In Search of Naturally Occurring Host Resistance to Banana Bunchy Top Virus

Abstract

Banana bunchy top virus (BBTV) is the most serious disease of banana in Hawaii today. It is vectored by the banana aphid Pentalonia nigronervosa, and both of Hawaii’s main commercial banana cultivars, the Cavendish clone ‘Williams’ and the Pome clone ‘Dwarf Brazilian’, are susceptible. Our objectives were to screen a diverse collection of banana germplasm 1) in the field to determine whether differences in onset or severity of symptoms can be identified, and 2) in the greenhouse using manual inoculations to determine whether truly resistant genotypes exist. A collection of 43 genotypes was assembled, representing the major genomic groups of edible bananas, as well as related wild species. Six replicates of each were planted at Waimanalo, Oahu, in March 2012. From its installation, the planting was exposed to natural populations of virus-vectoring aphids, and symptom development was recorded from August 2012 until November 2014. Four edible cultivars, ‘Kayinja’, ‘NPV’, ‘Highgate’ and ‘Cocos’, and one wild species, Musa acuminata subsp. malaccensis, displayed low incidence of BBTV over the course of field observation, and have favorable agronomic or breeding characteristics. These five most desirable field clones were also manually inoculated with viruliferous aphids in the greenhouse and observed for a period of three months. All plants were evaluated for disease symptoms, and presence or absence of virus was confirmed by PCR assays. The top performing cultivars have a higher degree of BBTV resistance than ‘Williams’ or ‘Dwarf Brazilian’, and may be useful additions to the diversity of bananas grown in Hawaii to maintain production in the presence of BBTV.