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.

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Climate change and variability is already reducing agricultural productivity and opportunities for employment, pushing up food prices and affecting food availability and production of formerly adapted crop types. Such is the case in cotton production in Zimbabwe, where it was the only viable commercial crop in marginal areas. As a form of adaptation, there is need for African farmers to have a range of agricultural techniques as coping strategies and tactics to enable sustainable production of crops and deal with extreme events. Such techniques include water conservation and introduction of new adapted crop genetics to cope with the new environment. The emerging trends in climate change will force farmers to adopt new crops and varieties and forms of agricultural production technologies. The objective of this study is to determine the contribution of combining in-field water harvesting and early maturing cotton varieties in curbing drought in cotton in semiarid Zimbabwe. The results show that both water harvesting in form of planting basins significantly (P <0.05) increased boll number and branch number of cotton across all varieties. The varieties M577 and M567 out-performed the conventional varieties in early growth, branch number, and boll number. Tied contour ridges gave a significantly (P <0.05) higher moisture content in 0–5 cm and the 6–10 cm depth compared to conventional tillage. The new varieties displayed early phenological development. Despite the existence of rainfall gaps, the in-field water harvesting techniques captured enough moisture and prevented moisture losses through runoff which resulted successful flowering and fruiting in the short varieties compared to conventional tillage on conventional varieties. In this regard, water harvesting and early maturing varieties offer considerable hope for increasing crop production in arid and semiarid areas of Zimbabwe.

Sesame (Sesamum indicum L.) production is lucrative to resource poor farmers in marginalised areas of Zimbabwe, although most farmers have reportedly been failing to derive maximum economic benefits from sesame production due to poor productivity. Low productivity has been attributed to several factors including challenges of weed control due to absence of registered herbicides for use in sesame in Zimbabwe. Laboratory enzyme assays were conducted using different sorghum aqueous leaf and stem extract concentrations at 0, 2.5, 5.0, 7.5, and 10.0% wv−1 to determine the effect of sorghum aqueous extracts on plant defense enzymes polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia lyase (PAL) in sesame and selected weeds. Greenhouse experiments were conducted to assess the effect of sorgaab or sorgaab-Agil postemergence sprays on the seedling growth and physiology of sesame and weeds. The exposure of sesame, black jack, and goose grass to sorghum aqueous extracts caused a significant (p<0.05) concentration-dependent increase on the activity of antioxidant enzymes PAL, POD, and POD. Similarly, postemergence sprays of sole sorgaab, herbicide, and sorgaab-herbicide combination significantly (p<0.05) increased sesame and black jack seedling growth, chlorophyll content, and fluorescence but not of goose grass. From this study, it could be concluded that the allelochemicals in sorghum aqueous extracts were not effective at inhibiting the growth and physiological processes of sesame and the weeds. Therefore, resource-poor farmers cannot rely on sorgaab to control weeds in sesame but there is a need to integrate weed control options to form an effective integrated weed management program.

Striga asiatica (witchweed) is a parasitic weed that is a serious threat to maize (Zea mays L.) production in semi-arid environments in Africa. A pot experiment was conducted under glasshouse conditions to screen nine maize cultivars for their tolerance / tolerance to Striga infection at the University of Zimbabwe in the 2012 / 2013 rainfall season. Striga did not significantly (P > 0.05) reduce the final maize height of the maize cultivars, with the exception of three maize cultivars, namely, PHB3253, PHB30G19 and PHB30B50. Furthermore Striga did not significantly (P > 0.05) reduce the stem biomass, leaf biomass and cob biomass of all the maize cultivars evaluated. Generally the maize cultivars had significantly (P < 0.05) higher root / shoot ratios in the Striga infected plants compared to the uninfected plants. It was concluded that all the maize genotypes used in this study could possibly be tolerant to S. asiatica.