A New Root-Knot Nematode, Meloidogyne baetica n. sp. (Nematoda: Heteroderidae), Parasitizing Wild Olive in Southern Spain

ABSTRACT High infection rates of wild olive (Olea europaea sp. sylvestris) feeder roots and soil infestation by a new root-knot nematode were found in sandy soil at Vejer de la Frontera (Cádiz), southern Spain. Morphometric traits and analyses of the nematode esterase electrophoretic pattern as well as of the internal transcribed spacer 1 (ITS1)-5.8S gene and D2-D3 fragment of the 28S gene of rDNA showed that specimens differed clearly from known root-knot nematodes. Studies of host-parasite relationships showed a typical susceptible reaction in naturally infected wild olive plants and in olive planting stocks (cvs. Arbequina and Picual) artificially inoculated with the nematode. However, the nematode did not reproduce in artificially inoculated chickpea, pea, and tomato. Because of the ability of this new nematode to infect wild and cultivated olives only, we suggest the common name, "Mediterranean olive root-knot nematode." The species is herein described and illustrated, and named as Meloidogyne baetica n. sp. The new root-knot nematode can be distinguished from other Meloidogyne spp. by (i) the perineal pattern, which is almost similar to that of M. artiellia, characterized by distinct inner striae forming two distinct longitudinal bands, extending throughout the perineum to just below the vulva; (ii) female excretory pore anterior to the level of stylet knobs, excretory pore distance from anterior end/length of stylet ratio extremely small (0.5 to 0.8); and (iii) second-stage juveniles with elongate-conoid tail. Phylogenetic trees derived from maximum parsimony analyses showed that M. baetica is closely related to M. artiellia, the cereal and legume root-knot nematode.     

Protection of olive planting stocks against parasitism of root-knot nematodes by arbuscular mycorrhizal fungi

The effects were investigated, under controlled conditions, of single and joint inoculation of olive planting stocks cvs Arbequina and Picual with the arbuscular mycorrhizal fungi (AMF) Glomus intraradices , Glomus mosseae or Glomus viscosum , and the root-knot nematodes Meloidogyne incognita and Meloidogyne javanica , on plant performance and nematode infection. Establishment of the fungal symbiosis significantly increased growth of olive plants by 88·9% within a range of 11·9–214·0%, irrespective of olive cultivar, plant age and infection by M. incognita or M. javanica . In plants free from AMF, infection by Meloidogyne spp. significantly reduced the plant main stem diameter by 22·8–38·6%, irrespective of cultivar and plant age. Establishment of AMF in olive plants significantly reduced severity of root galling by 6·3–36·8% as well as reproduction of both Meloidogyne spp. by 11·8–35·7%, indicating a protective effect against parasitism by root-knot nematodes. Infection by the nematodes influenced root colonization by AMF, but the net effect depended on the AMF isolate–olive cultivar combination. It is concluded that prior inoculation of olive plants with AMF may contribute to improving the health status and vigour of cvs Arbequina and Picual planting stocks during nursery propagation.     

九叶青花椒根结线虫病的病原鉴定

为确定四川省蓬溪县九叶青花椒种植区发病植株花椒根结线虫的种类, 进而为九叶青花椒根结线虫病防治提供依据, 本文根据根结线虫雌虫与2龄幼虫的形态特征及雌成虫的会阴花纹、雌虫酯酶同工酶图谱, 并结合特异性扩增及rDNA-ITS扩增, 根据ITS序列构建系统发育树, 对该地区九叶青花椒根结线虫病的病原进行了种类鉴定。结果表明该病原为南方根结线虫Meloidogyne incognita (Kofold & White) Chitwood。这是我国首次在九叶青花椒上发现南方根结线虫。     

