Creeping Bentgrass Cultivars Research Articles

Suitability of Creeping Bentgrass and Bermudagrass Cultivars for Black Cutworms and Fall Armyworms (Lepidoptera: Noctuidae).

The black cutworm, Agrotis ipsilon Hufnagel, and fall armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), are common turfgrass pests of golf courses in the southeastern United States. Heat-tolerant bentgrass (Agrostis stolonifera L.) cultivars are expanding the range of bentgrass further south, but these cultivars have not been studied for their potential host plant resistance to black cutworm or fall armyworm. The goals of the study were to investigate feeding response of black cutworm and fall armyworm to these newer heat-tolerant creeping bentgrass cultivars, as well as commonly used cultivars of bermudagrass [Cynodon dactylon (Loppers.)]. Choice and no-choice feeding assays and fecundity tests were conducted in the laboratory and greenhouse to evaluate performance and preference of the two insects. When given a choice, neither black cutworm nor fall armyworm showed a preference for the majority of new cultivars tested. There were no differences in leaf area consumption or insect development for either pest in no-choice feeding assays. Black cutworm females preferred laying eggs in bentgrass compared with bermudagrass, but will oviposit onto bermudagrass, suggesting that both turf species are suitable hosts of this pest. The broad host ranges of generalist caterpillar pests of turfgrass hinder the application of host plant resistance in integrated pest management on golf courses.

Phytohormone Responses and Cell Viability during Salinity Stress in Two Creeping Bentgrass Cultivars Differing in Salt Tolerance

Salinity stress is becoming more prevalent in turfgrass management with the increasing use of recycled water for irrigation. Creeping bentgrass (Agrostis stolonifera) is a cool-season turfgrass species that contains significant cultivar variation in salt stress tolerance, but the mechanism related to this cultivar variation is not well understood. Our objectives were to determine whether differential hormone content could play a role in cultivar variation of salt responses and to evaluate whether cell viability assays using dye techniques could differentiate salt stress damage levels in turfgrass species. Therefore, a growth chamber study with potted plants was conducted to evaluate salt ion concentrations, physiological responses, and hormone analysis [abscisic acid (ABA), indole-3-acetic acid (IAA), jasmonic acid (JA), salicylic acid (SA), zeatin riboside (ZR), and ethylene] at 4, 8, and 12 dS·m−1 in relatively salt-tolerant ‘Mariner’ compared with salt-sensitive ‘Penncross’ creeping bentgrass. A hydroponics-based growth chamber study was performed for evaluation of whether dead-cell stains coupled with image analysis could be a quick method for indicating cell viability variation between cultivars. Greater salt tolerance was evident in ‘Mariner’ at 12 dS·m−1, which showed significantly lower electrolyte leakage, higher leaf relative water content (RWC), osmotic potential, photochemical efficiency, and photochemical yield compared with ‘Penncross’. A higher K+ and lower Na+ content was maintained in leaves of ‘Mariner’ compared with ‘Penncross’ while roots of ‘Mariner’ maintained higher Ca2+ content under stressed and nonstressed conditions. Phytohormone levels showed a decline in salt-stressed roots compared with nonstressed plants but ‘Mariner’ roots were able to maintain levels higher than ‘Penncross’. ‘Mariner’ leaves showed an increased accumulation of ABA, JA, SA, and ZR while roots maintained higher IAA and SA compared with ‘Penncross’. The results suggest that ‘Mariner’ was able to mitigate salt stress by better ion regulation and differential regulation of hormones compared with ‘Penncross’. ‘Mariner’ leaves and roots showed significantly lower dead cells compared with ‘Penncross’ under salt stress. The results suggest that staining for cell viability could be a useful technique for studying turfgrass stress or other cellular responses.

Sclerotinia homoeocarpa overwinters in turfgrass and is present in commercial seed.

