Relativity Of Genetic Diversity And Drought-related Genes Expression With Drought Tolerance In Perennial Ryegrass

In order to characterize phenotypic diversity of drought tolerance within and among accessions in relation to genetic diversity in perennial ryegrass and the relativity between water deficiency and the drought-related genes expression and the affection to the plant growth and expression pattern of drought genes under water deficiency.Five individual genotypes from each of 6 accessions varying in origin and growth habits were subjected to drought stress in a greenhouse. The result as such:l.Leaf wilting, plant height (HT), chlorophyll fluorescence (Fv/Fm) and leaf water content (LWC) differed significantly among accessions as well as among genotypes within each accession under the control and drought conditions. Across accessions, Fv/Fm was highly correlated with LWC under drought stress.2.Genetic diversity among and within accessions were identified by using previously characterized 22 simple sequence repeat markers. Across accessions, the mean major allele frequency, gene diversity and heterozygosity values were 0.66,0.43 and 0.66, respectively. Accessions with closer genetic distance generally had similar drought responses, while accessions with far genetic distance showed distinct drought tolerance.3.Significant differences in drought tolerance among and within accessions, especially for individual genotypes within one accession, indicated that variations of drought response could be used for enhancing breeding program and studying molecular mechanisms of stress tolerance in perennial ryegrass.4.Under the water deficiency condition, although the drought tolerant type had a higher relative water content (RWC) than susceptible type, but its net growth rate was smaller, and so was its water use efficiency (WUE).5.As the water deficient stress continues to increased, chlorophyll a/b binding protein LHCB genes, iron superoxide dismutase FeSOD gene, as well as type 1 plasma membrane intrinsic protein PIP1 gene expression appeared different changes, especially iron superoxide dismutase FeSOD gene showed divergent expression pattern between drought-tolerant accession and drought susceptible accession with water deficient stress continued increasing.