BANANA WEEVIL RESISTANCE AND CORM HARDNESS IN MUSA GERMPLASM

Banana weevil (Cosmopolites sordidus Germar) is a major limiting facto r in the cultivation of plantains and bananas (Musa spp. L.) in sub-Sa haran Africa. The larvae damage the crop by tunneling in the corm. Che mical control is feasible but not sustainable, whereas host plant resi stance is safe and has long term benefits. Banana weevil damage and in festation levels and corm hardness were assessed in Musa germplasm in order to determine the genetic control and potential mechanisms of res istance to this insect pest. Susceptibility/resistance to weevil was m easured by the percentage coefficient of infestation (PCI) and damage in cross sections (CS) of the corm. All plantains were equally suscept ible to the banana weevil, while a wild banana accession and some cook ing and dessert banana cultivars showed high levels of resistance. Dif ferential genotypic responses were observed in euploid plantain-banana hybrids. Segregation results suggest that host plant response to weev il in Musa is controlled by gene(s) exhibiting partial dominance towar ds the resistant parent and modifier genes with additive and dosage ef fects for susceptibility in the plantain parent. In natural banana ger mplasm, resistant clones showed increased corm hardness, as measured b y a penetrometer in longitudinal acid cross sections of outer and cent ral corm tissues. This might suggest a non-preference mechanism for we evil resistance. However, the lack of correlation between corm hardnes s with PCI and CS scores in the segregating progenies suggested that o ther mechanisms may be more important in conferring resistance to bana na weevil.