Impact of adoption of drought-tolerant maize varieties on total maize production in south Eastern Zimbabwe

Drought is a huge limiting factor in maize production, mainly in the rain-fed agriculture of sub-Saharan Africa. In response to this threat, drought-tolerant (DT) maize varieties have been developed with an aim to ensure maize production under mild drought conditions. We conducted a study to assess the impact of smallholder farmers’ adoption of DT maize varieties on total maize production. Data for the study came from a survey of 200 randomly sampled households in two districts of Chiredzi and Chipinge in southeastern Zimbabwe. The study found that 93% of the households were growing improved maize varieties and that 30% of the sampled households were growing DT maize varieties. Total maize yield was 436.5 kg/ha for a household that did not grow DT maize varieties and 680.5 kg/ha for households that grew DT maize varieties. We control for the endogeneity of the DT adoption variable, by using the control function approach to estimate total maize production in a Cobb–Douglas model. The results show that households that grew DT maize varieties had 617 kg/ha more maize than households that did not grow the DT maize varieties. Given that almost all farmers buy their seeds in the market, a change in varieties to DT maize seeds gives an extra income of US$240/ha or more than nine months of food at no additional cost. This has huge implications in curbing food insecurity and simultaneously saving huge amounts of resources at the household and national levels, which are used to buy extra food during the lean season

Targeting drought-tolerant maize varieties in southern Africa: a geospatial crop modeling approach using big data

Maize is a major staple food crop in southern Africa and stress tolerant improved varieties have the potential to increase productivity, enhance livelihoods and reduce food insecurity. This study uses big data in refining the geospatial targeting of new drought-tolerant (DT) maize varieties in Malawi, Mozambique, Zambia, and Zimbabwe. Results indicate that more than 1.0 million hectares (Mha) of maize in the study countries is exposed to a seasonal drought frequency exceeding 20% while an additional 1.6 Mha experience a drought occurrence of 10–20%. Spatial modeling indicates that new DT varieties could give a yield advantage of 5–40% over the commercial check variety across drought environments while crop management and input costs are kept equal. Results indicate a huge potential for DT maize seed production and marketing in the study countries. The study demonstrates how big data and analytical tools enhance the targeting and uptake of new agricultural technologies for boosting rural livelihoods, agribusiness development and food security in developing countries

Identification of drought, heat and combined drought and heat tolerant donors in maize (Zea mays L.)

Low maize yields and the impacts of climate change on maize production highlight the need to improve yields in eastern and southern Africa. Climate projections suggest higher temperatures within drought-prone areas. Research in model species suggests that tolerance to combined drought and heat stress is genetically distinct from tolerance to either stress alone, but this has not been confirmed in maize. In this study we evaluated 300 maize inbred lines testcrossed to CML539. Experiments were conducted under optimal conditions, reproductive stage drought stress, heat stress and combined drought and heat stress. Lines with high levels of tolerance to drought and combined drought and heat stress were identified. Significant genotype x trial interaction and very large plot residuals were observed; consequently, the repeatability of individual managed stress trials was low. Tolerance to combined drought and heat stress in maize was genetically distinct from tolerance to individual stresses, and tolerance to either stress alone did not confer tolerance to combined drought and heat stress. This finding has major implications for maize drought breeding. Many current drought donors and key inbreds used in widely-grown African hybrids were susceptible to drought stress at elevated temperatures. Several donors tolerant to drought and combined drought and heat stress, notably La Posta Sequia C7-F64-2-6-2-2 and DTPYC9-F46-1-2-1-2, need to be incorporated into maize breeding pipelines

Evidence and perceptions of rainfall change in Malawi: Do maize cultivar choices enhance climate change adaptation in sub-Saharan Africa?

