Paternal Contribution to Banana (Musa sapientum L.) & Plantain (Musa paradisiaca L.) Progenies & Progeny Ploidy Composition in a Polycross Mating System Using RAPD & Flow Cytometry

Abstract

Aims: A 4x – 2x polycross mating design of 4 tetraploid female parents was established to determine paternal contributions of 3 diploid male parents to resulting progenies, their ploidy composition and genetic diversity of synthetic hybrids.
 Study Design: The polycross mating design comprised 2 blocks having both maternal and paternal selections, with seed parents replicated at 12 plants per clone. Each crossing block had 31 plants of each of the three male parents.
 Place and Duration of Study: International Institute of Tropical Agriculture (IITA) High Rainfall Station, Onne (4º51’N, 7º03’E, 10 m above sea level), Rivers State, South-South Nigeria for a period of 24 months.
 Methodology: At maturity of maternal parents (TMPx 2796-5; TMPx 1658-4; TMPx 5511-2; and TMPx 7152-2), fruit bunches were harvested, ripened and the seeds extracted. Hard seeds obtained were germinated in vivo in seed trays and emerging seedlings transplanted to perforated nursery bags. At 12 weeks, DNA was extracted from candle leaf for RAPD analysis of 80 progenies and the 3 pollen parents. Ploidy status of progenies was determined using flow cytometry method.
 Results: There was significant unequal paternal contribution to Musa polycross progenies with 3 maternal parents; TMPx 2796-5, TMPx 5511-2, and TMPx 1658-4. Two of the 3 paternal parents had progenies with all 4 maternal parents while TMB2x 5105-1 did not have any progeny with TMPx 2796-5. Progenies exhibited 4 ploidy levels with frequency differing with each female parent: TMPx 7152-2 produced 100% 3x progeny; TMPx 5511-2, 63% 3x and 37% 2x; TMPx 2796-5, 91% 3x and 9% 2x and TMPx 1658-4, 82% 3x, 9% 2x, 6% 4x and 3% 5x. The 5x progeny was recorded in the first ratoon crop. The second ratoon crop had only triploids.
 Conclusion: The high frequency of 3x progenies from all maternal types in this study, suggests the effectiveness of the polycross mating design in Musa improvement.