The African yam bean (Sphenostylis stenocarpa Hochst ex A. Rich) is a leguminous crop found in the Volta Region of Ghana. Three expeditions were undertaken in the region between September 1998 and March 1999 to investigate the extent of cultivation and use of the bean as the basis for research into its development and promotion as a major crop. Its cultivation is currently localized around Nkwanta and Ho West Districts. It is grown as a minor crop in mixed association with yam and cassava. It is used extensively in various dietary preparations and has potential for supplementing the protein requirements of many families throughout the year. Its current low status as a minor crop means that this potential is largely unexploited. Research efforts are required to improve its agronomic characteristics and promote its cultivation and use as a major crop.

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Two self-incompatible Upper Amazon cacao clones, T85/799 and T79/501, were pollinated with compatible Amelonado pollen subjected to varying doses of gamma irradiation (10-100 Gy). The proportion of flat non-viable beans to fully formed, viable beans in the pods increased with an increase in dosage of gamma rays. At 60 Gy all the beans produced were fiat and non-viable, beyond this dosage fruit set was zero. Pollinating the self-incompatible cacao clones with a 1 : 1 mixture of compatible mentor pollen irradiated at 60 Gy and normal self pollen produced a mixture of flat, non-viable beans and fully-formed viable beans. Similar experiments using irradiated pollen with a marker gene suggested that the fully-formed viable beans resulted from selfing. Increasing the proportion of the radiation-treated compatible pollen in the mixture increased the number of fully-formed beans. However, when compatible pollen which had been treated either at 80 Gy or with temperatures of 35 ° C, 40 ° C and 45 ° C for periods of five, ten and fifteen minutes in factorial combination were mixed with self pollen, no successful pollinations were achieved. Pollen viability tests indicated that, whilst pollen treated at 60 Gy were about 50% viable, those treated at either 80 Gy or with temperatures of 35-45 ° C were mostly not viable. This suggests that, to overcome the incompatibility in cacao, the tubes of the mentor pollen grains used should at least grow into the style. The possible causes for overcoming the self-incompatibility in cacao are discussed.

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