Shoot production was examined for two clones at four sites in western Kenya, differing by up to 300 m in altitude and from 16.4 to 18.1°C in mean air temperature. The duration of the shoot growth cycle increased with altitude, and the rate of shoot extension decreased, mainly because of the temperature differences. Outside a dry season, linear regressions of both extension rate and 1/duration on temperature were significant for Clone S.15/10, and gave apparent base temperatures around 7.5°C, but were not significant for Clone TN.14/3 which responded only slightly to temperature. The dry weight per shoot was stable and the growing point frequency did not change systematically with altitude. Analysis that excluded the effects of drought indicated that the yield of Clone S.15/10 decreased from 740 g m-2 at the lowest site by about 10% per degree fall in temperature, whereas the yield of TN.14/3 did not change systematically with altitude.

Varietal selection is particularly difficult for very heterogeneous environments where farmers have a range of preferences. To address these issues in Rwanda, local bean experts, generally women, are invited to the research station to assess cultivars and to select those they prefer for their plots. Farmers use observed yield as only one of several criteria to predict varietal performance in their more stressed home environments. The varieties they choose are often higher yielding on-farm and are retained longer by farmers than those selected by the breeders. The results of early farmer involvement also compare favourably with those of the standard breeding programme in terms of enhanced genetic diversity and reduced research costs. There are few pre-conditions for developing such a client-driven breeding programme.

Papel del agricultor en la selección de variedades para una estación inaestigación

The performance of two contrasting pearl millet (Pennisetum glaucum) genotypes was compared following five planting dates under rainfed conditions in deep sandy soils at Bengou, Niger in 1986 and 1987. The early and partially photo-sensitive cultivar HKB yielded more grain than the late and photo-sensitive cultivar Somno when planted with the first two seasonal rains. But after delayed planting, the crop growth rate and harvest index of cultivar HKB were reduced, leading to smaller grain yields even though the growth period, rainfall, radiation and temperature were similar at all the planting dates. In contrast, cultivar Somno maintained a small but stable harvest index over various planting dates, so that although its growth period and crop growth rate were reduced by delayed planting, the reduction in grain yield was less. Since agronomic manipulation, such as increased plant density and fertilizer application, can be used to increase crop growth rate, photo-sensitive millet genotypes such as cultivar Somno could be used for late July plantings in the Sudano-Sahelian zone.