Cowpeas are grown for their leaves and grains both of which are used as relish or side dishes together with the staple food. Little information is available on the nutritional quality of local and improved cowpea varieties grown in Tanzania as well as the recipes in which they are ingredients. This study was done to investigate cowpea utilization in Iringa and Dodoma regions of Tanzania. A cross-sectional survey was carried out where a total of 517 farmers were interviewed using a pre-tested structured questionnaire. Proximate and mineral composition of different varieties of cowpea grains and leaves were determined using standard AOAC methods. More than half of the households interviewed consumed cowpeas in one or more forms. Most cowpea recipes included them as relish being eaten with rice or stiff porridge (ugali), a mixture of dehulled maize and cowpea grains (kande) and cowpea buns (bagia). Improved cowpea varieties had relatively higher fat content ranging from 8 to 11.2% compared to local varieties (5.4%). Local cowpea grains had higher levels of calcium varying between 958.1 and 992.4 mg/kg than dehulled cowpea (360 to 364 mg/kg) and cowpea flour (303 to 311 mg/kg). Zinc ranged from 32.6 to 31.5 mg/kg, while iron content ranged from 27.6 to 28.9 mg/kg. Fresh cowpea leaves had the highest levels of minerals, with calcium varying between 1800.6 and 1809.6 mg/kg, zinc between 36.1 and 36.0 mg/kg and iron between 497.0 and 499.5 mg/kg. The improved cowpea varieties, IT99K-7212-2-1 (23.8 mg/kg) and IT96D-733 (21.2 mg/kg) had the highest iron content. IT99K-7-21-2-2-1 (32.2 mg/kg) and IT97K499-38 (28.3 mg/kg) had the highest zinc concentration. The bagia (cowpea buns), prepared in Dodoma had higher mineral composition, calcium (893mg/kg), zinc (13.7 mg/kg) and iron (16.3 mg/kg) compared to those prepared in Iringa; calcium (32.6mg/kg), zinc (4.96 mg/kg) and iron (5.2 mg/kg). The cowpea daily per capita consumption for the majority of the households surveyed ranged from 41 to 200 gm. The contribution of micro and macro nutrients is significant for both developed lines and local varieties but with leaves having greater mineral content than the grains; hence, promotion of consumption of the leaves alongside the grains would be of nutritional advantage. Additionally, farmers should be encouraged to plant the higher yielding cowpea varieties and preferred local varieties.

Summary Three cultivars of maize (TMV‐1, Katumani and Staha) were grown in the absence and presence of the root hemiparasite Striga asiatica in the field in eastern Tanzania. Infested Katumani and TMV‐1 plants yielded 22% and 25% less grain than uninfested plants; however, the grain yield of Staha was similar in both infested and uninfested plants. Measurements of gas exchange and the quantum yield of photosystem II (ΦPSII) revealed that photosynthesis and stomatal conductance were lower in infested plants of TMV‐1 and Katumani than in control plants, but were not as severely affected in S. asiatica‐infested plants of the cultivar Staha. Chlorophyll fluorescence measurements, particularly the Fv/Fm ratio, showed that S. asiatica predisposed TMV‐1 to greater photoinhibition than control plants after exposure to irradiances of 2000 µmol quanta m−2 s−1 in the field during the day. The lowering of the Fv/Fm ratio resulted from a decrease in Fm rather than in Fo. In contrast to TMV‐1, infested Staha plants were not more photoinhibited than control plants by mid‐afternoon. We suggest that the ability of Staha to yield well in the presence of S. asiatica may result, in part, from the ability of this cultivar to maintain high rates of photosynthesis in the field, thus limiting the extent of photoinhibition.

Ten cultivars of maize, a number of which are high yielding in the presence of the weed Striga asiatica in sub-Saharan Africa, were tested for resistance and tolerance to this root hemiparasite. Observed in rhizotrons, Striga asiatica attached and developed on roots of all cultivars, indicating that none exhibited a true resistance mechanism. However, root exudates from two cultivars, IWD STR Co and Zea diploperennis BC4C2, stimulated relatively little germination of S. asiatica, indicating low xenognosin production, with few parasites attaching and no significant decrease in host height or biomass apparent after 55 days of infec-tion. Cultivar 98 Syn WEC also exhibited no significant differences in height and biomass on infection despite high xenognosin production and a lack of resistance to parasite attachment and development, indicating the operation of a tolerance mechanism. Cross-breeding of these low xenognosin-producing maize cultivars and Striga-tolerant lines could produce cultivars that perform exceptionally well on Striga-infested soils. This study highlights the need for cereal breeders to distinguish between the different mechanisms underpinning host performance in the presence of Striga.

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