Creeping Bentgrass Cultivars Research Articles

142 Root Mortality and Nutrient Uptake of Creeping Bentgrass in Response to Differential Root and Shoot Temperatures

This study was designed to compare and determine root growth and nutritional responses of creeping bentgrass cultivars that differ in heat tolerance to deferential, supraoptimal shoot and root temperatures. Shoots and roots of `Penncross' (heat sensitive) and `L-93' (heat tolerant) were exposed to four differential air/soil temperature regimes (20/20-control, 20/35, 35/20, and 35/35 °C) in water baths and growth chambers. Exposing roots to supraoptimal root temperature (35 °C) while maintaining shoots at normal temperature (20 °C), or at 35 °C in particular, reduced root fresh weight, root number, the content of N, P, and K in shoots and roots, and accelerated root death for both cultivars. High root temperature had a greater detrimental effects on root growth and nutrient accumulation than high shoot temperature for both cultivars. Reducing root temperature at supraoptimal shoot temperature improved root growth, reduced root mortality, and increased N, P, and K content in shoots and roots. Among the three nutrient elements, K was the most sensitive to changes in root temperature. L-93 generally maintained higher root fresh weight and number, and N, P, K content in shoots and roots, particularly K in roots, under high root (20/35 °C) or shoot/root (35/35 °C) temperatures. The results indicated that root growth and nutrient accumulation, particularly K, played an important role in creeping bentgrass tolerance to heat stress imposed to shoots by high air temperature or to roots by high soil temperatures. Reducing root temperature under supraoptimal ambient temperatures enhanced root growth and nutrient relations, and thus could lead to the improved shoot growth in cool-season grasses as reported previously.

Nitrogen Utilization in Creeping Bentgrass

Abstract N utilization, including plant dry weight (DW) production, total N and nitrate N (NO3-N) content accumulation, N utilization efficiency (NUE), root absorption efficiency (RAE), reduced N accumulation, and nitrate assimilation capacity (NAC) were determined for creeping bentgrass cultivars grown in hydroponic culture. Possible mechanisms affecting N utilization including nitrate reductase activity (NRA) and root morphology were also examined. Four cultivars, selected from an initial screening of creeping bentgrasses were grown under both low and high levels of N in a flowing solution culture system. The relationship between NUE and plant growth for two different creeping bentgrass cultivars was investigated through tissue culture, The results indicate a genotypic variation in N utilization and absorption. The NAC was not the primary factor involved in genotypic differences in NUE. However, NRA was probably one of the mechanisms for the regulation of NUE. N utilization was affected by the level of ...

Heat Stress Injury in Relation to Membrane Lipid Peroxidation in Creeping Bentgrass

Understanding physiological and biochemical factors involved in heat‐stress injury would help improve heat tolerance of cool‐season grasses. The objective of this study was to investigate lipid peroxidation of cell membranes in relation to heat‐stress tolerance in creeping bentgrass (Agrostis palustris Huds.). Two creeping bentgrass cultivars differing in heat tolerance, L‐93 (heat tolerant) and Penncross (heat sensitive) were grown under two temperature regimes: 22/16°C (day/night) and 35/25°C for 56 d in growth chambers. Photochemical efficiency (Fv/Fm) and chlorophyll content of leaves; and electrolyte leakage (EL); content of the lipid peroxidation product, malondialdehyde (MDA); and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in leaves and roots were determined biweekly during heat stress. Leaf Fv/Fm ratio and chlorophyll content decreased, whereas EL and MDA contents of both leaves and roots increased under heat stress in both cultivars, but to a greater extent in Penncross. The activities of SOD and CAT decreased, whereas POD activity increased in both leaves and roots, which occurred to a greater extent for Penncross. The increases in MDA content and POD activity under heat stress were greater for leaves than for roots in both cultivars. These results suggest that decreased activities of antioxidant enzymes could result in an increased level of lipid peroxidation. Thus, decreased activities of antioxidant enzymes could contribute to damage of cell membranes and to leaf senescence as demonstrated by increased EL and reduced Fv/Fm, and by decreased chlorophyll content during heat stress. Cultivar variations in antioxidant enzyme activities were associated with their differences in heat tolerance as evidenced by Fv/Fm ratio, chlorophyll content, and EL.

