Host range, purification and some properties of two carlaviruses from hop (Humulus lupulus): hop latent and American hop latent

Hop latent virus (HLV) occurs in virtually all commercial hop plants in England, without causing apparent symptoms. It was transmitted between hop plants in a non-persistent manner by the aphid Phorodon humuli, but was not seed-borne in hop. The virus infected six species in four families out of 40 in 13 families which were inoculated, but infection was systemic only in Dianthus deltoides and hop. Only Phaseolus vulgaris and Chenopodium murale developed symptoms. Purification of HLV from hop extracts was hampered by aggregation of virus particles but this was minimised either by resuspending pellets in phosphate-buffered saline containing Tween 20 or by avoiding ultra-centrifugation. Virus was purified from extracts treated with Triton X-100 by precipitation with polyethylene glycol (PEG) followed either by centrifugation through sucrose density gradients or by exclusion chromatography through columns of Sephadex G-25 and Sepharose 4B. Purified preparations contained filamentous particles c. 675 × 14 nm composed of c. 6% single stranded RNA of mol. wt c. 2.9 × 10⁶ and a single protein species of mol. wt c 33 000. Immunosorbent electron microscopy (IEM) decoration tests suggested that HLV was serologically related to carnation latent, Helenium virus S, lily symptomless and Nerine latent viruses. American hop latent virus (AHLV) was found in two introductions to England from Corvallis, USA in 1975 and 1976. It was transmitted between hop plants in the non-persistent manner by P. humuli. The virus infected 17 species in seven families out of 41 species in 13 families which were mechanically inoculated and was systemic in nine species. It did not cause symptoms in any of five English hop cultivars. C. quinoa was a convenient propagation host and countable local necrotic lesions and ringspots occurred in leaves of Datura stramonium. AHLV was purified by PEG precipitation and centrifugation in sucrose density gradients. Preparations contained filamentous particles c. 680 × 15 nm composed of c. 6% single-stranded RNA of mol. wt c. 3.0 × 10⁶ and a single protein species of mol. wt c. 33 000. In IEM decoration tests AHLV was serologically related to Nerine latent virus but did not react with antisera to 14 other carlaviruses.     

Assessment of UK hops for the occurrence of hop latent and hop stunt viroids

The occurrences and distributions of hop stunt (HSVd) and hop latent (HLVd) viroids were assessed by a nucleic acid hybridisation assay, using samples from 476 commercial hop plantings in the UK. These samples represented about half of the UK production.
HLVd was detected in c. 17% of the samples, with infection in different cultivars ranging from 0% to 89%. This viroid was found in all cultivars sensitive to Verticillium wilt except cv. Sunshine, an old cultivar grown on only one farm in the UK. Two minor wilt-tolerant cultivars were also found to be infected at low frequencies, but the main commercially-important wilt-tolerant cultivars were all uninfected. A high proportion of the nuclear stock mother plants in the "A +" house at the Institute of Horticultural Research Dept of Hops Research, Wye College were infected. Circumstantial evidence, based on the planting dates of infected gardens, suggests that infection became established in the hop propagation system during the late 1970s and that there was a major increase in the prevalence of HLVd as a result. Whether this contamination of propagating material arose because of spread from long-standing infections or because the viroid was newly introduced into the UK, is not known.
All samples were also tested for HSVd but this viroid was not detected in any UK hop material.     

The etiology of hop chlorotic disease

Hop chlorotic disease was first described in England in 1930, but it has since been seldom seen and its etiology has remained unknown. In 1983 a patch of plants with the disease occurred in a large area of hops (Humulus lupulus) cv. Bramling Cross planted at Yalding, Kent in 1967. All plants in a rectangular area enclosing the disease outbreak were infected with hop mosaic, hop latent and prunus necrotic ringspot viruses; the diseased plants were additionally infected with arabis mosaic virus (AMV). The disease was also associated with seed-transmitted AMV, and was induced in hop seedlings inoculated with partially purified preparations of AMV originating from chlorotic disease-affected hops prepared from Chenopodium quinoa. The disease appears to be caused by AMV, but AMV isolates from hops with chlorotic disease were serologically indistinguishable from AMV isolates from hops with symptoms of bare-bine and/or nettlehead and showed similar pathogenicity in diagnostic hosts. The basis of the difference between isolates in their pathogenicity in hop remains unknown.     

