Agro-ecological gradients shape Enset (Ensete ventricosum (Welw.) Cheesman) landrace diversity and disease dynamics in Central Ethiopia

Abstract

Enset (Ensete ventricosum (Welw.) Cheesman) is a cornerstone of food security in Ethiopia; however, the integrated effects of agro-ecological gradients on its on-farm genetic diversity and disease pressure remain poorly quantified. This study provides empirical evidence by jointly analyzing landrace diversity and bacterial wilt incidence along a pronounced altitudinal gradient in the Gurage Zone. Surveys were conducted across six districts spanning 1617–2986 m a.s.l., representing lowland, mid-altitude, and highland agro-ecologies. A total of 70 locally named landraces were identified. Landrace richness exhibited a strong positive relationship with altitude (r = 0.84, P < 0.001), with highland systems maintaining the highest richness (S = 25–32), Shannon diversity (H′ = 2.88–3.16), and Simpson’s index (1–D = 0.93–0.95). In contrast, lowland areas showed reduced diversity (S = 13–16) and were dominated by stress-tolerant landraces, while mid-altitudes displayed intermediate patterns. Sørensen similarity indices (0.03–0.80) revealed clear agro-ecological structuring of landrace composition, indicating strong environmental filtering and localized farmer selection. Notably, bacterial wilt incidence, caused by Xanthomonas campestris pv. musacearum, also increased significantly with altitude (r = 0.73, P < 0.01), demonstrating a concurrent rise in disease pressure along the same gradient. By explicitly linking diversity patterns with disease dynamics across agro-ecological zones, this study advances current understanding of how environmental gradients simultaneously shape crop genetic resources and phytosanitary risks. These findings highlight the importance of agro-ecology-specific strategies for in situ conservation, participatory breeding, and targeted deployment of resilient, farmer-preferred landraces in enset production systems.