Patterns of domestication in the Ethiopian oil‐seed crop noug (Guizotia abyssinica)

Abstract

Noug (Guizotia abyssinica) is a semidomesticated oil-seed crop, which is primarily cultivated in Ethiopia. Unlike its closest crop relative, sunflower, noug has small seeds, small flowering heads, many branches, many flowering heads, and indeterminate flowering, and it shatters in the field. Here, we conducted common garden studies and microsatellite analyses of genetic variation to test whether high levels of crop–wild gene flow and/or unfavorable phenotypic correlations have hindered noug domestication. With the exception of one population, analyses of microsatellite variation failed to detect substantial recent admixture between noug and its wild progenitor. Likewise, only very weak correlations were found between seed mass and the number or size of flowering heads. Thus, noug's ‘atypical’ domestication syndrome does not seem to be a consequence of recent introgression or unfavorable phenotypic correlations. Nonetheless, our data do reveal evidence of local adaptation of noug cultivars to different precipitation regimes, as well as high levels of phenotypic plasticity, which may permit reasonable yields under diverse environmental conditions. Why noug has not been fully domesticated remains a mystery, but perhaps early farmers selected for resilience to episodic drought or untended environments rather than larger seeds. Domestication may also have been slowed by noug's outcrossing mating system.

New Transcriptome-Based SNP Markers for Noug (Guizotia abyssinica) and Their Conversion to KASP Markers for Population Genetics Analyses

“…In an EST-SSR-based study, Dempewolf et al [22] reported a significant population differentiation accounting for 6% of the total variation, which is quite similar to the result of the present study. An EST-SSR based study in the Ethiopian potato (Plectranthus edulis), an outcrossing species, and a clonally propagating crop, also revealed very low genetic differentiation (2.5%) among populations [76].…”

“…The results reflect the advantage of co-dominant markers, such as SNPs and SSRs over dominant markers as have been reported in various previous publications [67][68][69]. On the other hand, the higher genetic variation reported in an EST-SSR (multi-allelic)-based study in noug [22] when compared to the present study (bi-allelic SNPs) is likely because of a higher effective number of alleles per locus (2.2) and a larger sample size of the former.…”

“…Hence, the development and utilization of genome-wide markers are highly desirable to determine and manage genetic diversity within gene pools of crops. In line with this, expressed sequence tags (ESTs) and microsatellite (SSR) markers have been developed for noug [ 18 ], and a number of molecular marker-based studies have been conducted mainly to understand its population genetics [ 19 , 20 , 21 , 22 ]. However, molecular breeding has not been implemented in noug, mainly because available genomic resources and tools are highly limited.…”

Genetic Analysis of Domestication Parallels in Annual and Perennial Sunflowers (Helianthus spp.): Routes to Crop Development

“…Therefore, the defining characteristics of its domestication may not necessarily apply to the neo-domestication of Maximilian sunflower as an oilseed crop. Selection for a Maximilian sunflower ideotype as an oilseed may parallel other small-seeded Compositae oilseeds such as safflower (Carthamus tinctorius) and noug (Guizotia abyssinica) both of which exhibit contrasting domestication syndromes to annual sunflower (Pearl et al, 2014;Dempewolf et al, 2015), having retained a branched architecture and selection for greater seed production. Similarly, successful oilseed crops in Western Canada such as canola (B. napus L.) retain a branched architecture, small seed size, and are still prone to considerable shattering losses under certain conditions (Gulden et al, 2003;Cavalieri et al, 2016).…”

Genetic Variability Correlation and Path Coefficient Analysis of Niger Seed (Guizotia Abyssinica[I.F.] Cass.) Genotypes

“…Niger has received little attention by scientists and considered as underutilized or orphan crop. The availability of limited genetic information and semi domesticated nature of the crop has been an obstacle for further improvement programs (Dempewolf et al, 2008 and2015). Ethiopian niger is inherently diverse with a broad genetic potential.…”