Turfgrass (Cynodon dactylon L.) sod production on sandy soils: II. Effects of irrigation and fertiliser regimes on N leaching

The effects of irrigation and fertiliser regimes on N leaching from the production of couch grass (Cynodon dactylon L.) sod, on a free-draining sandy soil, were evaluated in a 22-month field study. The experimental design used a randomised-block, split-plot design with three replicates. Main plots consisted of two irrigation treatments: 70 and 140% daily replacement of pan evaporation; four subplot fertiliser types (water-soluble (predominately NH₄NO₃), control-release, pelletised poultry manure and pelletised biosolids); and three N application rates (100, 200 and 300 kg N ha⁻¹ per crop). Nitrogen leaching was assessed by measuring the leachate volumes and concentrations of N species leached from soil lysimeters (250 mm in diameter by 950 mm in length) installed in 10 m² turfgrass plots. Nitrogen leaching ranged from 33 to 167 kg N ha⁻¹ over 22 months, depending upon the irrigation and fertiliser treatment. Irrigation treatment affected N leaching more than fertiliser treatment, and increasing the irrigation from 70 to 140% replacement of daily pan evaporation increased N leaching for all fertiliser types, and by up to four times. Forty six to 76% of losses occurred from the high irrigation treatments during the first 16 weeks after the turfgrass was planted as rhizomes. By contrast, N leaching did not appear to increase following harvest of sod. At the high irrigation treatment, N leaching was greater for the pelletised biosolids than the control-release; while at the low irrigation treatment, N leaching did not vary between fertiliser types. A significant proportion of the N leached was in the organic form. Therefore, we recommend total N and mineral N be measured when assessing N leaching from turfgrass. Nitrogen leaching from turfgrass production is low from all fertiliser types when the irrigation matches turfgrass water use and N is applied at a rate and frequency that approximates turfgrass requirements. Section Editor: P. J. Randall     

Evaluation of populations of fluorescent pseudomonads related to decline of take-all patch on turfgrass

Take-all on turfgrass caused by Gaeumannomyces graminis var. avenae (Gga) occurs as patches of yellowish plants. On some patches the central zone was recolonized by the same grass species, Festuca sp., previously damaged by the fungus despite the centrifugal extension of the disease. This disease remission was assimilated to decline. Rhizosphere bacterial counts showed that total population of bacteria was nearly the same in all zones across the patches. However, the ratio of fluorescent Pseudomonas spp./ total bacteria was 1/22, 1/15.4, 1/3.5 and 1/2.9 in the disease free area, the front margin of the patch, in the damaged part of the patch, and in the recolonized central part respectively. Furthermore, in this last mentioned zone, 44 to 82% of the fluorescent Pseudomonas spp. were antagonistic in vitro to Gga, whereas only 12 to 34% from the disease free area were antagonistic. So the development of take-all on turf induced quantitative and qualitative changes in populations of fluorescent pseudomonads. The remission of the disease in the center was correlated to higher amount of antagonistic fluorescent pseudomonads in this part of the patches. This typical patch with the well defined zones can provide a good model for the study of changes in bacterial populations related to the build up of take-all decline.     

Transgenic creeping bentgrass overexpressing Osa‐miR393a exhibits altered plant development and improved multiple stress tolerance

MicroRNA393 (miR393) has been implicated in plant growth, development and multiple stress responses in annual species such as Arabidopsis and rice. However, the role of miR393 in perennial grasses remains unexplored. Creeping bentgrass (Agrostis stolonifera L.) is an environmentally and economically important C3 cool‐season perennial turfgrass. Understanding how miR393 functions in this representative turf species would allow the development of novel strategies in genetically engineering grass species for improved abiotic stress tolerance. We have generated and characterized transgenic creeping bentgrass plants overexpressing rice pri‐miR393a (Osa‐miR393a). We found that Osa‐miR393a transgenics had fewer, but longer tillers, enhanced drought stress tolerance associated with reduced stomata density and denser cuticles, improved salt stress tolerance associated with increased uptake of potassium and enhanced heat stress tolerance associated with induced expression of small heat‐shock protein in comparison with wild‐type controls. We also identified two targets of miR393, AsAFB2 and AsTIR1, whose expression is repressed in transgenics. Taken together, our results revealed the distinctive roles of miR393/target module in plant development and stress responses between creeping bentgrass and other annual species, suggesting that miR393 would be a promising candidate for generating superior crop cultivars with enhanced multiple stress tolerance, thus contributing to agricultural productivity.     

