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

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.

Leaf morphology and stable isotope ratios of carbon and nitrogen in Acacia senegal (L.) Wild trees vary with climate at the geographic origin and ploidy level

“…Variation among trees in their leaf morphological traits, including stomatal density and distribution, and epidermal features is of special interest in relation to climatic adaptation, because such traits may affect gas exchange and thereby plants' responses to key environmental factors such as light, atmospheric humidity, and CO 2 levels (Xu and Zhou 2008). It is known that leaf morphology can reflect environmental conditions (Halloy and Mark 1996;Traiser et al 2005;Royer et al 2008;Peppe et al 2011;Schmerler et al 2012;Koksheeva et al 2017), and link to drought adaptation (Abrams et al 1990). For example, plants in dry regions tend to have small leaves compared to plants from humid areas (McDonald et al 2003).…”

“…Diallo et al (2016) showed that polyploid seedlings grew faster than diploids under drought-stress conditions, suggesting that the existence of different ploidy levels in A. senegal can increase its potential to adapt to future climatic fluctuations in Africa. Recently, Sarr et al (2021) found that diploid and tetraploid populations differed in their foliar isotope ratios of carbon in a progeny trial in Senegal. However, only 15% of the variation in isotope composition was explained by the ploidy level, which suggests the existence of other factors affecting WUE in A. senegal.…”

“…C isotopic composition differed substantially among trees in our study, to a large extent as a consequence of ploidy level. Sarr et al (2021) suggested that others factors may impact A. senegal WUE, since only 15% of the variation in isotopic composition was related to variation in ploidy level. Even when combined, the study of Sarr et al and the study presented here represent a limited sample of tetraploid individuals, and further investigations will be needed to clarify the implication of poplyploidy in adaptive traits of A. senegal.…”

A review of public versus private reforestation programs in the Senegalese Sahel: taking stock of realities and challenges

“…To optimize the restoration opportunities a model and scenarios should be identified to determine the feasible profitability and help in tracking progress. However, inevitably, many uncertainties affect key parameters concerning tree survival and growth, gum yield and price, all of which determine the profitability of this kind of restoration initiative (Mujawamariya & D'Haese 2012; Sarr et al 2021). Moreover, the model should be tested and approved first in a pilot area of at least 2,000 ha (Beatty et al 2018).…”

“…Knowledge of genetic resources of important sahelian tree species as well as their ability to adapt to drought conditions is crucial for sustainability of plantations/restoration initiatives and would increase benefits for local people. For instance, recent outputs based on research revealed promising S. senegal diploid and tetraploid trees as good sources for the diffusion of increased gum yield production and well drought‐adapted planting material in the Senegalese Sahel for future ecosystem restoration works (Diallo et al 2015, 2016; Sarr et al 2021). These results might be a good starting point to develop management tools for species conservation and economic incentives to sustain ecological resilience.…”