Molecular and morpho-physiological study on drought tolerance in turfgrasses.

摘要

Drought stress is a major limiting factor for the growth of cool season grasses, particularly in the transitional and warm climatic regions. Selecting grasses with improved drought tolerance is the best strategy to increase survival and growth of grass during time of drought. An Atlas fescue (Festuca mairei, Fm) selection and three tall fescue (F. arundinacea Schreb.) cultivars were subjected to drought treatment. The drought stress had a significant negative effect on leaf elongation, leaf water content, and leaf water potential for all grasses. Fm maintained leaf growth, leaf water content, and leaf water potential longer than the tall fescue grass species and had an exceptional ability to accumulate water in leaf tissue when under severe drought stress, suggesting the better drought tolerance of Fm and its potential value for grass drought tolerance improvement.; Intergeneric hybridization between Festuca and Lolium can generate improved cultivars by combining stress tolerance of Festuca and rapid establishment of Lolium. However, wide-distance hybridizations usually result in the wild genome being eliminated from the hybrid. RAPD and SSR markers were used to detect the parental genome composition of hybrids and backcross derivatives from crosses between Fm and perennial ryegrass (Lolium perenne). Each progeny exhibited integration of Fm and perennial ryegrass genomes with varying levels of genome ratios. The non-coinheritance of the linked markers suggested chromosome crossover between two parents. Cluster and principle component analyses of the progeny consistently revealed four groups. These results would be useful to guide the breeding program.; Increasing knowledge of genes induced by drought in Fm would be essential to understand the molecular mechanism of drought tolerance in grasses and to facilitate gene manipulation for grass breeding programs. In order to apply cDNA amplified fragment length polymorphism (cDNA-AFLP) technique to identify genes involved in drought tolerance in Fm, we empirically evaluated the experimental conditions of this technique in Festuca species. Results showed that NspI coupled TaqI were a pair of efficient enzymes for transcript derived fragment (TDF) discovery in Fm. The number of repeatable bands was not affected by magnesium concentration and dilution of pre-amplification products, suggesting the high reproducibility of this technique. The chimeric fragments derived from ligation between digested fragments were not eliminated by increasing adapter concentration. The application of the cDNA-AFLP technique to identify genes responding to drought stress in Fm revealed a total of 464 (4.1% of 11,346 TDFs) differentially expressed fragments (DEFs). The differential expression pattern for 171 (42.1% of 406) DEFs were confirmed by macroarray hybridization analysis. Functional analysis of confirmed DEFs using BLASTX revealed 17 functional categories. Some novel genes were identified in Fm during the drought response procedure. The combination of data from studies on the genetic model plant and on diverse plant species will provide a better understand the underlying mechanism of drought tolerance in plants.