Studies on the reproductive biology of white yam (Dioscorea rotundata Poir.)
Investigations were conducted on the identification and distribution of yam natural pollinators, flowering pattern and hybridization of white yam (Dioscorea rotundata Poir.) at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, in order to provide informations for producing hybrid seeds needed for vam genetic improvement.
Insects belonging to the Coleoptera (48.0%), Diptera (20.4%), Hymenoptera (20.0%), Hemiptera (5.8%), and Thysanoptera (5.8%) were caught around yam plants and presumed to be pollinators: they entered open-receptive-flowers and their presence on yam plants coincided with the duration of the flowering period.
Studies on the flowering pattern revealed that: (i) Male and female clones differed in their periods of flower initiation as well as the flowering duration; (ii) Seed production and conventional breeding methods are feasible if staggered planting, water and soil fertility could be managed to ensure that flowering periods of males and females nick and also extend flowering.
Artificial pollinations within white yam and between white yam and yellow yam (D. cayenensis Lam) using the camel hair brush method were successful, but resulted in a relatively low fruit set (31.8% maximum). This method was more effective than natural pollination (19.2%) and can thus supplement it for the production of hybrid seeds for introducing genetic variation in yam breeding populations.
Key wordsDioscorea rotundata white yam flowering pattern pollination reproductive biology
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- Akoroda, M.O., 1981. Studies on the genetics and floral biology of yams (Dioscorea rotundata Poir, and D. cayenensis Lam.). Ph.D. thesis, University of Ibadan, Nigeria, 298 pp.Google Scholar
- Akoroda, M.O., 1983. Floral biology in relation to hand pollination of white yam. Euphytica 32: 831–838.Google Scholar
- Akoroda, M.O., 1985. Pollen Management for controlled hybridization of white yam. Scientia Hortic. 25: 201–209.Google Scholar
- IITA, 1974. 1974 Annual Report. IITA, Ibadan, Nigeria.Google Scholar
- Martin, F.W., 1966. Sex ratio and sex determination in Dioscorea. J. Hered. 57: 95–99.Google Scholar
- Okoli, O.O., 1975. Yam production from seeds: Prospects and problems. Paper presented at the 11th Conference of the Agricultural Society of Nigeria, Enugu, Nigeria, July 1–15, 1975.Google Scholar
- Okoli, O.O., 1981. Parameters for selecting parents for yam hybridization. In: E.R. Terry, K.A. Oduro & F. Caveness (Eds), Tropical Root Crops: Research Strategies for the 1980's. Proceedings of the first triennal symposium of the International Society for Tropical Root Crops (Africa Branch), Ibadan, Nigeria, 1981. pp. 163–165.Google Scholar
- Pitkin, B.R., 1973. Larothrips dentipes (Thysanoptera, Thripidae), a new genus and species of Thrips from yam flowers in Nigeria. Bull. Entomol. Res. 62: 415–418.Google Scholar
- Sadik, S. & O.U. Okereke, 1975a. A new approach to improvement of yam Dioscorea rotundata. Nature 254: 134–135.Google Scholar
- Sadik, S. & O.U. Okereke, 1975b. Flowering, pollen grain germination, fruiting, seed germination and seedling development of white yam, Dioscorea rotundata Poir. Ann. Bot. 34: 597–604.Google Scholar