Sorghum In sub-Saharan Africa Research Articles

A review of the adaptive capacity of sweet sorghum to improve food security and poverty alleviation in sub-Saharan Africa

• Sweet sorghum can address socioeconomic challenges for African smallholder farmers. • A neglected multiuse crop, it is utilised for food, fuel, fibre, and fodder. • This grain crop can grow under water limited- and low nutrient input conditions. • Adoption of sweet sorghum in smallholder farming requires investment in research. Current challenges facing smallholder farmers in sub-Saharan Africa (SSA) require holistic adoption of crops that have diverse socioeconomic and agronomic significance. Sweet sorghum, an underutilised grain crop, has such potential, especially for bioethanol production, due to its adaptation to harsh conditions. Despite being native to SSA, its neglect and underuse is a concern given its wide potential to improve socioeconomic conditions of farmers in this region. This review highlights sweet sorghum's potential by discussing its adaptive capability against major production constraints such as water availability, soil nutrition, plant population, planting date, and harvest time. The review highlights sweet sorghum as a crop that maximises its growth and development under water stress conditions due to its high-water use efficiency. Furthermore, sweet sorghum can be cultivated under marginal soils compared to its biofuel counterparts (e.g., maize, sugarcane, and sugar beet) and can still be high yielding (grain) at high plant densities, with early planting dates also resulting in high yields. These attributes are significant in smallholder farming systems due to their susceptibility to socioeconomical and agronomic challenges. In addition, it was identified that there is lack of research relating to pests and diseases that plague sweet sorghum, with some measures and recommendations being based on grain sorghum. Therefore, the need for research and development on sweet sorghum in SSA may not only intensify its benefits to farmers but can also improve efficient cultivation under local environmental conditions.

The Potential of Ethanol Production from Sweet Sorghum in Sub-Saharan Africa as Affected by Variety and Sowing Time

Renewable bio-energy is receiving worldwide importance in view of depleting fossil energy. Research works on sorghum as bio-fuel crop in sub-Saharan Africa are meager. The study aimed to investigate the potential of sweet sorghum for ethanol production from stem-juice. The experiment was conducted in Sudan, Khartoum State, during 2016-2017. Forty local and exotic sweet sorghum varieties arranged in RCB Design were investigated under irrigated conditions across three sowing times. Yields of cane, juice, sugar, ethanol and related attributes were studied. Highly significant differences (P=.01) were detected among varieties and interaction with sowing time. Ethanol yield potentials for some varieties were comparable to those reported in India and USA (1162-1416 L ha-1). High brix values (20-22%) and cane yields (45-51 ha-1) were encountered. Juice yield was low (3673-13743 L ha-1) probably due to reduced milling efficiency. The exotic materials performed better than the local ones in theoretical ethanol productivity and related attributes other than cane yield. Eight exotic and five local varieties were recommended for ethanol production. None of the Ankolib materials appeared to have notable potential for ethanol production. Interaction of sowing time with variety has great impact on ethanol yield implying the importance of variety option for different sowing times. It was concluded that the study furnished basic data needed for assessing the economic feasibility of ethanol production from irrigated sweet sorghum in sub-Saharan Africa-Sudan.

Assortments of Digestive Enzymes Induced in First Instar Larvae of Busseola fusca Feeding on Different Plants.

The stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is an important pest of maize and sorghum in sub-Saharan Africa. This insect has oligophagous feeding habits, feeding mostly on maize and sorghum with a narrow range of wild Poaceous plant species. We hypothesised that first instar B. fusca larvae, the critical stage for successful establishment on a host plant, can establish and then grow on a particular plant as a result of induction of a complement of digestive enzymes that mediates host acceptance at first instars. A fast semi-quantitative analysis of potentially digestive enzymatic activities present in the first larvae previously fed for 4 days on leaves of host and non-host plants was performed using the API-ZYM kit system able to detect a multiplex of enzyme activities. Regardless of the plant species, the larvae exhibited higher activities of the carbohydrate metabolising enzymes than of aminopeptidases and proteases. In addition, highest activities of carbohydrates degrading enzymes were exhibited by larvae that consumed leaves of the most preferred plant species of B. fusca. Conversely, esterases were only detected in neonate larvae that consumed leaves of the less preferred and non-host plants. No alkaline phosphatase and lipase activities were detected. The significance of these results was discussed in terms of food requirements of first instar larvae when settling on a plant.

Influence of plant silicon in Busseola fusca (Lepidoptera: Noctuidae) larvae - Poaceae interactions.

