Diversity, Genome Classification, Commercial Viability and Pest Status of Musa Cultivars Identified in Kerala

Kerala is blessed with rich diversity of Musa cultivars and each of them is characterized by unique taste, flavor, aroma and nutritive values. Farmers doing commercial cultivation are highly selective and interested only in cultivating commercially viable cultivars such as Nendran, Palayankodan, Kappa, Gnalipoovan and Robusta. Intensive application of urea containing synthetic fertilizers has resulted in the lushness of plants leading to the low content of secondary metabolites, which made them highly susceptible to pest attack. Non-selective application of systemic insecticides in edible crops leads to the contamination of toxins in fruits and their entry into food chain. Among 80 Musa cultivars identified during field study in various sites of Kerala, 60 are indigenous and 20 are hybrids of exotic. Ten cultivars among the indigenous group are diploid with genome constitution AA, and all of them are resistant to pest attack. Farmers are reluctant to cultivate diploid and pest resistant Musa cultivars due to some characters such as small fruit bunch, low market value, and low glucose content leading to the lack of pleasant taste, long duration to set flower and long duration for the replanted suckers to sprout. Analysis of genome constitution of 80 indigenous cultivars revealed that 12% of them are diploid with AA, 10% are AB, 15% are AAA, 13% with ABB and other 50% are AAB. Some of the cultivars with AAB genome constitution also showed high degree of resistance against insect pests, due to very high content of flavanoids, total phenols, very high activity of Phenylalanine ammonialyase, Polyphenol oxidase and Peroxidase in the pseudostem and leaves. No tetraploid Musa cultivars were identified in Kerala during the course of study. Wide spread transformation of agriculture lands to rubber plantation has resulted in the depletion of diversity of Musa cultivars. Many exotic Musa cultivars, introduced in Kerala, did not have wide acceptance from the public and among farmers, due to the lack of pleasant taste compared to indigenous types. RAPD analysis of the indigenous Musa cultivars revealed that they exhibited high degree of genetic variability and genetic polymorphism. In Kerala, 90% of the Musa cultivation is done by small scale farmers and most of them do not have their own land for cultivation and hence, they took land at lease for one year contract from owners. They are very particular to cultivate Musa which can give harvest within one year. Most of the cultivars identified during the course of study were unable to give harvest within one year. This is the reason for the abundance of only few commercially viable cultivars in the agroecosystems. Each Panchayath should take active conservation measures to conserve the diploid and indigenous cultivars which are resistant to pests. These cultivars can be used in future for breeding programmes to develop pest resistant and commercially viable Musa cultivars.

Keywords: Flavanoids, Musa diversity, Peroxidase, Pest resistance, Pest susceptibility, Phenols, Phenylalanine ammonia lyase, Polyphenol oxidase.