Dollar spot is the most economically important disease of amenity turfgrasses in the United States, yet little is known about the source of primary inoculum for this disease. With the exception of a few isolates from the United Kingdom, Sclerotinia homoeocarpa, the causal agent of dollar spot, does not produce spores. Consequently, it was assumed that overwintering of this organism in soil, thatch, and plant debris provides primary inoculum for dollar spot epidemics. Overwintering of S. homoeocarpa in roots and shoots of symptomatic and asymptomatic creeping bentgrass turfgrass was quantified over the course of a three-year field experiment. Roots did not consistently harbor S. homoeocarpa, whereas S. homoeocarpa was isolated from 30% of symptomatic shoots and 10% of asymptomatic shoots in the spring of two out of three years. The presence of stroma-like pathogen material on leaf blades was associated with an increase in S. homoeocarpa isolation and colony diameter at 48 hpi. Commercial seed has also been hypothesized to be a potential source of initial inoculum for S. homoeocarpa. Two or more commercial seed lots of six creeping bentgrass cultivars were tested for contamination with S. homoeocarpa using culture-based and molecular detection methods. A viable, pathogenic isolate of S. homoeocarpa was isolated from one commercial seed lot and contamination of this lot was confirmed with nested PCR using S. homoeocarpa specific primers. A sensitive nested PCR assay detected S. homoeocarpa contamination in eight of twelve (75%) commercial seed lots. Seed source, but not cultivar or resistance to dollar spot, influenced contamination by S. homoeocarpa. Overall, this research suggests that seeds are a potential source of initial inoculum for dollar spot epidemics and presents the need for further research in this area.

고산지역에서의 크리핑 벤트그래스 품종 생육특성 비교

고산지역 기후 환경에서 크리핑 벤트그래스품종의 생육특성을 비교 분석하여 그린과 페어웨이조건에 적합한 품종을 선발하기 위해본 실험을 실시하였다. 먼저 경기중부, 영서시내, 영서 고산지대의 기후환경 데이터를 비교 분석하였을 때, 고도에 따른 기후의 차이가 위도에 따른 지역 차이보다 큰 것으로 분석되었다. 영서산악지대에 USGA 방식의 그린용 지반과 캘리포니아식의 페어웨이 지반의 시험포장을 조성한 후 5가지 종류의 크리핑 벤트그래스 품종을 파종하여 두 지반에 따라 깎는 높이를 달리하여 3년간 생육기간의 품종별 생육특성을 비교 분석하였다. 봄철 그린 업 측정한 결과 'T-1'과 'CY-2'는 타 품종들 보다 좀 그린업이 빨랐으나 'Penncross'는 그린업이 가장 더딘 것으로 나타났다. 그린과 페어웨이 예고환경에서 비슷한 결과가 나타났다. 실험기간 중 'T-1' 품종이 전반적인 시각적 품질평가 결과와 전반적인 뿌리길이에서 가장 우수하였으나 하절기에는 'Penncross'의 뿌리 길이와 건중량이 높았고, 'Penn A-1' 품종이 가장 낮은 결과를 보였다. 전반적으로 페어웨이에서도 그린조건에서와 같이 'T-1', 'CY-2' 품종이 엽색, 피복도, 뿌리길이 등 양호한 생육특성을 보였다. This experiment was carried out for the selection of suitable cultivars on the green and fairway at the mountain area. The climate data showed that differences of altitude influenced greater than latitude on temperature and rainfall when compared with 3 areas of the central of Gyeong-gi and Yeong-seo, and the mountain area at Yeong-seo. The plot was prepared with the USGA profiles for green and modified California style for fairway at the mountain golf course in Wonju, Korea. The growth characteristics were compared on two different profiles for 3 years of growing seasons after seeding with 5 creeping bentgrass cultivars. 'T-1' and 'CY-2' showed a rapid greenup compare with other cultivars in spring of 2010 with the both green and fairway mowing height. However, 'Penncross' resulted the slowest among cultivars. 'T-1' showed the most prominent visual quality of overall rate and the deepest root length after one year of seeding, while 'Penncross' showed an excellent result of root length and weight during summer season. However, 'Penn A-1' had an imperial result in that season. Comparison of the growth characteristics under green and fairway conditions, 'T-1' and 'CY-2' showed exellent overall results at the mountain area at Yeong-seo area in Korea.