Some effects of hop latent viroid on two cultivars of hop (Humulus lupulus) in the UK

Some effects of infection by hop latent viroid (HLVd) on two commercial plantings of hop, one each of two high alpha-acid cultivars, are described. The cultivar Omega was severely affected: yield of cones and individual cone weights from infected plants were both lower than from uninfected plants by c. 35% and the alpha-acids content (as assessed by HPLC) of the cones c. 30% lower. Wye Northdown was less severely affected: cone weight was 8% less (though this was not statistically significant) and alpha-acids content lower by c. 15%. In both cultivars beta-acids were higher in infected plants which, together with differences in other chemical components, suggested that cones on infected plants had matured, or were maturing, earlier than those on uninfected plants. These effects, together with the previous finding that HLVd occurs frequently in some cultivars (Barbara, Morton & Adams, 1990), suggest that HLVd is a potentially important constraint on hop production in the UK and should be eliminated if possible.     

The hop downy mildew pathogen Pseudoperonospora humuli

Pseudoperonospora humuli is an obligate biotrophic oomycete that causes downy mildew, one of the most devastating diseases of cultivated hop, Humulus lupulus. Downy mildew occurs in all production areas of the crop in the Northern Hemisphere and Argentina. The pathogen overwinters in hop crowns and roots, and causes considerable crop loss. Downy mildew is managed by sanitation practices, planting of resistant cultivars, and fungicide applications. However, the scarcity of sources of host resistance and fungicide resistance in pathogen populations complicates disease management. This review summarizes the current knowledge on the symptoms of the disease, life cycle, virulence factors, and management of hop downy mildew, including various forecasting systems available in the world. Additionally, recent developments in genomics and effector discovery, and the future prospects of using such resources in successful disease management are also discussed.TaxonomyClass: Oomycota; Order: Peronosporales; Family: Peronosporaceae; Genus: Pseudoperonospora; Species: Pseudoperonospora humuli.Disease symptomsThe disease is characterized by systemically infected chlorotic shoots called “spikes". Leaf symptoms and signs include angular chlorotic lesions and profuse sporulation on the abaxial side of the leaf. Under severe disease pressure, dark brown discolouration or lesions are observed on cones. Infected crowns have brown to black streaks when cut open. Cultivars highly susceptible to crown rot may die at this phase of the disease cycle without producing shoots. However, foliar symptoms may not be present on plants with systemically infected root systems.Infection processPathogen mycelium overwinters in buds and crowns, and emerges on infected shoots in spring. Profuse sporulation occurs on infected tissues and sporangia are released and dispersed by air currents. Under favourable conditions, sporangia germinate and produce biflagellate zoospores that infect healthy tissue, thus perpetuating the infection cycle. Though oospores are produced in infected tissues, their role in the infection cycle is not defined.ControlDowny mildew on hop is managed by a combination of sanitation practices and timely fungicide applications. Forecasting systems are used to time fungicide applications for successful management of the disease.Useful Websites https://content.ces.ncsu.edu/hop‐downy‐mildew (North Carolina State University disease factsheet), https://www.canr.msu.edu/resources/michigan‐hop‐management‐guide (Michigan Hop Management Guide), http://uspest.org/risk/models (Oregon State University Integrated Plant Protection Center degree‐day model for hop downy mildew), https://www.usahops.org/cabinet/data/Field‐Guide.pdf (Field Guide for Integrated Pest Management in Hops).     

