No description available.

No description available.

No description available.

Two previously uncharacterized plant rhabdoviruses, infecting Bermuda grass (Cynodon dactylon (L.) Pers) and soybean (Glycine max) respectively, have been found in South Africa. To determine the morphology and virion size of these viruses, embedded ultra-thin sections of infected plant samples were observed under a transmission electron microscope. The virion distribution within the cell, the bulletshaped morphology and the virion sizes indicated that both these viruses might belong to the Rhabdoviridae family. Degenerate polymerase chain reaction (PCR) primers were designed by alignment of the polymerase gene sequences of several plant rhabdoviruses in order to identify conserved regions. Standard PCR and sequencing protocols were used to determine a partial polymerase gene sequence of the viruses that was then compared to the most closely related sequences available on Genbank. The analysis indicated that the Cynodon rhabdovirus was most closely related to known nucleorhabdoviruses; and the rhabdovirus-infecting soybean (Soybean blotching mosaic virus proposed name) was closely related to other known cytorhabdoviruses. These results indicate that both the viruses are new members to the Nucleo- and Cytorhabdovirus genera, respectively. / Dissertation (MSc)--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted

Five clones of giant type bermudagrass, Cynodon dactylon (L.) pers. vars. aridus and afghanicus Harlan et de Wet, progenies from crosses among those five, and crossed, selfed, and open pollination progeny from selected F₁ plants were evaluated for response to simazine (2-chloro-4,6-bis(ethylamino)-s-triazine). The first two generations were also evaluated for their response to ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine). Two techniques were used. Culm cuttings, rooted in wet vermiculite, were placed into test tubes of simazine or ametryn suspensions at various concentrations or water. Culms were rated (1 to 9, 9 normal, 1 dead) for herbicide injury. Seeds were placed into petri dishes on moist filter paper, germinated in a germinator (day 35C, night 21C) and treated with 8ppm simazine or water in a greenhouse. Seedlings were rated visually for herbicide injury (7 normal, 5 affected, 1 dead) weekly, later daily, until a final drying and weighing of seedlings after all those in simazine were dead. Tolerance of all treated materials was expressed as percentage of control. There were significant differences among plants in tolerance to simazine with significance up to .001, although there was great variance within genotypes affected. The correlation between ametryn and simazine reaction was low. Tolerance scores were affected by condition of culms (significance .05), dosage, and nutrient levels. The clone by nutrient level interaction was significant at .01. Tolerance to simazine varied widely (more than 60%) among progeny of any plant as maternal parent. Progeny of reciprocal crosses between resistant and susceptible clones had similar (45 to 46) mean tolerance scores intermediate between parental scores indicating no dominance. Plants with the same cytoplasm ranged from most resistant (88%) to most susceptible (11%). Maternal effect on tolerance appears absent. The range of response for progeny of parents of any tolerance level indicates several pairs of genes are involved. Open pollination seedlings from consistently resistant plants averaged more resistant than seedlings from consistently susceptible plants. Giant bermudagrass simazine tolerance must be quantitatively inherited, possibly additive, with penetrance varying with plant condition, dosage, and other environmental constraints.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 72-77). Also available via the Internet.

No description available.

The most importunate problem in using bermudagrasses (Cynodon sp.) for turf in the northern extremity, where semitropical grasses are adapted, is winter survival. This research was primarily conducted to investigate the effects of deacclimation of dormancy, duration of dormancy, and freezing temperatures on survival of bermudagrasses. 'Tifgreen' bermudagrass taken from the field in February, 1976, was deacclimated for 0, 2, 4, or 8 days at 27C/13C (day/night). Subsequently, rhizomes and stolons were subjected to +2, 0, -2, -4, or -6C for 24 hours. One third of the samples from each treatment were planted after 0, 45, and 90 days storage at 2.8C±1.6C. Rhizomes and stolons subjected to -4 or -6C did not survive. Deacclimation of rhizomes up to 8 days augmented growth as compared to no deaccli~ation. Increased storage periods caused decreased rhizome growth. At +2 and 0C, the percent rhizome growth was similar but significantly higher than at -2C. With 0 storage, stolon growth declined after 8 days deacclimation; however, after 45 or 90 days of storage, significant reductions occurred after only 4 days deacclimation. Fully deacclimated as well as dormant field samples of 'Midiron', 'Tifdwarf', 'Tifgreen', 'Tifway' and 'Tufcote' taken in March and April, 1977, were subjected to -2, -4, and -6C. All cultivars survived -4C whether dormant or actively growing. 'Tifgreen' bermudagrass frozen while dormant and 'Tifgreen' and 'Tifdwarf' frozen while actively growing had high recuperative potentials during regrowth. Comparing these cultivars under field conditions showed best winter survival for 'Midiron', which was the only cultivar that survived with simulated traffic. Traffic imposed immediately prior to bermudagrass dormancy reduced spring recovery more than for traffic imposed during winter. / Master of Science

Examination of use of terminology using "carbohydrates" to describe reserve energy to plants. / Master of Science

The most important problem in using bermudagrass (Cynodon sp.) for turf at the northern limit of its adaptation is winter survival. Bermudagrass used for athletic complexes is exposed to the additional problem of uncontrolled or excessive traffic. This research was conducted to determine the effects of: 1) traffic and mineral nutrition; 2) clear plastic covers and cultural treatments and; 3) overseeding and late winter freezing on bermudagrass winter survival. Four separate experiments were conducted on field cultured Midiron bermudagrass. Various regimes of traffic, N and K fertility, clear plastic covers, cultural treatments and growth regulators were utilized to determine their affect on bermudagrass winter survival. A laboratory freeze was used, in two experiments, on plant samples taken from the field. Following the freezing procedure, the samples were then grown in the greenhouse. From these experiments, it was found that traffic applied just as turf growth initiates in the spring was the most damaging. Potassium fertility had no effect on post dormancy growth. Nitrogen did improve post dormancy growth of bermudagrass exposed to a late winter laboratory freeze and when plastic covers were applied during winter dormancy. Plastic covers enhanced post dormancy growth and offset the detrimental effect of imposed traffic. 'Stayz Green' turf colorant did increase early post dormancy growth. While, the cultivation treatments using a vertical mower alone and with an aerifier reduced early green up. Flurprimidal reduced early post dormancy growth of bermudagrass; while, mefluidide had no detrimental effect. Both growth regulators reduced the growth of the overseeded ryegrass, and mefluidide enhanced the competitiveness of bermudagrass in the ryegrass canopy. / M.S.