Text

theses

As potable water restrictions continue to tighten and there is an increase in effluent water use, it is necessary to identify turfgrasses with improved salinity tolerance. High salinity levels can cause injury to turfgrass plants resulting in poor or unusable turfgrass sites. As more turfgrass sites become salt affected, there is a need for the development of salt tolerant turfgrass. Because salinity tolerance is a complex quantitative trait, the development of salt tolerant cultivars has been slow. Additionally, most screenings for salinity tolerant germplasm is conducted on mature plants. It has been observed that a different set of genes control salt tolerance of germinating seedlings when compared to mature plant tolerance. Past screening procedures for germination under saline conditions have been conducted in vitro on blotter paper, agar, and in hydroponic solutions. The goals of the first two chapters of this thesis were to develop novel screening techniques that would mimic realistic soil properties for germinating perennial ryegrass seeds. To achieve these goals, a greenhouse and a growth chamber experiment were conducted using native soil and topdressing sand respectively. A diverse range of perennial ryegrass cultivars were used and numerous measurements were utilized to quantify salinity stress during germination. Significant differences were observed based on the salinity level and cultivar used. Overall, salinity delayed germination of the perennial ryegrass seeds as salinity levels increased. Interestingly, there was no cultivar x treatment interaction indicating that cultivars that performed well under saline conditions, also performed well in the untreated control. Additional salinity research was conducted on perennial ryegrass to further understand the endophytic fungi that lives between the plant cells. The Neotyphodium endophyte in perennial ryegrass has been shown to convey resistance to various abiotic and biotic stresses but the study of salinity-endophyte interactions has been lacking in turfgrass. To further understand this interaction, a study was developed using perennial ryegrass clones both containing and not containing the endophytic fungi. The objective of this chapter of the thesis was to determine whether salinity tolerance is genotype-endophyte specific, or whether there is an overall endophyte effect on salinity tolerance in perennial ryegrass. Data obtained from this study showed a specific endophyte-host interaction where some plant genotypes perform better with the endophyte while other genotypes perform worse. Due to the complexity of salinity tolerance, evaluating aspects of this trait during plant growth and germination has been difficult.

ETD_6220

M.S.

Includes bibliographical references

by Eric D. Koch

doi:10.7282/T3668G2R

ETD graduate

The author owns the copyright to this work.