Ecologically Based Approaches to Management of Phytophthora Blight on Bell Pepper.

Phytophthora blight, caused by the oomycete pathogen, Phytophthora capsici, is a devastating disease on bell pepper and cucurbit crops in the United States and worldwide (29,40). P. capsici causes a root and crown rot, as well as an aerial blight of leaves, fruit, and stems, on bell pepper (Capsicum annuum), tomatoes, cucumber, watermelon, squash, and pumpkin (29,35, 40,57,73). The disease was first described on bell pepper in New Mexico in 1922 (40). In recent years, epidemics have been severe in areas of North Carolina, Florida, Georgia, Michigan, and New Jersey. Oospores are believed to provide the initial source of inoculum in the field, and the disease is polycyclic within seasons (1,7,59,60,67). In this article, we discuss the biology and epidemiology of Phytophthora blight on bell pepper and also describe management strategies that can be implemented based on existing knowledge of the ecology of this devastating pathogen. The objectives of ecologically based pest management (EBPM) are the safe, profitable, and durable management of pests that includes a total systems approach (25). EBPM relies primarily on biological input of knowledge concerning a pathogen life cycle, and secondarily, when necessary, on physical, chemical, and biological supplements for disease management. An understanding of the ecological processes that are suppressive to plant diseases is emphasized rather than secondary inputs (25). Fortunately, we have a considerable amount of information available on the biology and ecology of P. capsici, which can now be integrated to improve our ability to manage the disease using ecologically based approaches. Strategies recommended for management of Phytophthora blight involve integrated approaches that focus first on cultural practices that reduce high soil moisture conditions, but also include monitoring and reduction of propagules of P. capsici that persist in the soil, utilization of cultivars with resistance to the disease, and when necessary, judicious fungicide applications. Symptoms and Life Cycle P. capsici can infect virtually every part of the pepper plant. The pathogen causes a root and crown rot on pepper (Fig. 1) and also forms distinctive black lesions on the stem (Fig. 2). P. capsici can also infect the leaves and causes lesions that are circular, grayish brown, and water-soaked (Fig. 3). Leaf lesions and stem lesions are common when inoculum is splash dispersed from the soil to lower portions of the plant. The pathogen can also infect fruit and causes lesions that are typically covered with white sporangia, a sign of the pathogen (Fig. 4). P. capsici typically causes a fruit rot or stem rot on cucumbers and squash (Fig. 5). P. capsici reproduces by both sexual and asexual means (Fig. 6). The pathogen produces two mating types, known as the A1 and A2. These are actually compatibility types and do not correspond to dimorphic forms. Each mating type produces hormones that are responsible for gametangia differentiation in the opposite mating type. Both A1 and A2 mating types are common in fields in North Carolina and have also been identified within the same plant (59). P. capsici produces a male gametangium, called the antheridium, and a female gametangium, called the oogonium. The antheridium is amphigynous in this species. Meiosis occurs within the gametangia, and plasmogamy and karyogamy result

Dollar Spot Severity as Influenced by Trinexapac‐ethyl, Creeping Bentgrass Cultivar, and Nitrogen Fertility

AbstractDollar spot (Sclerotinia homoeocarpa F.T. Bennett) is a widely distributed and destructive pathogen of turfgrass in the United States. A 2‐yr field study was conducted at Columbus, OH, to determine the influence of a plant growth regulator, creeping bentgrass (Agrostis stolonifera L.) cultivars, and N fertility on dollar spot severity. ‘Crenshaw’ creeping bentgrass was seeded alone or in a 50:50 blend by weight with ‘Penncross’ creeping bentgrass. Plots were fertilized at 0, 24.4, or 48.8 kg N ha−1 per application. One‐half of each plot received trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxo‐cyclohexanecarboxylic acid methyl ester] at 0.8 L ha−1. The TE and fertilizer treatments were initiated in May 1995 and 1996 with four subsequent applications made at 30‐d intervals. Initially, the cultivar blend reduced the rate of dollar spot development compared with Crenshaw alone; however, neither the blend nor Crenshaw provided commercially acceptable dollar spot suppression throughout the study. Both TE and N fertilization significantly (P ≤ 0.05) reduced dollar spot severity over the 2‐yr period. Trinexapacethyl applied alone effectively suppressed dollar spot activity, but efficacy increased with increasing N rates. Dollar spot symptoms decreased and thatch thickness increased at elevated N levels. During this 2‐yr study, interactions between TE and N fertility resulted in a significant (P ≤ 0.05) reduction in dollar spot severity. Thus, on golf course fairways where dollar spot may be severe, incorporation of these two treatments into a turfgrass management program will enhance dollar spot suppression and reduce fungicide inputs.