Physiological Responses of Creeping Bentgrass Cultivars to Carbonate, Chloride, and Sulfate Salinity

ABSTRACTEvaluation of creeping bentgrass (Agrostis stolonifera L.) salt tolerance often showed inconsistent results. The objective of this study was to investigate the reactions of ‘Seaside II’ and ‘T‐1’ to NaCl, Na2CO3, Na2SO4, and CaCl2, each at concentrations of 0, 25, 75, 125, 175, and 225 mM. Chlorophyll a (Chla) content was the lowest in the CaCl2 treatment followed by Na2CO3 and Na2SO4 and highest in NaCl whereas chlorophyll b (Chlb) content was lowest in Na2CO3 followed by CaCl2 and Na2SO4 and highest in NaCl. Turfgrass visual quality and green density were reduced the most by the Na2CO3 and CaCl2 treatments. Evapotranspiration (ET) decreased in the order of treatments CaCl2, Na2SO4, Na2CO3, and NaCl at 1 wk after treatment (WAT), but at 4 WAT there were no difference among CaCl2, Na2SO4, and Na2CO3. Significant salt type × concentration interaction existed, and the first order or second order coefficient of regression equation ranked the changing rate of physiological parameters differently in different salts. Leaf K+:Na+ ratio was affected differently by salts and a threshold of 1 appeared at different salt concentrations depending on salt types and cultivars. The pH, osmotic potential, and electrical conductivity of salt solutions were confounded making the interpretation of mechanisms of physiological stress difficult. Nevertheless, this study showed that different salts rank creeping bentgrass salt tolerance differently.

Quantifying Nitrogen Requirement for Creeping Bentgrass Putting‐Green Cultivars

Nitrogen is perhaps the most important nutrient for turfgrasses because it improves color, density, and recuperative ability when applied at adequate rates. Although numerous unique traits, such as dark genetic color and improved stress tolerance have been identified, there is a lack of published data comparing creeping bentgrass cultivar N use. Therefore, a field study was initiated in 2009 and 2010 to identify creeping bentgrass (Agrostis stolonifera L.) putting‐green cultivars that required the least amount of N to maintain acceptable color while maintaining desirable agronomic traits and good overall playability. Eighteen creeping bentgrass cultivars were planted on 2 July 2006 and maintained at a 3.2‐mm mowing height. Nitrogen, liquid urea, was applied at 49, 147, or 294 kg ha−1 yr−1. Nitrogen applications were applied every 2 wk from April to October. Data collection included turfgrass color, relative chlorophyll index (RCI), clipping yield, lateral regrowth, ball‐roll distance, and thatch accumulation. Increasing N rates resulted in higher RCI, more top growth, faster lateral regrowth, and shorter ball‐roll distances. Regarding thatch accumulation, no significant differences were detected between cultivars. Overall, the creeping bentgrass cultivars that maintained acceptable color with the least amount of N input included ‘007’, ‘Authority’, ‘Penn A‐4’, ‘Shark’, and ‘T‐1’. These cultivars also maintained desirable agronomic traits, such as high RCI, reduced clipping yield, increased lateral regrowth, and adequate ball‐roll distance. This research indicates creeping bentgrass cultivar is an important selection criterion if a reduction in N use is a relevant consideration.

First Report of Dollar Spot Caused by Sclerotinia homoeocarpa on Agrostis stolonifera in North Dakota.

