Using SNP markers and morphological data to compare diversity between generations in composite cross populations of landraces and cultivated barley (Hordeum vulgare).

Modern crop varieties have been bred in order to provide high yields under high input management, which has led to a relatively lower genetic diversity in modern cultivars compared to wild or traditional crop varieties. This depletion of variation present in modern crops is believed to have a big effect on traits involving response to environmental pressures (Suneson 1956, Allard 1988, Goldringer et al. 2006, Harlan 1921, Ibrahim & Barrett 1991, Paillard et al. 2000). In order to study whether a higher amount of variation would create crops that are better in dealing with their environment and to measure their genetic diversity, we have been developing highly heterozygous populations by hybridizing approximately 25 lines of barley (Hordeum vulgare) landrace and modern cultivar material in four generations. We have measured life history traits (height, seed number, ear number) and genotyped up to 384 SNP (single nucleotide polymorphism) markers per individual for every generation. The aim of this project was to measure the stability of different traits between generations and sites and to see whether the morphological traits of the more heterozygous populations (F4) showed less variability than those of the less heterozygous ones (parental). We found that there was a higher degree of heterozygosity but similar amounts of genetic variation present in later generations relative to earlier ones. We found variable outcomes for morphological measurements: for example, traits like plant height and grain number showed less variation in later generations, whereas ear length variability remained stable but the population average increased over time. In the coming years, we will test these composite cross populations under field conditions at multiple sites for life history traits and output but also for disease resistance and nitrogen use efficiency.