Nitrogen requirements for deficit-irrigated bermudagrass (Cynodon spp.) fairways in South Florida

Several new bermudagrass cultivars are available and commonly used on golf course fairways. However, little is known about their cultural requirements or how these cultivars perform under lower inputs regimes. A 2-year study was conducted at University of Florida, Fort Lauderdale Research and Education Center, to assess performance of four hybrid bermudagrass [Cynodon dactylon L. Pers. X Cynodon transvaalensis (Burtt-Davy)] cultivars (‘Latitude 36’, ‘Tifway 419’, ‘TifGrand’ and ‘TifTuf’), and 2 common bermudagrass (Cynodon dactylon L. Pers.) cultivars (‘Bimini’ and ‘Celebration’) irrigated at either 50% or 80% reference evapotranspiration (ET_o) and fertilised at either 0, 146, 244, or 342 kg N ha⁻¹ year⁻¹. Plots were evaluated monthly for turfgrass quality, dark green colour index (DGCI), normalised difference vegetation index (NDVI), and Chlorophyll Index, and seasonally for N tissue content. Plots watered at 80% ET_o enhanced bermudagrass quality compared to 50% ET_o, DGCI and NDVI only in two months out of 24. Latitude 36 and Celebration were the top-rated cultivars, and their quality was not affected by no N fertilisation. Conversely, TifGrand, TifTuf and Tifway that received no N fertilisation resulted in insufficient quality during the second year of the study. Insufficient quality may be linked to reduced N metabolization compared to the highest rated cultivars. Results show that new cultivars such as Latitude 36 and Bimini could be maintained at sufficient quality levels with reduced water and N inputs in South Florida.     

四种草坪草对干旱胁迫的反应及抗旱性评价

以大穗结缕草、沟叶结缕草、普通狗牙根和百慕大4种草坪草为材料,对其干旱胁迫过程中生理指标进行了研究,并采用隶属函数法对其抗旱性进行比较,以期为我国干旱和半干旱地区草坪草的栽培提供试验依据。结果表明：叶片相对含水量（RWC）在胁迫15d时比对照降低、而相对电导率（REC）、超氧化物歧化酶（SOD）和过氧化物酶（POD）活...     

Determination of Fatty Acid Composition of Turfgrass by High‐Performance Liquid Chromatography

Abstract

The fatty acid composition of warm‐season turfgrasses is physiologically regulated by environmental changes, particularly temperature. Species or cultivars, which have increased degree of unsaturation, usually have a greater freeze resistance. Quantifying fatty acid composition not only can help understand the freeze‐resistant mechanism of warm‐season turfgrasses but also in practice develop a management strategy for better turf. A high‐performance liquid chromatography (HPLC) method was developed for this purpose. The method is based on the bromophenacyl reaction of fatty acids and separation on a C8 column with gradient elution. Information on limit of identification, linearity of quantification, response factor, and derivatization conditions is presented and discussed. The method presented is simple to apply and provides an alternative to the traditional gas chromatography (GC) method. The results of fatty acid composition from a field freezing‐resistance experiment are discussed.     

几种城市绿地草坪草需水规律研究

为对城市绿地草坪草进行更合理的种植灌溉,采用小区微灌试验,对剪股颖、马蹄金、早熟禾和白三叶四种具有代表性的绿地草坪草的需水规律进行研究。试验结果表明:（1）供试草坪草根系在土层中的分布呈“伞”形结构,83%～94.4%的根系聚集在0—10 cm的土层中,不耐干旱,需适时补充灌溉,以维持其正常生长;（2）供试草坪草年需水总量在1 000 mm左右,66%的需水量集中在6—9月4个月内。在水资源紧缺的北方城市绿地建设中,不宜大面积配置草坪草;（3）草坪草的灌水周期以5 d,次灌水量33 mm较为适宜。     

Plants regenerated from embryo cultures of an apomictic clone of Kentucky bluegrass (Poa pratensis L. ‘Baron’) are not apomictic in origin

Plants were regenerated from tissue cultures of embryos dissected from seeds that were harvested from a self-pollinated clonal selection of Kentucky bluegrass (Poa pratensis L.) ‘Baron’, an apomictic cultivar. Plants were regenerated from 35 embryo-derived callus cultures of the 3280 embryos that were plated. Flow-cytometric (FCM) and RAPD-marker analyses were performed to determine if regenerants were or were not apomictic in origin. Fifteen regenerants with a 3c DNA content were classified as arising from 2n + n aberrant embryos, which was a higher frequency than expected, based on a chi-square analysis. Of the remaining 20 regenerants with a 2c DNA content, a chi-square test showed that all could have arisen from n + n sexually-derived embryos, based on the observed segregation of n + n regenerants, which fit the expected 3:1 ratio of dominant:recessive RAPD-marker phenotypes. The apparent lack of regenerants of apomictic origin, and implications for genetic transformation and breeding of Kentucky bluegrass are discussed.     