Dollar spot disease is a major concern for golf courses nationwide, resulting in poor turf quality and significant damage to playing surfaces. To manage this disease effectively, fungicides need to be applied regularly. This management strategy represents a significant cost to turfgrass managers and may impact the economics of the industry in North Dakota. In the summer of 2011, small, circular, sunken brown patches of dead turf approximately 5 cm in diameter and resembling dollar spot disease were observed on a creeping bentgrass (Agrostis stolonifera L.) variety trial at the North Dakota State University Agricultural Experiment Station in Fargo, ND. Fresh individual leaf specimens with distinct lesions having straw colored centers and reddish brown margins were collected. Leaves were surface disinfected in a 0.05% sodium chloride solution for 60 s, rinsed three times in sterile distilled water, then placed onto potato dextrose agar (PDA). Three isolates were obtained from the disease infested leaves with similar morphology to that described for Sclerotinia homoeocarpa F.T. Bennett (1). Fungal colonies were initially colorless followed by the development of sparse white columnar aerial mycelia with cinnamon colored bases. Hyphae were 5 to 8 μm wide and thin walled with dense granular contents and septations at irregular intervals. Fourteen days after culturing, dark brown to black mycelial stroma developed. A single representative isolate was selected to conduct inoculations. Inoculum was produced by placing six 5-mm-diameter plugs of PDA with actively growing mycelium into an Erlenmeyer flask with 40 g of sterile millet seed. The inoculum was incubated for 14 days at ambient temperature (20 to 25°C). Three creeping bentgrass cultivars, Crenshaw, Declaration, and L-93, were inoculated (two pots per cultivar). Following inoculation, the pots were misted with water, sealed in separate plastic bags, and placed in the dark for 48 h. For the next 5 days, plants were placed for 8 h outside of bags on a bench with full spectrum fluorescent bulbs, followed by 16 h in plastic bags in the dark. Finally, pots were placed on a bench for 48 h. Signs and symptoms of S. homoeocarpa developed on all pots, whereas the controls remained asymptomatic. The same fungus was reisolated from grass leaves, satisfying Koch's postulates. To confirm the identity of the fungus, the internal transcribed spacer was amplified using the ITS4 and ITS5 primers (2). The amplicon was sequenced, generating a 549-bp sequence (Accession No. JQ735942) with 100% similarity to sequences of S. homoeocarpa in GenBank (Accession Nos. GQ924924.1, GQ924923.1, and EU123801.1). To our knowledge, this is the first confirmed report of dollar spot in North Dakota.

Construction of a linkage map for quantitative trait loci associated with economically important traits in creeping bentgrass (Agrostis stolonifera L.)

Creeping bentgrass (Agrostis stolonifera L.) is the most widely cultivated and high-value turfgrass species. Genetic linkage maps of creeping bentgrass were constructed for quantitative trait loci (QTL) analysis of gray snow mold (Typhula incarnata) resistance, recovery and leaf width. A segregating population of 188 pseudo-F2 progeny was developed by two-way pseudo-testcross mapping strategy. Amplified fragment length polymorphism, new developed Agrostis specific expressed sequence tag-single sequence repeat (SSR), random amplified polymorphic DNA and genomic SSR markers corresponding to DNA polymorphisms heterozygous in one parent and null in the other, were scored and placed on two separate genetic linkage maps, representing each parent. In the male parent map, 100 markers were mapped to 14 linkage groups covering a total length of 793 cM with an average interval of 8.2 cM. In the female parent map, 146 markers were clustered in another 14 linkage groups spanning 805 cM with an average distance of 5.9 cM between adjacent markers. We identified three putative QTL for leaf width and one QTL for snow mold disease resistance. The construction of a linkage map and QTL analysis are expected to facilitate the development of disease resistant creeping bentgrass cultivars by using molecular marker-assisted selection.

Seasonal Development of Dollar Spot Epidemics in Six Creeping Bentgrass Cultivars in Maryland

This 3-year field study evaluated the incidence and severity of dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in six creeping bentgrass (Agrostis stolonifera L.) cultivars maintained as a golf course fairway. Comparison of area under the disease progress curve (AUDPC) data clearly indicted two resistance groups among the six cultivars. ‘Crenshaw’ and ‘Backspin’ were classified as highly susceptible (HS) and the other four cultivars (i.e., ‘Penncross’, ‘Providence’, ‘L-93’, and ‘007’) were classified as moderately susceptible (MS) to dollar spot. In all three study years, there were three epidemics that began in May. Data could not be collected in HS cultivars after the first epidemic in each year as a result of severe damage. In MS cultivars, the first epidemic ended and a second began between early July and late August. The second epidemic ended approximately mid-October and a third epidemic appeared in MS cultivars between late October and early December. The second epidemic was longest and most severe, and the third fall epidemic was least severe and of shortest duration. The first epidemic in HS cultivars developed up to two weeks earlier and progressed more rapidly and severely than in MS cultivars. A growing degree-day (GDD) model, using a base air temperature of 15 °C and a start date of 1 Apr., was accurate in predicting the onset of the first epidemic in HS (60 to 70 GDD) and MS (105 to 115 GDD) cultivars during each of the three study years. Growing degree-day models are greatly influenced by the many microclimates found on golf courses and need to be evaluated for accuracy in diverse environments.

