Eight seeded bermudagrass cultivars, representing the new releases of high quality, dense types, were germinated under 3 levels of drought stress: 0, -0.125 Mpa, and -0.25 Mpa (0, -1.25 and -2.5 bars). Total cumulative germination rates decreased with increasing time with all cultivars. The most vigorously germinating cultivars under both drought and control conditions were (in decreasing order): OKS91-11, Sahara, Mirage, and Pyramid. Four other cultivars exhibited low cumulative germination rates under all conditions: PST-R63, PST-R64, FMC-77 (Princess), and FMC-8 (Sultan). Increasing drought stress reduced cumulative germination rates for all cultivars.

As water shortages continue to escalate in the Southwest, water allocations for turfgrass continue to become more limiting for irrigation. Resultant drought stress demands aggressive breeding programs and development of more drought tolerant turfgrass cultivars. Turfgrasses are especially sensitive to drought during the germination stage, making turf establishment particularly difficult with insufficient water, as the germination stage typically requires a large amount of supplemental irrigation. Substantial research has been done in screening turfgrass cultivars for salt tolerance during germination. Cultivar differences in salt tolerance have been noted among creeping bentgrasses (1), buffalograsses (2), Kentucky bluegrasses (3, 4), red fescues (5), perennial ryegrasses (6), and tall fescues (7). In contrast, there has been very little research on turfgrass germination under drought stress. Germination in the field of "Rebel" tall fescue was delayed when seeds were irrigated with 50% potential ET, versus 100% (8). Germination under alternating wet and dry conditions in the field was tested using tall fescue, red fescue, and several other grass species (9). Differences were noted between the species. In a controlled study, seeds of the turfgrasses 'Cheyenne' bermudagrass, 'Flyer' creeping red fescue, 'Huntsville' Kentucky bluegrass, 'Finelawn' tall fescue, 'Sunrise' perennial ryegrass, and 'Triple Play' ryegrass blend were germinated under drought stress using polyethylene glycol (PEG) (10). Best germination under drought occurred in 'Finelawn' tall fescue, while poorest germination occurred in 'Cheyenne' bermudagrass.

There have been no reports of seed germination studies concerning bermudagrass salinity tolerance, and the only germination study concerning bermudagrass drought tolerance included only one cultivar ('Cheyenne'). There is no basically no knowledge available concerning bermudagrass cultivar drought tolerance at germination.

Experiments will be performed to determine bermudagrass germination under drought stress. The experiment will be done twice (i.e. two replications in time). Eight seeded bermudagrass cultivars, representing divergent germplasm, and currently (or soon to be) considered important in the bermudagrass seed industry will be studied:

1) Mirage (International Seeds)

2) Pyramid (International Seeds)

3) OKS 91-11 (Oklahoma State U.)

4) FMC 77 - Princess (Seeds West)

5) FMC 8 - Sultan (Seeds West)

6) PST-R63 (Pure Seed Testing)

7) PST-R64 (Pure Seed Testing)

8) Sahara (common standard)

Cultivars will be seeded, unhulled, into Petri dishes, 50 seed per dish. Each dish will contain blotters soaked with the treatment solution. Two levels of drought stress, 0.125 and 0.25 Mpa, plus a control, will be used, each drought level/cultivar combination being replicated 4 times. Actual stress levels will be determined from a preliminary germination test to give the best range in separating the cultivars from one another. Drought stress will be achieved using polyethylene glycol 8000 (PEG 8000), an inert, water-binding compound which accurately mimics drought stress under dry-soil conditions. Each Petri dish will be replicated 4 times, giving 336 dishes per experiment. Dishes will be placed in high-humidity boxes within controlled-environment germinators set at 25C (77F). The number of seeds germinated in each dish will be counted daily for a period of 2 weeks. Germination rate (cumulative through time) will be determined for each cultivar.

Germination increased at a decreasing rate (cumulative germination rate decreased) as time went on for most cultivars. The PST and FMC cultivars had very low cumulative germination rates under all treatments (Figure 1). In contrast, OKS91-11 was the most vigorous germinator under all treatments, reaching 70% total germination within 3 days of planting under no drought stress. Cumulative germination rate declined for cultivars in the following order: OKS91-11, Sahara, Mirage, and Pyramid. Increasing drought stress decreased cumulative germination rates of all cultivars.

1) McCarty, L.B. and A.E. Dudeck. 1993. Salinity effects on bentgrass germination. HortScience 28:15-17.

2) Wu, L. and H. Lin. 1993. Salt concentration effects on buffalograss germplasm seed germination and seedling establishment. Intl. Turfgrass Soc. Res. Jour. 7:823-828.

3) Horst, G.L. and R.M. Taylor. 1983. Germination and initial growth of Kentucky bluegrass in soluble salts. Agron. Jour. 75:679-681.

4) Torello, W.A. and A.G. Symington. 1984. Screening of turfgrass species and cultivars for NaCl tolerance. Royal Netherlands Soc. of Agric. Sci. 155-161.

5) Jonsson, H.A. and C. Nilsson. 1977. Tolerance to a high salt concentration in Festuca rubra Weibulls Grastips 20:29-30.

6) Horst, G.L. and N.B. Beadle. 1984. Germination and initial growth of perennial ryegrasses

in soluble salts. Agron. Abstracts p. 151.

7) Horst, G.L. and N.B. Beadle. 1984. Salinity affects germination and growth of tall fescue cultivars. J. Amer. Soc. Hort. Sci. 109(3):419-422.

8) Fry, J.D. and J.D. Butler. 1989. Water management during tall fescue establishment. HortSci. 24:79-81.

9) Wood, G.M.and P.A. Kingsbury.1969. Seedling emergence and survival of several cool season grasses subjected to induced drouth stress. Agron. Abstr. 61:56.
 

10) Little, R., E.B. Williams, and K.J. Hillsman. 1990. Germination response of several turfgrass seed to PEG-induced moisture stress. Agron. Abstr.:178.

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