11. Study of the Reproductive Characteristics of Nine Cassava Accessions

Abstract

Reproductive behaviour of two cultivars (AF and AN) and seven breeding lines (BA, AS, LA, BS-1, HO-008, ME and SE) of cassava (Manihot esculenta Crantz) was studied to obtain information pertaining to flowering habits and other reproductive characteristics of these potential parents required for future hybridization programmes. The accessions were grown on the Research Farm of the Biotechnology and Nuclear Agriculture Research Institute in the coastal savanna agro-ecological zone of Ghana between April 2008 and December 2009. For each accession, 40 stem cuttings, each bearing five to eight nodes, were prepared from the mid-section of healthy cassava stems and planted at a spacing of 1.5 m x 1.0 m while accessions were separated by a distance of 2 m. Ten plants were tagged per accession for the collection of data on key reproductive characteristics. All accessions flowered, suggesting that flower production may not be a limiting factor under the prevailing climatic conditions. Light microscopy revealed that one accession (BA) produced dysfunctional male flowers which were devoid of pollen. Mean days to flowering and fruiting varied significantly (P < 0.05) among the accessions, indicating the need to use different planting dates for different accessions to ensure synchronization of flowering. The accessions also differed significantly (P < 0.05) with respect to plant height at various levels of branching, as well as number of inflorescences, staminate and pistillate flowers, and fruit produced per branching level. There was also variation in percent seed set, embryo formation and fruit drop. The extensive variability observed among the accessions provides breeders with immense opportunities for carrying out cross combinations to generate new genotypes to meet specific objectives.