Gum Arabic Production and Population Status of Senegalia senegal (L.) Britton in Dryland Forests in South Omo Zone, Ethiopia

Senegalia senegal (L.) Britton is a multi-purpose dryland tree species that produces gum arabic, a commercially valuable product. However, this resource is underused in Ethiopian dryland areas. The aim of this study was to evaluate the population status and potential gum yield of S. senegal growing in natural stands in South Omo Zone, Ethiopia. Forty-five sample plots, each measuring 20 × 20 m, were established at 500 m intervals along transects, with 1 m2 subplots located within the main plots to determine regeneration. S. senegal trees with a diameter at breast height of between 2 and 12 cm were most prevalent. Forty-two tree species were associated with S. senegal, of which 16 were gum- and resin-producing species. S. senegal was positively associated with Vachellia tortilis, Senegalia mellifera, Vachellia nilotica, Commiphora edulis, and Dobera glabra. Senegalia senegal comprised approximately 35% of regenerating trees. The maximum gum arabic yield obtained was 3948 g tree−1. Linear models of dendrometric variables indicated that gum arabic yield is better predicted by tree diameter than by height. Despite the limitations of this pioneer survey, the population status and yield potential suggest that gum arabic could be sustainably produced and commercialized in natural stands of S. senegal in the studied dryland areas, providing local communities with supplementary seasonal incomes.

Drought resistance and gum yield performances in a Senegalia senegal (L.) Britton progeny trial in Senegal

With continued global change as a result of land use changes, invasive species and changing climatic patterns, it is becoming increasingly important to understand the adaptability of Senegalia senegal provenances to maximize resilience in managed and natural populations of this species. The objective of this study is to investigate Senegalia senegal genotypic differences in water use efficiency (WUE) measured by stable 13C isotope composition in foliage according to their ploidy levels. Secondary objectives are to discuss inherent adaptive variation related to soil pH, survival, growth indexes, gum arabic yield and WUE within provenance in the climate change context. A Senegalia senegal progeny trial, in Dahra, Senegal was used in this study: 443 adult trees consisting of 60 families nested within 4 provenances were assessed in this study. Results showed significant differences in gum yield among provenances (P = 0.0002) and families (P < 0.0001). Diamenar and Ngane provenances showed overall similar annual gum yield despite a lower tree survival rate of Ngane than Diamenar. Growth traits, especially stem volume index and crown area index were larger on Ngane provenance, which also displayed significantly higher foliar WUE and lower leaf area index (LAI) than the other provenances. WUE was positively correlated with gum yield (P = 0.0302), but the coefficient of determination was only 2%. Foliar δ13C varied significantly (P < 0.0001) between diploids (− 27.91‰) and polyploids (− 27.12‰). However, within each provenance no significant difference was found. Only 15% of isotope compositions could be explained by ploidy level variation. Differences found in growth and gum yield may be attributed to genotype-specific variation. However, a significant correlation between soil pH and tree survival rate was found (P = 0.0051; r = 0.60). This study confirmed a possible improvement of the gum arabic sector through genotype based selection. Ngane and Diamenar seem to be more profitable to grow in Dahra than the other tested provenances. Future research should investigate the effect of soil pH, other soil physical and chemical properties, and management activities to improve site quality on tree survival and gum yields among provenances. Further, more research is needed to clarify inherent traits underlying drought tolerance in the field and gum yield performance.

Bioefficacy of Some Botanicals Against Gum Arabic Borer, Bruchus baudni Caill (Coleoptera: Bruchidae) on Stored Senegalia senegal Seeds

The use of bio-pesticides has proven to be successful approach in controlling agricultural insect pests. Study was conducted in the Laboratory of the Department of Crop Protection, Faculty of Agriculture, Bayero University, Kano to study the Biology of Bruchus baudni on treated Senegalia senegal seeds. Seed oils and leaf powders of K. senegalensis and M. oleifera at three concentrations each, a chemical insecticide (Aluminum phosphide as standard check) and a control were laid out in a Completely Randomized Design (CRD) and replicated three times. Data collected were oviposition, egg hatchability and developmental stages. The results indicated significant reduction in the number of eggs laid (1% and 1.38%) and hatchability (0.00% and 0.57%) on both seed oil and leaf powder treatments, respectively; however, the control recorded the highest eggs laid (99.9%) and number of emerged B. baudni (99.2%). The present findings showed that seeds and leaves of mahogany and moringa were effective as protectant against some of the development stages of B. baudni. Therefore, based on the present results, mahogany and moringa seeds and leaves could be explored to replace the synthetic insecticides in the management of B. baudni especially as components of integrated pest management strategy.