Vegetative Compatibility Group (VCG) characterization of Fusarium oxysporum f. sp cubense in Asia

Recent epidemics of Panama disease (Fusarium wilt) in China and the Philippines caused by the virulent Tropical Race 4 (TR4) of Fusarium oxysporum f. sp. cubense (Foc) have posed a serious threat to the banana industry in Asia, and beyond. This race, belonging to the Vegetative Compatibility Group (VCG) 1213/16, is extremely important because it attacks the widely grown and traded Cavendish varieties, and many local cultivars grown by smallholder farmers. A study to determine the geographic distribution of the various pathogenic VCGs of Foc in Asia was carried out as a key step towards designing policies and measures to prevent further spread of TR4. Samples were collected from diseased banana plants between 2006 and 2009 from 12 countries in tropical Asia. Foc was isolated from these samples, single-spored, and nit-1 and nit-M mutants generated in laboratories in Australia and South Africa. These mutants were then paired with an international VCG-tester set for Foc using the technique described by Puhalla in 1985. Nine VCGs (1213/16, 0120/15, 0121, 0123, 0124/5, 0126, 0128, 01218, 01220) were identified in Asia. VCG1213/16 (TR4), was the dominant VCG from samples collected in China, Indonesia, Malaysia, Philippines, and Taiwan but not found in samples from the other countries. VCG 0124/5, a VCG associated to Foc Race 1, was the dominant VCG in samples from India, Bangladesh, Cambodia, Sri Lanka, Vietnam, and Thailand. No Foc infection of banana was found in Papua New Guinea during these surveys