Crop Wild Relatives, Genetic Diversity, and Adaptation to Climate Change

Abstract

This study compared the genetic diversity of crop wild relatives (CWRs) and wheat (Triticum aestivum L.) for an analysis of the extent to which CWRs contribute to adaptation to climate change in wheat. Cultivated wheat varieties and representative of their wild relatives (Aegilops tauschii and wild emmer wheat Triticum dicoccoides) were collected from available germplasm and agricultural resources. Twenty polymorphic simple sequence repeat (SSR) markers were used to investigate genetic variability among accessions, with young leaf material being used for genomic DNA extraction using a standard cetyltrimethylammonium bromide (CTAB) extraction procedure. The genetic diversity indices, the polymorphism level and the relationships between accessions were estimated using PowerMarker and GenAlEx software and cluster analysis and principal component analysis (PCA) were carried out to reveal the genetic relationships and the distinct accession groups. A subset of the accessions from each group was then tested for drought and heat stress under contrasting conditions to determine the physiological and yield-related traits associated with climate resilience and correlation analysis of adaptive trait performance and genetic diversity was then performed. Wild relative accessions had significantly higher allelic richness, expected heterozygosity and polymorphism information content than cultivated varieties and cluster analysis and principal component analysis showed a clear separation between accessions into three distinct groups, based on species of origin. In both drought and heat stress, relative water content, membrane stability, and grain yield retention were significantly higher in wild relative accessions than cultivated varieties, and were significantly and positively related to the climate-resilience trait scores, while the genetic diversity indices were significantly and positively correlated to the climate-resilience trait scores. The results indicate that there is a considerable untapped potential of genetic variation of climate resilience in these crop wild relatives and they serve as important underutilized sources for a climate resilient wheat breeding program.