Terpene biosynthesis in glandular trichomes of hop

Hop (Humulus lupulus L. Cannabaceae) is an economically important crop for the brewing industry, where it is used to impart flavor and aroma to beer, and has also drawn attention in recent years due to its potential pharmaceutical applications. Essential oils (mono- and sesquiterpenes), bitter acids (prenylated polyketides), and prenylflavonoids are the primary phytochemical components that account for these traits, and all accumulate at high concentrations in glandular trichomes of hop cones. To understand the molecular basis for terpene accumulation in hop trichomes, a trichome cDNA library was constructed and 9,816 cleansed expressed sequence tag (EST) sequences were obtained from random sequencing of 16,152 cDNA clones. The ESTs were assembled into 3,619 unigenes (1,101 contigs and 2,518 singletons). Putative functions were assigned to the unigenes based on their homology to annotated sequences in the GenBank database. Two mono- and two sesquiterpene synthases identified from the EST collection were expressed in Escherichia coli. Hop MONOTERPENE SYNTHASE2 formed the linear monterpene myrcene from geranyl pyrophosphate, whereas hop SESQUITERPENE SYNTHASE1 (HlSTS1) formed both caryophyllene and humulene from farnesyl pyrophosphate. Together, these enzymes account for the production of the major terpene constituents of the hop trichomes. HlSTS2 formed the minor sesquiterpene constituent germacrene A, which was converted to β-elemene on chromatography at elevated temperature. We discuss potential functions for other genes expressed at high levels in developing hop trichomes.     

The distribution and spread of hop latent viroid within two commercial plantings of hop (Humulus lupulus)

The distribution and spread of hop latent viroid (HLVd) in two adjacent plantings of the hop cultivars Omega and Wye Challenger have been studied for three seasons. The planting of cv. Omega was heavily infected at the start of the survey and spread was rapid; the density of infection was lower in the planting of cv. Wye Challenger and spread was much slower. It is not known whether the difference in rate of spread was a varietal effect or because of the higher density of infection in the Omega planting. The distribution of known infections in 1991 suggests that plant-to-adjacent-plant spread, either by contact or on tools, does occur. However, the overall distribution of infection and the occurrence of new infections not adjacent to existing ones, suggests that this is not the only means of transmission; whether a vector is involved is not known.     

Nutritional effects on the hop curl disease and comparison of the chemical composition of diseased and healthy hop plants

Whereas experiments directed towards proving the infectious character of the hop curl disease did not give reliable proof of its virus character (we have not been able to transfer it neither by cuttings nor by graft), but made possible its differentiation from the English nettlehead hop virus disease, the practical experiences and results presented in this paper show that nutritional conditions essentially affect the known variability of the external manifestations of the hop curl disease. Especially such nutrients play a role which with the normal fertilising techniques are not returned to the soil in sufficient quantity. Since the hop curl disease was noticeably inhibited in a nutritional field experiment on application of the salts of some elements, predominantly of B, Mg, Mo, Mn, Ni, I and Zn, it appears possible to apply “symptomatic therapy” of the hop curl disease, which could have wide practical importance for limiting this disease. In order to supplement the provocation field experiments, comparative investigations of the chemical composition of the leaves from healthy and hop curl diseased plants were carried out. Quantitative analysis of the biogenic elements carried out by the usual methods and by polarography showed a regularly higher content of P, K, Ca and a lower content of Zn in the diseased plants as compared to healthy ones. The differences observed in the content of N, Na, Mg, S, Fe and Cu were not always in the same sense. Chemical analysis was accompanied by parallel spectral analysis of ash. This made it possible to obtain a considerably complete survey of the qualitative and approximately quantitative representation of a whole series of other elements in healthy and diseased plants; however, no characteristic differences were recorded. Finally the results obtained in the present work are confronted with the findings of other researches, especially from Germany, and discussed.     

Double-stranded cDNAs of hop stunt viroid are infectious

Restriction fragments composed of only hop stunt viroid (HSV) cDNA were prepared from recombinant clone pHS-P4P, which carries four tandemly repeated HSV cDNAs, and inoculated into cucumber cotyledons. The results showed that double-stranded cDNAs consisting of 1 to 3 units of HSV sequences were infectious. In cucumber plants inoculated with these double-stranded cDNAs, infectious RNA molecules indistinguishable from authentic HSV were propagated.     

