Core Ideas These selected varieties were compared with the best commercial check varieties on‐farm across 94 locations in eastern and southern Africa in a randomized complete block design with three replications for two seasons. The new drought tolerant hybrids showed a yield advantage over the commercial check varieties both in the early and medium‐late maturing categories by 4 to 19%. Among the CIMMYT hybrids, CZH0616 showed wide adaptation under stress and non‐stress conditions, making it an ideal genotype for smallholders’ farmers. Under farmers’ fields CZH0616, CZH0837, CZH0935, and CZH0928 were high yielding and stable across locations in eight countries that represent major maize production environments in eastern and southern Africa. Maize (Zea mays L.) is the most important staple food in eastern and southern Africa (ESA) with human maize consumption averaging 91 kg capita−1 yr−1. Current maize yield averages 1.2 t ha−1 and is barely sufficient for the region’s requirements due to drought and low N stresses. The objective of this study was to compare new drought tolerant (DT) maize hybrids and open pollinated varieties (OPVs) against the best commercial varieties in ESA under farmer management conditions and to validate on‐station results. Maize varieties were simultaneously selected on‐station in four types of environments across 44 locations in ESA during the 2008/2009 and 2009/2010 seasons. During the 2010/2011 and 2011/2012 seasons, 20 promising DT maize hybrids and OPVs were selected from the on‐station based on their mean grain yield and stability. These selected varieties were compared with the best commercial check varieties on‐farm across 80 locations in ESA in a randomized complete block design for two seasons. The genotype + genotype × environment comparison biplot showed variety CZH0616 together with other new DT hybrids to be stable and high yielding across 44 locations on‐station in the ESA region compared to the commonly grown checks such as SC513. The new DT hybrids showed a yield advantage over the commercial check varieties both in the early and medium‐late maturing categories by 4 to 19%, and the gains were bigger under stress conditions. Under farmers’ fields CZH0616, CZH0837, CZH0935, and CZH0928 were high yielding and stable across locations.

Early‐maturing maize (Zea mays L.) genotypes yield 15 to 30% less than late‐maturing genotypes. One strategy for improving grain yield in the early‐maturing group involves assessment of grain‐filling traits as secondary traits for selection for high grain yield. In this study, we investigated the possibility of using grain‐filling rate and duration for improving grain yield in early‐maturing tropical maize. Forty‐four hybrids generated using North Carolina design II were evaluated at CIMMYT‐Zimbabwe during the 2011/2012 season under irrigated and nonirrigated environments. Although grain‐filling rate and effective grain‐filling duration were negatively correlated, several hybrids were distinctly above the trend line. The earliest‐maturing hybrid took 127 d to reach physiological maturity and produced grain yields comparable to those of the medium‐maturing genotypes (7 t ha−1). It had a high grain‐filling rate of 2.40 g per plant d−1 (18% higher than those of the low‐yielding hybrids) and a relatively longer effective grain‐filling duration. Grain‐filling rate and effective grain‐filling duration had high coefficients of genetic determination, positive correlations with grain yield, low error terms, and low genotype × environment interactions, making them appropriate selection traits for improved grain yield. The study shows that it is possible to develop high‐yielding early‐ to medium‐maturing maize hybrids based on favorable combining ability values for grain‐filling rate and duration.

Striga asiatica (L.) Kuntze, an obligate hemiparasite, can cause grain yield loss of 20 to 80% in cereal crops such as maize (Zea mays L.). In Sub‐Saharan Africa, maize breeding programs have focused on productivity of normal endosperm maize under Striga infestation while neglecting quality protein maize (QPM). This study aimed at determining levels of resistance or tolerance of eight new QPM genotypes and four non‐QPM checks to Striga asiatica in the field, pot, and agar gel experiments. Under field conditions, genotypes were evaluated in three different Striga‐endemic locations during the 2014–2015 and 2015–2016 cropping seasons using a four‐by‐three α‐lattice design with three replications. In the pot experiment, genotypes were arranged in 12 × 2 factorial treatments in a six‐by‐four α‐lattice design replicated four times. In the agar gel experiment, genotypes were arranged in a randomized complete block design replicated four times. In the field experiment, genotype × environment interaction was significant (p < 0.001) for grain yield, and MQ623, SC643, SC527, and SC535 were high yielding and more stable than non‐QPM genotypes. In the pot experiment, these genotypes also exhibited desirable Striga tolerance, whereas variation was significant (p < 0.05) for Striga treatments and genotype main effects, as well as for Striga × genotype interaction for root biomass and root/shoot biomass ratio. Five QPM genotypes (MH1416, MQ623, SC643, SC527, and SC535) produced higher and more stable grain yields than most of the non‐QPM checks in Striga‐infested fields. These genotypes provided alternative QPM sources that can perform relatively well in Striga‐endemic areas.

Sweetpotato (Ipomoea batatas) is an important root crop in Uganda, where yield potential and quality attributes have not been fully exploited due to limited breeding efforts and poor knowledge on the inheritance of some of its agronomic traits. A study was carried out at Makerere University to phenotypically characterise selected sweetpotato cultivars with special reference to sweet potato virus disease (SPVD) resistance, growth habit, flowering and seed set ability, tuber yield and shape, tuber skin and flesh colour, dry matter, starch, sugar and β-carotene content. Twenty cultivars were selected for use in the assessment of their breeding potential and for improvement of yield and quality attributes. Cultivar Munyeera displayed the highest level of SPVD resistance followed by New Kawogo and Polyster as exhibited by relative area under disease progress curves following natural field infection and graft inoculation with SPVD causing viruses, Sweet potato chlorotic stunt virus and Sweet potato feathery mottle virus. Flowering ability was low in some cultivars and a few did not flower at all. Some cultivars e.g. Munyeera, New Kawogo, Silk and Sowola which showed high flowering ability failed to fertilise and set seed when crossed to specific cultivars. Preliminary genetic analysis for yield and quality following crossing elite 7 female and 6 male cultivars in a North Carolina 2 mating design showed wide genetic variability in the F 1 s for the important traits, and heterosis was observed for some traits such as tuber size and number of tubers per plant. Up to five genes may be involved in β-carotene synthesis and probably in combination with other genes in different genetic backgrounds that can modify flesh colour from white to purple. The results demonstrate the possibility to improve sweetpotato for yield and quality using the available germplasm.