Occurrence and molecular identification of the zoysiagrass mite Aceria zoysiae (Acari: Eriophyidae) in turfgrasses in Korea

Mites are one of the serious pests of turfgrass. Our survey of turfgrass fields from 2013 to 2015 in Korea showed that the occurrence of leaf chlorotic symptom has gradually extended to at least 60% of the examined golf courses. We identified the zoysiae mite Aceria zoysiae in most damaged zoysiagrasses. Artificial infestation of A. zoysiae into zoysiagrasses in pots resulted in symptoms of chlorosis and marginal rolling of the leaves within 3 weeks. We firstly determined the nucleotide sequence of mitochondrial cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA region of A. zoysiae. The variations in COI and ITS2 between A. zoysiae and other species of the genus were 20.9%–43.0% and 7.5%–67.3%, respectively, suggesting significant genetic divergence within the genus. Our study provides valuable information for the rapid diagnosis and infestation monitoring of A. zoysiae in turfgrass fields.     

NaCl胁迫对6种暖季型草坪草新选系生长的影响

利用水培法研究了NaCl胁迫对沟叶结缕草(Zoysia matrella'Z123')、结缕草(Z.japonica'Z080')、狗牙根(Cynodon dactylon'C291')、海雀稗(Paspalum vaginatum'P006')、假俭草(Eremochloa ophiuroides'E126')和钝叶草(Stenotaphrum secundatum'S004')6种暖季型草坪草新选系生长的影响,并对它们的抗盐能力进行了评价。结果表明,随NaCl浓度的提高,6个选系的叶片枯黄率均增大,但不同选系的变化幅度有显著差异;6个选系抗NaCl能力从强到弱依次为'Z123'、'C291'、'P006'、'S004'、'Z080'、'E126'。5g.L-1NaCl对选系'C291'、'S004'和'Z080'地上部分和根系生长有促进作用,而对选系'Z123'、'P006'和'E126'则有抑制作用;随NaCl浓度的提高,除选系'E126'的根冠比迅速下降外,其他选系的根冠比均增加或缓慢下降;各选系的枝叶含水量均随NaCl浓度提高而下降,但选系'S004'、'P006'和'E126'的枝叶含水量均高于选系'C291'、'Z123'和'Z080'。     

Long‐term evaluation of field‐wide oriental beetle (Col., Scarabaeidae) mating disruption in blueberries using female‐mimic pheromone lures

The oriental beetle, Anomala orientalis (Waterhouse) (Col., Scarabaeidae), is the most important root‐feeding pest of blueberries and turfgrass in New Jersey, USA. Previous studies showed that mating disruption is a feasible option for oriental beetle management; however, assessing its efficiency can be challenging, and little is known on its long‐term effects. Accordingly, we conducted studies to investigate low‐dose pheromone lures equivalent to oriental beetle females (i.e. female mimics) as easy‐to‐use indicators of mating disruption success, determine the distance at which oriental beetle males respond to female‐mimic lures and assess the long‐term (3‐year) effects of mating disruption on oriental beetle populations in entire blueberry fields. Our studies showed that rubber septa baited with 0.3 μg of the oriental beetle sex pheromone (Z)‐7‐tetradecen‐2‐one attract similar numbers of males as compared with virgin females and can thus be used as a female mimic. The range of attraction of this lure was found to be also similar to virgin females and <30 m. In blueberries, mating disruption provided 87% inhibition of oriental beetle populations (trap shutdown) over a 3‐year period. Oriental beetle male captures in disrupted fields were threefold higher along the field edges than in the field interiors, indicating movement of males from nearby areas into the pheromone‐treated fields. In addition, mating disruption reduced male attraction to female‐mimic lures by 93% in all 3 years and reduced the number of larvae in sentinel potted plants in 1 of 2 years. These results show for the first time that mating disruption provides consistent long‐term field‐wide control of oriental beetle populations and that female‐mimic pheromone lures can be used as a new tool to assess oriental beetle mating disruption success.     

草坪草育种研究进展 (综述)

介绍草坪草传统育种和转基因育种的历史与现状,概述草坪转基因育种的操作过程,对植物特别是草坪草转基因过程中存在的一些问题如基因丢失,基因沉默,基因流引起的转基因安全性等进行评述。     

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.