Imidazolinone-tolerant crops: history, current status and future

Imidazolinone herbicides, which include imazapyr, imazapic, imazethapyr, imazamox, imazamethabenz and imazaquin, control weeds by inhibiting the enzyme acetohydroxyacid synthase (AHAS), also called acetolactate synthase (ALS). AHAS is a critical enzyme for the biosynthesis of branched-chain amino acids in plants. Several variant AHAS genes conferring imidazolinone tolerance were discovered in plants through mutagenesis and selection, and were used to create imidazolinone-tolerant maize (Zea mays L), wheat (Triticum aestivum L), rice (Oryza sativa L), oilseed rape (Brassica napus L) and sunflower (Helianthus annuus L). These crops were developed using conventional breeding methods and commercialized as Clearfield* crops from 1992 to the present. Imidazolinone herbicides control a broad spectrum of grass and broadleaf weeds in imidazolinone-tolerant crops, including weeds that are closely related to the crop itself and some key parasitic weeds. Imidazolinone-tolerant crops may also prevent rotational crop injury and injury caused by interaction between AHAS-inhibiting herbicides and insecticides. A single target-site mutation in the AHAS gene may confer tolerance to AHAS-inhibiting herbicides, so that it is technically possible to develop the imidazolinone-tolerance trait in many crops. Activities are currently directed toward the continued improvement of imidazolinone tolerance and development of new Clearfield* crops. Management of herbicide-resistant weeds and gene flow from crops to weeds are issues that must be considered with the development of any herbicide-resistant crop. Thus extensive stewardship programs have been developed to address these issues for Clearfield* crops.     

Alien invasive species in Siberia:current status and problem

Although alien and invasive plant species have been researched extensively in the European part of Russia,the situation in Siberia is another matter.Hitherto,alien and invasive species in Siberia have not received much attention because this problem was not especially acute in Siberia.The lack of attention on alien and invasive species in Siberia is attributed to three major reasons:1) Low vegetative productivity and sparse human populations in the Siberian territory have limited botanical research interest in the area.2) Severe Siberian climate likely prevents many alien and invasive species from increasing their distribution into Siberia.3) Most Siberian plant communities have not been human-transformed and thus may be resistant to newcomers.Nevertheless,recent increased economic activities have resulted in increasing plant migration to Siberia,and this process should be monitored.Furthermore,global environmental changes may also have made Siberia more favorable for more alien and invasive species.Currently,research on alien and invasive species has begun in the Altai-Sayan region(Western Siberia) and the Magadan region(Northeastern Asia).     

Natural products as sources of herbicides: current status and future trends

Although natural product-based discovery strategies have not been as successful for herbicides as for other pesticides or pharmaceuticals, there have been some notable successes. Phosphinothricin, the biosynthetic version of glufosinate, and bialaphos are phytotoxic microbial products that have yielded commercial herbicides. Cinmethylin, a herbicidal analogue of cineole, has been sold in Europe and Asia. The triketone herbicides are derivatives of the plant-produced phytotoxin leptospermone. These products represent only a small fraction of commercialized herbicides, but they have each introduced a novel molecular target site for herbicides. Analysis of the literature reveals that phytotoxic natural products act on a large number of unexploited herbicide target sites. The pesticide industry's natural product discovery efforts have so far concentrated on microbially derived phytotoxins, primarily from non-pathogenic soil microbes, involving the screening of large numbers of exotic isolates. Plant pathogens usually produce potent phytotoxins, yet they have received relatively little attention. Even less effort has been made to discover plant-derived phytotoxins. Bioassay-directed isolation has been the preferred method of discovery after a producing organism is selected. This laborious approach often leads to rediscovery of known compounds. Modern tandem separation/chemical characterization instrumentation can eliminate much of this problem by identification of compounds before they are bioassayed.     

Prospects,challenges and current status of RNAi through insect feeding

RNA interference is a phenomenon in which the introduction of double‐stranded RNA (dsRNA) into cells triggers the degradation of the complementary messenger RNA in a sequence‐specific manner. Suppressing expression of vital genes could lead to insect death, therefore this technology has been considered as a potential strategy for insect pest control. There are three main routes of dsRNA administration into insects: (i) injections to the hemolymph, (ii) topical, and (iii) feeding. In this review, we focus on dsRNA administration through feeding. We summarize novel strategies that have been developed to improve the efficacy of this method, such as the use of nano‐based formulations, engineered microorganisms, and transgenic plants. We also expose the hurdles that have to be overcome in order to use this technique as a reliable pest management method. © 2019 Society of Chemical Industry     