Variation Among Creeping Bentgrass Cultivars in Recovery from Epidemics of Dollar Spot.

Dollar spot was allowed to develop from natural inoculum in 15 cultivars of creeping bentgrass (Agrostis palustris) until epidemics were well established. At that time, initial disease intensities were assessed, and one-half of each plot was treated with cyproconazole at 0.3 kg a.i./ha. For each cultivar, disease intensities were assessed 6 to 14 days after treatment in both treated and untreated subplots. Three general patterns of recovery were observed: (i) significant recovery only with fungicide treatment; (ii) some recovery without treatment but greater recovery with treatment; and (iii) equal recovery with or without treatment. Only one cultivar exhibited the same recovery pattern in all 3 years; 10 of 15 cultivars exhibited the same pattern in 2 years of testing. In 1991 and 1993, nearly all cultivars tested recovered more quickly when treated with cyproconazole than when left untreated. In contrast, nearly half of the cultivars in 1992 exhibited the same level of recovery in both treated and untreated subplots. Weather conditions during the 1992 test period were cooler and wetter than during the other years of the study, which probably favored host growth and turfgrass recovery. While some cultivars exhibited partial resistance to dollar spot, no consistent association was found among creeping bentgrass cultivars between the level of partial resistance to, and recuperative ability from, dollar spot. Although the recuperative potential of cultivars varies in different environments, the ability to recover quickly from a disease outbreak could be a valuable cultivar attribute, particularly if it can sometimes occur without a curative fungicide application.

Potential of RAPD Markers for Use in the Identification of Creeping Bentgrass Cultivars

The production of RAPD markers is rapid and provides a reliable mechanism for generating an almost infinite number of polymorphisms useful in cultivar identification. The potential use of RAPD markers to identify bulk seed samples of 13 synthetic creeping bentgrass (Agrostis stolonifera L. var. stolonifera) cultivars was examined. Two seed lots were evaluated for five of the 13 cultivars. Eight of the 50 oligonucleotide primers screened produced unique polymorphic amplification fragments that identified 11 of the 13 cultivars. Two cultivars could not be identified because the amplification fragments that distinguished one seed lot were not present in the second seed lot of the same cultivar. These observed differences among seed lots were repeatable. The results demonstrate that RAPD markers have the potential to be a valuable tool for the identification of synthetic turfgrass cultivars as long as precautions are taken to account for the possibility of seed lot effect.

Relationships among Creeping Bentgrass Cultivars Based on Isozyme Polymorphisms

An understanding of the genetic variability within a crop species is essential to its improvement. The objectives of this research were to study the utility of isozyme patterns for creeping bentgrass (Agrostis palustris Huds.) cultivar identification and to estimate the relationships between creeping bentgrass cultivars based on isozyme patterns. Seventy to 73 plants from each of 18 creeping bentgrass cuitivars and 25 plants from one plant introduction were scored for 24 isozyme polymorphisms representing six loci. All cultivars except a small group containing the cultivars Pennlinks, Pro/Cup, Southshore, and Lopez were uniquely characterized based on a 20% or greater band frequency in one cultivar versus absence of the band in the most closely clustered cultivar. The isozyme patterns from each plant were used to calculate the genetic distance within a cultivar, and the average band frequency within a cultivar was used to calculate genetic distances between cultivars. The cultivars Pennlinks, Pro/Cup, Southshore, and Lopez had the highest average within‐cultivar genetic distances indicating that additional marker loci will be needed to distinguish these cultivars. The unweighted pair group method with arithmetic average (UPGMA) cluster analysis generated from the between‐cultivar genetic distance matrix divided the cultivars into two groups. One group contains 10 cultivars including the variety Seaside which may have provided initial germplasm for this group. The second group contains the cultivars Pennlinks, Southshore, Pro/Cup, Lopez, and four cultivars with unique allozymes. The plant introduction PI251945 was distantly related to the cultivated U.S. germplasm indicating that European material can be a source of genetic diversity to broaden U.S. bentgrass germplasm.

