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IntroductionBiofortified maize varieties could contribute to the fight against hunger and malnutrition of the increasing human population and help meet the high demand of maize for human consumption, industrial use and feed for animal and poultry. The understanding of the genetic mechanisms conditioning the inheritance of grain yield and other agronomic and quality traits is essential in the development of superior maize genotypes. The main objective of this study was to determine the combining ability for grain yield and other agronomic traits of QPM and non-QPM inbred lines crossed with two QPM and two non-QPM testers.Materials and methodsA total of 130 hybrids were obtained by crossing 10 non-QPM and 23 QPM lines with four elite testers (two QPM and two non-QPM). The 130 single cross hybrids were evaluated at 13 sites in 2018 and 2019.Results and discussionThe results showed significant general combining ability (GCA) for lines and testers as well as significant specific combining ability (SCA) for hybrids for most of the measured traits. Non-additive gene action controlled the inheritance of grain yield while agronomic and quality traits were controlled by additive gene action. QPM lines 11, 14 and 28 and non-QPM tester CML444 showed desirable GCA effects for grain yield, indicating that these lines in combination with tester CML444 should be considered when targeting development of superior maize genotypes with QPM traits.ConclusionsBased on the SCA values, crosses 120, 108, 105, 99, 85, and 41 were identified as the best hybrids across the locations. It is recommended that maize breeding programs targeting the development of high yielding QPM hybrids should exploit QPM lines with high GCA values for heterosis to be realized. In addition, the identified superior hybrids may be further evaluated and consequently promoted for commercial release which could increase incomes of farmers and help to alleviate poverty, hunger and malnutrition in southern Africa and sub-Saharan Africa at large.

Sweetpotato is grown in diverse environments of South Africa by both commercial and subsistence farmers. The aim of the present study was to assess the stability, agronomic performance and palatability of new ARC cultivars bred for the informal market, and to make cultivar recommendations. Eight new cultivars with cream to yelloworange flesh were evaluated in multi-environment trials using a randomised complete block design in six provinces. Data were recorded on root yield, percentage dry mass, palatability and vine vigour. An additive main effects and multiplicative interactions model was employed for data analysis. New cultivars with high potential were Ndou, Letlhabula and Monate, with root yields similar to or slightly lower than the commercial control cultivar Blesbok. Ndou and Monate had vigorous vine growth, high dry mass and good end-user acceptability and offered the best combination of important traits for the informal market. Letlhabula seemed more suitable for the commercial market to lower dry mass. The new improved cultivars will be advantageous, firstly, to farmers as a result of high yield and, secondly, to consumers owing to better palatibility.Keywords: additive main effects and multiplicative interaction, end-user acceptability, genotype by environment interaction, multi-environment trials, sweet potato

Amplified fragment length polymorphism (AFLP) analysis was used to assess the genetic relationships among 46 accessions of sorghum (Sorghum bicolor (L.) Moench) collected from the north-western, western and central parts of Ethiopia as well as South Africa. Six AFLP primer combinations were used for the analysis of DNA fragment amplification. Dice similarity coefficients were calculated and a dendrogram was constructed following the UPGMA method of cluster analysis. A total of 186 fragments were amplified of which 78 (43.10%) were polymorphic. The number of polymorphic fragments amplified per primer combination varied from 9 to 21. Genetic polymorphism present among sorghum accessions was low, as evidenced by the high level of similarity in the AFLP marker profiles of different sorghum accessions. Pair-wise genetic similarity coefficients ranged from 0.87 to 0.99, with an average of 0.92. This indicates low levels of genetic diversity among tested sorghum accessions. The landraces were genetically very similar, while the differences between landraces, the Ethiopian cultivars and the South African cultivars were relatively higher. Genetic similarity within the South African and the Ethiopian cultivars was very high. Almost all accessions clustered according to the geographical origin. Results of this study indicate that the landraces were related, and this most likely results from the exchange of seeds between farmers in the collection regions, although no duplications were found in the material.Key words: Amplified fragment length polymorphism (AFLP), accessions, genetic diversity, sorghum.