Rapid Evolution of wild barley: R-Evolve

Genetic diversity is the fuel that drives crop improvement. However, in our major cereal crops, by continually crossing closely related high performing individuals, traditional methods of crop improvement have resulted in a drastic loss of overall diversity. While strategies for mobilising diversity controlling simple traits (e.g. disease resistance) from more diverse wild accessions or landraces into cultivars do already exist, none are effective for introducing components of key complex traits that include such as tolerance to biotic or abiotic stresses, or components of yield. We propose to develop a radically different approach to refreshing the diversity in the barley breeding genepool. Our proposed enrichment strategy involves the partial domestication of wild genotypes by incorporating key domestication genes and genes required for modern NW European agriculture in a wild barley background. We will then evaluate the new partial domesticates as both inbreds and F1 hybrids, the latter generated efficiently using a male sterile derivative of a contemporary elite cultivar. We expect to construct completely novel and diverse germplasm pools that will have value for future barley breeding. In the process we will address a fundamental issue that is vexing the genetic resources and breeding communities, i.e. how to efficiently extract value from diverse germplasm in crop improvement programs for complex and multigenic traits.

To refresh our increasingly narrow crop breeding genepools and address the issue of improving complex traits using diverse germplasm, we recently proposed parallel strategies that involved partially domesticating wild relatives of our crop plants2. Here we want to test one of these strategies. We propose to introgress three alleles essential for NW European barley cultivation by marker assisted selection (MAS) from a domesticated, fully sequenced, donor genotype (cv. Planet) into nine selected, exome sequenced, wild species recipient genotypes. These are the recessive allele of BRITTLE RACHIS1 responsible for grain retention on the spike at maturity, the recessive X-ray induced DENSO (sdw1) gene that induces a morphological and developmental program typical of barley cultivated in NW Europe and, as wild barleys are 'facultative winter types', the dominant spring-type VRN1-2 allele. Molecular diagnostics will be used to identify partially domesticated 'triple homozygote' progeny early in a breeding program designed to maintain, rather than erode, the wild (donor) genome. Advancing rapidly through single seed descent (SSD) we will enhance allelic shuffling by applying a heat treatment when plants are undergoing meiosis. At >F5, individual plant genome composition will be assessed using 50K SNP array data, which will allow us to project alleles at other 'adaptation loci' (e.g. HvPPDH1 and HvCEN) revealed in the available sequence data directly onto the partially domesticated lines. The breeding potential of the partial domesticates will be assessed directly under field conditions as inbred lines and as F1 hybrids generated using 'RIPE' male sterile technology. We will use biomass and harvest index as preliminary indicators of novel beneficial alleles in the partial domesticates. The outcome of the project will be a radically different partially domesticated genepool which could quickly find application in crop improvement programmes.