Dissection Of Resistant Genes To Northern Corn Leaf Blight In CIMMYT Maize Cultivar Ent17 And Bioinformatics Analysis Of Candidate Sequences Between Two Flanking Markers Linked With Resistance Gene Ht1

Northerne corn leaf blights (NCLB), caused by Exserohilum turcieum, and is one of the most destructive diseases in maize production worldwide. As the rapid variation and mutation of the races of Exserohilum turcicum, maize varieties lost their resistance to NCLB disease caused by new races of E. Turcicum. The maize resistance to E. turcicum can be divided into qualitative and quantitative resistance. The use of resistant cultivars is the most economical and effective strategy to control this disease. Despite Ent17 was highly resistant to NCLB, genes conferring resistance to NCLB in Ent17 were not determined. The objectives of this study were to detect NCLB resistance gene in Ent17, using SSR markers linked to NCLB resistance genes, to molecularly map the resistance genes and evaluate the effect of resistsance gene pyramiding, conduct bioinformatics analysis of Candidate Sequences between Two Flanking Markers Linked with Resistance Gene Htl to Exserohilum turcicum in maize. The results are as follows:1. Ent17 contains resistance genes Htl and Ht2.9 SSR markers linked to NCLB resistance genes linked to Htl.11 SSR markers linked to NCLB resistance genes linked to Ht2.The flanking markers umc1042 and bnlg198 linked to Htl and flanking markers umc1777 and umc1665 linked to Ht2 can be used to assist breeding for pyramiding Htl and Ht2 into maize cultivrs.2. In order to get Htl candidate sequence(s), bioinformatics method was employed to analyze sequences between two flanking markers umc22a and umcl22a linked with Htl. Sixty-three open reading frame (ORF) sequences were found, fourteen of which encoded protein domains. The amino acid sequences encoded by these ORF sequences were blasted with the 24 cloned R-gene amino acid sequences, and a phylogenetic tree was constructed. Among the fourteen ORF sequences, gpm565a with nucleotide binding site (NBS), containing a lot of random coils, had both high identity and close relationship with Xal resistant to bacterial blight, and was predicted to be related with Ht1. The remaining thirteen ORF sequences had no enough evidence to show any relationships with Ht1 due to lack of conserved domains, low identity or distant relationships.