Disease complex in coffee involving Meloidogyne arabicida and Fusarium oxysporum

Coffee corky-root disease, also called corchosis, was first detected in 1974 in a small area of Costa Rica where the root-knot nematode Meloidogyne arabicida is the dominant species. An epidemiological study revealed a constant association between Meloidogyne spp. and Fusarium sp. in cases of corky root. No corky root appears to have been reported in association with Meloidogyne exigua , which is the prevalent root-knot nematode on coffee in Costa Rica. Fusarium spp. are often cited as components of disease complexes in association with nematodes. Combined inoculations using M. arabicida or M. exigua with Fusarium oxysporum under controlled conditions showed that only the combination with M. arabicida produced corky-root symptoms on Coffea arabica cvs Caturra or Catuai. Fusarium oxysporum alone was nonpathogenic. Meloidogyne exigua or M. arabicida alone caused galls and reduction in shoot height, but no corky-root symptoms. When cultivars susceptible and resistant to M. arabicida were studied under field conditions for 5 years, all the susceptible cultivars exhibited corky-root symptoms on 40–80% of their root systems. Cultivars that were resistant to M. arabicida but not to M. exigua showed no corky root. These observations lead to the conclusion that corky-root disease has a complex etiology, and emphasize the dominant role of M. arabicida as a predisposing agent to subsequent invasion by F. oxysporum . Consequently, genetic resistance to M. arabicida appears to provide an effective strategy against the disease.     

The interaction between Meloidogyne arenaria and Cylindrocladium parasiticum in runner peanut

Cylindrocladium black rot (CBR), caused by Cylindrocladium parasiticum , and root-knot nematode, Meloidogyne arenaria , both infect and cause damage to the roots of peanut. Greenhouse and microplot experiments were conducted with the runner type peanut genotypes C724-19-15, C724-19-25 and Georgia-02C with different levels of resistance to nematode and CBR to better understand the interactions between the two pathogens. In the greenhouse, inoculation of 500–3000 eggs per plant of M. arenaria did not affect the level of root rot induced by 1·0 to 5·0 microsclerotia of C. parasiticum per g soil. In microplots, the root rot ratings from Georgia-02C and C724-19-25 were higher in plots infested with M. arenaria (0·4–2·0 eggs per cm³ soil) and C. parasiticum than in plots with C. parasiticum alone; however, M. arenaria did not increase the root rot ratings on the nematode resistant C724-19-15. This was inconsistent with results in the greenhouse. Gall indices were not affected by C. parasiticum inoculations in the greenhouse or microplots. In both 2006 and 2007, a significant interaction between C. parasiticum inoculum densities and nematode level was observed on plant mortality. CBR inoculum greatly increased mortality on C724-19-25 and Georgia-02C, but not on C724-19-15, in the presence of M. arenaria . The mortality increase was more apparent at lower inoculum levels of both pathogens, but on the nematode-susceptible cultivars plant mortality was more with co-inoculations of the two pathogens than from either alone. Simultaneous inoculation with the two pathogens decreased yield of C724-19-25 and Georgia-02C as C. parasiticum inoculum levels increased, but even the largest inoculum of M. arenaria (2·0 eggs per cm³ soil) did not decrease yield of C724-19-15.     

云南省紫茎泽兰根结线虫病病原种类鉴定

为明确云南省紫茎泽兰根结线虫病的病原种类,于2019年2月在云南省澜沧县林下三七种植区采集根部带有明显根结的紫茎泽兰根系进行根结线虫分离,通过观察所分离根结线虫的2龄幼虫、雌成虫、会阴花纹特征对其进行形态学鉴定,并利用序列比对、系统发育树分析、序列特异性扩增区段(sequence characterized amplified region,SCAR)对其进行分子生物学鉴定。结果表明,该病原线虫雌成虫会阴花纹呈圆形至卵圆形,背弓中等高或低平,侧区一侧或两侧延伸形成翼状,尾区有刻点,2龄幼虫、雌成虫形态特征及形态测量指标与北方根结线虫Meloidogyne hapla相似;该病原线虫rDNA的ITS序列和mtDNA的COI序列与NCBI数据库中已登录的北方根结线虫相应序列相似度较高,分别达99.35%和98.05%以上;该病原线虫rDNA的ITS序列、mtDNA的COI序列分别以99%、100%的支持率与北方根结线虫聚为同一分支;利用SCAR特异性引物,该病原线虫均能扩增出大小约1 500 bp的基因特异性条带。综合形态学和分子生物学鉴定结果将云南省紫茎泽兰根结线虫病病原种类鉴定为北方根结线虫。     

