Population Structure Of Fusarium Spp.and The Resistance Of Maize To Maize Ear Rot In Northeast China

Maize is widely cultivated in northeast China as the country's largest food crop.It plays an irreplaceable role in maintaining grain production,production safety,and increasing farmers' income.In recent years,Fusarium ear rot has become more and more serious due to changes in climatic conditions,which seriously affects maize yield and quality.Fusarium is the main pathogen causing Fusarium ear rot,the dominant pathogens of Fusarium ear rot are different due to the differences in climate conditions and planting varieties.Based on the traditional morphological identification,modern molecular biology techniques were used to study the population structure of Fusarium which is a pathogenic bacterium of Fusarium ear rot,the genetic diversity,toxin detection,and the pathogenicity of Fusarium verticillioides;At the same time,the comparison of inoculation methods for Fusarium ear rot and analysis of maize's resistance to Fusarium ear rot was carried out.The results are as follows: 1.The major pathogenic population structure of Fusarium ear rot disease in northeast China was defined.122 Fusarium isolates were obtained from maize ear rot samples collected from 27 counties including Liaoning province,Jilin province,Heilongjiang province and Inner Mongolia Autonomous Region.Based on morphological characters,the genomic DNA EF-1? sequence analysis technique was used to assist in the identification of Fusarium species,The results showed that 122 Fusarium isolates causing Fusarium ear rot belongs to 4 species.F.verticillioides was the most prevalent species,representing 64.41 % of the total isolates,The isolation frequency of F.proliferatum,F.subglutinans,F.graminearum was respectively 7.38 %,10.66 % and 4.92 %.2.The genetic diversity of Fusarium verticillioides in maize ear rot and Fusarium verticillioides are fumonisin producers.Genetic diversity analysis of 40 isolates of Fusarium verticillioides was performed by using ISSR molecular marker technology.The results showed that there were 45 clear bands amplified using the 8 primers selected,of which 27 were specific bands and the proportion of polymorphic sites was 60 %;Heritability and cluster analysis showed that the genetic similarity coefficient of the tested strains ranged from 0.75 to 1.00,the tested strains were all separated when the genetic similarity coefficient was 0.97.It was indicated that the intraspecific genetic differentiation of F.verticillioides was significant,and there was no obvious correlation between the classification of ISSR taxa and the geographic origin of the strains.F.verticillioides from different provinces and cities had rich genetic diversity,but the strains maintain a high genetic similarity in the same counties.Based on the fum 5,which is polyketone synthase gene essential for fumonisin biosynthesis,specific primers P 1/P 2,P 3/P 4,and Fum 5 F 21/Fum 5 R 1 was designed.Detection of fumonisin PCR for F.verticillioides(94 strains)of Fusarium ear rot was performed,the PCR products obtained were 888 bp,702 bp and 1040 bp respectively.The identification results showed that all 94 F.verticillioides produced fumonisin.3.Pathogenicity of Fusarium verticillioides in maize ear rot is not related to its geographic location.The results of pathogenicity test showed that 31 % of Fusarium ear rot disease had an average disease level of 3.6-5.4,69 % of Fusarium ear rot have an average disease level of 1.6 to 3.4,among them,the average disease level of Fusarium ear rot disease inoculated with F.graminearum was between 1.8 and 5.4,the average disease level of maize ear rot disease inoculated with F.verticillioides was between 1.6 and 5.0.Among all tested strains,the highest grade was 5.4 and the lowest was 1.6.This shows that there is no correlation between the pathogenicity of F.verticillioides and F.graminearum and the geographical origin of the strains,and there is no difference in pathogenicity between F.verticillioides and F.graminearum.4.Maize varieties were highly resistan to Fusarium ear rot as a whole.The results of maize germplasm resistance to Fusarium ear rot showed,the average number of grades is 5.62 by tooth pick inoculation,whose incidence is higher than the silk channel inoculation method and acupuncture spike method,tooth pick inoculation is simple and desired in operation.When inoculated,the pathogen can directly contact the corn kernel,which is beneficial to the invasion and incidence of pathogen.The results of pathogenicity test showed that a total of 325 hybrids were involved in the identification of resistance in two years,of which 24 % of the hybrids were moderately resistant,62 % of the hybrids were resistant,and 11 % of the hybrids were highly resistant.