The relationship between mineral concentration, electric conductibility and pH values in the late fall dew water on the two creeping bentgrass cultivars’ turf

The relationship between mineral concentration, electric conductibility and pH values in the late fall dew water on the two creeping bentgrass cultivars’ turf

Lateral Spread and Dry Matter Partitioning of Creeping Bentgrass Cultivars

ABSTRACTCreeping bentgrass (Agrostis stolonifera L.) cultivars are available that possess varying vegetative characteristics. A better understanding of the vegetative growth among creeping bentgrass cultivars is essential to its culture and would aid breeders in selecting for improved turf characteristics in germplasm screening programs. Our objectives were to identify differences in establishment rates among cultivars of creeping bentgrass and to determine the factors associated with differing growth rates by using growth analysis techniques. Spaced plantings of 24 cultivars of creeping bentgrass were evaluated for stolon characteristics and lateral spread. Two cultivars with differing lateral spread were used for further growth analysis in a growth chamber. ‘Penncross’ exhibited greater lateral spread and longer internodes compared with recently developed cultivars. ‘Bengal’ had the slowest lateral spread and the shortest mean stolon and internode length. Internode and stolon length were positively correlated as well as internode length and establishment rate indicating that cultivars with long internodes also possess fast establishment rates and longer stolons. Growth analysis indicated that Penncross and Bengal produce similar amounts of dry matter but Penncross allocates more dry matter into stolons than leaves. Variation in dry matter partitioning could partially explain differences in lateral spread among cultivars of creeping bentgrass. The vegetative characteristics should be matched with desired site usage requirements for optimum performance when selecting cultivars of creeping bentgrass.

Root Distribution and Tiller Densities of Creeping Bentgrass Cultivars and Greens-type Annual Bluegrass Cultivars in a Putting Green

Little knowledge exists regarding root distribution of creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua) in root zones of golf course putting greens. To compare root distribution between these species, three experimental cultivars of greens-type annual bluegrass and two commercial cultivars of creeping bentgrass (‘Penncross’ and ‘Penn A-4’) were established on an experimental golf green and managed under two nitrogen (N) fertility levels (195 and 65 kg N/ha/year) over a 2-year period. Creeping bentgrass had two and three times the total root mass compared with annual bluegrass during the first and second years of the experiment, respectively. At soil depths of 3–12 cm and below 12 cm, creeping bentgrass had three to four times the root mass compared with annual bluegrass at various times during the experiment. During the first year of the experiment, both species exhibited greater than 50% decrease in total root mass from June to August. During the second year, creeping bentgrass total root mass decreased 10% to 15% and annual bluegrass total root mass decreased 25% to 30% over the same period. Of the two bentgrasses, ‘Penn A-4’ creeping bentgrass exhibited greater total root mass only in the second year; however, ‘Penn A-4’ exhibited greater root mass than ‘Penncross’ below 12 cm in both years. Creeping bentgrass cultivars showed greater root mass below 12 cm at 65 kg N/ha/year compared with 195 kg N/ha/year on some sampling dates in both years. Annual bluegrass cultivars showed no change in any root mass parameters in response to N rates (data not shown), but specific root length (SRL) of annual bluegrass increased under the 65 kg N/ha/year rate compared with the 195 kg N/ha/year rate, whereas SRL of creeping bentgrass was similar at both N rates. Tiller densities of both species increased under the 195 kg N/ha/year rate. ‘Penn A-4’ exhibited higher tiller densities than ‘Penncross’ throughout the experiment and at times was equivalent to the tiller densities of the annual bluegrass cultivars. These results suggest that although creeping bentgrass increases root mass deeper in a putting green root zone mix at lower N rates (65 kg N/ha/year), annual bluegrass exhibits plasticity in specific root length in response to different N rates.