分子标记在啤酒花种质资源研究中的应用

该论文利用分子生物学中常用的DNA分子标记对世界各地现存的野生和栽培的啤酒花种质资源遗传多样性研究的应用进展做一综述。通过查阅和研读20世纪90年代以来发表的各类文献进行归纳总结。发现DNA分子标记相比形态学标记和细胞学标记具有结果准确、稳定的特点,常用的分子标记技术有RAPD、RFLP、ISSR、SSR、AFLP、EST等;研究发现北美洲的啤酒花遗传多样性要高于欧洲的啤酒花,基因变异程度也相对较高;野生啤酒花的基因序列具有丰富的基因多样性,可在分子杂交遗传育种中作为一个种质去改善栽培品种的某些不良性状。因此,利用分子标记研究啤酒花的遗传多样性将对啤酒花的优良育种提供理论指导和技术支持,目前较为理想的技术是SSR和AFLP。     

Test-retest reliability of 4 single-leg horizontal hop tests

The purpose of this study was to determine the test-retest reliability of 4 single-leg horizontal hop tests (i.e., single hop for distance, triple hop for distance, crossover hop for distance, and 6-m hop for time), with a time interval of approximately 4 weeks separating the 2 testing sessions. Eighteen healthy, young, adult men, all cadets enrolled at the U.S. Air Force Academy, Colorado, performed the single hop for distance, the triple hop for distance, the crossover hop for distance, and the 6-m hop for time during 2 testing sessions separated by 31.2 +/- 0.4 days. Reliability data for each of the single-leg hop tests were studied through a repeated measures analysis of variance, intraclass correlation coefficients (ICCs), and standard errors of measurement (SEMs). The ICCs ranged from 0.92 to 0.97 for the 4 single-leg hop tests. The SEMs for the single-leg hop tests that assessed the distance hopped ranged from 4.61 to 17.74 cm. The SEM for the 6-m hop for time test was 0.06 seconds. No significant differences were noted when the mean scores of the 2 test trials were compared by a repeated measures analysis of variance for any of the single-leg hop tests. These results indicate that the single-leg hop tests examined in this study offer strength and conditioning professionals a reliable method to assess the single-leg horizontal hopping capabilities of healthy, young, adult men, with intervals of approximately 4 weeks between testing sessions.     

Effect of fatigue on single-leg hop landing biomechanics

The objective of this study was to measure adaptations in landing strategy during single-leg hops following thigh muscle fatigue. Kinetic, kinematic, and electromyographic data were recorded as thirteen healthy male subjects performed a single-leg hop in both the unfatigued and fatigued states. To sufficiently fatigue the thigh muscles, subjects performed at least two sets of 50 step-ups. Fatigue was assessed by measuring horizontal hopping ability following the protocol. Joint motion and loading, as well as muscle activation patterns, were compared between fatigued and unfatigued conditions. Fatigue significantly increased knee motion (p = 0.012) and shifted the ankle into a more dorsiflexed position (p = 0.029). Hip flexion was also reduced following fatigue (p = 0.042). Peak extension moment tended to decrease at the knee and increase at the ankle and hip (p = 0.014). Ankle plantar flexion moment at the time of peak total support moment increased from 0.8 (N x m)/kg (SD, 0.6 [N x m]/kg) to 1.5 (N x m)/kg (SD, 0.8 [N x m]/kg) (p = 0.006). Decreased knee moment and increased knee flexion during landings following fatigue indicated that the control of knee motion was compromised despite increased activation of the vastus medialis, vastus lateralis, and rectus femoris (p = 0.014, p = 0.014, and p = 0.017, respectively). Performance at the ankle increased to compensate for weakness in the knee musculature and to maintain lower extremity stability during landing. Investigating the biomechanical adaptations that occur in healthy subjects as a result of muscle fatigue may give insight into the compensatory mechanisms and loading patterns occurring in patients with knee pathology. Changes in single-leg hop landing performance could be used to demonstrate functional improvement in patients due to training or physical therapy.     

