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Cassava (<i>Manihot esculenta</i> Cranzt) is an important food security crop for poor rural communities particularly in Africa. However, little is known about variability of critical root nutritional and quality traits of African cassava germplasm. Cassava roots contain low levels of important micronutrients and its quality can be influenced by the levels of cyanogenic glucosides. Roots from fourteen accessions comprising Kenyan local landraces and improved clones were screened for their nutritional traits including the contents of cyanogenic glycosides, protein and the micro nutrients iron and zinc. Trait stability and the effects of the environment on the expression of the nutritional traits were evaluated using various genotype (G) by environment (E) interaction study models. There were significant (p ≤ 0.05) differences for all the nutritional traits in the three test sites of Baringo, Kericho and Nakuru in Kenya. Contents of cyanogenic glycosides in both roots and leaves, total root proteins, root iron and zinc ranged from 31.8 ppm to 90.8 ppm; 20.8 ppm to 154.4 ppm; 1.15% to 3.47%; 17.81 ppm to 59.69 ppm and 39.39 ppm to 118 ppm, respectively. The sites were also significantly (p ≤ 0.05) different from each other with the highest cyanogenic content in leaves and roots expressed at the Nakuru site. Regression analysis was used to assess genotype response to environments. Regression coefficients (b_i) obtained ranged from 0.13 to 2.23 for all traits combined indicating wide variability in quality trait among the test germplasm. Analysis for sensitivity to environmental change <i>SE_i² </i>revealed that cassava genotypes differed in their level of sensitivity. The root cyanide trait had the highest mean <i>SE_i²</i> which indicated that it was the least stable quality trait in the cassava germplasm. This implies that the same cassava genotypes will give food of different quality depending on growing environment. The observed values for protein and mineral contents suggest the potential for improving the nutritive value of local cassava germplasm

Sweetpotato (Ipomoea batatas L.) plays a significant role in food and nutritional security in Kenya. However, production is constrained by: (i) Sweet potato virus diseases (SPVD) and weevils (Cylas spp.); (ii) shortage of clean planting materials; (iii) lack of suitable varieties for high altitude agroecosystems; (iv) poor postharvest handling; and (v) poor market access. In order to enhance the role of sweetpotato for food security, a breeding programme was initiated at Kenya Agricultural Research Institute (KARI)-Njoro with the objective of developing varieties with desirable genetic and agronomic attributes which include high yields, resistance to SPVD and weevils, improved food quality, and market acceptability for high altitudes. Thirty-six potential parents were identified in initial screening of 440 accessions from landraces, improved and imported accessions. Hand and polycrossing process was performed to generate a breeding nursery of 2200 seedlings. Forty-three entries were identified for advancement to preliminary yield evaluation. Out of these, ten entries were advanced to multi-location testing in five sites under the oversight of the National Performance Trials committee. The multi-location trials were conducted on a randomized complete block design with three replicates at Kabianga (LH1-1745 m above sea level (masl)), Ravine (LH3-2167 masl), KARI-Lanet (LH4-1920 masl), Lare (LH4-1900 masl) and KARI-Njoro (LH3-2166 masl). The sites were in the Central Rift Valley region. Participatory variety evaluation by researchers, extensionists, plant regulators and farmers was adopted in all the trials. Standard operating procedures and analyses as prescribed by the International Potato Center and the Kenya Plant Health Inspectorate Service were used to evaluate: (i) yields; (ii) viruses and weevils; (iii) dry matter content; (iv) beta-carotene; and (v) acceptability by consumers. The main result of the trials' evaluation was the release of five new varieties - three orange-fleshed Kenspot-4, Kenspot-5 and Kenspot-3; yellow-fleshed Kenspot-1; and white-fleshed Kenspot-2. The improved varieties have better average root yields (20 t/ha) compared with the national average root yields (12.8 t/ha); moderate field resistance to SPVD and weevils; moderate dry matter content (26-32%); and consumer acceptability. The orange-fleshed sweetpotato varieties will provide consumers and farmers with moderate provitamin A contents which will alleviate vitamin A deficiency in Kenya. Through participatory breeding, production capacity of sweetpotato at high altitudes has increased providing food security, farmer adoption knowledge has improved, market strategies have been determined and food quality has improved. Variety recommendation is agroecological specific.

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