Study On Resistance Evaluation Of Oat Germplasm To Powdery Mildew And Its Biocontrol

Oat powdery mildew is one of the main diseases in oat production.It occurs in Inner Mongolia,Hebei,Gansu and other major oat producing areas in China,influences the quality and yield of oats.Therefore,in order to provide a scientific basis for the utilization and effective prevention and control of oats against powdery mildew.This study investigated the occurrence of powdery mildew in the main oat producing areas of Gansu Province with the method of naturally infection and identified its pathogen,evaluated the field resistance of oat germplasm resources,and compared the control effects of different biocontrol reagents on oat powdery mildew.The main results are as follows:(1)The oat powdery mildew was prevalent in all producing areas of Gansu Province,but the incidence was significantly different.No powdery mildew was found in Hezuo and Luqu County,and sweet oat had the highest disease index(50.10)in Tianzhu County,followed by Baiyan 7 in Yongdeng County(43.29).The disease index of Mulesi and Jiayan No.2 in Shandan County were lower(0.28 and 0.34,respectively).(2)The incidence of the same oat varieties in different survey areas was quite different.The disease index of sweet oats in Tianzhu County was 3.40~50.10;that of Baiyan 7 in Yongdeng County was 43.29,and only 1.22 in Tongwei County.No occurence was observed in Shandan County and Minle County.The differences in disease severity among different oat varieties in the same area were obtained.No powdery mildew was found on Baiyan No.7 grew in Minle County,while the disease index of Northern Canada oat and Mulesi were 0.22 and 1.85,respectively.(3)Total genomic DNA was extracted from 20 samples of pathogenic fungus of oat powdery mildew,ITS r DNA and 28 S r DNA were amplified,and two different powdery mildew specific types were identified integrated with morphological characteristics.Both of them belong to Blumeria graminis(DC.)Speer.The one collected from Tianzhu County was similar to B.graminis(DC.)f.sp.secalis,while the others were B.graminis(DC.)f.sp.avenae.(4)Using the relative disease resistance index,the evaluation of powdery mildew resistance of 28 oat germplasm planted in semiarid area of Gansu Province(Lanzhou Forage Experiment Station of Gansu Agricultural University)and Alpine Mountainous Area(Huajialing Town of Tongwei County)were conducted under natural conditions in the field.The results showed that the environment of the wrowth area had significant impact on oat resistance to oat powdery mildew.The average severity of the disease in the Station was higher than that in the Huajialing.Among the 28 materials,4628,Galileo and Qingyongjiu-307 showed high resistance in the Station while high sensitive in Huajialing.709,Qing yongjiu-316 and Qingyongjiu-49 were highly susceptible to powdery mildew in the Station but high resistance in Huajialing.The relative resistance index of 4628 had the biggest variation among all tested materials.The material 4641 and 99AS207 had stable relative resistance index and showed higher resistance in the two sites.Materials such as 4607,Rigdon,DA92-3F4,Qingyongjiu-252,Qingyongjiu-9 and Qingyongjiu-98 had stable medium resistance to oat powdery mildew in both sites;the resistance were unstable.(5)The field control effects of three types of 7 biocontrol reagents on oat powdery mildew were studied in Huajialing Township of Tongwei County.The results showed that the biocontrol reagents had certain control effects but their quick-acting effect was slightly lower than that of the chemical agents.Their control effect 7 d after the first application(70.91%~85.01%)was generally inferior to the chemical agents(84.52%~86.09%),but showed better lasting-effect.After 20 days of the second application,the control effect of Physcion(85.12%)was equivalent to that two chemical agents(80.60% and 84.12%).The control effect of Carvacrol,Matrine,Bacillus subtilis,Osthole was between Triazolone and Myclobutanil.The fungicide improved the relative content of chlorophyll in oat flag leaf by controlling powdery mildew,promoted photosynthesis,increased 1000-grain weight and seed yield.0.5% Physcion achieved 16.77% oat grain yield increase.Considering control effect,persistence and oat seed yield increase,0.5% Physcion gave the best performance in controlling powdery mildew in oat field.