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- Author or Editor: T. Karl Danneberger x
The usefulness of random amplified polymorphic DNA (RAPD) in characterizing two perennial ryegrass (Lolium perenne L.) synthetic cultivars, `Accolade' and `Caravelle', was tested. Two out of 10 arbitrary primers produced three RAPD markers that distinguished bulk samples of 30 seedlings. Additional fragments were apparent when DNA from individual seedlings was amplified. Amplification products from bulk samples were not simply the sum of amplification products of individual seedlings and did not reflect all the diversity within or between the cultivars. The study illustrates the need to screen individuals to accurately evaluate the genotypic composition of a synthetic cultivar or heterogeneous population.
As the number of perennial ryegrass (Lolium perenne L.) cultivars increases, the development of reliable identification methods becomes more important. Randomly amplified polymorphic DNA (RAPD) markers show promise in cultivar identification. Since perennial ryegrass cultivars are composites of genotypes rather than a single genotype, finding markers that distinguish cultivars is difficult. The ideal cultivar identification procedure would use seed tissue as a DNA source and evaluate a single sample as representative of a cultivar. The objective of this research was to determine whether RAPD markers could be used to consistently distinguish bulk seed samples of perennial ryegrass cultivars. Two extraction protocols were evaluated. A quick, simple extraction resulted in the amplification of few consistent RAPD markers. The more labor-intensive extraction with hexadecyltrimethyl ammonium bromide (CTAB), however, produced more reliable RAPD markers. Eight of 11 cultivars were distinguished by using RAPD markers produced using bulk seed samples together with four of 30 primers that were screened. These results show the potential of RAPD markers to provide the turfgrass industry, breeders, and certification agencies additional options to ensure the genetic integrity of perennial ryegrass seed lots and cultivars.
Decreased light quantity or quality affects the growth of turfgrass plants. Shade causes thinning of turfgrass stands and loss in surface quality. Plant changes include increased chlorophyll levels, lower soluble sugars, and loss of canopy cover. The objective of this research was to investigate if applications of foliar nitrogen and trinexapac-ethyl [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (TE) would result in beneficial biochemical changes in creeping bentgrass (Agrostis stolonifera L. cv. Penncross) grown in different shaded environments. Foliar applications of three nitrogen treatments, (NH2)2CO, Ca(NO3)2, or (NH4)2SO4, were made weekly at 0.43 g N/m2. Growth regulator treatments consisted of an untreated control or TE applied biweekly at an a.i. rate of 0.057 kg·ha−1. Plots were established in full sun (FS), neutral shade (NS), and deciduous shade (DS). Chlorophyll content, soluble carbohydrates, flavonoids, clipping yield, and color were measured. Nitrogen treatments caused some variation in levels of soluble carbohydrates in shaded conditions. Chlorophyll (Chl) levels varied between TE treatments, with increased levels of chlorophyll b (Chl b) found in TE-treated plots under FS. Application of TE resulted in higher flavonoid concentrations in leaf tissue in shaded conditions. Repeated applications of (NH2)2CO significantly improved color (P = 0.05). Turfgrass managers maintaining creeping bentgrass in shade may benefit from applications of TE and (NH2)2CO.
Creeping bentgrass (Agrostis stolonifera L.) is a turfgrass species that is widely used on golf courses throughout the United States. In field settings, plants are often subjected to more than one stress at a time, and studying stresses independently is likely insufficient. Stresses, such as heat stress and salt stress, can affect plant hormone levels and, in turn, plant hormone levels can affect how well the plant tolerates stress. The objectives of the experiments were to determine if the levels of heat stress and salt stress used would be detrimental to creeping bentgrass health, and if applying plant growth regulators could improve plant health during stress. During the first experiment, creeping bentgrass was transplanted to hydroponics systems in two different growth chambers. One chamber was set to have day and night temperatures of 35 °C and 30 °C (heat stress), respectively, and the other had day and night temperatures of 25 °C and 20 °C, respectively. Within each chamber, one block received a 50 mM NaCl treatment (salt stress) and the other did not (control). The stress treatments were applied for 14 days. Results of the first experiment indicated that the treatments were sufficient to negatively affect creeping bentgrass growth and health as indicated by fresh shoot and root weights, tillering, electrolyte leakage, and total chlorophyll content (TCC). There were significant interactions of temperature × salt level detected for shoot and root weights and electrolyte leakage. Plants that were exposed to both heat stress and salt stress were more negatively affected than plants exposed to either heat stress or salt stress alone for all metrics except for tillering. The presence of salt reduced tillering regardless of the temperature regimen. During the second experiment, plants were treated the same, but the plant growth regulator (PGR) treatments were also applied. The PGR treatments consisted of two different gibberellic acid (GA) synthesis inhibitor products, 2,4-dichlorophenoxyacetic acid, two different rates of aminoethoxyvinylglycine (AVG), an ethylene synthesis suppressor, and plants that were not treated with the PGR. In addition to the measurements of plant health and growth, dry shoot and root weights were measured. For the TCC, there was a two-way interaction between temperature × PGR treatment. For electrolyte leakage, there was a three-way interaction between temperature × salt level × PGR treatment. Combined heat stress and salt stress negatively affected all plants regardless of PGR treatment, but there were differences between PGR treatments. Plants treated with AVG exhibited improved health and growth compared with the other PGR treatments. These plants had the highest shoot and root masses. Plants treated with GA synthesis inhibitors had the lowest shoot and root masses as well as the lowest TCC when subjected to stress.
Turf grown in shade exhibits increased stem elongation. Dwarfism could improve turfgrass quality by reducing elongation. The purpose of this study was to examine the effect of GA2-oxidase (GA2ox) overexpression on creeping bentgrass (Agrostis stolonifera L.) performance under restricted light conditions and low mowing heights. Greenhouse studies were conducted at The Ohio State University, Columbus, OH, from 1 Sept. to 31 Oct. in both 2008 and 2009. Two experimental lines, Ax6548 and Ax6549, transformed with CP4 EPSPS and PcGA2ox gene; and a nontransformed control (NTC) was subjected to four light environments: full sun, reduced red to far red light ratio (R:FR), neutral shade [reduced photosynthetic photon flux (PPF)], and canopy shade (reduced PPF and R:FR). Turf was evaluated every 10 days for color and percent coverage. GA2ox overexpression resulted in darker green color in both transgenic lines under all light treatments as compared with NTC plants. No differences in overall turfgrass coverage were noted in full sun conditions among the lines. A significant decrease in turf coverage occurred for all shade treatments regardless of line. However, Ax6549 decreased the least. Overall data indicated that GA2ox overexpression can improve quality of turfgrass under reduced light conditions.