Identification and screening of grasses with excellent drought tolerance is a desirable strategy in breeding drought-tolerant turf and forage cultivars. Not all fescue selections and cultivars may be equally drought tolerant. An Atlas fescue (Festuca mairei St. Yves) selection and three tall fescue (Festuca arundinacea Schreb.) cultivars—Barolex, Kentucky 31, and Falcon II—were subjected to increasing drought stress for a 12-week period. Soil water content (SWC), leaf elongation (LE), leaf water content (LWC), and leaf water potential (Ψw) were measured weekly, and root length (RL) and biomass (RM) were recorded after 12 weeks. The SWC declined progressively during the 12-week drought treatment for all grasses. However, for the three tall fescue cultivars, the SWC decreased at a faster rate than for Atlas fescue. This indicated that Atlas fescue extracted soil water more slowly and developed less-intensive stress than the three tall fescue cultivars. The LE, LWC, and leaf Ψw decreased in drought-treated plants of all grasses; nevertheless, the values for the Atlas fescue remained similar to control plants for a longer period of time than the values for the three tall fescue cultivars. Drought stress significantly reduced root biomass and root length of the grasses. These four Festucas avoid drought stress through changes in leaf and root morphology and probably through osmotic adjustment to maintain sufficient turgor pressure in the growing zone for leaf elongation. The slower decrease in LE, LWC, and leaf Ψw for Atlas fescue during the drought-stress period suggested greater drought tolerance and the potential value for improving this character in a breeding program.
Six grass species representing vegetative and seeded types of native, warm-season and cool-season grasses, and pennsylvania sedge (Carex pensylvanica) were evaluated in the greenhouse for resistance to root-feeding grubs of european chafer (Rhizotrogus majalis). Potted bermudagrass (Cynodon dactylon), buffalograss (Buchlöe dactyloides), zoysiagrass (Zoysia japonica), indiangrass (Sorghastrum nutans), little bluestem (Schizachyrium scoparium), tall fescue (Festuca arundinacea), and pennsylvania sedge grown in a greenhouse were infested at the root zone with 84 grubs per 0.1 m2 or 182 grubs per 0.1 m2. The effects on plant growth, root loss, survival, and weight gain of grubs were determined. Survival rates were similar for low and high grub densities. With comparable densities of grubs, root loss tended to be proportionately less in zoysiagrass and bermudagrass than in other species. European chafer grubs caused greater root loss at higher densities. Grub weight gain and percentage recovery decreased with increasing grub density, suggesting a food limitation even though root systems were not completely devoured. Bermudagrass root weight showed greater tolerance to european chafer grubs; another mechanism is likely involved for zoysiagrass. Variation in susceptibility of plant species to european chafer suggests that differences in the ability of the plants to withstand grub feeding damage may be amenable to improvement by plant selection and breeding.
We evaluated the effect of fertilization treatments in combination with clippings disposal on perennial ryegrass (Lolium perenne L.) in two adjacent locations. Clippings left on turf during mowing decreased dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in both locations during three summers compared with clippings removed in mower baskets. However, brown patch (Rhizoctonia solani Kuhn) increased during July and Aug. 1995 when clippings were left on turf. Dollar spot was more severe with N (kg·ha–1·year–1) at 120 compared to 240; brown patch was more severe at 240. While clippings disposal had significant effects on disease incidence, implementation may not be practical because of the contrary responses of the observed diseases to this management approach.
Rhizomes of zoysiagrass (Zoysia spp.) were subjected to controlled freezing tests in Jan. and Mar. 1993 and 1994 to determine their low-temperature tolerance. In 1994, `Belair', `Korean `Common', `Meyer', and `TGS-W10' rhizomes survived temperatures as low as -18 °C, while rhizomes of `Sunburst' survived -14 °C. `Cavalier', `Crowne', `Palisades', `Emerald', and `El Toro' were killed at -10 °C or warmer temperatures. Entries surviving exposure to -14 to -18 °C in 1994 controlled freezing tests received post-winter survival ratings in the field of 6.7 to 8.7 (9 = 100% green). Entries killed at higher freezing test temperatures were slower to recover after winter in the field, with ratings of 2.0 to 3.0. Shoot number produced after freezing was a better measurement for assessing low temperature tolerance than was shoot mass. Controlled freezing tests, using regrowth as a measure of hardiness, appear to be useful for identifying low temperature tolerance of zoysiagrasses in the early years of a field study.
Zoysiagrass rhizomes were sampled at various intervals, from October through March, to determine their susceptibility to low-temperature injury. Five-node rhizome sections of the following genotypes were subjected to sub-freezing temperatures at each date: `Belair', `DAL 8507', `El Toro', `Emerald', `Korean Common', and `Meyer'. Rhizome sections of each cultivar were wrapped in moistened cheesecloth, enclosed in aluminum foil, and placed in a freezing chamber at –2C. After 2 h at –2C, samples then were cooled at 1C/h to temperatures estimated to result in tissue injury. Fifteen rhizomes of each genotype were removed from the chamber at each test temperature. After thawing for 12 h, rhizomes were planted and regrown in a growth chamber at 34C day/28C night for 4 weeks. In the freezing test conducted on 12 Oct. 1994, rhizomes of `Meyer' and `Emerald' had greater shoot regrowth than those of `El Toro' after exposure to –6C. The only rhizomes that produced shoot growth after exposure to –8C were those of `Korean common', `Meyer' and `Belair'.
The objective of the present study was to characterize the diversity of 15 Festuca rubra accessions collected from northern Spain on the basis of amplified fragment length polymorphism (AFLP) and flow cytometry variation. Additionally, all accessions along with the cultivar Wilma (Festuca nigrescens ssp. nigrescens) were evaluated for susceptibility to one isolate of dollar spot fungus (Sclerotinia homoeocarpa F.T. Bennett) collected in Asturias. Five AFLP primer combinations of EcoRI and MseI produced 980 bands; 82.3% were polymorphic and used for analysis. The best combination of primers was EcoRI-AGC+MseI-CAG, because these displayed the highest degree of polymorphism. Jaccard's similarity coefficients between accessions varied from 0.30 to 0.63 and revealed low genetic similarity. Both the unweighted pair group method with arithmetic mean dendrogram and principal coordinate analysis distinguished two groups of accessions. Genetic variability in these accessions was not related to the geographic origin or to the agronomic data. Three accessions exhibited moderate resistance to dollar spot disease and may be valuable parent material for introducing this resistance in other susceptible cultivars.