Abstract
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.
Highlights
Gum arabic from Senegalia senegal is a valuable non-timber forest product, and it represents a substantial component of household income for many local communities in Africa and in the Sahel (Barbier 1992; Chikamai and Odera 2002; Bradley and Grainger 2004; Wekesa et al 2010; Mujawamariya and D’Haese 2012)
The objectives of this study are to 1) discuss inherent adaptive variation related to survival, soil pH, growth indexes, gum yield and water use efficiency (WUE) within provenances of Senegalia senegal, and 2) investigate genotypic differences in WUE measured by stable 13C isotope composition in foliage to their ploidy levels
We suggest that Ngane and Diamenar, predominantly polyploid and diploid respectively (Diallo et al 2015) may be promising sources to investigate in terms of gum yield and drought adaptation to improve gum Arabic production in Senegal
Summary
Gum arabic from Senegalia senegal is a valuable non-timber forest product, and it represents a substantial component of household income for many local communities in Africa and in the Sahel (Barbier 1992; Chikamai and Odera 2002; Bradley and Grainger 2004; Wekesa et al 2010; Mujawamariya and D’Haese 2012). Institut Sénégalais de Recherche Agricole developed seed orchards and provenance/progeny tests to support plantation operations and develop a deep understanding of challenges underlining gum yield variabilities.
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