Z oysiagrass (Zoysia 1 spp. Willd. 2) is an introduced, perennial, sod-forming species in the United States that is well adapted for use as a turf in the transitional and warm climatic regions and requires minimal maintenance inputs. Three 3 primary species of zoysiagrass [Zoysia japonica Steud. 4 , Zoysia matrella (L. 5

The tetraploid germplasm of bahiagrass, Paspalum notatum Flüggé, is an unexploited source of variability that can be used for the genetic improvement of this species as forage or turf. The objectives of this research were to develop a segregating population by hybridizing induced sexual and apomictic clones and to characterize the resulting population for mode of reproduction, seed fertility, growth habit, seasonal growth pattern, and frost resistance. A population of 591 hybrids had a 4:1 ratio between sexual and apomictic (facultative + obligate apomictic) plants and an 8:1 ratio between others (facultative apomictic + sexual) and obligate apomictic plants. The general fertility of the progeny was higher than that of the induced sexual parents. Significant differences were observed for self‐ and cross‐fertility among apomictic progeny and for self‐fertility among sexual progeny. Most sexual progeny set the same amount of seed when self‐ or cross‐ pollinated, indicating an absence of self‐incompatibility. Marked variation was observed for growth habit, seasonal growth patterns, and frost resistance among the progeny. Heritability estimates obtained for these characteristics indicate that selection can be successfully used for the genetic improvement of this species.

Manipulating apomixis for fixing tetraploid bahiagrass (Paspalum notatum Flüggé) hybrids exhibiting superior agronomic characteristics would be a valuable tool for the genetic improvement of this species. The objectives were to create a second generation of hybrids by crossing sexual first-generation tetraploid hybrids (FGTH) and unrelated apomictic FGTH or ecotypes, determine the segregation for mode of reproduction, and estimate the resulting genetic variation and heterosis for several agronomic characteristics. The segregation for mode of reproduction was analyzed using mature embryo sac observations. Field measurements and visual ratings were used to evaluate the growth habit, production of inflorescences, cool-season growth and freeze resistance of hybrids. A ratio of 4.6:1 between sexual and apomictic hybrids was observed. Only 3% of the progeny was classified as highly apomictic. The low proportion of highly apomictic progeny restricts the feasibility of this breeding approach. Large genetic variation was observed among hybrids for growth habit, cool-season growth and freeze resistance. The proportion of hybrids exhibiting heterosis was high for plant height, cool-season growth, and freeze resistance. The tetraploid bahiagrass germplasm contains a large diversity for traits of agronomic importance that can be exploited for the genetic improvement of this species.

Bahiagrass (Paspalum notatum Flüggé) is one of the major forage grasses used for beef cattle production in the southern USA. Description of the reproductive characteristics of bahiagrass germplasm is needed for genetic improvement of this forage crop. The objective was to determine and compare the mode of reproduction of diploid and tetraploid germplasm of bahiagrass. Reproductive behavior was determined by embryo sac observations and a series of controlled pollination studies in the greenhouse and field in 2004 and 2005. Two sexual diploid populations (‘Pensacola’ and ‘Tifton 9’) were not different in self‐ or cross‐fertility, indicating that the general fertility of the crop was not affected by phenotypic mass selection. Sexual diploids, as a group, were determined to be primarily cross‐pollinated, with low but variable levels of self‐fertility. A group of 20 artificially induced tetraploids was determined to be primarily sexual and cross‐pollinated. Fertility of these autotetraploids was lower than the original diploids. Two selected sexual tetraploids produced similar amounts of seed when self‐ or cross‐pollinated. In contrast, six other tetraploids, including the cultivars Argentine and Wilmington, the experimental hybrid Tifton 7, and three plant introductions 315732, 315733, and 315734 reproduced primarily by apomixis. The sexual or apomictic expression, the general fertility, and other agronomic characteristics of these groups of tetraploids define their usefulness for genetic improvement research.