Development of colchicine‐induced tetraploid St. Augustinegrass (Stenotaphrum secundatum) lines

St. Augustinegrass is well suited for lawns and commercial landscapes. While many genotypes are cross‐fertile, all cultivars are propagated vegetatively in sod production. To ensure varietal purity, development of sterile triploid hybrids by crossing tetraploid and diploid genotypes has been successfully used in other warm‐season turfgrasses. Applying this model in St. Augustinegrass would be beneficial to sod producers and turf managers who require purity for certification and uniformity for performance, respectively. This study was conducted to develop colchicine‐induced tetraploid lines of St. Augustinegrass. Seeds of cultivar ‘Raleigh’ were treated with four colchicine concentrations at four exposure times. A non‐treated control was included among the treatments. Seedlings that germinated were screened for genome size changes using flow cytometry. Line DSA 13005 and two progeny lines derived through selfing, DSA 16001 and DSA 16016, were corroborated as tetraploids (2n = 4x = 36) through chromosome counts. These lines will be used in future breeding efforts to attempt development of sterile triploid cultivars of St. Augustinegrass.     

三种草坪草种子萌发对水分的响应

种子吸收一定量的水分后能够正常发芽,在这个过程中,种子将消耗外部环境的水分,这种改变将影响种子对水分的吸收,并最终导致种子的发芽率不同。试验以三种草坪草为研究对象,通过限定灌水量来模拟地下滴灌方式,讨论了10个水分梯度下种子吸胀吸水和萌发的变化情况。结果表明,在灌水量不同的情况下,萌发前外部环境水分变化率差异显著,但当灌水量超过60%时,差异不显著;种子开始萌发后,萌发初期种子发芽较快,然后逐渐变慢,最终达到稳定状态,当灌水量达到一定值时,累计发芽率达到最大值,但当水分含量超过这一定值时,反而会抑制种子的发芽,其中多年生黑麦草种子对水分最敏感,能最快达到最大发芽率,而草地早熟禾对水分反应不敏感,则最慢达到最大发芽率。研究结果可用于描述种子发芽过程中外部水分变化与发芽率的关系,并有助于种子发芽最优水量的确定和提高水分的利用效率。     

草坪草外源功能基因转化研究进展

草坪草的转基因技术已经有了很大的发展,目前已经在多种草坪草上转入了抗除草剂、抗病虫、抗旱抗盐、抗寒抗热和延长绿期以及抗重金属等外源的功能基因,获得了抗逆性提高的转基因植株。综合分析认为,在抗逆机理研究的基础上选择更关键的抗逆基因进行遗传转化、转化草坪草矮化和养分高效吸收的基因、转基因技术与传统育种方法相结合以及转基因草坪草的安全性评价是将来需要重点展开的研究工作。     

Evaluation of bermuda and paspalum grass types for urban landscapes under saline water irrigation

In the arid regions, turfgrass cover is an integral part of landscape to protect the soil from erosion, enhance the aesthetic value, and improve the microclimate. The salinity and the scarcity of fresh water of the arid region are the major challenging factors in turfgrass production. Therefore, the need for salt tolerant turfgrass with functional quality is necessary to improve the turf performance. The detrimental effects of salinity include growth suppression, and lowered osmotic potential ultimately leading to firing of the leaf blades. In this context, the study was undertaken to determine the relative salt tolerance and growth response of turfgrass genotypes in order to recommend turfgrass cultivars that can tolerate high salinity irrigation and maintain excellent visual and functional qualities under United Arab Emirates (UAE) condition. The paspalum cultivars maintained the highest succulence percentage compared to the bermudagrass cultivars under enhanced salinity levels. The shoots count, fresh weight (FW), and dry weight (DW) were found highest in paspalum types. The chlorophyll a, chlorophyll b and the total chlorophyll content was found higher in bermuda grass types under high salinity levels. The bermudagrass cultivars showed significantly higher carotenoids, anthocyanins and proline compared to the paspalum types under salt stress condition. In the case of princess 77 and Yukon, an inherently high amount of proline was recorded which confirmed an increase up to 10,000 ppm and drastically declined beyond this concentration. Sea Dwarf paspalum and Sea Isle 2000 maintained uniformity in the proline level at all levels of salinity without significant variation. These findings point to the fact that both paspalum and bermuda types exhibited varied responses to different physiological and biochemical parameters under the saline conditions. Paspalum types have an edge over the bermudagrass in terms of shoot density, which is a potential factor in determining the high-quality turfs. Bermudagrass types can be applied in lower salinity conditions based on the responses as evidenced from the present results.     

RFLP markers are an effective tool for the identification of creeping bentgrass (Agrostis stolonifera L.) cultivars

The potential use of RFLP molecular markers for the identification of four creeping bentgrass (Agrostis stolonifera L.) cultivars and one variety of A. tenuis Sibth. used as control, was investigated. Seven probes out of the total 44 screened were able to differentiate all five cultivars at once. On the basis of their genetic similarity the varieties bred at the Pennsylvania State University were grouped closely together, whereas the variety Prominent and the A. tenuis control were more distantly related.