Effect of nitrogen rates and mowing heights on color, density, uniformity, and chemical composition of creeping bentgrass cultivars in winter

Abstract Creeping bentgrass (Agrostis palustris Huds.) is used on golf course putting greens in Japan, however, this turfgrass goes dormant and loses color in the winter. Two levels (0.8 and 9.6 gm2) of nitrogen (N) and two mowing heights (5 and 12 mm) were used to determine their effects on turf quality (color, uniformity, and density) and chemical composition of 12 cultivars of creeping bentgrass during the winter. High N rate or mowing height increased color of the plants significantly during the experiment, but high N rate was more effective than high mowing height. High N rate increased the levels of N, potassium (K), boron (B), phosphorus (P), sulfur (S), and magnesium (Mg), but reduced the levels of calcium (Ca), zinc (Zn), manganese (Mn), molybdenum (Mo), and copper (Cu) in the plant tissues. High mowing height resulted in an increase in K content, but reduction in N, P, S, Ca, and Mo levels, though the levels of other nutrients were not affected. The level of N of plants under low N rate was belo...

Relationship of shoot morphology between seedlings and established turf in creeping bentgrass

Shoot morphological characteristics are important determinants of turf quality in creeping bentgrass. The objectives of this research were to determine differences for tiller and stolon characteristics among creeping bentgrass cultivars and germplasms and compare these characteristics between seedlings and established turf. Two experiments involving 10 and 15 entries were grown in controlled environment chambers and harvested as seedlings at 21, 35 and 49 d and 21, 28 and 35 d, respectively. Nine and fifteen creeping bentgrass entries were grown in separate field experiments on sand-based golf greens and core samples were taken for subsequent measurements at 3 yr and 1 yr, respectively. Tiller and stolon measurements included seedling tillers plant−1 in the controlled environment; tillers m−2 on established turf; and leaf number, leaf width, plant height/stolon length, internode length, internode number, and stolon diameter in all experiments. The correlation coefficient for seedling tillers plant−1 at 35 d between the two controlled environment experiments was r = 0.835 and for tiller density between the two field experiments was r = 0.930. There were differences among the creeping bentgrass entries for tiller number (9 7 to 20.2) and internode length (20 to 54 mm) when measured at 35 d and for tiller density (67 to 227 × 103 m−2) in established turf. Correlation coefficients between seedling tillers plant−1 at 35 d and tiller number m−2 in established turf ranged from r = 0 701 to r = 0 826. There was also a high correlation for stolon internode length between seedling and established turf, with r values ranging from r = 0 725 to r = 0.948. These results document differences for tiller and stolon characteristics between creeping bentgrass cultivars and germplasms and indicate the potential for plant improvement of these characteristics in creeping bentgrass using 35-d-old seedlings in a controlled environment. Key words: Creeping bentgrass, tiller number, tiller density, stolons, turf, seedling

Transformation and Regeneration of Creeping Bentgrass (Agrostis palustris Huds.) Protoplasts

