Improvement of apomictic seed and parthenocarpic fruit development in MUSA. Borneo and Calcutta

Osinbajo Fredrick Okonji

Abstract

Apomixis and parthenocarpy are broadly botanically defined as embryo and seed, and fruit development respectively, in the absence of fertilization. The objectives of this study were to genetically elucidate the development of apomictic seed and parthenocarpic fruit development in MUSA. Borneo and Calcutta 4 plants were vegetatively propagated and were assayed in replicates of 2 and 6, respectively at Onne and Ibadan, Nigerian locations. Each mother and ratoon was assayed over 2 flowering cycles, resulting in a total of 16 inflorescences analyzed. Pollination barrier procedures were performed involving bagging of the inflorescences, isolating them from natural pollinators. Scoring for apomixis was based on seed-set in isolated (bagged) inflorescences without pollination. Parthenocarpy was determined by seedless pulp development in open pollinated or as artificial pollination by Calcutta 4, using standard MUSA crossing procedures. Floral and fruit developmental traits indicated that Borneo was monoecious, comprising traits of apomixis and vegetative parthenocarpy. Borneo × Calcutta 4 cross, a P1-lacking, P2 and P3 modelled MUSA, suggests that Borneo may be genetically modelled to comprise P1 but lack P2 and/or P3. Such modifier genes appear to correlate with rates of genome by environment dependent seed development regimes and if not synchronized with fruit development regimes, results in dehiscence, death of developing fruit, and non-parthenocarpic expression.