SummaryBahiagrass ( Paspalum notatum Flugge) is a prime candidate for molecular improvement of turf quality. Its persistence and low input characteristics made it the dominant utility turfgrass along highways in the south-eastern USA. However, the comparatively poor turf quality due to reduced turf density and prolific production of unsightly inflorescences currently limits the widespread use of bahiagrass as residential turf. Alteration of endogenous gibberellin (GA) levels by application of growth regulators or transgenic strategies has modified plant architecture in several crops. GA catabolizing AtGA2ox1 was subcloned under the control of the constitutive maize ubiquitin promoter and Nos 3'UTR.A minimal AtGA2ox1 expression cassette lacking vector backbone sequences was stably Transgenic plants also showed decreased stem length and delayed flowering under controlled environment and field conditions. Consequently, turf quality following weekly mowing was improved in transgenic bahiagrass. Transgene expression and phenotype were transmitted to seed progeny. Argentine bahiagrass produces seeds asexually by apomixis, which reduces the risk of unintended transgene dispersal by pollen and results in uniform progeny.

Cynodon transvaalensis Burtt-Davy (African bermudagrass) is used as a turfgrass and in interspecific hybridization to produce turfgrass cultivars. Information is lacking on the magnitude of intraspecific genetic variation for traits related to turfgrass performance. A Design II mating population comprised of 320 F 1 plants (4 parental sets, 16 crosses set 21 , 5 F 1 hybrids cross 21 ) was used to estimate genetic parameters for 21 traits. The F 1 plants were evaluated in replicated field (13 traits) and greenhouse (8 traits) experiments in Stillwater, OK during 2002-2003. Genetic variation was detected for 17 of the 21 traits as indicated by significant (P , 0.05) differences among families within sets. Both additive and dominance genetic effects were detected for most of the 17 traits, but dominance effects usually prevailed over additive effects. Broad sense heritability estimates varied from 0.42 to 0.96. Population improvement via recurrent selection techniques would be possible but difficult as indicated by low levels of additive genetic variation for genetic color, raceme number, seed number, and percent seed set. Dominance effects might be exploited to select clonally propagated F 1 hybrid cultivars with enhanced sensor-rated color, density, turf quality, spring greenup, fall dormancy, percent living cover, raceme number, raceme length, number of florets per inflorescence, plant height, stolon length, number of internodes, internode length, and leaf length.

RESEARCH S t. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is widely adapted as a lawn grass in warm, tropical and subtropical regions of the world (Sauer, 1972). The grass is highly resistant to weed infestation (Busey, 2003), grows well in a broad range of soil conditions, and exhibits good performance under shade conditions relative to other warm-season grasses (Busey and David, 1991; Busey et al., 1982b). Broad leaf blades and rapid stolon production allow the grass to form a coarse-textured monostand that is well suited for sod production, home lawns, and commercial landscapes. All these characteristics make St. Augustinegrass a valued turfgrass in the southern United States. The genus Stenotaphrum is comprised of seven species, all indigenous to coastlines from East Africa to islands of the South Pacific (Busey, 1995; Sauer, 1972). Pembagrass [S. dimidatum (L.) Brongn.] is the most closely related species to St. Augustinegrass. Evidence of introgression from this species in some polyploid St. Augustinegrass introductions has been observed (Busey, 1993, 1995). The base chromosome number of S. secundatum is

Water shortages have become more chronic as periodic droughts prolong and water demand for urban and agricultural use increases. Plant drought responses involve coordinated mechanisms in both above‐ and below‐ground systems, yet most studies lack comparisons of root and canopy responses under water scarcity and recovery. This is particularly true of research focused on warm‐season turfgrasses in sandy soils with extremely low water holding capacity. To address the lack of examination of coordinated stress and recovery responses, this study compared the above‐ and below‐ground plant responses during a dry‐down period of 21 days and recovery among four warm‐season turfgrass species in the field. Canopy drought responses and recovery were quantified using digital image analysis. In situ root images were captured using a minirhizotron camera system. Common bermudagrass [Cynodon dactylon (L.) Pers.] endured the entire drought period without losing 50% green cover while other species lost 50% green cover in 11–34 days predicted from the regression. The interspecific differences in drought resistance were mainly due to root characteristics. Other drought mechanisms appear to be responsible for differences identified in drought resistance between “Zeon” and “Taccoa Green” manilagrass [Zoysia matrella (L.) Merr.]. Recovery was delayed for up to 2 weeks in the second year, warranting further evaluation for turfgrass persistence under long‐term drought. Three‐week drought posed no threat to the survival of zoysiagrass. Species and genotypic variations were found in achieving full post‐recovery, which can be used to develop water conservation strategies and to adjust consumer expectations.