Abstract
Societal Impact StatementHazelnut is consumed worldwide and is of critical economic importance to the rural communities of Turkey's northern coast. A new disease outbreak has drastically decreased yields across Turkey and climate change is emerging as a new threat to cultivation. Our study is the first to provide a genomic perspective on diversity in this vulnerable crop, which will prove valuable for future breeding efforts. Such research into perennial crops like hazelnut can help to improve farmer livelihoods and ensure the sustainability of crop production in a changing world. Summary Assessing and describing genetic diversity in crop plants is a crucial first step toward their improvement. The European hazelnut, Corylus avellana L., is one of the most economically important tree nut crops worldwide. It is primarily produced in Turkey where rural communities depend on it for their livelihoods. Despite this, we know little about its domestication history and the genetic diversity it holds. We use double digest restriction‐site associated DNA (ddRAD) sequencing to produce a genome‐wide dataset containing wild and domesticated hazelnut. We uncover patterns of population structure and diversity, determine levels of crop‐wild gene flow, and estimate the relationships among different genetic clusters. We use a dataset of over 60k single nucleotide polymorphisms to find that genetic clusters of cultivars do not reflect their given names and that there is limited evidence for a reduction in genetic diversity in domesticated individuals. We find evidence that hazelnut may have been domesticated more than once and that admixture has likely occurred multiple times between wild and domesticated hazelnut. We provide the first genomic assessment of Turkish hazelnut diversity and suggest that there has not been an extreme bottleneck during the domestication of this crop, leading to cultivars at different stages of domestication. Our study provides a platform for further research that will protect hazelnut from the threats of climate change and an emerging fungal disease.
Highlights
Understanding genetic diversity in crop plants and their wild relatives is critical for improving breeding programmes (Zamir, 2001), combatting disease (Zhu et al, 2000) and determining the impact of domestication (Wright, 2005)
We find that genetic clusters of cultivars do not reflect their given names and that there is limited evidence for a reduction in genetic diversity in domesticated individuals
Our results indicate that cultivated hazelnut may not have experienced a strong domestication bottleneck that reduced genetic diversity
Summary
Understanding genetic diversity in crop plants and their wild relatives is critical for improving breeding programmes (Zamir, 2001), combatting disease (Zhu et al, 2000) and determining the impact of domestication (Wright, 2005). Methods are available that can be used in non-model crop species to sequence across the entire genome cheaply and efficiently (Andrews et al, 2016) This has unlocked the potential for genomic studies in non-model crop species such as the Scarlett runner bean, Phaseolus coccineus (Guerra-García et al., 2017) and the curcurbit bottle gourd, Lagenaria siceraria (Xu et al, 2013). These approaches can be applied to crops that may not be widely cultivated but are critical to the economies and communities of developing regions. One such economically important yet understudied crop is the European hazelnut, Corylus avellana L
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