Genetic variation of Indonesian Fusarium oxysporum f.sp. cubense isolates and their pathogenicity on wild and cultivated banana species

Fusarium wilt of banana – also known as Panama disease – is caused by the soil-borne fungus Fusarium oxysporum f.sp. cubense (Foc). Foc strains have been divided into races (1, 2 and 4) based on their pathogenicity towards certain banana varieties. The recent outbreak of Foc Tropical Race 4 (FocTR4) is threatening the global banana production and thus endangers food security, livelihoods of smallholders and the banana export trade. A better understanding of Foc pathogenic diversity is necessary to ensure a long-term solution for resilient banana cropping systems. We isolated a set of 75 Foc strains from Indonesia, the center of origin of both banana and Foc, which was phenotyped on an explorative set of wild and cultivated banana varieties comprising the well-known edible triploids Grand Naine and Gros Michel, and the wild diploids Musa acuminata var. malaccensis “Pahang” and “Pisang Rejang”. Moreover, each strain was genetically characterized by genotyping-by-sequencing using DArTSeq technology. Analyses of variance showed a highly significant banana host x Foc isolate interaction component, indicating specific gene action. The majority of Foc strains was highly pathogenic on both Grand Naine and Gros Michel and were therefore classified as FocTR4, which was also confirmed by FocTR4-specific molecular diagnostics. However, FocTR4 isolates clearly differed in their aggressiveness towards Grand Naine, suggesting underlying genetic variation despite their generally accepted clonal nature. Foc strains that were solely pathogenic on Gros Michel were classified as Foc Race1 and negative for the FocTR4 diagnostic. Interestingly, “Pahang” and “Pisang Rejang” were highly resistant to the majority of Foc strains, including the most aggressive FocTR4 isolates. These data will contribute to a better understanding of the genetic basis of host-pathogen interactions in Foc-banana pathosystem.