Identification Of Quantitative Trait Loci For Resistance To Northern Leaf Blight And Southern Leaf Blight In Maize

Northern leaf blight(NLB)and southern leaf blight(SLB)are important foliar diseases in maize,which threaten maize production seriously.Genetic resistance is an important approach to control disease.Multiple disease resistance loci are prefered for resistance breeding due to their durability and broad-spectrum.In this study,209 F6:7 recombinant inbred lines(RILs)generated from a cross between PH4 CV and KB020 were used to map disease resistance QTL for both NLB and SLB.The main results are as follows:1.The NLB resistance was evaluated at Baoji in 2020 and 2021,and at Xunyi in 2021.The SLB resistance was evaluated at Yangling in 2020 and 2021,and at Minquan in 2021.KB020 was highly resistant to both NLB and SLB,while PH4 CV was susceptible to both diseases.The phenotypic data from all the environments showed normal distribution for both diseases,suggesting that the population was good for QTL mapping.The Maize6H-60 k Chip with 61214 SNP markers was used to genotype all the RILs.A total of 6,158 SNP markers were used to construct the genetic map.The total length of the map is 6722.65 c M.The average density is 1.09 c M.2.QTL in bins1.1、2.06、3.04、4.05、5.07 and 10.04 were identified from at least two environments for NLB.Bin3.04 accounted for the largest phenotypic variation of 15.53%,with the resistance allele origined from KB020.Bin10.04 could explained 11.91% of the phenotypic variation,while the resistance allele origined from PH4 CV.3.QTL for SLB were found in bins1.1、2.06、3.04、3.06、4.05、4.06、5.06、5.07 and8.02 from at least two environments.Bin3.04 and bin4.05 could explain higher phenotypic variation of 17.36% and 10.41% respectively.4.The co-localized QTL for NLB and SLB were in bins1.1,2.06,3.04 and 4.05.Bin1.1originated from PH4 CV,while other QTL were orginated from KB020.B in3.04 could explain the highest phenotypic variation.5.We verified the effects of QTL in bins10.04/05 for NLB and bin3.08 for SLB resistance according to mapping result from 2020.The resistance allele in bin10.05 from KB020 could significantly improve NLB resistance,showing dominant resistance.The QTL in bin3.08 with resistance allele from PH4 CV could significantly improve SLB resistance,showing dominant resistance.