Identification Of The Pathogens And Pathogenicity Of Maize Stalk Rot In Henan Province

Corn plants which have the typical symptoms of maize stalk rot had been collected from Zhengzhou experimental farm of Henan Agricultural University, Zhongmou, Fengqiu, Xunxian, Sanmenxia, Fangcheng, Taikang, Xiping in Henan Province. The pathogens were isolated using tissue isolation method with PDA and WA medium. The results showed that the pathogens of maize stalk rot in Henan Province primarily are Fusarium and Pythium. Fusarium has the highest isolation frequency, and with a wide distribution range. It can be isolated in all sampling sites; Pythium has narrow distribution range, and was isolated in Zhengzhou experimental farm, Xunxian and Sanmenxia sampling site.The pathogenicity of all isolated pathogens, including F. graminearum, F. moniliforme, F. moniliforme var. intarmadium and P. arrhenomanes, were tested in laboratory and field with inoculation. The results of the seeding stage in laboratory test showed that F. graminearum is strongest pathogenicity with 100% morbidity and 69.44 disease index; P. arrhenomanes is followed with 100% morbidity and 52.78 disease index; the third one is F. moniliforme var. intarmadium with 100% morbidity and 44.44 disease index; and F. moniliforme has the weakest pathogenicity with 100% morbidity and 30.56 disease index. The pathogenicity results in the field indicated that P. arrhenomanes has a lower morbidity than F. graminearum, but higher than F. moniliforme var. intarmadium. The morbidity of mixed inoculation with Fusarium and Pythium don’t increase than the separated inoculation. The result of field pathogenicity test in the autumn stage is consistent with laboratory test in the seedling stage, but the morbidity in the field is lower than in the laboratory.According to the cultural and morphology characteristics, referencing to Fusarium classification systems, FZZ01 and FSMX02 isolates were consistented with F. graminearum; FZZ03 and FHN05 isolates were consistented with F. moniliforme var. intarmadium,and FZM04 isolate was consistented with F. moniliforme. The five pathogen isolates(FZZ01, FSMX02, FZZ03, FZM04 and FHN05)were cloned and sequenced with the internal transcribed spacer (ITS) and 5.8S rDNA using the universal primers ITS1 and ITS4, and were compared with published sequences in GenBank database. The measured sequences were consistented with Gibberella zeae and Gibberella moniliforme which published in GenBank with 100% homology. According to the results of morphological and molecular identification, FZZ01 and FSMX02 isolates were identified F. graminearum; FZZ03 and FHN05 were identified F. moniliforme var. Intarmadium; FZM04 was identified F. moniliforme.According to the morphology characteristics, PZZ06 and PSMX07 isolates were consistented with Pythium spp.. PZZ06 and PSMX07 isolates were cloned and sequenced with the internal transcribed spacer 1 (ITS1) using the universal primers ITS1 and ITS2, and were compared with published sequences in GenBank database. The measured sequences were consistented with P. arrhenomanes which published in GenBank. PZZ06 and PSMX07 compared with P. arrhenomanes which published in GenBank, the sequence homologies were 99% and 98%. According to the results of morphological identification and molecular identification, PZZ06 and PSMX07 isolates were identified as P. arrhenomanes.This study defined the pathogens of corn stalk rot in Henan Province is Fusarium and Pythium, F. graminearum was the dominant pathogen. In the isolated pathogens, F. graminearum has the highest isolation frequency and strongest pathogenicity, P. arrhenomanes has the lower isolation frequency and stronger pathogenicity, F. moniliforme var. intarmadium has the higher isolation frequency but has the weaker pathogenicity, F. moniliforme has the lowest isolation frequency and weakest pathogenicity.