Study On Tomato Powdery Mildew In Zhangye City

In this study, the method which combined field experiments with indoor study, and morphological resistance with physiological and biochemical resistance has been uesd.The expansion dynamic of tomato powdery mildew in the field in 2006 and 2007,and the efficiency of chemical control test had been investigated. The density of leaf hair and stomata,the size of stomata of 6 tomato varieties,as well as the correlation between defense enzymes activity and resistance to Erysiphe polygony DC. after inoculation has been studied.The resistance to Erysiphe polygony DC. has been investigated or identificated both in the field and indoors.The main results were showed as follow:1 Identification of the pathogenAccording to the shape, the size of conidia and the characteristics of mycelium, etc.,the pathogen of tomato powdery mildew were identified as Erysiphe polygony DC. preliminaryly in Gansu province.2 The investigation of resistance to Erysiphe polygony DC. in the fieldAll 64 tomato varieties can be infected by Erysiphe polygony DC. in the field,and there were no immunity varieties,all of them could be divided into 5 types:â… H igh disease-resistant varieties(including 06-1,Zuan-shi,TOMO629D etc.), Disease index is about 0.1 to 5;â…¡D isease-resistant varieties(including SM07,T05-8, T05-16 etc.),Disease index is about 5.1 to 10;â…¢Middle infectious varieties(including 06-3,06-11,Z00-73,Qu Pi Da Guo,2272,2G-2 etc.),Disease index is about 10.1 to 20;â…£Infectious varieties(including Q019,SH3,Shi-hong NO.3,Q020, Kang Fan 37,Kang-jia NO.2,344,170,Q021 etc.),Disease index is about 20.1 to 35;â…¤High infectious varieties(including Hong Bao Shi,Kang-jia NO.1,3144 etc.),Disease index is from 35.1 to 100.3 The identification of resistance to Erysiphe polygony DC. indoorAll 21 tomato varieties can be infected by Erysiphe polygony DC. after inoculation in indoor(brushing down the spores, keeping relative humidity 80%~90% for 48h), and there were no immunity varieties,too. Analysis of variance showed that there were significant difference of disease incidence and index between different varieties. The results of correlation analysis showed that there were positive correlation of disease incidence both in indoors and in the field(P<0.01),and the disease index,too(P<0.01).That is to say,the resistance has consistent performance both in indoors and in the field.Therefore,the method we preliminary established could be used for the identification of resistance in tomato varieties.4 The expansion investigation of tomato powdery mildew in the fieldGenerally the symptom emerged in mid-July or late in the field in Zhangye City, it was spreaded vertically in the center area at the very beginning,and then horizontally, it only needed 7~10d from the developing of center area to occurring commonly in the field. The basis for preventing the epidemic of tomato powdery mildew was provided in this study.5 The chemical control test in the fieldThe control efficiency of 24% thifluzamide-1200 times, 15% triadimefon-750 times and 30% difenoconazole ? propiconazole-2000 times reached the maximum at the 7th ,which were 83.4%, 81.4%,and 81.3%, respectively.Meanwhile, the control efficiency of 40% flusilazole of three concentration gradient (3 000 times, 5 000 times and 7 000 times) were 72.2%, 72.5% and 71.1%,respectively. At the 10th, however, the control efficiency of 40% flusilazole of three concentration gradient were 73.3%,75.5% and 78.2%, which indicated that 40% flusilazole were longer in duration and stable in efficacy.6 The relationships between morphological and resistance of Erysiphe polygony DC.There were positive correlation between density of leaf hair and resistance,and negative correlation between density of stomata and resistance, but no correlation between the size of stomata and resistance.7 The relationships between physiological characteristics and resistance of Erysiphe polygony DC.The activity of PAL,POD,PPO and CAT was significantly increased with 2 peaks at the 0.5d or 1d and 7d or 10d,and the SOD activity showed a continuous increasing tendency during 10d in high resistance varieties while others only got 1 peak at 7d; there was significant difference of defense enzymes activity between different varieties after inoculated, but no significant difference in control, the correlative analysis indicated that there was positive correlation between 5 defense enzymes and resistance after the treatment.