An efficient plant regeneration system from protoplasts of creeping bentgrass (Agrostis palustris Huds.) cultures is essential for gene transfer to these grasses through direct DNA uptake into protoplasts. A simple and efficient plant regeneration system for protoplasts isolated from embryogenic suspension cultures of seven creeping bentgrass cultivars was established. Suspension cultures were derived from embryogenic callus cultures established from surface‐sterilized mature seeds. Four creeping bentgrass cultivars were tested to determine their effect as feeders on plating efficiencies, callus development, and regeneration of protoplasts. Embryogenic suspension cultures from all four cultivars worked as feeders with plating efficiencies ranging from 0.05 to 0.32%. Protoplast derived calli formed within 3 wk after isolation and were regenerated with, or without, the addition of cytokinin to the regeneration medium. Some cultivars required the use of a particular feeder to regenerate plants. Plants were regenerated from all the cultivars tested. The bar gene, which confers resistance to the herbicide bialaphos [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid], was transformed into protoplasts by means of either PEG or electroporation. Bialaphos‐resistant colonies were obtained from five creeping bentgrass cultivars. Resistant colonies of the cultivar Cobra were regenerated into plants. One hundred fifty‐three Cobra transformants analyzed were resistant to five times the field rate of commercial formulation of the herbicide. Molecular characterization of the transformants revealed the stable integration of the bar gene into the genome and expression of transcripts corresponding to the bar gene.

Biska creeping bentgrass

Biska is a creeping bentgrass cultivar (Agrostis palustris Huds.) selected for increased tiller density, dark green colour and seed yield. In comparison with other bentgrasses, Biska has shown higher tiller densities and higher seed yields under Manitoba conditions.Key words: Cultivar description, creeping bentgrass, Agrostis palustris Huds.

Creeping Bentgrass Cultivar Water Use and Rooting Responses

Low evapotranspiration (ET) rates and deep extensive root systems are desirable drought avoidance characteristics. In this study, 10 creeping bentgrass (Agrostis palustris Hudson) cultivars were evaluated for ET and rooting responses. Evapotranspiration measurements were made in the field during 1987 and 1988 using minilysimeters filled with fritted clay. Crop coefficients (Kc) were determined for each cultivar using a Nebraska modified Penman equation for potential ET. Root distribution experiments were conducted in a controlled environment using a specially designed hydroponic system. Cultivar ET rate differences were repeatable over the 2‐yr field study. ‘Seaside’ and ‘SR‐1020’ ranked high in ET and had Kc values consistently >1, while ‘Pennlinks’ and ‘National’ ranked low, with Kc values consistently <1. Cultivars differed for total root production and root distribution. ‘Cobra’, ‘Penncross’, Pennlinks, ‘Providence’, and SR‐1020 produced roots to depths of 600 to 750 ram. ‘Emerald’, ‘Prominent’, and ‘Penneagle’ did not produce roots beyond 450 ram. Evapotranspiration rate and root distribution variability among creeping bentgrass cultivars could serve as selection criteria in a turfgrass breeding program interested in improving drought resistance.

Color Variation of Creeping Bentgrass Cultivars as Related to Iron and Chlorophyll1

Abstract Color Variations of creeping bentgrass (Agrostis palustris Huds.) are correlated with the iron and Chlorophyll content in leaf tissues. The color value and Chlorophyll content of ‘Cohansey’, a light green cultivar, increases significantly 2 hours after the application of ferrous sulphate. However, ‘IaGreen 4-45’, a dark green cultivar, shows little response. Increases in Chlorophyll or color following iron treatment are temporary. Chlorophyll content of creeping bentgrass cultivars varied during the growing season, and peaked in August.

Electrophoretic Identification of Agrostis palustris and Poa pratensis Cultivars1

The feasibility of creeping bentgrass (Agrostis palustris Huds.) and Kentucky bluegrass (Poa pratensis L.) cultivar identification by acrylamide gel disc electrophoresis was investigated. Fresh leaf protein was extracted at 4 C by grinding in a mortar with a 0.2 M phosphate buffer, pH 7.0 containing 0.1 M sodium ascorbate, 10 mM sodium diethyldithiocarbamate, 0.06 mM 2‐mercaptobenzothiazole, and 1.0 mM disodium ethylenediaminetetraacetate. Tris and unmodified phosphate buffers proved unsuccessful. The protein extract was squeezed from the tissue and centrifuged at 10,000 g for 30 min at 4 C. The supernatant was used for electrophoresis. Electrophoresis was run with a 7% acrylamide gel and a Tris‐glycine electrode buffer, pH 8.3. Protein bands were stained with Coomassie Blue. Six creeping bentgrass cultivars could be individually distinguished. Ten Kentucky bluegrass cultivars were examined. Six could be placed into groups of two, and two could be identified singly, while two showed no characteristic banding.