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- Author or Editor: Wayne W. Hanna x
In our study, we sought to determine if an experimental cultivar of centipedegrass [`TC178'; Eremochloa ophiuroides (Munro) Hack.] had superior turf characteristics under extended droughts. Common centipedegrass (CC), vegetatively propagated `TC178' (VG178), and seed-propagated (F3) `TC178' (SD178) were evaluated in a 2-year controlled watering study that compared turf characteristics and drought resistance. The grasses were established under an automated rainfall shelter and were subjected to three drought regimes: watered twice per week (no stress), 2 to 3 weeks between watering (moderate), and 4 to 6 weeks between watering (severe). Turf characteristics (visual rating and clipping biomass) were measured weekly and soil water content profiles were measured daily. Visual ratings among cultivars were similar for no-stress conditions, but visual ratings of SD178 and VG178 were 18% higher than for CC for moderate stress and 28% higher for severe stress. At the end of moderate stress periods, clipping biomass of VG178 was 24% greater than for CC, but by the end of the severe stress periods, biomass from VG178 was 22% lower than for CC. Available soil water content profiles indicated that the three cultivars extracted soil water at the same rate. Visual ratings and growth decline with survival under severe stress showed that VG178 and SD178 had significantly better drought resistance than CC. `TC178' provides a superior appearance turf that will stand up to the droughts common in its adapted region.
`TifEagle' (2n = 3x = 27) hybrid bermudagrass [Cynodon dactylon (L.) Pers. (2n = 4x = 36) × Cynodon transvaalensis Burtt-Davy (2n = 2x = 18)] is an ultradwarf cultivar for greens, and `TifSport' (2n = 3x = 27) is a more versatile hybrid used on fairways, athletic fields, and lawns. To develope a transformation system and determine if somaclonal variation was present in regenerated plants, both cultivars were tested for their ability to produce embryogenic callus from which plants could be regenerated. Sliced nodes of both cultivars and immature inflorescences from `TifSport' were used as the explant sources. Cultures were initiated on Murashige and Skoog medium supplemented with 6.79 μm 2,4-D and 0.044 μm BA (`TifSport' and `TifEagle') or 6.79 μm 2,4-D plus 200 mg.L-1 casein hydrolysate (`TifSport'). In total, 51 plants were regenerated from callus of a single node of `TifEagle'. Nodes from `TifSport' did not produce embryogenic callus. In total, 29 plants were regenerated from callus of `TifSport' produced from immature inflorescences. These plants were grown in the field for at least one season, and 5-cm-diameter plugs were harvested, repotted in a greenhouse, and allowed to reestablish. Data on canopy height, leaf width, leaf length, and number of stolons were collected. Seven `TifEagle'-derived entries (14%) were not significantly different (α = 0.05) from `TifEagle' harvested from the breeder plot in Tifton, Ga., for all measured traits, and 41%, 24%, and 22% differed by one, two, or three measurements, respectively. Flow cytometry indicated that 33% (13 plants) of the `TifEagle' regenerants were hexaploid (2n = 6x = 54) and the rest remained triploid. One `TifSport' regenerant was significantly different (α = 0.05) for plant height.
Hibiscus acetosella Welw. ex Hiern. ‘Panama Red’ PP20,121 (Malvaceae) has generated public and grower interest due to its attractive red foliage and vigorous growth, however, a horticultural goal is to develop more compact forms. Even though organs of induced polyploids are often larger than the wild type, whole plants are often shorter in stature. Three studies were conducted to induce polyploidy and to evaluate the growth and reproductive potential of the resulting polyploids. In study 1, seeds were soaked for 24 hours in aqueous solutions of 0%, 0.2%, 0.4%, or 0.5% colchicine (w/v) plus 0.5% dimethyl sulfoxide. In studies 2 and 3, apical meristems of seedlings at the cotyledon stage were treated for 1 or 3 days with 0, 50, 100, or 150 μm oryzalin solidified with 0.8% agar. Visual observations and measurement of guard cells were used to identify plants that potentially had their chromosome number doubled. Flow cytometry of nuclei stained with DAPI was used for confirmation of polyploidy. No induced polyploidy was observed following seed treatment with colchicine at the rates and duration used in this study. One-time application of 50 μm oryzalin resulted in a single mixoploid (4x + 8x) in which the ploidy of the L-I, L-II, and L-III histogenic layers were identified as a 4–4-4 + 8, respectively. Three-day applications with 100 and 150 μm oryzalin resulted in an octoploid (8x) and a mixoploid (4x + 8x), respectively. The mixoploid from the 3-day treatment stabilized at the 8x level before flowering, but was identified as a 4 + 8-x-4 cytochimera. Plant height was reduced, leaves were smaller, internodes were shorter, and canopy volume was reduced in the octoploid (8x) form compared with the tetraploid (4x) form. Furthermore, in contrast to the tetraploid, the octoploid produced no self-pollinated seed and performed poorly as a staminate and pistillate parent in controlled crosses. This represents the first time oryzalin has been reported to induce polyploidy in Hibiscus L. section Furcaria DC. H. acetosella is an allotetraploid species with the genome composition AABB. The resulting autoallooctoploid (AAAABBBB) form of ‘Panama Red’ exhibits a more compact habit and reduced production of seed.