The alien flora of Albania: history,current status and future trends

The first synthesis of the alien flora of Albania is presented here. In order to be able to compare with other published studies, the categories of the aliens are described using widely accepted terms. However, additional terms are also introduced in the text. Altogether, 196 alien species occur outside cultivation, including 81 naturalised and 16 partly naturalised weeds, 11 remnants of the former cultivation, nine old and 38 new casuals, 41 presumably extinct aliens and no invasives. Some authors regarded 25 native species incorrectly as aliens and nine alien species were erroneously documented as members of the Albanian flora. The changes of the alien flora of Albania differ considerably from that of most European countries, and the actual proportion of aliens in the Albanian flora is the lowest in Europe. The low number of aliens, the lack of invasives and the relatively low frequency of aliens in Albania are the consequences of the long‐term seclusion of the country during the 20th century, and the low level of economic development, the extended land use and also the fact that aliens have been present only for quite a short time in the flora. All recent social and economic changes facilitate the establishment and spread of aliens in the country, especially in the lowlands.     

Xanthomonas arboricola disease of hazelnut: current status and future perspectives for its management

This review presents an overview of bacterial blight, the predominant and emerging hazelnut disease worldwide. Here, disease symptomatologies, disease cycle, epidemiology, detection and identification methods are thoroughly discussed. It also focuses on plant health regulations and control strategies. The information reported throughout the review could help to give a better understanding of the hazelnut–bacterial blight pathosystem. A thorough knowledge of this pathosystem is important for the effective management of bacterial blight across the hazelnut orchards of the world.     

Ray blight of pyrethrum in Australia: a review of the current status and future opportunities

Ray blight caused by Stagonosporopsis tanaceti is one of the most important diseases of pyrethrum (Tanacetum cinerariifolium), a perennial herbaceous plant cultivated for the extraction of insecticidal pyrethrins in Australia. The disease is responsible for complete yield loss in severe outbreaks. Infected seed is considered as the principal source of S. tanaceti. Infection hyphae remain only in the seed coat and not in the embryo, resulting in pre- and post-emergence death of seedlings and latent infection. Therefore, quantification of the level of infection by S. tanaceti within seed using a qPCR assay is important for efficient management of the disease. Stagonosporopsis tanaceti completes its life cycle within 12 days after leaf infection through production of pycnidia and can infect every tissue of the pyrethrum plant except the vascular and root tissues. Ray blight epidemics occur in pyrethrum fields through splash dispersal of pycnidiospores between adjacent plants. Besides steam sterilization, thiabendazole/thiram and fludioxonil are effective seed-treating chemicals in controlling S. tanaceti before planting begins. Ray blight is currently managed in the field through the foliar application of strobilurin fungicides in the first 1–2 years of crop establishment. Later on, difenoconazole and multisite specific fungicides in the next 2–3 years during early spring successfully reduce ray blight infestation. Avoiding development of resistance to fungicides will require more sustainable management of ray blight including the development and deployment of resistant cultivars.     

靶向G-四链体的抗番茄丛矮病毒卟啉类衍生物的筛选

为寻找具有高活性抗病毒化合物,开发绿色抗植物病毒剂,设计合成了21个α-羟基-γ-丁内酯类化合物,其结构经过核磁共振氢谱、碳谱以及高分辨质谱确认,并初步测定了它们对烟草花叶病毒 (TMV) 的钝化活性、保护活性和治疗活性。结果表明：该类化合物具有较好的抗TMV活性,其中化合物 8o 表现出显著的钝化活性,其EC₅₀值为226.2 μg/mL,优于对照药剂病毒唑 (EC₅₀ 值308.4 μg/mL)。     

