Ecological niche, genetic variation in natural populations, and harvest maturity of Senegalia macrostachya (Rchb. ex DC) Kayl. & Boatwr., a promising wild and perennial edible-seeded crop

Abstract

Senegalia macrostachya is a wild, perennial, and promising legume that can help alleviate food insecurity in sub-Saharan Africa’s drought-prone regions. However, it has been for a long time overlooked, underutilized, and scarcely studied. This study shed light on its ecological niche, genetic variation in natural populations, and seeds’ harvest maturity. Three populations of S. macrostachya were selected along an environmental gradient, and their structures, based on their plants’ pod characteristics (i.e., unique morphological differentiation trait amongst the plants), were assessed. Then, the seeds’ development was investigated following their morphological transformation, mass accumulation, and the mobilization of their proteins and secondary metabolites. S. macrostachya has revealed low genetic variation and fitness to poor soils, warm and semi-arid climates in sub-Saharan Africa, prone to droughts and low to medium agricultural productivity. The maturation of the seeds involved the accumulation of specific late embryogenesis abundant proteins (60, 48, and 14 kDa), identified as chilling-responsive dehydrins, and the degradation of the chlorophylls and carotenoids, which could be used as biochemical landmarks of the harvest maturity. Besides, an aging symptom (high seed abortion rate (14–20%)) was observed in the study populations. This work provides unprecedented information that will assist in predicting the eco-climate suitability and climate resilience, identifying the conservation strategies, and planning the harvesting, reforestation programs, and domestication of S. macrostachya. In parallel, the dehydrins identified from S. macrostachya can be tapped into for drought-resistant crop development. Further research is needed to evaluate the impacts of the mother plants’ aging and larger climate gradient on the performance (i.e., seed productivity and regeneration ability) of S. macrostachya.