Identification of additional /novel QTL associated with resistance to cassava green mite in a biparental mapping population

PLoS One. 2020 Apr 2;15(4):e0231008. doi: 10.1371/journal.pone.0231008. eCollection 2020.

Abstract

Cassava green mite [CGM, Mononychellus tanajoa (Bondar)] is the most destructive dry-season pest in most cassava production areas. The pest is responsible for cassava fresh root yield losses of over 80%. Deployment of CGM resistant cultivars is the most cost-effective and sustainable approach of alleviating such production losses. The purposes of this study were to validate the stability of CGM resistance genes found in previously published results, to identify new genes for CGM resistance in bi-parental mapping population and estimate the heritability of the trait. A total of 109 F1 progeny derived from a cross between CGM resistant parent, TMEB778 and a very susceptible parent, TMEB419 were evaluated under CGM hotspot areas in Nigeria for two cropping seasons. A total of 42,204 SNP markers with MAF ≥ 0.05 were used for single-marker analysis. The most significant QTL (S12_7962234) was identified on the left arm on chromosome 12 which explained high phenotypic variance and harboured significant single nucleotide polymorphism (SNP) markers conferring resistance to CGM and leaf pubescence (LP). Colocalization of the most significant SNP associated with resistance to CGM and LP on chromosome 12 is possibly an indication of a beneficial pleiotropic effect or are physically linked. These significant SNPs markers were intersected with the gene annotations and 33 unique genes were identified within SNPs at 4 - 8MB on chromosome 12. Among these genes, nine novel candidate genes namely; Manes.12077600, Manes.12G086200, Manes.12G061200, Manes.12G083100, Manes.12G082000, Manes.12G094100, Manes.12G075600, Manes.12G091400 and Manes.12G069300 highly expressed direct link to cassava green mite resistance. Pyramiding the new QTL/genes identified on chromosome 12 in this study with previously discovered loci, such on chromosome 8, will facilitate breeding varieties that are highly resistant CGM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Breeding / methods
  • Chromosome Mapping / methods
  • Chromosomes, Plant / genetics
  • Disease Resistance / genetics*
  • Genetic Linkage / genetics
  • Genetic Markers / genetics
  • Male
  • Manihot / genetics*
  • Manihot / parasitology
  • Mites / pathogenicity*
  • Nigeria
  • Phenotype
  • Plant Diseases / genetics*
  • Plant Diseases / parasitology
  • Polymorphism, Single Nucleotide / genetics
  • Quantitative Trait Loci / genetics*

Substances

  • Genetic Markers

Grants and funding

Financial support for this work from the Bill and Melinda Gates Foundation (gatesfoundation.org) and UKAid (gov.uk) who funded the authors under Grant No. 1048542. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.