青藏高原高寒草甸土壤环境对线虫功能多样性的影响

土壤线虫是地下食物网的重要组成部分, 在生态系统能量流动和物质循环中起着至关重要的作用。大量研究报道了肥力等土壤环境对土壤线虫物种多样性及各功能群多度的影响, 而我们对土壤线虫功能多样性如何响应土壤环境变化依然知之甚少。本研究以群落水平个体大小和个体大小多样性表征土壤线虫功能多样性。在青藏高原高寒草甸选择3个研究点, 调查和分析了不同生境(沟底平地、阴坡、阳坡和山顶)土壤线虫物种多样性、各功能群多度和功能多样性及其与土壤理化因子和植物多样性的关系。结果表明: (1)土壤线虫个体多度和物种多样性在阳坡最高, 随土壤pH值和土壤总磷增加而升高; 而基于个体大小的土壤线虫功能多样性主要受土壤养分影响, 随土壤总氮和有机质增加而增加, 随土壤总磷含量增加而减少; (2)食细菌和食真菌线虫多度在沟底最高, 植食与捕食杂食线虫多度在山顶最低; 除捕食杂食线虫外, 各功能群多度也主要随土壤磷增加而升高; 除食真菌线虫外, 各功能群多度随植物物种丰富度的增加而减少。本研究强调了土壤线虫物种和功能多样性受不同土壤环境因子的影响, 丰富了土壤线虫多样性研究的内容, 为理解高寒草甸土壤动物多样性形成、维持和变化提供了更广阔的 视角。     

Helminth Collection and Identification from Wildlife

Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are "roundworms" (nematodes), "thorny-headed worms" (acanthocephalans), "flukes" (trematodes), and "tapeworms" (cestodes). The optimum method for collecting helminths is to examine a host that has been dead less than 4-6 hr since most helminths will still be alive. A thorough necropsy should be conducted and all major organs examined. Organs are washed over a 106 μm sieve under running water and contents examined under a stereo microscope. All helminths are counted and a representative number are fixed (either in 70% ethanol, 10% buffered formalin, or alcohol-formalin-acetic acid). For species identification, helminths are either cleared in lactophenol (nematodes and small acanthocephalans) or stained (trematodes, cestodes, and large acanthocephalans) using Harris'' hematoxylin or Semichon''s carmine. Helminths are keyed to species by examining different structures (e.g. male spicules in nematodes or the rostellum in cestodes). The protocols outlined here can be applied to any vertebrate animal. They require some expertise on recognizing the different organs and being able to differentiate helminths from other tissue debris or gut contents. Collection, preservation, and staining are straightforward techniques that require minimal equipment and reagents. Taxonomic identification, especially to species, can be very time consuming and might require the submission of specimens to an expert or DNA analysis.     

Effectors of root sedentary nematodes target diverse plant cell compartments to manipulate plant functions and promote infection

Sedentary plant-parasitic nematodes maintain a biotrophic relationship with their hosts over a period of several weeks and induce the differentiation of root cells into specialized feeding cells. Nematode effectors, which are synthesized in the esophageal glands and injected into the plant tissue through the syringe-like stylet, play a central role in these processes. Previous work on nematode effectors has shown that the apoplasm is targeted during invasion of the host while the cytoplasm is targeted during the induction and the maintenance of the feeding site. A large number of candidate effectors potentially secreted by the nematode into the plant tissues to promote infection have now been identified. This work has shown that the targeting and the role of effectors are more complex than previously thought. This review will not cover the prolific recent findings in nematode effector function but will instead focus on recent selected examples that illustrate the variety of plant cell compartments that effectors are addressed to in order reach their plant targets.     

Nematodes associated with date palm and their control measures

Date palm, Phoenix dactylifera L., is dioecious and can be artificially pollinated by man, and one-third of all the dates of the world are grown in Iraq. In Egypt, there are about 12?million date palm trees grown in 99,867?feddans (fed.?=?4200?m²). Productivity is 1352,954?million?tons with yield 111.7?kg/tree. Plant parasitic nematodes associated with date palm are Criconemoides spp., Helicotylenchus spp., Hemicriconemoides spp., Hemicycliophora spp., Hoplolaimus spp., Meloidogyne incognita, Meloidogyne arenaria, Meloidogyne javanica, Pratylenchus brachyurus, Pratylenchus jordanensis, Pratylenchus coffeae, Pratylenchus neglectus, Pratylenchus thornei, Trichodorus spp., Tylenchorhynchus goffarti, Tylenchorhynchus latus and Xiphinema spp.; Meloidogyne incognita-infected roots of susceptible cultivar favoured giant cell and galls formation. Date palm roots infected with Pratylenchus penetrans showed puncture of epidermal cells and disarrangement of cortical cells with large empty abnormal cavities. As control measures, it is advised to; 1 – plant immune or resistant cultivars against pathogenic nematodes, 2 – use oil cakes or poultry manure as organic amendments and a nematicide, carbofuran.These were tested and found effective in the control of Helicotylenchus multicinctus and P. penetrans, 3 – treat nematode-infested date palm seedlings with hot water at a suitable temperature for a given period before transplanting to open field, 4 – plant nematode -free date palm seedlings, 5 – soil solarisation and tillage before planting, 6 – weed control, 7 – intercrop with nematode-resistant horticultural crops and 8 – induce resistance in susceptible date palm cultivars against root knot nematode.     