Differential proteomic responses to water stress induced by PEG in two creeping bentgrass cultivars differing in stress tolerance

Protein metabolism and expression play important role in plant adaptation to water stress. The objectives of this study were to examine proteomic responses to water stress induced by polyethylene glycol (PEG) in creeping bentgrass ( Agrostis stolonifera L.) leaves and to identify proteins associated with stress tolerance. Plants of two cultivars (‘Penncross’ and ‘Penn-A4’) differing in water stress tolerance were grown in sand irrigated daily with water (control) or PEG solution (osmotic potential of −0.66 MPa) to induce water stress, for 28 d in growth chambers. Shoot extension rate, relative water content and cell membrane stability were measured to compare drought tolerance between the two cultivars. All parameters maintained at a significantly higher level in ‘Penn-A4’ than in ‘Penncross’ under PEG treatment. After 28 d of water stress, proteins were extracted from leaves and separated by difference gel electrophoresis. Among 56 stress-responsive protein spots, 46 were identified using mass spectrometry. Some proteins involved in primary nitrogen and carbon metabolism were down-regulated by PEG-induced water stress in both cultivars. The abundance of antioxidant enzyme proteins (ascorbate peroxidase, catalase and glutathione-S-transferase) increased under water stress, particularly ascorbate peroxidase in ‘Penn-A4’. The abundance levels of actins, UDP-sulfoquinovose synthase and glucan exohydrolase were greater in ‘Penn-A4’ than in ‘Penncross’ under PEG treatment. Our results suggest that proteins involved in membrane synthesis, cell wall loosening, cell turgor maintenance, and antioxidant defense may play roles in perennial grass adaptation to PEG-induced water stress.

Aggressiveness of Three Snow Mold Fungi on Creeping Bentgrass Cultivars under Controlled Environment Conditions

Snow molds are the most important winter diseases of turfgrass in the United States and Canada. Eight isolates of three snow mold fungal species (three isolates of Typhula ishikariensis, three of T. incarnata, and two of Microdochium nivale) were collected from infected turfgrasses on golf courses. The isolates were evaluated for their relative aggressiveness on three cultivars (L-93, Penncross, and Providence) of creeping bentgrass (Agrostis palustris) under the same controlled conditions. Four plant ages (15, 19, 23 and 27 week-old plants from germination to inoculation) were evaluated for their susceptibility to the three pathogens and for the recovery of the plants. Regardless of age or cultivar of the host plant, M. nivale was found to be more aggressive and faster to infect and colonize than Typhula species. After three weeks recovery, M. nivale-inoculated plants showed higher disease severity than plants inoculated with the two Typhula species. Plants infected by Typhula species displayed no significant difference in disease severity. As creeping bentgrass plants get older, the severity of disease caused by three snow molds gradually decreases. This effect was observed in all cultivars tested, suggesting expression of age-related resistance as the bentgrass plants matured.

The characteristics and the mineral nutrient concentrations in the leaf tissue of creeping bentgrass cultivars in summer

The characteristics and the mineral nutrient concentrations in the leaf tissue of creeping bentgrass cultivars in summer

Tolerance of Creeping Bentgrass Cultivars and Selections to Anthracnose in New Jersey

Tolerance of Creeping Bentgrass Cultivars and Selections to Anthracnose in New Jersey

Evaluation of Drought Tolerance and Avoidance Traits for Six Creeping Bentgrass Cultivars

The objectives of this study were: 1) to compare drought responses between the more recently developed creeping bentgrass cultivars to standard cultivars and 2) to determine differential drought tolerance and avoidance characteristics associated with cultivar variation in drought resistance. Six cultivars of creeping bentgrass (Agrostis stoloniferia) (‘Penn A-4’, ‘Independence’, ‘Declaration’, ‘L-93’, ‘Penncross’, and ‘Putter’) were maintained in growth chambers at 20 °C day/15 °C night either well-watered or exposed to drought stress by withholding water for 17 days. Cultivars varied in turf performance and physiological responses (leaf relative water content and photochemical efficiency) to drought stress, which was reflected in their differences in drought tolerance (osmotic adjustment) and drought avoidance traits (water use rate and efficiency, root viability, root length, and number). ‘Penn A-4,’ ‘Independence,’ and ‘L-93’ generally performed better than other three cultivars under drought conditions, mainly through maintaining higher water use efficiency, root viability, root elongation, or root production. The majority of physiological parameters evaluated suggested that of the six creeping bentgrass cultivars examined in this study, the three cultivars with better ability to survive drought stress used mainly avoidance traits related to water use and water uptake.

Genetic Relationships Among Magnaporthe poae Isolates from Turfgrass Hosts and Relative Susceptibility of 'Penncross' and 'Penn A-4' Creeping Bentgrass.

