider the toxin play a crucial role in pathological mechanism, therefore, implement toxin research of Verticillium dahliae will have a far-reaching significance both in theory and practice. This research analysed characters of liquid culture, tested biological activity of toxin, and tested physiology and biochemistry values(SOD, POD, PAL, MDA, Lignin) in cotton seedlings after treated with toxin of V. dahliae, The results were as follows:1. Observing and testing the characters of liquid culture for 16 V. dahliae stains which from different areas in Shannxi, the result showed:there were marked difference in the colour of nutrient solution, the concentration of spore and protein concentraion among the strains, they were three types according to the cultivation characters:the first type:liquid culture was white, with no microsclerotia and high protein concentration of toxin; the second type:liquid culture was light brown, with. a small quantity of microsclerotias and moderate protein concentration of toxin; the third type:liquid culture was dark brown, with plenty of microsclerotias and low concentration of protein toxin.2. The result to biological activity testing showed:pernicious effects of toxin to resistant and susceptible breeds was sharp difference, after toxin treatment, the onset time of susceptible variety (Zhongmianl9) is earlier than resistant(Shan2365), and the wilting index is higher either. We found that ater treated seedings by with different toxin concentration, that the wilting index would ris if the concentration of protein increased, indicated that concentration of toxin showed positive associations with wilting intensity.3. The research of pernicious effects to cotton seedlings of toxin from different toxin showed:the strains with white colour and no microsclerotia in fluid culture had a higher wilting index, but the wilting index of those with brown colour and plenty of microsclerotias were lower. The characters of liquid culture had certain relations with biological activity of toxin.4. Testing dynamic change in activity of SOD, POD, PAL and content of MDA in leaf blade after treated resistant and susceptible cotton seedlings with toxin, the result showed:activity of SOD droped, it is declined more in Zhongmian19 than Shan2365; the activity of POD in Zhongmian 19 rose quicker, and decrease sharply when come to the peak value; the trend in changes of PAL activity to both of two varieties was similar. The activity in Shan2365 is higher than Zhongmian 19 all along, MDA and lignin content in two seedlings were increased, the growth rate and increment in Zhongmian 19 were higher than Shan2365.