Fusarium oxysporum formae specialis cubense (Foc) is a soil-borne fungus that causes Fusarium wilt, which is considered to be the most destructive disease of bananas. The fungus is believed to have evolved with its host in the Indo-Malayan region, and from there it was spread to other banana-growing areas with infected planting material. The diversity and distribution of Foc in Asia was investigated. A total of 594 F. oxysporum isolates collected in ten Asian countries were identified by vegetative compatibility groups (VCGs) analysis. To simplify the identification process, the isolates were first divided into DNA lineages using PCR-RFLP analysis. Six lineages and 14 VCGs, representing three Foc races, were identified in this study. The VCG complex 0124/5 was most common in the Indian subcontinent, Vietnam and Cambodia; whereas the VCG complex 01213/16 dominated in the rest of Asia. Sixty-nine F. oxysporum isolates in this study did not match any of the known VCG tester strains. In this study, Foc VCG diversity in Bangladesh, Cambodia and Sri Lanka was determined for the first time and VCGs 01221 and 01222 were first reported from Cambodia and Vietnam. New associations of Foc VCGs and banana cultivars were recorded in all the countries where the fungus was collected. Information obtained in this study could help Asian countries to develop and implement regulatory measures to prevent the incursion of Foc into areas where it does not yet occur. It could also facilitate the deployment of disease resistant banana varieties in infested areas.

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Isolation and characterization of resistance genes from local banana cultivars was important in order to support the development of FOC resistant banana cultivars. Resistance gene analogues (RGAs) were isolated and characterized form three fusarium resistant banana cultivars using degenerate primers based on NBS domains. From 91 fragments sequenced, 17 fragments were positively NBS-type sequences and encoded as MNBS1-MNBS17. Phylogenetic analysis of MNBS deduced amino classified into three groups; the first group consisted of 14 members (MNBS1-MNBS14) with 97.4% identity, and the other three groups consisted of one member (MNBS15, MNBS16 and MNBS17, respectively) with 28.5% identity. All MNBS sequences were categorized as non-TIR-NBS-LRR. Comparison and phylogenetic analysis of MNBS with other known RGA and R genes showed that deduced amino acid MNBSs shared 91.7-98.8% identity with Musa NBS-LRR and 19.9-35.5% identity with known R genes. Among them, MNBS17 shared 50.5% identity with RGC2 (ABY75802) that assosiated to FOC race 4 resistant Musa species.

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