Spatial analysis of Listronotus maculicollis immature stages demonstrates strong associations with conspecifics and turfgrass damage but not with optimal hosts on golf course fairways

For insects that develop on few hosts and/or have immobile immature stages, optimal oviposition theory suggests that females should seek high‐quality hosts that maximize larval development and reduce competition from conspecifics. However, there is a growing amount of evidence that suggests female choice may often be at odds with their offspring's development. Listronotus maculicollis (Kirby) (Coleoptera: Curculionidae) is a serious pest of golf course turfgrass in eastern North America. The weevil develops on few hosts and demonstrates improved fitness traits when developing on Poa annua L. (Poaceae). However, previous population studies observed either weak or no correlations between the spatial dispersion of larval populations and P. annua in the field. In this study, populations on three golf course fairways were monitored over a 4‐year period (2009–2012) to determine whether the lack of spatial associations between preferred hosts and immatures was a result of spatial scale or the density and distribution of conspecifics. Spatial Analysis by Distance IndicEs (SADIE) was used to characterize the spatial dispersion of populations of individual stages (larvae and pupae), P. annua, and turfgrass damage. Life stages were aggregated in each observation, independent of population density or the spatial dispersion of hosts. The distribution of consecutive and non‐consecutive immature stages was found to be correlated in all years, suggesting that females do not avoid patches already occupied by conspecific eggs. Surprisingly, significant spatial associations were not found between larvae and P. annua when the host plant was relatively abundant. Hence, multiple mechanisms may drive L. maculicollis oviposition site‐selection behavior, and a flexible strategy may allow the weevil to persist in areas where P. annua is not the dominant species. Future studies are required to determine what other factors (e.g., natural enemy‐free space, egg or time limitations) influence oviposition behavior.     

A First Report of Anguina pacificae in Ireland

Anguina pacificae is a significant pest of Poa annua golf course greens in northern California. This study presents the first confirmed case of an A. pacificae infestation outside of North America, where the nematode’s distribution is further restricted to a relatively limited coastal region. Species confirmation was made by morphometric and molecular methods and comparisons to closely related species including the European species, Anguina agropyri. The A. pacificae population detected on an Irish golf course was monitored over a 2-yr period and the life cycle compared with Californian population dynamics. A. pacificae was assessed for the potential risk of spreading to the local agricultural sector, in addition, the biosecurity risks from A. pacificae and plant parasitic nematodes in general were reviewed for northwest Europe.     

Germination-Arrest Factor (GAF): 3. Determination that the herbicidal activity of GAF is associated with a ninhydrin-reactive compound and counteracted by selected amino acids

A novel, naturally-occurring herbicide (Germination-Arrest Factor, GAF), produced by Pseudomonas fluorescens WH6 and several related isolates of rhizosphere bacteria, irreversibly arrests germination of the seeds of a wide range of graminaceous species, including a number of important grassy weed species. GAF activity has been shown previously to be associated with a hydrophilic, low molecular weight compound that contains an acid group. In the present study, thin-layer chromatography (TLC) of extracts of WH6 culture filtrate demonstrated that GAF activity migrates on TLC plates with a particular ninhydrin-reactive compound. This compound was found to be present in GAF-producing P. fluorescens isolates and absent in P. fluorescens strains that lack the ability to produce GAF. Treatments, including mutagenesis, which resulted in the loss of GAF activity in culture filtrates from P. fluorescens WH6 were shown to result in the disappearance of this ninhydrin-reactive compound from extracts of WH6 culture filtrates or in alteration of its appearance on TLC chromatograms. The ninhydrin-reactivity of GAF indicates that it probably contains an amino group, as well as the acid group previously demonstrated, and suggests that GAF may be a small peptide or amino acid analog. Biological investigations motivated by this conclusion demonstrated that the effects of GAF in inhibiting the germination of seeds of annual bluegrass (Poa annua L.) could be counteracted by treatment with alanine or glutamine and, to lesser extent, by several other amino acids, suggesting that this compound may act by interfering with some aspect of amino acid metabolism or function.     