Pathogenicity of the root-knot nematode Meloidogyne javanica on potato

Host–parasite relationships and pathogenicity of Meloidogyne javanica on potatoes (newly recorded from Malta) were studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to M. javanica under natural and artificial infections, respectively. In potato tubers, M. javanica induced feeding sites that consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P ) [0–64 eggs + second-stage juveniles (J2s) per cm³ soil] and growth of cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z ^{( P − T )}] was fitted to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits ( T ) for fresh shoot weight and shoot height of cv. Spunta plants infected with M. javanica were 0·50 and 0·64 eggs + J2s per cm³ soil, respectively. The m parameter in that model (i.e. the minimum possible y -values) for fresh shoot weight and shoot height were 0·60 and 0·20, respectively, at P  = 64 eggs + J2s per cm³ soil. Root galling was proportional to the initial nematode population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density ( P  = 4 eggs + J2s per cm³ soil).     

Effects of root- and stolon-infecting fungi on root-colonizing nematodes of white clover

The effects on white clover ( Trifolium repens ) of different combinations of the nematodes Meloidogyne trifoliophila , Helicotylenchus dihystera and Heterodera trifolii and nine stolon-infecting and three root-infecting fungi were studied in a glasshouse experiment. The presence of the fungus Phytophthora megasperma alone increased ( P  < 0·001) root-rot severity and reduced ( P  < 0·001) plant growth. Other species combinations, such as Phoma nebulosa and Alternaria alternata , interacted and increased root-rot severity. Combinations of P. megasperma with Pythium irregulare , and P. nebulosa with Phoma medicaginis or A. alternata , increased M. trifoliophila populations. Several other fungi ( P. irregulare , P. nebulosa , Colletotrichum coccodes , Macrophomina phaseolina , P. medicaginis and Phoma sp.) interacted with the nematode M. trifoliophila causing severe root-knot symptoms. The results indicated that fungi and nematodes interacted to cause root and stolon rot and reduced yields, and that poor persistence of white clover in pastures is likely to be a problem with a complex etiology.     

甘肃省党参根结线虫病发生、分布及病原种类鉴定

为明确甘肃省党参根结线虫病的发生、分布及病原种类,在甘肃省党参主产区调查、统计田间根结线虫病发生情况,并通过形态学和分子生物学方法进行种类鉴定。结果表明,甘肃省6个党参主产区均有根结线虫病发生,病田率、病株率分别为40.7%、13.2%,病情指数为10.4。依据根结线虫各虫态的形态测量值和雌虫会阴花纹等特征,将危害党参的根结线虫初步鉴定为北方根结线虫Meloidogyne hapla Chitwood, 1949。rDNA-ITS区段和28S rDNA D2D3区段序列比对和系统发育树显示,6个根结线虫群体无核苷酸差异,与多个北方根结线虫聚为一支且有较高的置信度。利用特异性引物Mh-F/Mh-R扩增得到北方根结线虫的特异性片段,大小为462 bp。故综合形态学和分子生物学特征,将危害甘肃省党参的根结线虫鉴定为北方根结线虫。     

The response of commercial cucurbit rootstocks to (a)virulent isolates of Meloidogyne incognita

Journal of Plant Diseases and Protection - Meloidogyne incognita is the predominant root-knot nematode (RKN) species infecting cucurbit plants. It causes galling on the roots of plants and...     

