Molecular Diagnosis and Vegetative Compatibility Group Analysis of Fusarium Wilt of Banana in Nepal

Abstract

Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc), is the most important constraint of the banana industry globally. In Nepal, epidemics resembling FWB have been increasingly observed on the Malbhog cultivar in the past several years. However, the disease has not been officially reported yet, and consequently, little is known about the pathogen present across the country. In this study, we characterized 13 fungal strains isolated from banana plants of the Malbhog cultivar (Silk, AAB) showing symptoms similar to FWB in banana plantations in Nepal. All of the strains were typed as belonging to the F. oxysporum and caused FWB symptoms when inoculated in the Malbhog and Cachaco (Bluggoe, ABB) cultivars. No symptoms were observed in the Williams cultivar (Cavendish, AAA). Vegetative compatibility group (VCG) analysis classified the strains as VCG 0124 or VCG 0125. PCR analyses conducted with primers specific for Foc race 1 (Foc R1) or Foc tropical race 4 (TR4) revealed that all the strains reacted positively for Foc R1 and none for TR4. Altogether, our results demonstrated that the pathogen populations causing FWB of the Malbhog cultivar in Nepal were Foc R1. This work reported, for the first time, the occurrence of FWB in Nepal. Further studies with larger Foc populations are needed to better understand disease epidemiology to design sustainable disease management strategies.

Genetic diversity of the banana Fusarium wilt pathogen in Cuba and across Latin America and the Caribbean

“…We assembled a nationwide collection of 170 isolates from symptomatic bananas primarily from 'Burro CEMSA' and 'Pisang Awak', which are extensively grown in Cuba (Martínez-de la . Although diagnostic PCRs and phenotyping assays showed that Race 1 and Race 2 prevailed in the collection, some isolates (isolates cub0043, cub0145 and cub0150) caused symptoms in both 'Gros Michel' and 'Burro CEMSA' which confirms previous field experiments in Cuba and greenhouse results with isolates from Brazil, East Africa, Florida, Nepal and Puerto Rico (Garcia et al, 2018;García-Bastidas, 2019;Martínez-de la Parte et al, 2024;Pant et al, 2023;Ploetz & Churchill, 2011). Hence, the current race concept in FWB is inadequate because these isolates do not fit in the classical race nomenclature (i.e., Race 1, Race 2 and Race 4).…”

“…However, when Black Leaf Streak Disease, caused by Pseudocercospora fijiensis (Arango Isaza et al, 2016), entered the country in the 1990s, the overall assembly of the national banana acreage changed. Since then, areas grown with susceptible Cavendish and plantain cultivars were significantly reduced and replaced by more resistant FHIA hybrids and Bluggoe cultivars (Pérez-Vicente et al, 2002), and 'Pisang Awak' became popular due to its higher rusticity and semi-acid taste. These changes caused a reemergence of FWB in Cuba, which is corroborated by our analyses that demonstrated that this disease is widespread across the entire country.…”

A deep genetic analysis of banana Fusarium wilt pathogens of Cuba in a Latin American and Caribbean diversity landscape

“…We assembled a nationwide collection of 170 isolates from symptomatic bananas primarily from ‘Burro CEMSA’ and ‘Pisang Awak’, which are extensively grown in Cuba (Martínez-de la Parte et al ., 2023). Although diagnostic PCRs and phenotyping assays showed that Race 1 and Race 2 prevailed in the collection, some isolates (isolates cub0043, cub0145, and cub0150) caused symptoms in both ‘Gros Michel’ and ‘Burro CEMSA’ which confirms previous field experiments in Cuba and greenhouse results with isolates from Brazil, East Africa, Florida, Nepal, and Puerto Rico (Ploetz & Churchill, 2011; Garcia et al ., 2018; García-Bastidas, 2019; Martínez-de la Parte et al ., 2023; Pant et al ., 2023). Hence, the current race concept in FWB is inadequate because these isolates do not fit in the classical race nomenclature (i.e., Race 1, Race 2, and Race 4).…”