Mapping the current and future distributions of Onosma species endemic to Iran

Climate change may cause shifts in the natural range of species especially for those that are geographically restricted and/or endemic species. In this study, the spatial distribution of five endemic and threatened species belonging to the genus Onosma (including O. asperrima, O. bisotunensis, O. kotschyi, O. platyphylla, and O. straussii) was investigated under present and future climate change scenarios: RCP2.6 (RCP, representative concentration pathway; optimistic scenario) and RCP8.5 (pessimistic scenario) for the years 2050 and 2080 in Iran. Analysis was conducted using the maximum entropy (MaxEnt) model to provide a basis for the protection and conservation of these species. Seven environmental variables including aspect, depth of soil, silt content, slope, annual precipitation, minimum temperature of the coldest month, and annual temperature range were used as main predictors in this study. The model output for the potential habitat suitability of the studied species showed acceptable performance for all species (i.e., the area under the curve (AUC)>0.800). According to the models generated by MaxEnt, the potential current patterns of the species were consistent with the observed areas of distributions. The projected climate maps under optimistic and pessimistic scenarios (RCP2.6 and RCP8.5, respectively) of 2050 and 2080 resulted in reductions and expansions as well as positive range changes for all species in comparison to their current predicted distributions. Among all species, O. bisotunensis showed the most significant and highest increase under the pessimistic scenario of 2050 and 2080. Finally, the results of this study revealed that the studied plant species have shown an acute adaptability to environmental changes. The results can provide useful information to managers to apply appropriate strategies for the management and conservation of these valuable Iranian medicinal and threatened plant species in the future.     

Fusarium rot of melon is caused by several Fusarium species

Fusarium rot of melon, caused by species of the genus Fusarium, has become an important postharvest disease for many Brazilian producers. Due to the delayed onset of symptoms, this disease is often only detected when fruits arrive at the importing country, thus generating economic loss for the exportation of the fruit. This study was developed with the aim of investigating which Fusarium species cause fruit rot in melon and to evaluate any differences in aggressiveness and development of symptoms. Species were identified through phylogenetic analysis of two loci and morphological markers. The 28 isolates obtained from diseased melon fruits of different commercial cultivars were identified as Fusarium falciforme (FSSC), F. sulawesiense, F. pernambucanum (FIESC), and F. kalimantanense (FOSC). Three isolates belong to a new phylogenetic lineage within the F. fujikuroi species complex (FFSC). All isolates were tested for pathogenicity, and first symptoms of rot in Canary melon were observed 2 days after inoculation. Isolates of F. falciforme and F. sulawesiense were shown to be more aggressive. Our results extend information on Fusarium species that cause fruit rot in melon and support the development of management strategies, as there is currently no efficient control for this disease. To our knowledge, this is the first report of the occurrence of species of the FSSC, FOSC, and FFSC from muskmelon fruits in Brazil.     

Predicting weed emergence: a review of approaches and future challenges

Summary In relatively short-term studies it is often difficult to identify the factors that are important in determining the patterns of emergence for different weed species. When results from longer-term studies are averaged over years, they demonstrate that some weed species follow characteristic, and potentially predictable, patterns of annual emergence. In recent years, our understanding of the seasonal changes in dormancy and germination behaviour, and the interaction of these processes with the environment, has advanced considerably. In particular, the capacity for computer-based statistical analysis and the ability to handle large datasets has made it possible to use this information in a predictive way. Currently, there are several approaches to developing predictive weed emergence modelling. Some researchers have taken an empirical approach, seeking to identify correlations between environmental variables and observed emergence patterns. Others have taken a reductionist approach, subdividing the emergence process into its component stages of dormancy, germination and pre-emergence growth, to work towards achieving an eventual understanding of the physiological processes involved. Despite recent advances, a number of major challenges remain (e.g. population variability, dormancy and the quality of the input data) that must be overcome before these emergence models can be implemented in practice. The level of complexity and degree of parameterization incorporated within such models must also be addressed in relation to the intended use of the model.     

Glyphosate-resistant crops: history, status and future

The commercial launch of glyphosate-resistant soybeans in 1996 signaled the beginning of a new era in weed management in row crops. Today, over 80% of the soybeans grown in the USA are glyphosate resistant. Since that time, many crops have been transformed that have allowed crop applications of many classes of herbicide chemistries. Crops currently under production include maize, soybean, cotton and canola. Transformation technology and selection methods have improved and the rate of development as well as the breadth of crops being considered as commercial targets has increased. On the basis of recent adoption rates by growers around the world, it appears that glyphosate-resistant crops will continue to grow in number and in hectares planted. However, global public acceptance of biotechnology-derived products will continue to impact the rate of adoption of this and other new innovations derived from transformation technology.     

