Studies On A New Oat Disease-bacterial Leaf Blight And Control Techniques Of The Main Diseases On Oat

Oat(Avena sativa L.)is a world-wide cultivated crop,which is a high-quality grain and feed crop.As one of the main oat producing areas in China,the planting area of oats in Gansu Province has increased year by year,and the disease has become one of the main factors restricting the growth and production of oats.In order to clarify the occurrence,damage and control measures of a new oat disease-bacterial leaf blight disease and main diseases in Gansu Province,this study is carried out to explore the occurrence dynamics and control technology of occurrence dynamics and main diseases in oat producing areas of Gansu Province from 2018 to 2021.The main results are as follows:1.The investigation and dynamic analysis of main diseases on oats in each growth period were carried out in Maojing of Huanxian County,Xiaonangou of Huanxian County,Qinchuan of Lanzhou New Area and Fengxiang of Dingxi City during 2020-2021,the results showed that red leaf disease(BYDV),leaf spot(P.avenae),powdery mildew(B.graminis),crown rust(P.coronata)and smut(U.avenae)were the main diseases in the field.The main diseases in oat seedling stage(Apr to Jun)were BYDV and leaf spot(LS).Among them,BYDV was the most commonly disease in oat whole growth period and all planting areas,and the average disease incidence and disease index reached to the maximum(50.66%and 23.72)in the milky stage(Jul to Sept).Powdery mildew(PM)and crown rust(CR)started at jointing stage(May to Jul),and their average disease incidence(28.26%and 22.41%)were separately reached to the maximum in milky stage and maturity stage(Aug to Oct).Smut started at heading stage(Jun to Aug)and the average disease index reached to the maximum(7.84)in maturity stage.The disease incidence and index of BYDV,PM and CR were significantly related to the temperature and precipitation in the planting area.2.A new leaf blight disease of oat was observed in oat fields in Huan county,Gansu Province of China,during 2018-2019.Disease incidence approximately 36 to100%and typical symptoms appeared as yellow-colored necrotic and water-soaked lesions.The lesions developed from tip to base of leaves and eventually resulted in leaf withering.A Gram-negative bacterium was isolated from the necrotic lesions of all samples,and was finally identified as Pantoea agglomerans.P.agglomerans could induce typical symptoms as observed in the field,and could infect other plant hosts,including S.sudanense,M.sativa,F.esculentum,S.italic and Z.mays.This is the first report of P.agglomerans causing bacterial leaf blight disease(LBD)on oat in the world.P.agglomerans isolated from oat seeds infected with LBD were also pathogenic to oat seeds and seedlings.After inoculation with P.agglomerans in oat seeds,the germination rate,germination potential,germination index and vigor index,shoot length,root length,ash,protein,total starch,?-glucan,phytic acid,total phosphorus and Ca of A.nuda and A.sativa seeds were significantly(P<0.05)decreased,and the average germination time was significantly(P<0.05)prolonged.3.LBD could inhibit the growth of oats,cause the losses of fresh grass,hay and seed yield,nutritional quality of forages and seeds.Compared with healthy oat plants,the hay yield of oat infected with LBD was reduced 1.38 to 23.48%,and crude fiber,acid detergent fiber,neutral detergent fiber and nitrogen free extract were significantly increased(P<0.05).The thousand grains weight,protein and?-glucan of infected oat were evenly reduced by 5.57%,12.9%and 21.51%,and the average content of fiber in diseased oat was increased by 8.4%.The growth characteristics,forage and seed yield and feeding value of A.sativa were higher than those of A.nuda,but the nutritional quality of A.nuda was higher than that of A.sativa,and the sensitivity of A.nuda to LBD was also higher than that of A.sativa.4.The results of laboratory toxicity test and field control of LBD(P.agglomerans)by using 13 kinds of bactericides indicated that Zhongshengmycin(3%)and Ethylicin(80%)had the highest bacteriostatic rates(85.04%and 84.79%)and the lowest EC₅₀(0.31 and 0.90).They also had the highest control efficacy on LBD in the field,and the average control efficacy after two times of spray were 77.42%and75.85,respectively.They were highly effective biological agent for the control of LBD.5.The evaluation and analysis of the resistance of 67 oat varieties to the main diseases(BYDV,LS,PM,CR and smut)were conducted in Maojing,Xiaonangou,Lanzhou New Area and Dingxi during 2020-2021,the results showed that 3 BYDV resistant varieties and 18 BYDV sensitive varieties were selected.There were 50 LS resistant varieties,of which 37 were high resistant.There were 35 PM resistant varieties(10 high resistant)and 4 sensitive varieties.There were 10 CR immune varieties,17 resistant varieties(10 high resistant)and one sensitive variety.There were 61 smut immune varieties and 6 resistant varieties.Based on the membership function analysis,the comprehensive evaluation of disease resistance was conducted,including effective tillers,plant height,length and width of flag leaf,fresh grass yield,hay yield,1000 grain weight,seed yield,disease incidence rate and disease index.A total of 11 comprehensive disease resistant varieties were screened out,which were Baiyan No.2,Dingyan No.2,Bluebird No.1,Haymaker,Sweet-oat,Longyan No.3,Dingyin No.1,Apollo,Bayou No.15,Everleaf 126 and Haywire,accounting for16.42%of all tested varieties.6.Five seed dressing treatments could reduce the disease incidence and disease index of BYDV,LS,PM and CR,and promote the plant growth and increase the yield of forage and seeds of oat.Oat seed coating agent and imidacloprid had the highest control efficacy on BYDV,with an average control efficacy of 92.69%and 91.06%,respectively.Thiram,Zhongshengmycin and Ethylicin had high control efficacy on oat fungal diseases(LS,PM and CR),with an average control efficacy of 69.46%,70.39%and 72.43%,respectively.7.Oat+vetch mixed sowing could significantly increase the effective tillers,plant height,length and width of flag leaf,fresh grass yield,hay yield,1000 seed weight and seed yield of oat.Compared with oat single sowing,the yields of fresh grass,hay and seed of oat after mixed sowing were increased by 17.47%,10.61%and 8.89%,respectively.Meanwhile,mixed sowing could also reduce the disease incidence and disease index of BYDV,LS,PM and CR on oat,and the average control efficacy of all diseases was 44.8%-83.09%.It can be an economic and effective measure for ecological control of oat diseases in the field.