9. Mutation for yield and postharvest traits

Abstract

Banana is the second most widely grown fruit crop in the Philippines and considered as the number one dollar earner and export winner. Out of the many diverse types and kinds of banana, the variety ‘Lakatan’ is the most popular in the domestic and to some extent, in the export market. However, improvement is difficult and breeding activities for this crop in the Philippines is nil due to the long life cycle and sterility. In order to address this, mutation breeding through gamma irradiation and induction of mutation through somaclonal variation can be an alternative solution. The researchers conducted studies to induce mutation using gamma irradiation on Philippine ‘Lakatan’ bananas. Moreover, the LD50 for Lakatan (shoot tips) was also established. The focus was on the effect of gamma ray in improving post-harvest traits in a banana variety. In another study, induction of somaclonal variation using long culture period and addition of high dosage of 2,4-D on the yield and other postharvest traits of ‘Lakatan’ somaclones were also conducted. For both studies, morphological evaluation was done using the INIBAP postharvest evaluation. Radio sensitivity test on shoot tip cultures established that the LD50 is 50 Gy gamma rays. Mutation induction was carried out for 500 shoot tips using 50 Gy gamma ray treatment. Stability of the mutated traits was also evaluated on the succeeding four generations. Mutations were observed on the bunch weight (kg), number of hands per bunch, number of fingers per hand and the shelf life (days). Moreover, positive and negative variations on prolonged subculture and high concentration of 2,4-D were observed. Positive variation was exhibited by heavier bunch weight, earlier flowering, longer shelf life and more number of hands. Negative variation, on the other hand, included dwarfism, delayed flowering and lesser number of hands. Hence, mutation induction can lead to enhanced heritable variation. This might be useful for functional genomics or breeding applications and can be exploited for banana postharvest improvement.