Apoptosis‐related genes confer resistance to Fusarium wilt in transgenic ‘Lady Finger’ bananas

Abstract

SummaryFusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most devastating diseases of banana (Musa spp.). Apart from resistant cultivars, there are no effective control measures for the disease. We investigated whether the transgenic expression of apoptosis-inhibition-related genes in banana could be used to confer disease resistance. Embryogenic cell suspensions of the banana cultivar, 'Lady Finger', were stably transformed with animal genes that negatively regulate apoptosis, namely Bcl-xL, Ced-9 and Bcl-2 3¢ UTR, and independently transformed plant lines were regenerated for testing. Following a 12-week exposure to Foc race 1 in small-plant glasshouse bioassays, seven transgenic lines (2 · Bcl-xL, 3 · Ced-9 and 2 · Bcl-2 3¢ UTR) showed significantly less internal and external disease symptoms than the wild-type susceptible 'Lady Finger' banana plants used as positive controls. Of these, one Bcl-2 3¢ UTR line showed resistance that was equivalent to that of wild-type Cavendish bananas that were included as resistant negative controls. Further, the resistance of this line continued for 23-week postinoculation at which time the experiment was terminated. Using TUNEL assays, Foc race 1 was shown to induce apoptosis-like features in the roots of wild-type 'Lady Finger' plants consistent with a necrotrophic phase in the life cycle of this pathogen. This was further supported by the observed reduction in these effects in the roots of the resistant Bcl-2 3¢ UTR-transgenic line. This is the first report on the generation of transgenic banana plants with resistance to Fusarium wilt.

Plant defense response against Fusarium oxysporum and strategies to develop tolerant genotypes in banana

“…Hence, transgenic expression of apoptosis-inhibition-related animal genes that negatively regulate apoptosis, namely Bcl-xL, Ced-9 and Bcl-2 3′ UTR, was tried in banana cultivar, 'Lady Finger'. Among these with over expression Bcl-2 3′ UTR line showed resistance to fusarium wilt (Paul et al 2011). RNAi-based strategy for banana resistance using dsRNAs of adenylate cyclase, DNA polymerase alpha and delta subunits against Foc spores in vitro displayed varying degrees of inhibition of spore germination (Mumbanza et al 2013).…”

Modifying Bananas: From Transgenics to Organics?

“…The majority of these studies have been reports from a glasshouse evaluation and therefore, it is difficult to determine whether they only represent experimental projects, or whether they are part of a program to progress to field trial, and ultimately, to general release. The most targeted traits have been pest and disease resistance, abiotic stress tolerance, and fruit ripening, and these have included resistance to BBTV using RNAi (RNA interference) [44,59], resistance to Fusarium wilt race 1 using antiapoptosis genes [60], RNAi [61] or a defensin gene [62], resistance to nematodes using plant-derived or synthetic peptides [63], and the over-expression of a banana-derived WRKY transcription factor to alter abiotic responses [64]. These reports, in addition to a number of others, have used a range of banana genes, RNAi constructs derived from banana pathogens, or genes not derived from bananas.…”

Efficient regeneration system applicable to five Musa cultivars

“…For example, Hu et al [14] established an efficient propagation protocol for Baxi banana using multiple bud clump explants, while Santos et al [3] established a method for a plantain-type banana cv., Three Hand Plenty (AAB genomic group, International Transit Center accession: ITC.0185). Paul et al [18] established an effective method for lady finger banana, Sreedharan et al [12] for banana cv. Rasthali, and Wei et al [6] for the edible banana M. acuminata cv.…”

“…Genetic transformation of banana has been an important tool for molecular breeding and identification of gene function in recent years [12,18] . However, the dependency of regeneration on banana plant genotype has made it difficult to repeat published results.…”