The noctuid stem borer Busseola fusca is an important pest of maize and sorghum in Sub-Saharan Africa. The presence of this species occurred mostly on cultivated than on wild habitats. Busseola fusca is oligophagous having a narrow range of a wild grass species. This might be due, in part, to differences in silicon (Si) content in plant tissues between cultivated and wild grasses. In the present study, we have tested this hypothesis by studying the survival and the relative growth rate (RGR) expressed as daily weight gains of B. fusca larvae on maize and six wild host plants, mostly present in the natural habitat where B. fusca occurred, and correlated with their Si contents. Survival and RGR of B. fusca larvae were considerably higher on maize and wild sorghum than on the other grass species, and they were negatively related to plant Si content. This was corroborated with results on RGR from artificial diets amended with increasing levels of Si. In addition, if Si was added to maize growing substrate B. fusca larval growth was significantly reduced confirming the involvement of Si in B. fusca larvae - Poaceae interactions. The results provide insight into the possible mechanisms of oligophagy of B. fusca and provide a correlative support for a physical role of plant endogenous Si in impeding feeding of B. fusca larvae.

Ecology of the African Maize Stalk Borer, Busseola fusca (Lepidoptera: Noctuidae) with Special Reference to Insect-Plant Interactions.

Busseola fusca (Lepidoptera: Noctuidae) is an important pest of maize and sorghum in sub-Saharan Africa. One century after its first description by Fuller in 1901, inaccurate information based on earlier reports are still propagated on its distribution (e.g., absent from the lower altitudes in East Africa) and host plant range (e.g., feeding on a large range of wild grass species). This review provides updated information on the biology, distribution and genetics of B. fusca with emphasis on insect-plant interactions. Related to this, new avenues of stem borer management are proposed.

Novel source of sorghum tolerance to the African stem borer, Busseola fusca

Sorghum (Sorghum bicolor) is an important cereal food crop in semi-arid tropics, but its productivity is curtailed mainly by insect pests and diseases. The African stem borer,Busseola fusca Fuller (Lepidopteran: Noctuidae), is among the most injurious pests of sorghum in sub-Saharan Africa and is responsible for >15% sorghum grain yield losses. Sorghum from India with records of stem borer invasion could provide supplementary and novel resources of tolerance to this pest. Utilization of tolerant varieties in combination with other methods of control is likely to offer a sustainable strategy for B. fusca management in sorghum production. The objective of this study was to evaluate several local and exotic sorghum genotypes for tolerance to B. fusca. Genotype Swarna from India which is known to be susceptible to Chilo partellus was used as a susceptible check. There is limited information regarding tolerant/resistant sorghum to B. fusca. Seven commercial cultivars and 20 introductions from India were evaluated for B. fusca tolerance at Kabete, in central province of Kenya, during long and short rainy seasons in 2010. Selection index were based on leaf damage, dead hearts, exit holes and stem tunneling. The following genotypes named ICSA 467, ICSA 473, MACIA and ICSB 464 were found to be the most tolerant to B. fusca. These tolerant genotypes, can be used as novel sources of tolerance, and could be introgressed into the local common varieties since they are well adapted to the local environment. Key words: Busseola fusca, Sorghum bicolor, resistance, tolerance, Kenya.

Niger-wide assessment of in situ sorghum genetic diversity with microsatellite markers

Understanding the geographical, environmental and social patterns of genetic diversity on different spatial scales is key to the sustainable in situ management of genetic resources. However, few surveys have been conducted on crop genetic diversity using exhaustive in situ germplasm collections on a country scale and such data are missing for sorghum in sub-Saharan Africa, its centre of origin. We report here a genetic analysis of 484 sorghum varieties collected in 79 villages evenly distributed across Niger, using 28 microsatellite markers. We found a high level of SSR diversity in Niger. Diversity varied between eastern and western Niger, and allelic richness was lower in the eastern part of the country. Genetic differentiation between botanical races was the first structuring factor (Fst = 0.19), but the geographical distribution and the ethnic group to which farmers belonged were also significantly associated with genetic diversity partitioning. Gene pools are poorly differentiated among climatic zones. The geographical situation of Niger, where typical western African (guinea), central African (caudatum) and eastern Sahelian African (durra) sorghum races converge, explained the high observed genetic diversity and was responsible for the interactions among the ethnic, geographical and botanical structure revealed in our study. After correcting for the structure of botanical races, spatial correlation of genetic diversity was still detected within 100 km, which may hint at limited seed exchanges between farmers. Sorghum domestication history, in relation to the spatial organisation of human societies, is therefore key information for sorghum in situ conservation programs in sub-Saharan Africa.