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Genetic analysis of a source of Fusarium wilt resistance in banana from Musa acuminata ssp. malaccensis

Elizabeth Aitken: School of Agriculture and Food Sciences, The University of Queensland

<div>Tropical Race 4 (TR4) of <em>Fusarium oxysporum</em> f.sp. <em>cubense </em>(<em>Foc</em>) threatens global banana production. This soil-borne fungus enters the roots and colonises the xylem to induce Fusarium wilt. We have identified resistance to <em>Foc</em>, including to TR4, in the wild banana <em>Musa acuminata</em> subsp <em>malaccensis.</em> Pathogenicity tests of F2 progeny showed segregation of a single dominant gene conferring resistance to race 1, sub-tropical race 4 and TR4. Comparison of resistant and susceptible progeny using Genotyping-By-Sequencing analysis revealed SNPs on a genome-wide scale. A region on chromosome 3 showed a strong level of association between SNP zygosity and resistance. This region has now been fine-mapped to reveal a 157 kb physical sequence containing 28 putative candidate genes, none of which are classic LRR genes. Only 15 genes are predicted to carry non-synonymous SNPs leading to changes in the encoded amino acid sequence. Expression profiles of these candidate genes from inoculated resistant and susceptible plants revealed varying expression levels. SNPs from the gene markers screened across diverse banana genotypes including diploids and cultivated polyploids, identified potential resistance in breeding program germplasm where Malaccensis was a progenitor. Utilisation of a molecular marker for genetic resistance to<em> Foc,</em> including to TR4, will greatly assist banana breeding programs and allow understanding of the mechanisms of resistance at the molecular level.</div>