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Biofortification of staple food stands as one of the most reliable methods of alleviating vitamin A deficiency (VAD). Evidence suggests that introducing provitamin A carotenoid (pVAC) cassava into the diets of preschool and primary school children in East Africa has led to improvements in their retinol levels. Notably, Kenya and Uganda have initiated cassava biofortification programs in the region. These efforts involve the assembly and characterization of pVAC cassava germplasm, alongside the development of essential tools such as genomic prediction (GP) models and molecular markers for accelerating genetic gains in the biofortification programs. However, several challenges have emerged, including a negative correlation between carotenoid content and dry matter content in cassava roots, diseases, the absence of affordable high‐throughput phenotyping methods, poor cassava flowering, poor pollen viability, low capacity in bioinformatics analyses, degradation of carotenoids during processing, and inadequate germplasm conservation facilities. To address these hurdles, cassava breeding programs in the region require enhanced infrastructure and human capacity to optimize efficiency in cassava biofortification with pVACs. [ABSTRACT FROM AUTHOR]

The African stem borer, Busseola fusca Fuller, is one of the most devastating insect pests of maize in tropical environments. Understanding of combining ability and heterosis may be useful for designing insect resistant hybrids. However, among the adapted maize inbred lines used in this study, the combining ability and heterotic orientation for grain yield and borer resistance is not known. The objective of this study was to determine combining ability and heterotic orientation of maize inbred lines under B. fusca infestation. Sixty six inbred lines were crossed to two single cross testers from CIMMYT in accordance with the line × tester mating scheme. The 132 three-way testcross hybrids and four checks were evaluated at two locations in Kenya. Data were analysed using PROC GLM of SAS statistical package. The genotypes × environment interactions were significant, therefore the two test locations were considered as ideal environments for genotype comparison. General combining ability effects were significant for B. fusca stem borer resistance and grain yield, suggesting a preponderance of the additive gene effects for borer resistance traits. Specific combining ability effects were significant for B. fusca borer resistance traits and grain yield indicating that non-additive effects were also influential. Based on grain yield heterosis data at Embu, 22 lines were allocated to group A, 18 to group B and 8 to group AB, while at Kakamega, 24 lines were oriented to group A, 13 to group B and 9 to group AB, whilst the remainder could not be classified. Based on the SCA effects, at Embu, 20 lines revealed positive SCA effects with both testers and were considered to be AB-oriented; while 12 and 7 lines were oriented towards A and B, respectively. A similar trend was observed at Kakamega but only one line exhibited positive SCA effects for grain yield with both testers, while the remainder had negative SCA effects. The identified lines and heterotic groups may be used by maize programmes that emphasize stem borer resistance in hybrids. [ABSTRACT FROM AUTHOR]

Stem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests of maize causing grain yield losses. Recurrent selection studies for stem borer resistance in maize are limited. However, maize populations carrying resistance genes to these stem borers have not been exploited fully in breeding programmes. The objective of the study was to separately improve resistance to B. fusca and C. partellus stem borers for two maize populations CML395/MBR C5 Bc and CML444/MBR/MDR C3Bc and therefore grain yield after two cycles of S1 progeny recurrent selection. Cycle 0 and the advanced generations (cycle 1-susceptible, cycle 1-resistant and cycle 2-resistant) were evaluated at three locations in Kenya using a 35 × 12 α-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from 0 to 69 % for both populations after two cycles of selection. In the two populations, each cycle of selection for borer resistance improved grain yield by 0.5-0.8 t ha. Actual net gains in grain yield with reference to cycle 0 were 43 % for population CML395/MBRC5 Bc under B. fusca infestation and 70 % under C. partellus infestation. For population CML444/MBR/MDR C3Bc, the actual net gains in grain yield were 25 % under B. fusca infestation and 36 % under C. partellus infestation. The reductions in the injurious effects attributable to leaf feeding damage, cumulative stem tunneling and number of exit holes contributed towards the 43 and 70 % net genetic gain in grain yield under B. fusca and C. partellus infestation respectively, for both populations. Broad sense heritability (H) for grain yield ranged from 2 to 98 % in both maize populations. The study showed that two cycles of S1 progeny recurrent selection was effective in accumulating favourable alleles for B. fusca and C. partellus stem borer resistance. [ABSTRACT FROM AUTHOR]