牛蒡上发生的根结线虫种类鉴定

2007～2009年,对我国牛蒡主产区的牛蒡及其根际土壤中的植物寄生线虫进行调查研究,发现根结线虫危害最为严重。根据根结线虫的形态学特征和分子生物学检测方法对其进行鉴定,结果表明,我国牛蒡主产区根结线虫种类为北方根结线虫(Meloidogyne hapla)。     

Effects of climatic factors on native arbuscular mycorrhizae and Meloidogyne exigua in a Brazilian rubber tree (Hevea brasiliensis) plantation

The root-knot nematode Meloidogyne exigua and arbuscular mycorrhizal (AM) fungi may both occur in the roots of Brazilian rubber trees ( Hevea brasiliensis ). AM fungi may stimulate plant growth whereas nematodes usually reduce it. Variations of native AM fungi and M. exigua populations in soil and roots of rubber trees were studied for one year in a Brazilian plantation. The number of AM spores in the soil was generally greater in the rainy season than in the dry season, although AM colonization of roots was unaffected by season. During the dry season, numbers of juveniles and eggs of M. exigua in roots were lower than in the rainy season. A site without nematodes in the soil or roots showed the greatest numbers of AM spores in soil and highest AM colonization of roots. A negative correlation was observed between the percentage of AM colonization and the number of second-stage juveniles in soil and second-stage juveniles and eggs in roots. Microscope observations revealed (i) tissue specificity for each of the microorganisms in the roots, with a cortical location of mycorrhizae and a mainly vascular cylinder location of nematodes, and (ii) that Gigaspora was the most abundant AM genus in the plantation soil.     

PGPR对番茄南方根结线虫病的影响

于温室盆栽条件下初步研究了4种根围促生细菌（PGPR）对番茄植株生长和南方根结线虫Meloidogyne incognit病发生情况的影响。结果表明接种多粘芽孢杆菌Bacillus polymyxa或芽孢杆菌菌株B697的番茄植株高度、地上部和地下部干重均显著大于对照,而巨大芽孢杆菌B. megaterium和固氮螺菌Azospirillum sp.菌株A135无促生作用。接种多粘芽孢杆菌＋南方根结线虫和B697菌株＋南方根结线虫两处理的二龄幼虫数、雌虫数、线虫总数、根上卵囊数、卵囊含卵量、发病率和病情指数显著低于只接种南方根结线虫的对照。多粘芽孢杆菌、B697菌株、巨大芽孢杆菌和A135菌株对南方根结线虫的防效分别达65.4%、68.2%、53.8%和53.8%。     

南方根结线虫中国分离群体种内变异分析

为调查我国不同地区和不同寄主上的根结线虫Meloidogyne spp.种类分布以及群体变异情况,基于酯酶和苹果酸脱氢酶同工酶图谱及SCAR分子标记技术对2017—2019年从6省19种植物根部组织分离到的40个根结线虫群体进行鉴定,针对南方根结线虫M. incognita群体分别通过寄主鉴别法进行生理小种鉴别,利用携带Mi抗性基因的番茄进行毒力测试,对2龄幼虫的口针长度和体长进行测量,并对核糖体ITS和线粒体Nad5基因序列进行比较分析。结果显示:根结线虫分离群体经鉴定包括38个南方根结线虫群体和2个象耳豆根结线虫M. erterolobii群体;38个南方根结线虫群体中有35个群体被鉴别为1号生理小种,其余3个群体被鉴别为2号生理小种;发现1个南方根结线虫群体CN19可在携带Mi抗性基因的番茄上侵染繁殖,为毒性群体,其余群体无法进行侵染和繁殖,为无毒群体。南方根结线虫群体2龄幼虫的口针长度和体长均差异较大,而不同寄主来源分离群体的ITS和Nad5基因序列也存在一定变异。基于ITS和Nad5基因序列构建的系统发育树将所有根结线虫群体归为南方根结线虫和象耳豆根结线虫组成的2个独立分支,...     

根结线虫在中国的新纪录种——西班牙根结线虫(Meloidogyne hispanica Hirschmann)

 A root-knot nematode, Meloidogyne hispanica Hirschmann, was first described and illustrated from roots of papaya in Danzhou, Hainan province in China. The perineal pattern of female was characterized by oval shaped to rectangular with a low dorsal arch; dorsal striae varied from fine and wavy to coarse; lateral lines forked with fringe-like striae between lines and phasmidial ducts distinctly appeared. Male had high and rounded head region with labial disc and medial lips fused to form elongate lip structures. Second-stage juve-nile had distinct body annules and stylet with rounded, posteriorly sloping knobs, and the tail terminus was slender with indistinct hyaline. This Chinese new record of M. hispanica had a unique esterase phenotype (S2-M1) which was different from that of other Meloidogyne species.     

