Reproductive isolation between wild and domesticated chaya (Cnidoscolus aconitifolius) in sympatry

Abstract

• Reproductive isolation is a necessary condition for plant domestication in their domestication centre where crops co-occur with their wild progenitors. However, the identification of reproductive barriers and their relative contribution to reproductive isolation have been overlooked in plants under domestication. • We assessed pre-and post-pollination reproductive barriers and their relative contribution to reproductive isolation between wild and domesticated chaya (Cnidoscolus aconitifolius) in its domestication centre. • We found that wild and domesticated chaya both exhibit a high degree of reproductive isolation. However, the reproductive isolation barriers exhibited some asymmetry: while pre-pollination barriers (differential pollen production and pollinator specificity) were only detected in wild plants, post-pollination barriers (pollen-pistil incompatibility and/or failure to set fruit) were observed in both wild and domesticated plants. • We conclude that complete reproductive isolation has evolved in sympatry in co-occurring domesticated and wild chaya.

Artificial Selection Optimizes Clonality in Chaya (Cnidoscolus Aconitifolius)

“…Despite their co-occurrence, there is almost complete reproductive isolation between wild and domesticated forms, mainly due to poor pollen production and reduced fertility of the latter 12 . Clonal propagation of the cultivar is, therefore, obligate.…”

“…While the relative contribution of sexual reproduction to the fecundity of clonal crops is often limited, the wild relatives of some of these crops are mainly seed reproduced (e.g. chaya: Cnidoscolus aconitifolius 12 and cassava: Manihot esculenta 13 ). Therefore, clonality has also evolved from sexually propagated plants by means of arti cial selection.…”

“…In contrast to their wild progenitors, the cultivar produces more, larger, non-stinging leaves, which have thicker stems that are used as propagules 25 . While the cultivar is exclusively clonally propagated and rarely produces pollen or viable seeds, wild plants only reproduce by seeds in nature 12 . The objective of this study was to assess the major changes that vegetative organs (stems) have undergone during domestication and that maximize their novel function as propagules.…”

Artificial selection optimizes clonality in chaya (Cnidoscolus aconitifolius)

“…Because clonal propagation has brought several advantages to growers relative to sexual propagation (i.e. easier cultivation, greater survival and reduced time to reach sexual maturity) 9 and some of the few clonal crops studied so far have wild ancestors that mainly reproduced sexually 12 , 13 , it is reasonable to think that clonality may also be a derived trait in some crops and that traits that facilitate clonal propagation have been artificially selected during the domestication process 9 . Clonality in crops may be also the result of selection for a different plant trait.…”

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

“…Loss of sexual reproductive capacity, if widespread across domesticated vegetative crops, could significantly hinder future crop breeding programmes and integration of useful alleles from crop wild relatives (Dempewolf et al 2014; Migicovsky and Myles 2017). Importantly, sexual reproductive capacity does not have to be completely lost – reduced fertility, viability, altered floral allometry or germination behaviour, as a result of deleterious mutations and genetic drift in reproductive traits, could still significantly hinder programmes that seek to recombine or conserve diversity as seeds (McClure et al 2014; Iriondo et al 2017; Migicovsky and Myles 2017; Munguía-Rosas and Jácome-Flores 2020). However, surprisingly few studies have attempted to survey the sexual reproductive capacity of vegetatively propagated crops in agricultural systems (Elias et al 2001; Scarcelli et al 2006).…”