辽宁省辣椒土传病害镰刀菌鉴定及rDNA-ITS序列分析

［目的］ 对分离的辣椒镰刀菌形态、基因序列进行研究,以确定病原菌的种类及这些菌的同源性,为进一步开展该病害诊断和防治研究奠定基础。［方法］ 对采自辽宁省各地辣椒土传病害的16株病菌进行形态观察及rDNA-ITS序列分析。［结果］ 引起辽宁省辣椒土传病害的主要镰刀菌有尖镰孢、茄镰孢、锐顶镰孢和串珠镰孢等4种,根据菌株分生孢子形态和rDNA ITS序列同源性,将ZW13、LY3、PJLJ、HC5、CY2、CY5、TLLJ、LY5、LY1菌株聚类为尖镰孢;FSLJ2和FSLJ3菌株聚类为茄镰孢;ZW和ZW18菌株聚类为锐顶镰孢;KPLJ、LZLJ、FSLJ1菌株聚类为串珠镰孢。［结论］ 从分子系统树和菌株间的遗传距离看出镰刀菌同种同源性都很高,不同种之间同源性相对较低,种间遗传差异较大。     

Fusarium head blight of cereals in Denmark: species complex and related mycotoxins

Quantitative real-time polymerase chain reaction differentiating 10 Fusarium spp. and Microdochium nivale or M. majus was applied to a total of 396 grain samples of wheat, barley, triticale, oat, and rye sampled across Denmark from 2003 to 2007, along with selected samples of wheat and barley from 1957 to 2000, to determine incidence and abundance of individual Fusarium spp. The mycotoxins deoxynivalenol (DON), nivalenol, zearalenone, T-2, and HT-2 were quantified using liquid chromatography-double mass spectrometry. Major differences in the Fusarium species complex among the five cereals as well as great yearly variation were seen. Fusarium graminearum, F. culmorum, and F. avenaceum were dominant in wheat, with DON as the dominant mycotoxin. F. langsethiae, F. culmorum, and F. avenaceum were dominant in barley and oat, leading to relatively high levels of the mycotoxins T-2 and HT-2. F. graminearum, F. culmorum, and F. avenaceum dominated in triticale and rye. The nontoxigenic M. nivale/majus were present in significant amounts in all cereal species. Wheat and barley samples from 1957 to 1996 exhibited no or very low amounts of F. graminearum, indicating a recent increase of this pathogen. Biomass and mycotoxin data exhibited good correlations between Fusarium spp. and their corresponding mycotoxins under field conditions.     

非转基因抗除草剂作物研究现状与展望

抗除草剂转基因作物的培育和推广明显提高了农田除草效率,取得了巨大的经济效益。但随着研究的深入,外源基因的不可预测性却越来越多地阻碍了转基因作物的发展。针对转基因作物与非转基因作物的优缺点,该文系统地综述了国内外抗除草剂作物的研究现状,重点阐述了非转基因抗除草剂作物的主要研究方法及存在的问题,并提出研究对策和发展方向。     

Use of zoophytophagous mirid bugs in horticultural crops: Current challenges and future perspectives

In recent years, the use of predatory mirid bugs (Hemiptera: Miridae) in horticultural crops has increased considerably. Mirid bugs are zoophytophagous predators, that is, they display omnivorous behavior and feed on both plants and arthropods. Mirid bugs feed effectively on a wide range of prey, such as whiteflies, lepidopteran eggs and mites. In addition, the phytophagous behavior of mirid bugs can activate defenses in the plants on which they feed. Despite the positive biological attributes, their use still presents some constraints. Their establishment and retention on the crop is not always easy and economic plant damage can be caused by some mirid species. In this review, the current strategies for using zoophytophagous mirid bugs in horticultural crops, mainly Nesidiocoris tenuis, Macrolophus pygmaeus and Dicyphus hesperus, are reviewed. We discuss six different approaches which, in our opinion, can optimize the efficacy of mirids as biocontrol agents and help expand their use into more areas worldwide. In this review we (i) highlight the large number of species and biotypes which are yet to be described and explore their applicability, (ii) present how it is possible to take advantage of the mirid‐induced plant defenses to improve pest management, (iii) argue that genetic selection of improved mirid strains is feasible, (iv) explore the use of companion plants and the use of alternative foods to improve the mirid bug management, and finally (vi) discuss strategies for the expansion of mirid bugs as biological control agents to horticultural crops other than just tomatoes. © 2020 Society of Chemical Industry     