Getting farmers to adopt new cultivars with greater tolerance for coping with climatic extremes and variability is considered as one way of adapting agricultural production to climate change. However, for successful adaptation to occur, an accurate recognition and understanding of the climate signal by key stakeholders (farmers, seed suppliers and agricultural extension services) is an essential precursor. This paper presents evidence based on fieldwork with smallholder maize producers and national seed network stakeholders in Malawi from 2010 to 2011, assessing understandings of rainfall changes and decision-making about maize cultivar choices. Our findings show that preferences for short-season maize cultivars are increasing based on perceptions that season lengths are growing shorter due to climate change and the assumption that growing shorter-season crops represents a good strategy for adapting to drought. However, meteorological records for the two study areas present no evidence for shortening seasons (or any significant change to rainfall characteristics), suggesting that short-season cultivars may not be the most suitable adaptation option for these areas. This demonstrates the dangers of oversimplified climate information in guiding changes in farmer decision-making about cultivar choice

Selection for drought tolerance in two tropical maize populations

Drought is a major factor limiting maize (Zea mays L.) yield in much of the world. The need to breed maize cultivars with improved drought tolerance is apparent. This study compared two maize populations, ZM601 and ZM607 for drought tolerance during flowering, the most drought-vulnerable period for the maize plant. Cultivar ZM601 had been improved through recurrent selection for two cycles for drought tolerance at flowering plus one cycle under rainfed ("random") drought stress, while ZM607 had been improved for high yield for three cycles under favorable growing conditions. A set of 143 random S1 lines from ZM601 was compared with 94 from ZM607 at two drought stressed and one well-watered environment for yield and secondary traits. The results did not show much difference in drought tolerance between ZM601 and ZM607. Differences between population means for grain yield, anthesis-silking interval (ASI), and number of ears per plant (EPP) were small. Frequency distributions for ASI and leaf rolling were different for the two populations. However, ZM601 had more lines with shorter ASI and less leaf rolling as compared to ZM607. Broad sense heritability of ASI was larger,while that of grain yield smaller, and the correlation between ASI and grain yield was larger at drought-stressed compared to unstressed sites. Absence of large differences in grain yield between ZM601 and ZM607 lines was attributed to little effect of the selection completed prior to this evaluation, to genetic similarities of the two populations prior to selection, and to large genotype-by-environment interaction between Mexico, where drought screening was conducted, and Zimbabwe, where this evaluation was conducted. Results confirmed the value of ASI (measured at drought-stressed sites) as an indirect selection criterion for improving grain yield under drought stress conditions. Key Words: Anthesis, heritability, recurrent selection, secondary traits, Zea mays, Zimbabwe Résumé La secheresse est un facteur majeur limitant la production du maïs (Zea mays) dans le monde. La nécessité de croiser les variétés de maïs avec des variétés résistantes à la sécheresse est apparente. Cette étude a comparé deux populations, ZM 601 et ZM 607 pour la tolérance à la sécheresse pendant la période de floraison, la periode la plus vulnérable pour le maïs. La variété ZM 601 a été amélioré à travers la sélection recurrente pour deux cycles pour la tolérance à la sécheresse à la floraison en plus d'un cycle pendant la période pluvieuse (au hazard) stress de sécheresse, alors que ZM 607 a été amélioré pour rendement élévé pour trois cycles dans des conditions favorables. Un ensemble de 143 races S pris au hazard de ZM 601 était comparé avec 94 races de ZM 607 à stress deux sécheresses et un environnement bien arosé pour le rendement et les traits sécondaire. Les résultats n'a pas montré de différence significative dans la tolérance à la sécheresse entre ZM 601 et 607. Les différences entre moyennes des populations concernant le rendement en grains, l'interval d'anthesis-silking, et le nombre d'oeillet par plante était petit. La distribution de frequence pour ASI et roulage des feuilles était differente pour les deux populations. Cependant, ZM 601 avait plus des lignes avec des coûts ASI et moins de roulage des feuilles comparé au ZM 607. L'héritabilité de ASI était très large, celle de rendement en grains faible, et la corrélation entre ASI et le rendement en grains était élévée pour les sites stressés par la sécheresse comparés aux sites non stressés. L'absence des différences larges dans le rendement en grains entre les races ZM 601 et 607 était attribué au faible effet de la sélection faite avant l'évaluation, aux similarités génétiques de deux populations avant la sélection, et à la grande intéraction génotype-environnement entre le Mexique ou dépistage a été conduit et le Zimbabwe ou l'évaluation a été conduite. Les résultats ont confirmé la valeur de ASI mesurée comme un critère de sélection indirect pour l'amélioration dans les conditions de stress de la sécheresse. Mots Clés: Anthesis, heritabilité, sélection recurrente, traits secondaires, Zea mays, Zimbabwe (Af Crop Sci J 2003 Vol 11 No 3 pp151-162