象耳豆根结线虫的PCR鉴定和检测方法

 象耳豆根结线虫是一种在中国具有潜在经济重要性的农作物病原物。为提供有助于控制象耳豆根结线虫传播扩散的方法,研制了该线虫的快速PCR鉴定和检测法。该方法PCR引物的扩增目标为rDNA-IGS2区域,其设计依据象耳豆根结线虫与南方、爪哇、花生和北方根结线虫在该区域核酸序列的差异。通过对6种近似根结线虫的不同地理群体及自然土壤线虫群体的测试,验证了设计的PCR引物针对象耳豆根结线虫的特异性和可靠性。本方法具有快速灵敏的特点,可用于象耳豆根结线虫单条线虫的直接鉴定以及混合土壤线虫群体中象耳豆根结线虫的检测。     

Assessment of PCR-based tools for the specific identification of some temperate Meloidogyne species including M. chitwoodi,M. fallax and M. minor

Several conventional PCR tests have been developed for the identification of the European quarantine root-knot nematodes Meloidogyne chitwoodi and M. fallax but data are lacking for the evaluation of their performance in terms of sensitivity, repeatability, reproducibility and specificity against a large range of populations. This study evaluated the performance criteria of three conventional PCR tests recommended by the consensus diagnostic protocol for Meloidogyne chitwoodi and Meloidogyne fallax published by the European and Mediterranean Plant Protection Organization (EPPO): a species-specific PCR (IGS target), a SCAR PCR, and a rDNA ITS PCR-RFLP. Evaluation was carried out with DNA extracts from juveniles, males and females according to EPPO recommendations for test validation. A minimum of 34 populations of target and non target nematode species were tested to check the specificity of these three PCR assays. The three PCR tests were ranked according to their specificity (with regard to cross reaction with other nematodes species or genus) and their sensitivity (detection of a single juvenile or mixed with other species). The species-specific PCR proved to be more sensitive but less specific than the SCAR PCR. The PCR-RFLP enables the identification of several Meloidogyne species but profile analysis can be difficult when several species are present in the mixture. Specific PCR products and RFLP profiles were also observed for M. arenaria and M. enterolobii, and described for M. minor and M. artiellia.     

黄花倒水莲根结线虫病的病原鉴定

2019年在福建省多个地方发现黄花倒水莲Polygala fallax遭受根结线虫的严重侵染,为明确病原线虫种类,运用形态学、rDNA-ITS序列分析及特异引物PCR扩增的方法对分离获得的根结线虫进行种类鉴定。结果表明,该病原线虫为南方根结线虫Meloidogyne incognita。黄花倒水莲根结线虫病在我国为首次报道。     

Histological Characterization of Resistance to Different Root-Knot Nematode Species Related to Phenolics Accumulation in Capsicum annuum

ABSTRACT In the pepper Capsicum annuum CM334, which is used by breeders as a source of resistance to Phytophthora spp. and potyviruses, a resistance gene entirely suppresses reproduction of the root-knot nematode (Meloidogyne spp.). The current study compared the histological responses of this resistant line and a susceptible cultivar to infection with the three most damaging root-knot nematodes: M. arenaria, M. incognita, or M. javanica. Resistance of CM334 to root-knot nematodes was associated with unidentified factors that limited nematode penetration and with post-penetration biochemical responses, including the hypersensitive response, which apparently blocked nematode migration and thereby prevented juvenile development and reproduction. High-performance liquid chromatography analysis suggested that phenolic compounds, especially chlorogenic acid, may be involved in CM334 resistance. The response to infection in the resistant line varied with root-knot nematode species and was correlated with nematode behavior and pathogenicity in the susceptible cultivar: nematode species that quickly reached the vascular cylinder and initiated feeding sites in the susceptible cultivar were quickly recognized in CM334 and stopped in the epidermis or cortex. After comparing our data with those from other resistant pepper lines, we suggest that timing of the resistance response and the mechanism of resistance vary with plant genotype, resistance gene, and root-knot nematode species.