Spatial distribution of colonizing Listronotus maculicollis populations: implications for targeted management and host preference

We characterized the spatio‐temporal distribution of emerging overwintered adult Listronotus maculicollis populations colonizing golf course fairways with Spatial Analyses by Distance IndicEs (SADIE) with the goal to better target management tactics and to test assumptions for weevil preference for annual bluegrass (Poa annua). Adults randomly colonized and moved throughout fairways. However, cumulative captures were significantly aggregated along fairway edges closest to overwintering sites demonstrating progressive movement through the edges. Spatial association analyses suggest that the spatial patterns of cumulative captures of adults rather than weekly patterns were strongly associated with larvae, indicating that the adults enter fairways from the edges and deposit eggs over the course of several weeks. We did not observe an effect of host species on the distribution of either adult or larval L. maculicollis which leads us to question traditional assumptions of host preference for short mown P. annua. Instead, we propose that the aggregated distribution of larvae is generated by a low encounter rate of short mown hosts, rather than preference for species or cultivar. This study indicates that caution need to be applied when using preference‐performance criteria in host preference studies. Future behavioural studies need to address the contributions of encounter rate and host species on L. maculicollis host selection and oviposition.     

Physiological mechanism of hypertolerance of cadmium in Kentucky bluegrass and tall fescue: Chemical forms and tissue distribution

Kentucky bluegrass (Poa pratensis) and tall fescue (Festuca arundinacea) are hypertolerant grasses to soil cadmium contamination. Little information is available on their tolerance mechanism. A sand culture and a hydroponic culture experiment were designed to investigate the Cd chemical form changes and its translocation in different tissues. The results showed that Kentucky bluegrass and tall fescue can tolerate 50–200 mg kg⁻¹ of soil Cd stresses and accumulate as high as 4275 and 2559 mg Cd kg⁻¹ DW, respectively, in their shoots without the loss of shoot biomass. Their Cd hypertolerance was correlated with an increase of the undissolved Cd phosphates in the leaves in both grass species, as determined by sequential solvent extraction procedures. The superior Cd tolerance of tall fescue to Kentucky bluegrass was associated with less Cd translocation into the stele of roots and less Cd transported to leaves. The pectate- and protein-integrated Cd forms may be involved in the symplastic translocation of Cd from cortex into stele, and this may lead the higher Cd concentrations in the stele of roots and then above ground leaves via long-distance transport in Kentucky bluegrass.     

草地早熟禾草坪土壤水分动态与根系生长分布

对草地早熟禾草坪土壤水分动态和根系生长发育状况进行研究,结果发现不同土壤层次水分变化有所不同,0～15cm变化最大,15～30cm次之,30cm以下土层水分变化不大;草地早熟禾的根系生长呈现双峰曲线模式,5月中旬和8月中下旬总根量处于峰值;其主体根系主要分布在0～30cm土层内,占总根量的85%以上;根重密度随土层深度呈指数衰减关系,0～30cm土层下降幅度较大,30cm以下土层根重密度相差不大;在0～30cm土层内不同层次根量占总根量的比例在不同时期亦有差异,春秋季节10～20cm和20～30cm土层内根量比例较大,说明此时期主体根系分布在较深的土层;综合分析认为草地早熟禾草坪主要利用土壤浅层水分,在降雨较少的春秋季节,根系较深,适宜深层灌溉,在降雨频繁的夏季,根系较浅,适宜浅层灌溉。     

Plant regeneration in Kentucky bluegrass (Poa pratensis L.) via coleoptile tissue cultures

Summary Plant regeneration in Kentucky bluegrass (Poa pratensis L. cv. Touchdown) via culture of seedling tissues was investigated. When coleoptile, leaf, and stem sections of dark-germinated seedlings were cultured on Murashige and Skoog (MS) medium, different types of callus were produced, depending on the expiant source and growth regulator combinations. Only compact-friable callus (type 3) and moderately compact, friable callus (type 2) produced shoots upon subculture. The nonstructured watery callus (type 4) produced roots without shoots. Shoot differentiation from callus tissues was highest when the culture medium contained 0.2 mgL^–1 picloram + 0.01 mgL^–1 -naphthaleneacetic acid (NAA). Calli grown from coleoptiles had higher shoot regeneration frequency (32%) than that obtained from either stem sections (12%) or young leaf tissues (2%) of the same seedlings. Some organogenic callus lines produced exclusively green plants, while others produced albino shoots or a mixture of green and albino shoots. The green plants were multiplied in a medium containing 0.1 mgL^–1 BAP plus either 0.2 mgL^–1 picloram or 0.1 mgL^–1 indole-3-acetic acid (IAA). Over 90% of the cultures in the shoot proliferation medium produced roots in 4 weeks. The rooted plants were successfully established in soil medium and grown in the greenhouse.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) medium - NAA -naphthaleneacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid - TDZ thidiazuron     