Effects of some plant extracts on larval hatch of the root-knot nematode,Meloidogyne incognita

Abstract

The inhibitory effect of water extract of seed, leaf and bark of five plants, viz., Tamarindus indica, Cassia siamea, Isoberlinia doka, Dolnix regia and Cassia sieberiana was evaluated on larval hatch of Meloidogyne incognita in the laboratory. All the plant parts inhibited larval hatch of M. incoginta Percentage inhibition was higher in the seeds followed by the leaves and bark. Degree of inhibition observed, was directly related to the concentration of the extract. The standard suspensions inhibited hatching by about 97% while dilutions of S/100 inhibited larval hatch by 3%. Nematicidal activity of the plant parts of the five plants showed that C. siamea was the most effective followed by C. sieberiana, I. doka, T. indica and D. regia.     

Population dynamics of Meloidogyne incognita on black pepper plants in two agro-ecological regions in Vietnam

The objective of our study was to examine the effect of local environmental conditions, especially air temperature and rainfall, in two agro-ecological regions in Vietnam on the population dynamics of Meloidogyne incognita on black pepper plants and on percentage root galling. The two study sites were situated in Cam Lo, Quang Tri province (North Central Coast) and Buon Ma Thuot, Dac Lac province (Central Highlands). At the study sites, 13 plant-parasitic nematode taxa belonging to 12 genera were identified. Ten of these taxa were present in both study sites. Helicotylenchus certus, Hemicriconemoides cocophilus and Pratylenchus coffeae were only found in Buon Ma Thuot. Based on nematode population densities, M. incognita was the most abundant taxon present. Rainfall and air temperature differed significantly between the two study sites. The most important climatic difference was rainfall: in Buon Ma Thuot, the rainy season lasted 2 months longer and the monthly rainfall during the rainy season was much higher compared to Cam Lo. Although this difference resulted in some differences in the population dynamics of M. incognita in the soil and roots of the black pepper variety Vinh Linh, the highest root population densities were observed in both study sites during the first half of the dry season. In Cam Lo, the highest percentage root galling was observed during the first half of the dry season. In Buon Ma Thuot, the highest percentage root galling was observed towards the end of the rainy season. Estimating the population densities if M. incognita to decide on the application of a management strategy should be done during the first half of the dry season.     

Use of some emulsified plant seed oils as a safe alternative for the management of Meloidogyne incognita infecting tomato

Abstract

The aim of the present study was to formulate six different plant seed oils namely canola, cotton, flax, olive, sesame and soybean as emulsifiable concentrates. The composition of the formulation comprises at least one organic solvent, one surfactant and one plant oil. Physico-chemical properties of the formulated oils (emulsion stability test, cold stability and heat stability tests) were measured. The successfully emulsified oils were evaluated for nematicidal activity against Meloidogyne incognita infecting tomato plants under greenhouse conditions. Emulsified canola oil proved to be the most effective oil as a protectant against M. incognita infection to tomatoes followed by soybean, cotton, flax and sesame oil. In addition, employing a high rate of the tested emulsified oils gave higher activity in suppressing nematodes both in the soil and in tomato roots than using a low rate. Moreover, all tested formulated oils at both rates of application had no adverse effect on the growth of tomato plants except sesame oil which significantly decreased the shoot length when compared to the control. The prepared plant oils might be used as potential sources for sustainable eco-friendly botanical nematicides to protect plants from nematode attack.     

Susceptibility of three lepidopteran pests to five entomopathogenic nematodes and in vivo mass production of these nematodes

Abstract

An investigation was conducted in pots to access the susceptibility of three lepidopteran pests, namely, gram pod borer, Helicoverpa armigera, greater wax moth, Galleria mellonella, and rice moth, Corcyra cephalonica, to two recently described species, Steinernema masoodi, S. seemae, and three indigenous S. carpocapsae, S. glaseri and S. thermophilum entomopathogenic nematodes (EPN). The suitability of these lepidopterans for the in vivo mass production of the nematodes was also estimated. Among the five species of EPN, S. masoodi, S. seemae and S. carpocapsae were found most pathogenic to C. cephalonica, bringing about mortality within 24 h, followed by H. armigera (36, 38 and 48 h, respectively) and G. mellonella (30, 36 and 48 h, respectively). The other species of EPN, viz., S. glaseri and S. thermophilum was the least pathogenic, which killed the larvae of C. cephalonica in 29 and 36 h, respectively, G. mellonella in 48 h, and H. armigera in 38 and 56 h, respectively. Galleria mellonella was found the most suitable host for the mass production of infective juveniles (IJs) of S. seemae, which yielded higher IJs than S. carpocapsae. Helicoverpa armigera was the next best suitable alternate host, which produced maximum IJs in case of S. seemae followed by S. masoodi, S. carpocapsae, S. glaseri and S. thermophilum. Rice moth, Corcyra cephalonica was the least suitable host. The susceptibility of H. armigera to five tested EPN species and susceptibility of G. mellonella and C. cephalonica to S. masoodi and S. seemae are new records.     

Field assessment of efficacy of nitrogen salts to control the root-knot nematode (Meloidogyne javanica) on tomato

Influence of different nitrogen salts at electrical conductivity levels (EC2, 4 and 8?mmhos/cm) on tomato and root-knot nematode (Meloidogyne javanica) and their interactions was evaluated under field conditions. It was found that both diammonium phosphate ((NH₄)₂HPO₄) and ammonium sulphate ((NH₄)₂SO₄) were more effective than ammonium chloride (NH₄Cl) in causing an obvious suppression of M. javanica infection on tomato through reducing root galling and nematode reproduction and improving tomato growth and yield and their suppressive effect was similar to that of oxamyl or ethoprophos. At higher ECs, the tested nitrogen salts did not greatly affect pH, EC and salinity of rhizospheric soil except NH₄Cl at EC8 that caused higher EC and salinity over the untreated control which makes NH₄Cl less suitable candidate. Therefore, the use of (NH₄)₂HPO₄ and (NH₄)₂SO₄ alone or in combination with other control measures could control M. javanica and improve the growth and yield of tomato under field conditions.