Banana bract mosaic virus in the Philippines: a comprehensive study on potential hosts and vectors, disease distribution, incidence, and genetic diversity

Banana bract mosaic disease (BBrMD) is a global threat to banana plantations, recognized by its dark red mosaic patterns on bracts and pseudostem, and leaf chlorotic streaks. The causal pathogen of this disease is the banana bract mosaic virus (BBrMV), a positive single-stranded RNA potyvirus that is transmitted non-persistently by Pentalonia nigronervosa. Owing to the limited information available, this study aimed to provide deeper knowledge about the disease in the Philippines, uncovering disease distribution, incidence, genetic diversity, and potential hosts and vectors. Disease mapping revealed a widespread distribution of BBrMD in the country, with 45-100% incidence recorded in more than 20 provinces surveyed. Testing of host range identified several potential alternate hosts of the virus, such as the ornamental plants Cheilocostus speciosus, Convallaria majalis, and Dieffenbachia sequine; rootcrops such as Maranta arundinacea, Manihot esculenta, Colocasia esculenta, and Ipomoea batatas; vegetable crops like Cucumis sativus, Psophocarpus tetragonolobus, and Capsicum sativum; and the weed species Cymbopogon citratus. However, only few plants exhibited mosaic-like patterns in the tests, with the majority remaining BBrMV-positive but asymptomatic. In addition to the known aphid vectors, Nephotettix virescens, a leafhopper pest of rice, was also suspected to be a potential vector for BBrMV. Furthermore, molecular analyses of three BBrMV genes, namely, helper component proteinase (HCPro), viral genome-linked protein (VPg), and coat protein (CP), revealed high genetic diversity in the collected Philippine BBrMV isolates as evidenced by high gene sequence variation, haplotype number, haplotype diversity, nucleotide diversity, and average nucleotide differences. Diversification was also evident in multiple phylogenetic clusters and complex haplotype networks, while no apparent recombination was detected. Neutrality tests using Fu's Fs and Tajima's D further showed negative and significant values implying recent population expansion in the country. These Comprehensive findings can significantly contribute to the development of disease prevention and control management strategies for BBrMD in the Philippines.