Drought stress is a major factor in turfgrass management; however, the underlying mechanisms of turfgrass drought tolerance are not well understood. This greenhouse study was designed to investigate proline and hormone responses to drought stress in two tall fescue [Festuca arundinacea (Schreb.)] cultivars differing in drought tolerance. The two cultivars, Van Gogh (relatively drought-tolerant) and AST7002 (relatively drought-sensitive), were established and grown under either well-watered (maintaining 90% container capacity) or drought stress (≈26% container capacity) and then re-watered. Drought stress reduced turfgrass quality, relative leaf water content (LWC), leaf indole-3-acetic acid (IAA) and cytokinin zeatin riboside (ZR) content, and increased proline and abscisic acid (ABA) content. ‘Van Gogh’ had greater turfgrass quality rating, LWC, proline, ABA, and ZR content relative to ‘AST7002’ under drought stress conditions. At the end of drought stress, leaf proline, ZR, and ABA content were 32%, 43%, and 50% higher in ‘Van Gogh’ relative to ‘AST7002’, respectively. No cultivar difference was observed under well-watered conditions. The results of this study suggest that the proline, ABA, and ZR content are associated with drought tolerance. Selection and use of the cultivars with higher proline, ABA, and ZR content under drought stress may be a practical approach to improve tall fescue drought tolerance.

Choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) catalyze the first and second steps in the biosynthesis of glycine betaine in betaine-accumulating plants. Over-expression of the Spinacia oleracea chloroplast choline monooxygenase (SoCMO) and betaine aldehyde dehydrogenase (SoBADH) genes has not been reported in Lolium perenne. In this investigation, the SoCMO and SoBADH genes have been used to generate transgenic L. perenne plants via particle bombardment. Transgenic plants have been confirmed with PCR, Southern blot, and Northern blot analyses. Enhanced salt stress tolerance has been observed from SoBADHSoCMO transgenic L. perenne plants. The dwarf phenotype was first observed 3 months after transgenic plants were established in soil and was to be stably inherited. Height of transgenic plants was decreased by 63% compared to the control. Measurement of endogenous GAs content demonstrated that the content of endogenous GA1 was decreased by 75.2%, and the content of endogenous GA4, GA12, GA19, and GA53 of transgenic plants was increased by 200%, 221%, 105%, and 108%, respectively, compared to the control plants. Dwarf trait of SoBADH-SoCMO transgenic L. perenne plants can be recovered by application of exogenous GAs. These results demonstrated that simultaneous expression of the SoCMO and SoBADH genes enhanced salt stress tolerance and induced dwarfism in transgenic L. perenne. Dwarfism induced by expression of the SoCMO and SoBADH genes was associated with synthesis of endogenous GAs and it could be recovered by application of exogenous GAs. This is the first report on dwarfism induced by expression of the SoCMO and SoBADH genes in a species in turfgrass.

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In order to further understand the stress tolerance of T1 generation of transgenic Perennial Ryegrass Lolium perenne with DREB1A gene, the research is focused on the analysis of the physiological properties of transgenic plants after saline and drought treatment at germination stage, with the control group of water treatment. Compared with the control group, stress treatment had a significant impact on all materials. The result of relative germination potential relative germination rate seedling height chlorophyll content wilting degree and survival range showed that, all materials with DREB1A gene showed a higher tolerance than the non-transgenic ones and the difference was significant. The contents of relative conductivity and relative water content showed the increased tolerance of transgenic plants, but the difference between transgenic plants and CK was not significant. This suggested that transgenic Perennial Ryegrass was stress-tolerant and could be extended in drought and salinity soil to improve drought and salinity land.

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