Influence of verticillium and fusarium wilts on the growth of melon

The susceptibility of the Greek melon cvs Kokkini Banana, Thraki, Peplos and Amynteou to Verticillium dahliae and Fusarium oxysporum f. sp. melonis was tested, by inoculating seedlings of the four cultivars by root immersion in a Verticillium and Fusarium inoculum suspension for 1 h. After 35 days, disease incidence was estimated from a disease index calculated as the product of the'leaf symptom index'and'vascular discoloration index'of each plant. In addition, plant height, main stem diameter, above-ground fresh and dry weight and root fresh and dry weight were measured. The disease severity of verticillium and fusarium wilts on plants was estimated by the correlation coefficient ( r ) between the disease index and the other characteristics. Both fungi had a significant negative effect on all the measured characteristics independently of the tested cultivar. Finally, the four melon cultivars showed different degrees of susceptibility to Verticillium and Fusarium indicating that tolerant selections can be achieved.     

Recent advances in biological electron microscopy

The main features of electron microscopy (EM) are outlined; transmission EM, high-voltage transmission EM, scanning EM, scanning transmission EM and their uses in biological research are discussed. The use of these techniques with X-ray analysis is mentioned and reference is made to the problems of specimen preparation.     

Benomyl-resistant Fusarium-isolates in ecological studies on the biological control of fusarium wilt in carnation

Ecological properties and stability of benomyl resistance of three benomyl-resistant mutants of nonpathogenicFusarium-isolates antagonistic to fusarium wilt in carnation, and three benomyl-resistant mutants of a pathogenic isolate ofFusarium oxysporum f.sp.dianthi were evaluatedin vitro and in glasshouse experiments. The benomyl resistance of the nonpathogenic mutants was stable under all conditions tested, also after a 1000-fold increase of the population in sterilized soil. Mutants of the pathogen were stable during allin vitro tests, but after proliferation in carnation stems only part of the population was benomyl resistant.Compared to the wild type, mutants of the pathogen were less pathogenic, also if thein vitro propeties were similar. Colonization of carnation by benomyl-resistant nonpathogenicFusarium in the presence of the pathogen showed that the antagonistic effect correlated with the presence of the nonpathogenic isolates within the carnation stem. The wild types and two of the mutant nonpathogenicFusarium-isolates controlled fusarium wilt in the susceptible cultivar Lena for 50% or more.UV-induced benomyl resistance appeared to be a valuable marker to distinguish between differentFusarium isolates and to study the population dynamics, but intensive screening of the mutants is a prerequisite since alterations in antagonism and pathogenicity can occur.     

Recent studies on biological control of plant diseases in Japan

Microorganisms play an enormously important role in plant disease control. Research on biological control of plant pathogens has received major impetus and attracted many researchers during the past few decades due to the increased public concern on hazards associated with the use of synthetic pesticides. From research on utilizing specific antagonistic microorganisms, many effective biological control agents (BCAs) have been found and are increasingly implemented in integrated pest management strategies to control plant diseases. Here current research results on biological control against plant diseases carried out in Japan are reviewed by focusing on major categories of BCAs: fungi, bacteria and actinomycetes and attenuated viruses.     

Effects of antagonist cell concentration and two-strain mixtures on biological control of fusarium dry rot of potatoes

ABSTRACT Eighteen bacterial strains were individually assayed against Gibberella pulicaris (5 x 10(5) conidia per ml) by coinoculating antagonist and pathogen in wounds in cv. Russet Burbank potatoes. All antagonist concentrations (10(6), 10(7), and 10(8) CFU/ml) decreased disease (38 to 76% versus control, P < 0.05). When four strains were assayed at 11 concentrations (range 10(5) to 10(8) CFU/ml) against G. pulicaris, linear regression of the log-dose, log-response data was significant for all four strains (P < 0.001 to 0.01, R(2) = 0.50 to 0.74). Challenging G. pulicaris with all possible antagonist pairings within 2 sets of 10 antagonist strains (5 x 10(5) CFU of each strain per ml) resulted in 16 of 90 pairs controlling disease better than predicted based on averaging the performance of the individual strains making up the pair (P < 0.10). Successful pairs reduced disease by ~70% versus controls, a level of control comparable to that obtained with 100 times the inoculum dose of a single antagonist strain. Neither strain genus nor soil of origin were useful in predicting successful antagonist pairs. Factors potentially influencing dose-response relationships and the effectiveness of antagonist pairs in controlling disease are discussed.     

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry     

The potential of nonpathogenic Fusarium oxysporum and other biological control organisms for suppressing fusarium wilt of banana

The aim of this study was to evaluate the ability of nonpathogenic F. oxysporum and Trichoderma isolates from suppressive soils in South Africa to suppress fusarium wilt of banana in the glasshouse. Several biological control agents and commercial biological control products were included in the study. The isolates were first screened in vitro on potato dextrose agar. In glasshouse evaluations, the fungal and bacterial isolates were established on banana roots before they were replanted in pathogen-infested soil, while the commercial biocontrol agents were applied as directed by the supplier. Banana plantlets were evaluated for disease development after 7 weeks. In vitro tests showed none of the nonpathogenic isolates suppressed Fusarium oxysporum f.sp. cubense ( Foc ), while slight suppression was observed with the two Trichoderma isolates. Results of the glasshouse evaluations revealed that two of the nonpathogenic F. oxysporum isolates, CAV 255 and CAV 241, reduced fusarium wilt incidence by 87·4 and 75·0%, respectively. The known biological control agent Fo47 did not suppress Foc significantly. Pseudomonas fluorescens strain WCS 417, known for its ability to suppress other fusarium wilt diseases (WCS 417), reduced disease incidence by 87·4%. These isolates should be further evaluated for potential application in the field, independently and in combination.     

