Screening And Application Of Biocontrol Agents Against Corn Stalk Rot

Maize is an important food crop in China.Corn stalk rot is an important soil-borne disease of maize,which seriously endangers the safe production of maize in China.Recently,due to changes in cultivation systems,tillage practices,and climate change,the incidence of corn stalk rot has been increased.In this study,we collected maize plants displaying typical symptoms of maize stem rot from different maize-growing regions in Shandong province,isolated and identified the main pathogens of corn stalk rot based on morphological and molecular biology methods,screened biological control agents antagonism against the main pathogen of corn stalk rot,and analyzed its ability to control maize stem rot in the field.The main results are as follows:(1)The main pathogens of stem rot in different maize-growing regions in Shandong Province were identified.Ninety-seven maize plants displaying typical stalk rot were collected from 11 regions in Shandong Province out of which 170 pure cultures were obtained.Identification of the 170 pure cultures by morphological and molecular screening revealed 149 strains belonged to the Fusarium spp.,including F.graminearum(33.9% isolation frequency),F.verticillioides(26.8%),F.incarnatum(26.1%),F.proliferatum(12.1%),F.asiaticum(1.3%)and F.subglutinans(0.6%);ten strains belonged to Trichoderma spp.;seven strains belonged to Mucor sp.;two strains belonged to Rhizoctonia sp.;and two strains belonged to Pythium spp.Selected strains from the identified species were verified according to Koch’s postulates,and it was found that all six representative Fusarium strains caused necrosis in the stem.(2)Five biological control agents(BCA)against different members of Fusarium spp.were obtained.Four BCA strains belonging to fungi and one BCA strain belonging to bacteria were obtained by dual culture.Biological and molecular screening showed that the obtained BCA strains 21 YTTh,21ZZTh-1,21ZZTh-4 and21 LYTh belonged to Trichoderma harzianum and the BCA strain 21 TABa belonged to Bacillus amyloliquefaciens.The dual culture experiments revealed that 21 YTTh has stronger inhibitory effects on F.graminearum and F.verticillioides with 78.52%and 69.68% inhibition respectively.Also,21ZZTh-4 has 70.13% inhibitory effects on F.proliferatum and 21 TABa has 75.00% inhibitory effect on F.incarnatum.(3)The growth-promoting and disease-controlling effects of different BCA strains on corn stalk rot were determined.The indoor and field experiments showed that the BCA strain 21ZZTh-4 has the best effect on the growth of maize roots and stems.There was a significant increase of 17.03% in radicle and 67.86% in plant height compared with the control;and a significant increase of 17.98% in the total dry matter accumulation of maize compared with the control.The weights of leaves,stalks and seeds were significantly increased by 18.54%,28.38% and 14.92%respectively compared to the control.Compared to the control treatment which showed a 21.67% incidence in stalk rot,the seed treatment with BCA strains significantly reduced the incidence of corn stalk rot by 5.83% in the field.