| Maize ear rot,a worldwide disease in maize,is also prevalent in summer corn in the Huang-Huai-Hai region with the trend of spreading and aggravating year by year,which is becoming a seriously threat to the corn production in China.In September 2016 and September 2017,we collected maize kernel samples from 5 Provinces of the maize producing areas including Henan,central and southern Hebei,northern Anhui,northern Jiangsu and the central and western parts of Shandong.After isolation from the tissue samples and purification of the isolates,morphological features and molecular based techniques were applied to identify the isolated pathogens.Therefore,the components of pathogens and the predominant species of maize ear rot in summer maize in Huang-Huai-Hai region were determinated.The genetic diversity of the dominant species of Fusairum verticilliorde,Fusarium proliferatum and Fusarium graminearum in the region was analyzed by URP-PCR technique.The pathogenicity of the strains representative in the major fungal species from different regions was also tested.Taken together,the genetic diversity level and pathogenicity differentiation of dominant species in the region were clarified along with some disease resistant germplasm resources.The main results are as follows:1.The Fusarium spp.were found to be the main pathogens causing the maize ear rot in the local area,including Fusarium verticillioides,F.proliferatum,F.graminearum,F.equiseti,F.oxysporum and F.fujikuroi,in which F.verticillioides,F.proliferatum and F.graminearum were the predominant species with the average isolation frequencies at 48.71%,24.14%,and 17.24%,respectively,while F.oxysporum,F.fujikuroi,and F.equiseti showed lower frequency at 2.30%,2.44%,and 0.72%,respectively.Except Fusarium spp.,the other fungal species including Trichoderma(T.virideand and T.harzianum),Aspergillus(A.flavus and A.niger),Penicillium(P.glaucum),and Alternaria(A.alternate)were also deteted with a frequency at 4.45%.The major fungal species varied from different regions,for example,the F verticillioides in southern Henan was predominant with the highest isolation rate reaching 56.96%,whereas in the middle and south part of Hebei with the lowest at 41.18%,and the frequency in the rest of the region was in the middle.2.Using PCR amplifications with the selected URP primers to generate3.The assay for the 73 strains of F.verticilliorde,F.proliferatum and F graminearum by the silk inoculation of spore suspension showed thatall the candidates had a certain pathogenicity to the ear of maize with the average incidence at 78.97%,76.94% and 82.32%,respectively,and the average disease index at 46.74%,46.33%,and 51.21%,respectively,indicating F.graminearum as the most pathogenic.Even strains from the same geographical origin the pathogenicity exhibited also differences For example,the strains of F.verticilliorde YY1-4 and YY1-5 from Xinxiang,there average severity index was 17.04 and 66.74,respectively;The strains of F.proliferatum HX13-6-1 and NH14-1-5 from Anyang,there average severity index was 33.09 and 62.96,respectively;The strains of F graminearum DJ26-1 and DJ26-1-2 from Huaibei,there average severity index was 36.85 and 77.89,respectively,that is the highest disease with 100% of the diease incidence,while the strain with the lowest index at 16.36 and the disease incidence at 73.33% was also found in Huaibei.There was no significant correlation between pathogenicity and geographical origin.4.A field artificial inoculation method was used to identify the disease resistance of 314 maize varieties from different breeding units.The results show that 52 varieties accounting for 16.56%,such as Jinxiu 26,Jinxiu35,Nonghe 668,YD685,etc.,had high resistance(HR).The 157 varieties,such as Dunyu 107,Yushan 726,Luoyu 612,Dazhong 313,etc.,showed resistance(R),accounting for 50% of the total.There are 62 varieties accounting for 19.75%,such as Jinyu 88,Shuoyu 168,Shuoyu 169,Baojing 711,etc.,exhibited Medium resistance(MR).There are 29 varieties accounting for 9.23 of the total,such as Baojing 712,Shangdu 368,Hangxing 188,etc.,displaying susceptibility(S).Small amount of e 14 varieties accounting for 4.46%,such as Zhengpinyu 476,Jincheng316,Jincheng35,Yudan931 etc.,were tested to be high sensitivity(HS). |
