Transgenic Banana Plants Resistant to Banana Bunchy Top Virus Infection

Abstract

Embryogenic cell suspensions (ECS) initiated from immature male flowers of banana cultivar 'Dwarf Brazilian' (AAB, Pome subgroup) were transformed using Agrobacterium tumefaciens containing one of four constructs derived from the replicase-associated protein (Rep) gene of the Hawaiian isolate of Banana bunchy top virus (BBTV). Each construct was engineered under control of a double CaMV 35S promoter and the AMV enchancer sequence in the binary plasmid pBI121. Constructs were transferred into A. tumefaciens strain AGL0 and used to transform banana ECS. Plantlets that survived antibiotic selection were acclimated to greenhouse conditions and challenged with viruliferous banana aphids (Pentalonia nigronervosa). Ten adult or late instar aphids were allowed to feed for 2-4 weeks on test plants. All test plants were kept in the greenhouse and monitored for symptom expression for a period of 6 months. Control plants transformed with empty vector pBI121 only were included in all tests. A total of 270 test plants and 63 control plants were screened for BBTV resistance using this approach. One of 32 test plants transformed with the M1 (mutant Rep gene) construct, 5 of 74 test plants transformed with the AS1 (antisense Rep gene) construct, 5 of 38 test plants transformed with the PR1 (partial Rep gene) construct, and 10 of 126 test plants transformed with the R/PR1 (full-length Rep gene fused to antisepses partial Rep gene) construct were found to be resistant to BBTV challenge and showed no bunchy top symptoms. All of the control plants became infected with BBTV under these experimental conditions. Plants that survived BBTV challenge were analysed by quantitative PCR (per) and Southern hybridisations to determine the number of transgenes that were present in their genomes. Results from these analyses indicated that the resistant plants contained from 2 to more than 9 copies of the NPTII (kanamycin resistance) transgene carried on the pBI121 plasmid.

Banana bunchy top disease (BBTD) symptom expression in banana and strategies for transgenic resistance: A review

“…BBTV transmission studies through aphids under greenhouse conditions. Bioassay to screen the transgenic banana and symptom expression observation made on transgenic and non-transgenic bananas (Borth et al, 2011;Elayabalan et al, 2013).…”

“…In 2011, it was reported that some transformed clones of 'Dwarf Brazilian' (AAB, Pome subgroup) were resistant to BBTV under experimental conditions in Hawaii (Borth et al, 2011). Two Indian research groups have claimed success.…”

Transgenic banana plants expressing small interfering RNAs targeted against viral replication initiation gene display high-level resistance to banana bunchy top virus infection

“…Further, no pathogen-derived resistance strategies have been reported to be fully efficacious in imparting resistance against BBTV infection in banana. Recently, Borth et al (2011) have succeeded in generating banana plants resistant to BBTV using the viral Rep gene. They have used a variety of constructs based on BBTV Rep gene sequence and its regulatory regions to achieve this resistance.…”

Genetic engineering strategies for biotic and abiotic stress tolerance and quality enhancement in horticultural crops: a comprehensive review

“…Also, transgenic papaya plants with the mutated replicase (RP) gene from PRSV showed high resistance or immunity against PRSV in the field (Xiangdong et al 2007). Borth et al (2011) developed transgenic banana (cv. Dwarf Brazilian) plants resistant to banana bunchy top virus (BBTV) by transforming four gene construct derived from the replicase associated protein (Rep) gene of the Hawaiian isolate of BBTV.…”