Dr. Agustin B. Molina
Bioversity International/Banana Asia Pacific Network
Western media is fixated with reporting that Panama Disease caused by Fusarium oxysporum f. sp. cubense (Foc TR4) will lead to the disappearance of Cavendish bananas from supermarkets. This is in reaction to certain researchers predicting the unavoidable incursion of the fungus into Latin American banana plantations, which are the major supplier of western markets. These researchers further claim that only molecular-based breeding, more specifically genetic engineering, can be used to develop resistant Cavendish bananas as a solution to the problem.
Epidemics of Panama disease on Cavendish banana plantations are common in Asia. They have been reported in Taiwan as early as 1967, in Indonesia and Malaysia in 1990, and in the Philippines and China in 2001. These epidemics have caused significant damage to the commercial banana plantations. Containing build up of epidemics in infested plantations is extremely difficult to achieve. The Taiwan banana Research Institute (TBRI) developed resistant Cavendish varieties through non-conventional way of selecting resistant variants from Giant Cavendish. These varieties became the corner stone of an integrated disease management that make Cavendish production still sustainable in Taiwan, and in Indonesia as well. Foc TR4- resistant Giant Cavendish Tissue Culture Variants (GCTCVs), are becoming practical options in managing epidemics of Foc TR4 in commercial plantations in the Philippines to sustain the more than 80,000 hectares Cavendish plantations that is bringing more than US$800 million annual export revenue, and more than 320,000 direct employments. Shared by Taiwan Banana Research Institute (TBRI), Bioversity International carried out a series of field evaluations in public-private partnerships. Two GCTCV varieties, namely, GCTCV 218 and GCTCV 219 proved to be most acceptable options in managing Foc TR4 epidemic. In commercial trials these varieties remained resistant even after 4 ratoons, while Gran Naine became severely infected even in the primary crop. GCTV 218, moderately resistant to Foc TR4, is more acceptable by growers. It has big bunches, thus, good box stem ratio, and fruit quality as good as Gran Naine. Fruits can be packed and ripened together with Gran Naine, and acceptable in current markets. Agronomically, GCTCV 218 is taller than Gran Naine, similar to Tall Williams, but has longer maturity by two to three weeks.
GCTCV 219, a variant of another resistant GCTCV 119, is highly resistant to Foc TR4. It is recommended for the rehabilitation of severely affected and abandoned farms of small growers. While GCTCV 219 is resistant and has sweet fruit thus has an opportunity for a special market, its bunch and agronomic characteristics are more inferior than that of GCTCV 218 and Gran Naine. GCTCV 219 is taller, longer maturing, less box-stem ratio and more of a floater thus prone to yield decline with time. Growers are satisfied with the level of resistance of GCTCV 219, but productivity and fruit quality are main concern.
The use of GCTCV 218 is now gaining wide acceptance by banana growers and companies. The Philippine government launched a $ 2.2 million programme to help small growers to rehabilitate affected farms and sustain livelihoods by an integrated approach around the use of GCTCV 218 and 219. The planting of these varieties with tissue culture seedlings in commercial scale also provides an opportunity to select for improved phenotypes.
The fundamental approach of preventing the incursion of Foc TR4 into new areas is essential. However, in the presence of Foc TR4, production and disease management paradigms have to change to sustain the industry. In the absence of other varieties from other breeding programmes, the GCTCVs seem to be the best our farmers could have at this time to save their livelihoods. The approach of using somaclonal selection is definitely a viable approach in Cavendish banana improvement. The prediction that Foc TR4 will cause the demise of the Cavendish-based export industry unless a GMO-resistant variety is developed appears a gross exaggeration.