Genome diversity in wild grasses under environmental stress

Timothy L. Fitzgerald, Southern Cross Plant Science, Plant Genomics, Southern Cross University, Lismore NSW
Frances M. Shapter, Southern Cross Plant Science, Plant Genomics, Southern Cross University, Lismore NSW
Stuart McDonald, Southern Cross Plant Science, Plant Genomics, Southern Cross University, Lismore NSW
Daniel LE Waters, Southern Cross Plant Science, Plant Genomics, Southern Cross University, Lismore NSW
Ian H. Chivers, Native Seeds Pty Ltd, Cheltenham VIC
Andre Drenth, Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Brisbane
Eviatar Nevo, Institute of Evolution, University of Haifa, Haifa, Israel
Robert J. Henry, Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Brisbane

Abstract

Patterns of diversity distribution in the Isa defense locus in wild-barley populations suggest adaptive selection at this locus. The extent to which environmental selection may act at additional nuclear-encoded defense loci and within the whole chloroplast genome has now been examined by analyses in two grass species. Analysis of genetic diversity in wild barley (Hordeum spontaneum) defense genes revealed much greater variation in biotic stress-related genes than abiotic stress-related genes. Genetic diversity at the Isa defense locus in wild populations of weeping ricegrass [Microlaena stipoides (Labill.) R. Br.], a very distant wild-rice relative, was more diverse in samples from relatively hotter and drier environments, a phenomenon that reflects observations in wild barley populations. Whole-chloroplast genome sequences of bulked weeping ricegrass individuals sourced from contrasting environments showed higher levels of diversity in the drier environment in both coding and noncoding portions of the genome. Increased genetic diversity may be important in allowing plant populations to adapt to greater environmental variation in warmer and drier climatic conditions.