Fungal Species In Incomplete Wheat Grains In Henan Province And Chemical Conto

In recent years,due to more rainfall during the harvest period of wheat,serious wheat spike disease has occurred and the rate of imperfect wheat grains has been a significant increasing,which has seriously affected the quality of wheat.The main cause of imperfect wheat grains in Henan Province is caused by black point and Fusairum head blight.In order to clarify the occurrence of imperfect wheat grains in different regions of Henan Province,causal agents,disease resistance of wheat variety,and chemical agents with high efficiency and low toxicity,the following work was carried out as follows in this study:The investigation and sampling of incomplete wheat grains from 13 different cities in Henan Province was conducted.The pathogens were isolated from the diseased grains following further identifiication of species along with analysis of geographical distribution.The results showed that the incomplete grains from eastern Henan exhibited the lowest disease incidence at rate of 1.19% while 4.10% in central Henan.The disease incidence in western Henan,southern Henan,and northern Henan were relatively high at rate of 7.56%,7.78%,and 7.99%,respectively.The variation of disease incidence from the same wheat variety also existed in different regions.For example,Bainong 418 had the most serious incidence in Jiyuan at 31.6%,followed by Anyang at 22.67%,while in Luohe and Jiaozuo reduced to 8.83% and 8.17%,respectively,but no incomplete disease symptom was detected in Shangqiu.A total of 963 fungal isolates were obtained from the imperfect grain samples in various regions.Though the identification with morphology and molecular character,7 fungal species were classified,of which 454 isolates were belonged to Alternaria alternata(47.1%)and 298 strains were known as A.tenuissma accounting for 30.9%;31 strains were Fusarium graminearum,accounting for 3.2%;and 28 strains were Bipolaris sorokiniana,accounting for 2.9%;The isolation frequency of these four fungi is higher.Sixty-eight of Alternaria spp.were selected for further genetic variety analysis and the phylogenetic tree was constructed using the Maximum Likelihood estimate of MEGA6.06 based on the sequences of r DNA-ITS,EF-1?,HIS and ACT.The result of phylogenetic analysis indicated that the genetic distances in the populations of Alternaria spp.from southern Henan(Xinyang,Nanyang)and west Henan(Jiaozuo,Jiyuan)are so closed,while the isolates from eastern Henan(Kaifeng,Shangqiu,Zhoukou)and Yuzhong(Xuchang,Pingdingshan,Weihe)regions had similar genetic distances.A single branch generated from the northern part of Henan(mainly in Anyang)implied a genetic distance far from other regions.The investigations for Fusarium head blight in field were carried out in the Yuanhui District of Chipingdian and Luohe in Zhumadian.The results showed that the disease incidence of wheat scab in Fuping was higher than that of in Weihe River as a whole,and there were differences between different wheat varieties in the same regionranging from 3.03% to 22.73% in rate of the diseased spike and from 1.32 to 16.23 in the disease index.The results of surveys of imperfect wheat in Fuping County and Xiping County of Zhumadian indicated that the incidence of imperfect grains in Fuping was higher than that in Xiping.The incidence of black embryo disease was higher in wheat in both regions,indicating that the main cause of imperfect wheat disease is black embryo.There were 27 varieties with the different displaying between the two regions.Among them,23 species were found to have a higher disease incidence than that in Xiping whereas five varieties in Xiping exhibited higher susceptibility than that in Fuping.Several fungicides were selected for indoor inhibition of pathogens growth and field efficacy trials of disease control.The results of indoor inhibition showed that 80% of carbendazim had an effective inhibition against A.alternata growth on the plates,but had poor effect against F.graminearum growth and B.sorokiniana.The chemical agents with better inhibition against Alternaria sp.had carbendazim,diniconazole and tebuconazole.The effective inhibition against F.graminearum and B.sorokiniana is from azoxystrobin;The assay in field showed that the three treatments containing carbendazim had the lowest incidence of diseased spikes at 1.11%,1.60%,and 1.82%,respectively.The treatment with tebuconazole showed a slightly higher disease incidence at 2.16% and 2.91%,respectively.The control effect of all the different treatment by fungicides was overall from 29.95% to 90.95%.Compound A and compound B contained carbendazim each had the best control effect on wheat scab,reaching to 90.95% and 89.95%.