Integrated management of fusarium wilt of chickpea with sowing date, host resistance, and biological control

ABSTRACT A 3-year experiment was conducted in field microplots infested with Fusarium oxysporum f. sp. ciceris race 5 at Córdoba, Spain, in order to assess efficacy of an integrated management strategy for Fusarium wilt of chickpea that combined the choice of sowing date, use of partially resistant chickpea genotypes, and seed and soil treatments with biocontrol agents Bacillus megaterium RGAF 51, B. subtilis GB03, nonpathogenic F. oxysporum Fo 90105, and Pseudomonas fluorescens RG 26. Advancing the sowing date from early spring to winter significantly delayed disease onset, reduced the final disease intensity (amount of disease in a microplot that combines disease incidence and severity, expressed as a percentage of the maximum possible amount of disease in that microplot), and increased chickpea seed yield. A significant linear relationship was found between disease development over time and weather variables at the experimental site, with epidemics developing earlier and faster as mean temperature increased and accumulated rainfall decreased. Under conditions highly conducive for Fusarium wilt development, the degree of disease control depended primarily on choice of sowing date, and to a lesser extent on level of resistance of chickpea genotypes to F. oxysporum f. sp. ciceris race 5, and the biocontrol treatments. The main effects of sowing date, partially resistant genotypes, and biocontrol agents were a reduction in the rate of epidemic development over time, a reduction of disease intensity, and an increase in chickpea seedling emergence, respectively. Chickpea seed yield was influenced by all three factors in the study. The increase in chickpea seed yield was the most consistent effect of the biocontrol agents. However, that effect was primarily influenced by sowing date, which also determined disease development. Effectiveness of biocontrol treatments in disease management was lowest in January sowings, which were least favorable for Fusarium wilt. Sowing in February, which was moderately favorable for wilt development, resulted in the greatest increase in seed yield by the biocontrol agents. In March sowings, which were most conducive for the disease, the biocontrol agents delayed disease onset and increased seedling emergence. B. subtilis GB03 and P. fluorescens RG 26, applied either alone or each in combination with nonpathogenic F. oxysporum Fo 90105, were the most effective treatments at suppressing Fusarium wilt, or delaying disease onset and increasing seed yield, respectively. The importance of integrating existing control practices, partially effective by themselves, with other control measures to achieve appropriate management of Fusarium wilt and increase of seed yield in chickpea in Mediterranean-type environments is demonstrated by the results of this study.     

Recent advances in the stereoselective synthesis of L-phosphinothricin

L -Phosphinothricin, the parent α-amino acid of the herbicide glufosinate-ammonium, has been obtained in high enantiomeric purity by three different methods. The stereoselective alkylation of a D -valine-derived bis-lactim ether, followed by the hydrolysis of the heterocyclic intermediate, represents an attractive approach for gram-scale quantities in the laboratory. Another very efficient access to L -phosphinothricin consists of the asymmetric hydrogenation of a prochiral α-acylamido acrylate with a chiral bis-phosphine-rhodium catalyst, while the reaction of chiral pre-built C-4-fragments, like L -vinylglycine or L -2-amino-4-halobutyric acid, which can be obtained from the inexpensive starting materials L -aspartic acid and L -glutamic acid, with (methyl)phosphinic acid derivatives represents a third route which allows the production of nearly enantiomerically pure L -phosphinothricin.     

我国作物病虫害生物防治研究与应用最新进展

本文总结了近5年来我国在作物病虫害生物防治研究和应用方面的最新进展, 包括作物害虫、病害(真菌、细菌和病毒病)和线虫的生物防治、植物免疫和昆虫性信息素的研究和应用, 以及新方法和新技术在作物病虫控制中的应用。同时, 与国外的研究进展进行了比较, 指出了存在的主要问题、发展趋势与对策建议。     

Recent advances in the chemistry of the pyrethroids. Forword

The sequences of compounds, leading from the natural pyrethrins to the present established pyrethroids, are described so as to provide a background for considering the more recent advances discussed in succeeding papers.     

Integrated control of fusarium head blight and deoxynivalenol mycotoxin in wheat

Fusarium head blight (FHB), a devastating disease that affects wheat, is caused by a complex of Fusarium species. The overall impact of Fusarium spp. in wheat production arises through the combination of FHB and mycotoxin infection of the grain harvested from infected wheat spikes. Spike infection occurs during opening of flowers and is favoured by high humidity or wet weather accompanied with warm temperatures. Available possibilities for controlling FHB include the use of cultural practices, fungicides and biological approaches. Three cultural practices are expected to be of prime importance in controlling FHB and the production of mycotoxins: soil preparation method (deep tillage), the choice of the preceding crop in the rotation and the selection of appropriate cultivar.     