Phospholipids undergo hop diffusion in compartmentalized cell membrane

The diffusion rate of lipids in the cell membrane is reduced by a factor of 5-100 from that in artificial bilayers. This slowing mechanism has puzzled cell biologists for the last 25 yr. Here we address this issue by studying the movement of unsaturated phospholipids in rat kidney fibroblasts at the single molecule level at the temporal resolution of 25 micros. The cell membrane was found to be compartmentalized: phospholipids are confined within 230-nm-diameter (phi) compartments for 11 ms on average before hopping to adjacent compartments. These 230-nm compartments exist within greater 750-nm-phi compartments where these phospholipids are confined for 0.33 s on average. The diffusion rate within 230-nm compartments is 5.4 microm2/s, which is nearly as fast as that in large unilamellar vesicles, indicating that the diffusion in the cell membrane is reduced not because diffusion per se is slow, but because the cell membrane is compartmentalized with regard to lateral diffusion of phospholipids. Such compartmentalization depends on the actin-based membrane skeleton, but not on the extracellular matrix, extracellular domains of membrane proteins, or cholesterol-enriched rafts. We propose that various transmembrane proteins anchored to the actin-based membrane skeleton meshwork act as rows of pickets that temporarily confine phospholipids.     

Properties of natural cellulose fibers from hop stems

This paper reports the development of natural cellulose fibers from hop stems with properties similar to that of hemp. Hop stems are currently considered as byproducts and have limited applications. Since hop belongs to the genus cannabis that also includes hemp, it should be possible to obtain natural cellulose fibers from the stems of hop plants with properties similar to that of hemp. A simple alkaline extraction was used to obtain fibers from the bark of hop stems. Fibers obtained have high cellulose content, low% crystallinity but show good orientation of the cellulose crystals to the fiber axis. The strength and modulus of the fibers are lower but elongation is higher than that of hemp. Based on the properties of the fibers, we expect that the hop stem fibers will be suitable for use in textiles and composites similar to the common cellulose fibers currently in use.     

The photosynthetic activity of the developing hop cone

Carbon dioxide exchange of the developing hop cone was measured in field and laboratory experiments. Older cones showed a clear response of CO₂ exchange to light intensity, indicating photosynthetic activity, but this rarely exceeded respiratory loss. Cones therefore made little photosynthetic contribution to their growth. Young cones showed no response of CO₂ exchange to light intensity and therefore possessed negligible photosynthetic activity. The initiation of photosynthesis was sudden and coincided with the onset of rapid cone growth and with the response of water loss to light intensity. It is suggested that the maturation of stomata is linked with the initiation of gas exchange.     

啤酒花抗性机制的研究进展

酒花苦味酸是构成啤酒风味的重要组分,也是啤酒生产过程中的天然抑菌剂,酒花苦味酸通过降低pH梯度而抑制啤酒花敏感菌生长。研究发现,啤酒花抗性菌是通过膜上转运蛋白将酒花苦味酸泵出细胞外,以降低膜上的质子流速,维持了细胞内的pH梯度。结合近年来酒花抗性相关研究结果,讨论了细胞膜上酒花抗性相关组分与酒花抗性间的关系,提出了酒花抗性机制的模型。     

Contributions to the antimicrobial spectrum of hop constituents

Humulus lupulus (hops) bitter acids, which are well known for their antimicrobial property against Gram-positive bacteria have negligible activity against Gram-negative bacteria. The hop acids are, however, antiprotozoal. Ciliated protozoa were more sensitive to hop acids than amoebae. Plasmodia were also sensitive but at a lower level than to the synthetic anti malarial drugs. Beta resin, tetra iso alpha acid and xanthohumol were studied and the latter was found to be particularly potent against the protozoa. Carbon dioxide enhanced the protozoicidal effect of hop acids. New data were also presented on specific antifungal activities. In agreement with the literature hop had very little antifungal property, however a slight coaction was seen between hop and sorbate on R. nigricans. Carbon dioxide had no enhancing effect on the inhibitory activity of hop against fungi as well as E. coli.