Introgression of Maize Lethal Necrosis Resistance Quantitative Trait Loci Into Susceptible Maize Populations and Validation of the Resistance Under Field Conditions in Naivasha, Kenya

Luka A O Awata; Beatrice E Ifie; Eric Danquah; MacDonald Bright Jumbo; L Mahabaleswara Suresh; Manje Gowda; Philip W Marchelo-Dragga; Michael Scott Olsen; Oluwaseyi Shorinola; Nasser Kouadio Yao; Prasanna M Boddupalli; Pangirayi B Tongoona

doi:10.3389/fpls.2021.649308

Introgression of Maize Lethal Necrosis Resistance Quantitative Trait Loci Into Susceptible Maize Populations and Validation of the Resistance Under Field Conditions in Naivasha, Kenya

Front Plant Sci. 2021 May 3:12:649308. doi: 10.3389/fpls.2021.649308. eCollection 2021.

Affiliations

¹ Directorate of Research, Ministry of Agriculture and Food Security, Juba, South Sudan.
² West Africa Centre for Crop Improvement (WACCI), College of Basic and Applied Sciences, University of Ghana, Legon, Ghana.
³ International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Bulawayo, Zimbabwe.
⁴ International Maize and Wheat Improvement Center (CIMMYT), World Agroforestry Centre (ICRAF), Nairobi, Kenya.
⁵ Department of Agricultural Sciences, College of Natural Resources and Environmental Studies, University of Juba, Juba, South Sudan.
⁶ Biosciences eastern and central Africa (BecA) Hub, International Livestock Research Institute (ILRI), Nairobi, Kenya.
⁷ John Innes Centre, Norwich, United Kingdom.

Abstract

Maize lethal necrosis (MLN), resulting from co-infection by maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV) can cause up to 100% yield losses in maize in Africa under serious disease conditions. Maize improvement through conventional backcross (BC) takes many generations but can significantly be shortened when molecular tools are utilized in the breeding process. We used a donor parent (KS23-6) to transfer quantitative trait loci (QTL) for resistance to MLN into nine adapted but MLN susceptible lines. Nurseries were established in Kiboko, Kenya during 2015-2017 seasons and BC₃F₂ progeny were developed using marker assisted backcrossing (MABC) approach. Six single nucleotide polymorphism (SNP) markers linked to QTL for resistance to MLN were used to genotype 2,400 BC₃F₂ lines using Kompetitive Allele Specific PCR (KASP) platform. We detected that two of the six QTL had major effects for resistance to MLN under artificial inoculation field conditions in 56 candidate BC₃F₂ lines. To confirm whether these two QTL are reproducible under different field conditions, the 56 BC₃F₂ lines including their parents were evaluated in replicated trials for two seasons under artificial MLN inoculations in Naivasha, Kenya in 2018. Strong association of genotype with phenotype was detected. Consequently, 19 superior BC₃F₂ lines with favorable alleles and showing improved levels of resistance to MLN under artificial field inoculation were identified. These elite lines represent superior genetic resources for improvement of maize hybrids for resistance to MLN. However, 20 BC₃F₂ lines were fixed for both KASP markers but were susceptible to MLN under field conditions, which could suggest weak linkage between the KASP markers and target genes. The validated two major QTL can be utilized to speed up the breeding process but additional loci need to be identified between the KASP markers and the resistance genes to strengthen the linkage.

Keywords: alleles; backcross; introgression; kompetitive allele specific PCR; maize; maize lethal necrosis.