Modifying Bananas: From Transgenics to Organics?

Abstract

Bananas are one of the top ten world food crops. Unlike most other major food crops, bananas are difficult to genetically improve. The challenge is that nearly all banana cultivars and landraces are triploids, with high levels of male and female infertility. There are a number of international conventional breeding programs and many of these are developing new cultivars. However, it is virtually impossible to backcross bananas, thus excluding the possibility of introgressing new traits into a current cultivar. The alternative strategy is to "modify" the cultivar itself. We have been developing the capacity to modify Cavendish bananas and other cultivars for both disease resistance and enhanced fruit quality. Initially, we were using transgenes; genes that were derived from species outside of the Musa or banana genus. However, we have recently incorporated two banana genes (cisgenes) into Cavendish; one to enhance the level of pro-vitamin A and the other to increase the resistance to Panama disease. Modified Cavendish with these cisgenes have been employed in a field trial. Almost certainly, the next advance will be to edit the Cavendish genome, to generate the desired traits. As these banana cultivars are essentially sterile, transgene flow and the outcrossing of modified genes into wild Musa species. are highly unlikely and virtually impossible in other triploid cultivars. Therefore, genetic changes in bananas may be compatible with organic farming.

Seed degeneration of banana planting materials: strategies for improved farmer access to healthy seed

“…Breeding programmes have largely focused on resistance to black leaf streak (Tirado & Zapata, 2003;Bakry et al, 2009), although cultivars have commonly been screened as well for nematode, weevil and Foc resistance. Genetic modification and gene editing have offered new promise for resistance through breeding, although the time line is uncertain (Dale et al, 2017a). Proof-of-concept transgenic banana lines have been developed for resistance to xanthomonas wilt (Tripathi et al, 2010;Namukwaya et al, 2011), TR4 (Hwang & Ko, 2004;Dale et al, 2017b), BBTD (Elayabalan et al, 2015) and nematodes (Tripathi et al, 2015).…”

I Have a Dream: Organic Movements Include Gene Manipulation to Improve Sustainable Farming

“…Dale and coauthors [7] strongly believe that the line between conventionally bred and genetically modified bananas is becoming increasingly blurred. They predict that it is highly likely that by genome editing of regulatory elements of genes involved in pro-vitamin A production, biofortified bananas with higher pro-vitamin A can be generated.…”

“…Therefore, the authors argue that genetic resistance to Fusarium wilt is the most appropriate control strategy and that genetic manipulation seems to be the only realistic solution, as conventional breeding is hardly possible. According to Dale et al [7], the major drawback of conventional breeding is that due to the low fertility, it is essentially impossible to repeatedly backcross the initial hybrids to the original cultivars and that fertile cultivars may lack desirable traits. In addition, many of the major cultivars contain integrated copies of the banana streak virus (BSV) which upon hybridization can form infectious BSV and symptoms of that infection.…”

“…Dale, Paul, Dugdale and Harding [7] review the potential of genetically modified bananas for organic farming. Bananas grown almost exclusively in the wet tropics and the sub-tropics are consumed worldwide as an in-country popular staple food or as a favorite fruit exported into most countries.…”

“…To address the problem of whether organic farming and gene manipulation may be compatible, I initiated a Special Issue in Sustainability by inviting experts of both fields to express their views on this topic [1][2][3][4][5][6][7]. I am most thankful to all contributors for joining this discussion, but also to the reviewers for evaluating these manuscripts.…”