杀虫植物非洲山毛豆的研究

非洲山毛豆原产于热带非洲,是一种优异的杀虫植物。本文对其生物活性、杀虫有效成分、作用机理、加工使用等方面进行了概述。     

小麦印度腥黑穗病菌鉴定方法的新进展

自1930年印度西北部Haryana邦的Kamal地区首次发现小麦印度腥黑穗病(Tilletia indicaMitra,以下简称印腥)以来,由于感病寄主的广泛种植和适宜环境条件的存在,该病已在世界范围内的不同生态区迅速传播蔓延,在70年左右的时间内从一个危害轻微的地方性病害发展为威胁世界小麦生产和贸易的危险性真菌病害.     

水稻病毒与植物寄主互作研究新进展

水稻是维持世界一半以上人口生存的主要粮食作物,其产量和品质关系到社会稳定。近年来,水稻病毒引起的病毒病严重影响作物的产量及品质。植物在与病毒长期的互作过程中进化出了多种有效的防御机制来抑制病毒侵染。本文围绕近年来国内外关于水稻抗病毒的研究进展,对植物激素、自噬与水稻病毒的互作关系进行总结,并提出了水稻病毒研究过程中所涉及到的一些问题,以期为开展水稻抗病育种相关研究提供参考。     

新型农药残留快速检测技术研究进展

农药残留检测关乎食品安全和人类健康问题。传统农药残留检测通常选择色谱法或色谱-质谱联用法等,具有准确、稳定等优势,但通常需要昂贵而复杂的大型仪器,样品前处理过程费时费力,对操作人员要求高。为了克服这些缺陷,一系列农药快速检测技术相继被开发出来。文章介绍了可用于农药残留快速检测的主要技术,包括生物传感器 (酶传感器、免疫传感器、适配体传感器、细胞传感器)、光谱技术 (近红外光谱、太赫兹时域光谱、拉曼光谱等) 与微流控技术,重点介绍了这些技术的原理、特点与最新研究进展,分析了目前农药快速检测技术存在的问题与未来的发展前景。     

我国近年植保研究工作的重大进展

介绍了我国近年植保学科领域在重要农作物病虫发生机制及控制技术、农作物病虫监测技术、超常规培育 抗性品种、人为增加天敌控制作用以及农药研究与应用等方面取得的重大成果和重要进展。     

Biological control of fusarium wilt of cucumber by chitinolytic bacteria

ABSTRACT Two chitinolytic bacterial strains, Paenibacillus sp. 300 and Streptomyces sp. 385, suppressed Fusarium wilt of cucumber (Cucumis sativus) caused by Fusarium oxysporum f. sp. cucumerinum in nonsterile, soilless potting medium. A mixture of the two strains in a ratio of 1:1 or 4:1 gave significantly (P < 0.05) better control of the disease than each of the strains used individually or than mixtures in other ratios. Several formulations were tested, and a zeolite-based, chitosan-amended formulation (ZAC) provided the best protection against the disease. Dose-response studies indicated that the threshold dose of 6 g of formulation per kilogram of potting medium was required for significant (P < 0.001) suppression of the disease. This dose was optimum for maintaining high rhizosphere population densities of chitinolytic bacteria (log 8.1 to log 9.3 CFU/g dry weight of potting medium), which were required for the control of Fusarium wilt. The ZAC formulation was suppressive when added to pathogen-infested medium 15 days before planting cucumber seeds. The formulation also provided good control when stored for 6 months at room temperature or at 4 degrees C. Chitinase and beta-1,3-glucanase enzymes were produced when the strains were grown in the presence of colloidal chitin as the sole carbon source. Partial purification of the chitinases, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and activity staining, revealed the presence of five bands with molecular masses of 65, 62, 59, 55, and 52 kDa in the case of Paenibacillus sp. 300; and three bands with molecular masses of 52, 38, and 33 kDa in the case of Streptomyces sp. 385. Incubation of cell walls of F. oxysporum f. sp. cucumerinum with partially purified enzyme fractions led to the release of N-acetyl-D-glucosamine (NAGA). NAGA content was considerably greater when pooled enzyme fractions (64 to 67) from Paenibacillus sp. were used, because they contained high beta-1,3-glucanase activity in addition to chitinase activity. Suppression of Fusarium wilt of cucumber by a combination of these two bacteria may involve the action of these hydrolytic enzymes.     

葡萄抗霜霉病机制研究进展

葡萄霜霉病是危害葡萄的重要病害之一,该病害发生时会给葡萄生产造成严重的经济损失。本文综合分析了国内外对葡萄抗霜霉病机制研究的结果,认为葡萄对霜霉病抗性受多种因素影响,主要表现为生理生化物质、叶片形态结构及抗病遗传基因三个方面。由于各种因素对霜霉病病原菌作用关系复杂,目前对于葡萄抗霜霉病的决定性因子还没有明确结论。