Assessment of Banana Streak MY virus-based infectious clone vectors in Musa ssp.

Abstract

Banana streak disease, caused by a complex of different banana streak viruses (BSVs), occurs in all banana-producing countries. BSVs are genetically very diverse and can exist both as episomal forms or integrated into the host genome and both can be infectious to banana.Several field studies have assessed the infectivity of one or more BSV species on different banana genotypes with significant differences reported in virus incidence and symptom expression between and within genotypes. These studies used a severity index, based on symptom expression, to determine the resistance/susceptibility levels of the genotypes.Because of the great genetic variability amongst BSV species, symptoms of banana streak disease may vary widely and may be influenced by the cultivar and/or environmental conditions. Also this system of screening does not reflect the level of viral DNA accumulation In the current study, symptom variability was considerable with different Musa genotypes expressing distinct symptoms. Quantification of the levels of virus DNA showed that virus accumulation differs between genotypes, but also within plants of the same accession, and that severity scores do not correlate well with the viral load as measured using qPCR.Modified vectors with either ORF1 or ORF2 deleted were not infectious and the addition of a GFP ORF into two sites in the genome did not result in expression of this heterologous sequence from the constructs used in this study. Interestingly, two constructs with small inserts, initially designed for the purpose of gene silencing, were found to retain infectivity and maintain a heterologous sequence up to 110 nt. These studies confirm that BSMYV is infective in a broad range of Musa genotypes and cultivars but that further work is required to develop suitable vectors for either gene expression or gene silencing studies in banana

Infectivity of an Infectious Clone of Banana Streak CA Virus in A-Genome Bananas (Musa acuminata ssp.)

“…Williams plants were previously indexed for banana bunchy top virus (BBTV), while the other eight genotypes included were indexed for BBTV, cucumber mosaic virus, banana mild mosaic virus, banana streak virus and banana bract mosaic virus. Plants were multiplied in tissue culture and subsequently grown in rooting media as previously described [14].…”

“…The observation that BSCAV could be detected in symptomless Zebrina plants shows that asymptomatic infections can also occur. Interestingly, infection of Zebrina with Banana streak MY virus was found to result in severe symptoms [14]. By preparing infectious clones of additional BSV species and inoculating these genotypes, the influence of Musa genotypes and virus species on symptom expression could be investigated further.…”