Reproductive biology of wild and domesticated Ensete ventricosum: Further evidence for maintenance of sexual reproductive capacity in a vegetatively propagated perennial crop

Abstract

Loss of sexual reproductive capacity has been proposed as a syndrome of domestication in vegetatively propagated crops, but there are relatively few examples from agricultural systems. In this study, we compare sexual reproductive capacity in wild (sexual) and domesticated (vegetative) populations of enset (Ensete ventricosum (Welw.) Cheesman), a tropical banana relative and Ethiopian food security crop. We examined floral and seed morphology and germination ecology across 35 wild and domesticated enset. We surveyed variation in floral and seed traits, including seed weight, viability and internal morphology, and germinated seeds across a range of constant and alternating temperature regimes to characterize optimum germination requirements. We report highly consistent floral allometry, seed viability, internal morphology and days to germination in wild and domesticated enset. However, seeds from domesticated plants responded to cooler temperatures with greater diurnal range. Shifts in germination behaviour appear concordant with a climatic envelope shift in the domesticated distribution. Our findings provide evidence that sexual reproductive capacity has been maintained despite long‐term near‐exclusive vegetative propagation in domesticated enset. Furthermore, certain traits such as germination behaviour and floral morphology may be under continued selection, presumably through rare sexually reproductive events. Compared to sexually propagated crops banked as seeds, vegetative crop diversity is typically conserved in living collections that are more costly and insecure. Improved understanding of sexual propagation in vegetative crops may have applications in germplasm conservation and plant breeding.

Maintenance and expansion of genetic and trait variation following domestication in a clonal crop

“…In contrast to Tesfamicael et al (2020), GO terms associated with flower initiation or seed development were not overrepresented. Therefore, we did not find evidence of selection against sexual reproductive capacity in clonal lineages, consistent with recent empirical studies (Tamrat et al, 2022).…”

“…Furthermore, enset is harvested for the pseudostem and underground corm prior to flowering, strongly limiting the potential for outcrossing in cultivation. As a result, wild and domesticated enset display a clear and analytically tractable distinction between sexual and clonal modes of evolution (Tamrat et al, 2022;Tesfamicael et al, 2020). The extensive indigenous knowledge associated with clonal propagation methods, compared to the absence of knowledge of sexual propagation, suggests that this cultivation system has been ubiquitous for a considerable length of time .…”

Maintenance and expansion of genetic and trait variation following domestication in a clonal crop

“…Furthermore, enset is harvested for the pseudostem and underground corm prior to flowering, strongly limiting the potential for outcrossing in cultivation. Therefore, in contrast to many crops for which both reproductive methods are employed (McKey et al, 2010; Simmonds, 1997), wild and domesticated enset displays a long‐term, consistent and analytically tractable distinction between sexual and clonal modes of evolution (Tamrat et al, 2022; Tesfamicael et al, 2020). Both wild and domesticated enset plants co‐occur in situ in some areas, and thus, present a system in which the consequences of contrasting reproductive strategies can be investigated.…”