Isolates of Magnaporthe poae from turfgrass hosts were analyzed for mating type, genetic relatedness according to ITS sequences, reaction to a previously developed species-specific poly-merase chain reaction (PCR) assay, and virulence on two creeping bentgrass cultivars in growth chamber experiments. Analysis of internal transcribed spacer (ITS) sequences revealed three clades, designated A, B, and C. Clade A contained isolates of both mating types from creeping bentgrass, annual bluegrass, and Kentucky bluegrass. Clade B contained only mating type 'A' isolates from annual bluegrass, whereas Clade C contained only mating type 'a' isolates from creeping bentgrass. The M. poae PCR assay failed to positively identify several North Carolina isolates from annual bluegrass and creeping bentgrass. M. poae isolates from Kentucky blue-grass were most virulent toward creeping bentgrass in growth chamber experiments. Although isolates of M. poae are not host specific, certain ITS clades may have a limited host or geographical range. The improved creeping bentgrass cv. Penn A-4 was more susceptible to summer patch than cv. Penncross. Additional research is needed to develop methods for accurate diagnosis of summer patch and other patch diseases in creeping bentgrass and to determine how creeping bentgrass cultivars vary in their susceptibility to these root pathogens.

Growth, Physiological, and Anatomical Responses of Creeping Bentgrass Cultivars to Different Depths of Waterlogging

Oxygen deficiency is one of the primary root stresses in waterlogged or flooded soils. The objective of this experiment was to identify growth, physiological, and anatomical traits of creeping bentgrass (Agrostis stolonifera L.) associated with tolerance to different depths of waterlogging (WL). Five cultivars (L‐93, A‐4, G‐6, Penncross, and Pennlinks) were subjected to the four WL treatments for 21 d: (i) drained control; (ii) water level at 15 cm (WL‐15); (iii) water at 5 cm (WL‐5); and (iv) water at 1 cm (WL‐1) below the soil surface, respectively. Waterlogging reduced turf quality (TQ), root dry weight (RDW), root water soluble carbohydrate content (RWSC), and root soluble protein content (RPRO), while no significant reductions in RWSC, RDW, or RPRO were observed among three depths of WL. Turf quality and chlorophyll content (Chl) decreased with increasing water level from 15 to 1 cm. At WL‐1, Chl, RDW, RWSC, and RPRO were reduced 27, 20, 44, and 22%, respectively, compared to the control. Cultivar differences in TQ, RDW, shoot water soluble carbohydrate content (SWSC), and RPRO were observed under WL. G‐6 and L‐93 had better quality than A‐4, Penncross, and Pennlinks under WL conditions. The formation of aerenchyma was enhanced at WL‐15 and WL‐5. Mitochondrial swelling occurred under WL, particularly at WL‐1. The results suggest that even partial WL (WL‐15 and WL‐5) could substantially affect turfgrass growth and physiological activities and cultivar variation in WL tolerance could potentially be used for enhancing breeding programs.

Mapping QTL for dollar spot resistance in creeping bentgrass (Agrostis stolonifera L.)

Dollar spot caused by Sclerotinia homoeocarpa F. T. Bennett is the most economically important turf disease on golf courses in North America. Dollar spot resistance in a creeping bentgrass cultivar would greatly reduce the frequency, costs, and environmental impacts of fungicide application. Little work has been done to understand the genetics of resistance to dollar spot in creeping bentgrass. Therefore, QTL analysis was used to determine the location, number and effects of genomic regions associated with dollar spot resistance in the field. To meet this objective, field inoculations using a single isolate were performed over 2 years and multiple locations using progeny of a full sib mapping population '549 x 372'. Dollar spot resistance seems to be inherited quantitatively and broad sense heritability for resistance was estimated to be 0.88. We have detected one QTL with large effect on linkage group 7.1 with LOD values ranging from 3.4 to 8.6 and explaining 14-36% of the phenotypic variance. Several smaller effect QTL specific to rating dates, locations and years were also detected. The association of the tightly linked markers with the LG 7.1 QTL based on 106 progeny was further examined by single marker analysis on all 697 progeny. The high significance of the QTL on LG 7.1 at a sample size of 697 (P < 0.0001), along with its consistency across locations, years and ratings dates, indicated that it was stable over environments. Markers tightly linked to the QTL can be utilized for marker-assisted selection in future bentgrass breeding programs.