Control of morningglory species using Fusarium solani and its extracts

Abstract

Natural products of an isolate of Fusarium solani App. & Wr. NRRL 18883 grown on rice medium were discovered to be phytotoxic to morningglory. This isolate was evaluated for biocontrol potential on morningglory species including ivyleaf [Ipomoea hederacea (L.) Jacq.], multicoloured (I. tricolor Cav.), paimleaf (I. wrightii Gray), pitted (I. lacunosa L.), purple moonflower (I. turbinata Lag.), red (I. coccinea L.), sharppod (I. cordatotriloba Dennstedt), smallflower (Jacquemontia tamnifolia (L.) Griseb], and tall [I. purpurea (L.) Roth] morningglory. When sprayed at a concentration of 10 g fungus‐infested rice per 50 ml of water, this isolate caused phytotoxic damage including necrosis, chlorosis, growth inhibition, and mortality. Deleterious effects were recorded in all species, ranging from necrotic spots to death, depending on the species. Mortality ranged from 0% at 3 weeks for purple moonflower to 89% for smallflower morningglory. Soil‐drench application (10–20 ml fungal material per 150 g soil) caused wilting and death. Root lengths of 7‐ and 10‐day‐old plants were reduced between 19 and 89% by soil‐drench application and 17–84% by spray application. Whole plant length reduction of 7‐ and 10‐day‐old plants ranged from 0 to 96%, and 39 to 96% for soil‐drench and spray applications, respectively. Testing of F. solani on weed and crop species showed that most broadleaved species were sensitive but monocotyledons were immune. Tests of the phytotoxic extract for known phytotoxins such as common trichothecene (deoxynivalenol) and non‐trichothecene compounds (fusaric acid, moniliformin, fumonisins) were negative. This is the first report of the use of F. solani against morningglory.     

我国农药管理现状及面临的挑战

我国有占世界19%的人口，但仅有占世界9%的耕地，因此保证国家粮食安全是头等大事。在确保生态环境安全的前提下，如何增加作物产量和保障农产品质量安全始终是我国农业快速发展面临的一大挑战。在高效、负责、透明的政府能力建设中，我国农业的绿色发展和高质量发展战略，我国农药管理的法制建设、市场监管、食品安全、环境监测、有害生物治理、应用技术服务及推广等都取得了显著进步。到2021年底，我国已经登记了740多个农药有效成分，41 433个农药产品。2021年，全国1 705家农药定点企业，共生产了化学农药原药249.8万t。不仅满足了国内有害生物防控的实际需要，还出口180多个国家和地区，农药出口额达到234亿美金。我国还有的10个高毒农药品种，已经控制在1.3%以下，且安排在未来5年内会陆续退市。本文还分析梳理了今后我国农药管理发展所面临的挑战。     

Auxin herbicides: current status of mechanism and mode of action

Synthetic compounds that act like phytohormonal ‘superauxins’ have been among the most successful herbicides used in agriculture for more than 60 years. These so‐called auxin herbicides are more stable in planta than the main natural auxin, indole‐3‐acetic acid (IAA), and show systemic mobility and selective action, preferentially against dicot weeds in cereal crops. They belong to different chemical classes, which include phenoxycarboxylic acids, benzoic acids, pyridinecarboxylic acids, aromatic carboxymethyl derivatives and quinolinecarboxylic acids. The recent identification of receptors for auxin perception and the discovery of a new hormone interaction in signalling between auxin, ethylene and the upregulation of abscisic acid biosynthesis account for a large part of the repertoire of auxin‐herbicide‐mediated responses, which include growth inhibition, senescence and tissue decay in sensitive dicots. An additional phenomenon is caused by the quinolinecarboxylic acid quinclorac, which also controls grass weeds. Here, the accumulation of phytotoxic levels of tissue cyanide, derived ultimately from quinclorac‐stimulated ethylene biosynthesis, plays a key role in eliciting the herbicidal symptoms in sensitive grasses. Copyright © 2009 Society of Chemical Industry     

Ecology,distribution and control of the invasive weed Nassella trichotoma (Nees) Hack. ex Arechav.: A global review of current and future challenges

Nassella trichotoma (serrated tussock) is a highly invasive perennial C₃ weed from South America. It grows in most soil conditions, can resist fire and frost, and is unpalatable to grazing animals. Each plant can produce up to 140,000 seeds annually, and together, these characteristics make it a damaging landscape weed. It has diminished the agricultural carrying capacity of pastures in south-eastern Australia, New Zealand and South Africa, and emerging populations have now been identified in Europe and the United States, and bioclimatic models suggest its distribution could significantly expand within these regions in the near future. Research into control methods for this weed has been explored, and these include herbicides applied alone and in combination, the establishment of plant competition, the introduction of seed mitigation fencing, grazing management and exclusion zones, specific biological management and alteration of soil composition. Currently, the most effective and widely used control method is the residual herbicide flupropanate (2,2,3,3-tetrafluoropropanoic acid). This review will investigate the ecology, distribution, current control techniques and past research on this species, and make recommendations for future research and management.