Selection for Drought Tolerance in Two Tropical Maize Populations

Drought is a major factor limiting maize ( Zea mays L.) yield in much of the world. The need to breed maize cultivars with improved drought tolerance is apparent. This study compared two maize populations, ZM601 and ZM607 for drought tolerance during flowering, the most drought-vulnerable period for the maize plant. Cultivar ZM601 had been improved through recurrent selection for two cycles for drought tolerance at flowering plus one cycle under rainfed ("random") drought stress, while ZM607 had been improved for high yield for three cycles under favorable growing conditions. A set of 143 random S1 lines from ZM601 was compared with 94 from ZM607 at two drought stressed and one well-watered environment for yield and secondary traits. The results did not show much difference in drought tolerance between ZM601 and ZM607. Differences between population means for grain yield, anthesis-silking interval (ASI), and number of ears per plant (EPP) were small. Frequency distributions for ASI and leaf rolling were different for the two populations. However, ZM601 had more lines with shorter ASI and less leaf rolling as compared to ZM607. Broad sense heritability of ASI was larger,while that of grain yield smaller, and the correlation between ASI and grain yield was larger at drought-stressed compared to unstressed sites. Absence of large differences in grain yield between ZM601 and ZM607 lines was attributed to little effect of the selection completed prior to this evaluation, to genetic similarities of the two populations prior to selection, and to large genotype-by-environment interaction between Mexico, where drought screening was conducted, and Zimbabwe, where this evaluation was conducted. Results confirmed the value of ASI (measured at drought-stressed sites) as an indirect selection criterion for improving grain yield under drought stress conditions.La secheresse est un facteur majeur limitant la production du maïs ( Zea mays ) dans le monde. La nécessité de croiser les variétés de maïs avec des variétés résistantes à la sécheresse est apparente. Cette étude a comparé deux populations, ZM 601 et ZM 607 pour la tolérance à la sécheresse pendant la période de floraison, la periode la plus vulnérable pour le maïs. La variété ZM 601 a été amélioré à travers la sélection recurrente pour deux cycles pour la tolérance à la sécheresse à la floraison en plus d'un cycle pendant la période pluvieuse (au hazard) stress de sécheresse, alors que ZM 607 a été amélioré pour rendement élévé pour trois cycles dans des conditions favorables. Un ensemble de 143 races S pris au hazard de ZM 601 était comparé avec 94 races de ZM 607 à stress deux sécheresses et un environnement bien arosé pour le rendement et les traits sécondaire. Les résultats n'a pas montré de différence significative dans la tolérance à la sécheresse entre ZM 601 et 607. Les différences entre moyennes des populations concernant le rendement en grains, l'interval d'anthesis-silking, et le nombre d'oeillet par plante était petit. La distribution de frequence pour ASI et roulage des feuilles était differente pour les deux populations. Cependant, ZM 601 avait plus des lignes avec des coûts ASI et moins de roulage des feuilles comparé au ZM 607. L'héritabilité de ASI était très large, celle de rendement en grains faible, et la corrélation entre ASI et le rendement en grains était élévée pour les sites stressés par la sécheresse comparés aux sites non stressés. L'absence des différences larges dans le rendement en grains entre les races ZM 601 et 607 était attribué au faible effet de la sélection faite avant l'évaluation, aux similarités génétiques de deux populations avant la sélection, et à la grande intéraction génotype-environnement entre le Mexique ou dépistage a été conduit et le Zimbabwe ou l'évaluation a été conduite. Les résultats ont confirmé la valeur de ASI mesurée comme un critère de sélection indirect pour l'amélioration dans les conditions de stress de la sécheresse