Evaluation And Diversity Of The Maize Hybrids Against Fusarium Spp. Causing Ear Rot On Maize Under The Conditions Of Natural Infection

Fusarium ear rot on maize is a serious disease rampant in all maize growing areas in worldwide,which leads to great threat to maize production.It is imperative to understand the species of pathogenic fungi causing ear rot,disease resistance and diversity of different commercial maize hybrids to design more efficient disease management programs.A total of 454 fungi strains were isolated from 69 commercial maize hybrids grown in Harbin,China,of which were F.subglutinan(34.8%),F.proliferatum(31.3%),F.verticillioides(20%),F.graminearum(9.7%),F.equiseti(4.2%),respectively.Among them,F.subglutinan,F.proliferatum,and F.verticillioides species complex were the dominant fungi causing ear rot on maize in the local.To determine resistance of the 59 commercial maize hybrids in 2015 and 2016,eleven hybrids(18.6%)were found to be high resistance by natural infection.Out of 59 hybrids,no hybrids were found to be immune varieties.And,eleven commercial varieties were found to be high resistance,such as Longdan25,Hongyu415,Fuer1,Xianfeng38905,Suiyu23,etc.Thirty-four commercial varieties were medium resistance,such as Zao50 and Zhongnong225,etc.And nine commercial varieties were susceptible,such as Zhedan37 and Suiyu19,etc.Mean-while five commercial varieties were indentified to be highly susceptible,such as Suiyu10 and Longyu828,etc.Simple sequence repeat(SSR)analysis using 6 pairs of primers resulted in 24 reproducible bands,the number of alleles for each of the loci ranged from 2 to 6 with an average of 4.When the genetic similarity coefficient was 0.69,59 commercial maize hybrid were clustered into 8 groups:Group I consisted of four varieties and exhibited resistance;Group II consisted of eight varieties:1 varieties exhibited high resistance(HR),3 varieties exhibited resistance(R),3 varieties exhibited susceptible cultivar(S),and 1 varieties exhibited high susceptible cultivar(HS);Group III consisted of eight varieties:1 varieties exhibited HR and 7 varieties exhibited R;Group IV consisted of twenty-six varieties:8 varieties exhibited HR,11 varieties exhibited R,4 varieties exhibited S and 3 varieties exhibited HS;Group V consisted of seven varieties:1 varieties exhibited HR,5 varieties exhibited R,1 varieties exhibited S;Group VI consisted of two varieties and exhibited R.Group VII consisted of two varieties and exhibited R and HS.Group VIII consisted of two varieties and exhibited R and S.No correlation was found between genetic diversity and disease resistance.Analysis of molecular variance indicated that about 99.71% of the genetic variation about disease resistance against ear rot on maize resided within populations.And there was little genetic differentiation associated with disease resistance.