MOLECULAR STUDIES ON BANANA BUNCHY TOP VIRUS

Abstract

Banana and plantains (Musa spp.) are the most important staple food and source of carbohydrates in different geographical regions mainly in Africa. Banana bunchy top babuvirus (BBTV) is the most destructive viral disease of banana for its negative impact on banana productivity in all banana cultivated countries. In this study, segment 5 (DNA-5) of BBTV encodes protein of 18.7 KDa which represents a new class of viral cell cycle modulators was investigated. The full length of BBTV DNA-5 was synthesized via polymerase chain reaction (PCR) then manipulated and cloned into PGEM-T easy vector and sequenced. Results showed that the size of the full length of DNA-5 was 1017 nucleotides (nts) and includes open reading frame (ORF) of 489 nts. The nucleotide sequences of the full length of DNA-5 of the Egyptian isolate (Q) was aligned with those of seven overseas isolates (three isolates from India, two from Taiwan, one from Hainan and one from Australia). Results showed that the major outcome of this alignment was restricted in two groups, the first group called South Pacific group that includes the Egyptian, Indian 1, Indian 2 and Australian isolates and the second formed the Asian group and contained isolates Taiwan 1, Taiwan 2 and Hainan. Moreover, the taxonomic role of CR-M of BBTV DNA-5 was elucidated in the study. Additionally, the role of Streptomyces chibaensis as a biological control agent against BBTV was estimated via induction of the plant resistance either as a cell free filtrate or spore suspension before and after virus transmission. Hence, enzyme-linked immunosrobent assay (ELISA) and PCR were employed in virus indexing in groups under study. Results showed that cell free filtrate of S. chibaensis appliedbefore virus transmission was very active to inhibit BBTV infection as it succeeded to give complete protection for the treated plants. On the other hand, the other groups of treatments didn’t acquire any protection against the virus. Additionally, an enhancement in the morphological and physiological characteristics of the treated plants was observed.