Epicuticular wax of Poa ampla leaves

Leaf wax of a glaucous variety of Poa ampla contains hydrocarbons (5%, C₂₃–C₃₅), esters (9%, C₃₆–C₅₆), free acids (3%, C₁₆–C₃₄), free alcohols (6%, mainly C₂₆); hentriacontane-14,16-dione (14%), 5-oxohentriacontane-14,16-dione (1%); hydroxy β-diketones (56%) and unidentified material (6%). The hydroxy β-diketones, which are more abundant in this wax than in others, were shown by ¹³C NMR to consist of 4-hydroxy (15%), 5-hydroxy (70%) and 6-hydroxy (15%) hentriacontane-14,16-diones.     

Is genetic engineering ever going to take off in forage,turf and bioenergy crop breeding?

Background

Genetic engineering offers the opportunity to generate unique genetic variation that is either absent in the sexually compatible gene pool or has very low heritability. The generation of transgenic plants, coupled with breeding, has led to the production of widely used transgenic cultivars in several major cash crops, such as maize, soybean, cotton and canola. The process for regulatory approval of genetically engineered crops is slow and subject to extensive political interference. The situation in forage grasses and legumes is more complicated.

Scope

Most widely grown forage, turf and bioenergy species (e.g. tall fescue, perennial ryegrass, switchgrass, alfalfa, white clover) are highly self-incompatible and outcrossing. Compared with inbreeding species, they have a high potential to pass their genes to adjacent plants. A major biosafety concern in these species is pollen-mediated transgene flow. Because human consumption is indirect, risk assessment of transgenic forage, turf and bioenergy species has focused on their environmental or ecological impacts. Although significant progress has been made in genetic modification of these species, commercialization of transgenic cultivars is very limited because of the stringent and costly regulatory requirements. To date, the only transgenic forage crop deregulated in the US is ‘Roundup Ready’ (RR) alfalfa. The approval process for RR alfalfa was complicated, involving several rounds of regulation, deregulation and re-regulation. Nevertheless, commercialization of RR alfalfa is an important step forward in regulatory approval of a perennial outcrossing forage crop. As additional transgenic forage, turf and bioenergy crops are generated and tested, different strategies have been developed to meet regulatory requirements. Recent progress in risk assessment and deregulation of transgenic forage and turf species is summarized and discussed.     

Population Response to Temperature in the Subfamily Tylenchorhynchinae

The effects of temperature on population development of 11 species of stunt nematodes in the subfamily Tylenchorhynchinae were compared on red clover or Kentucky bluegrass in constant-temperature tanks at 5-degree intervals from 10 to 35 C. The optimum temperature for population increase on red clover in 90 days was 30 C for Tylenchorhynchus agri, T. nudus, T. martini, and T. clarus, 25 C for T. sylvaticus and T. dubius, and 20 C for T. canalis, Merlinius brevidens, and Quinisulcius capitatus. The optimum was 30 C for T. robustoides and 25 C for T. maximus on Kentucky bluegrass. The temperature range for population increase was 20-35 C for T. agri, T. nudus, T. martini, and T. clarus, 20-30 C for T. sylvaticus and T. robustoides, 15-25 C for T. maximus, 10-25 C for T. dubius, and 10-20 C for M. brevidens and Q. capitatus. T. canalis increased only at 20 C. All species were recovered in numbers near their inoculum level at 10 C. There was no survival of T. sylvaticus, T. dubius, T. canalis, T. robustoides, T. maximus, M. brevidens, and Q. capitatus at 35 C, or of the last three of these species at 30 C. Temperature had no effect on sex ratio in final populations. Population increase was greatest in T. martini and least in T. canalis.