Resistance analysis of the rice variety Huaidao 5 against root-knot nematode Meloidogyne graminicola

Meloidogyne graminicola has emerged as one of the most destructive plant-parasitic nematodes affecting rice(Oryza sativa)production worldwide.Resistance to M.graminicola in rice could be the most effective option for its management.However,sources of germplasm with resistance to M.graminicola in rice remain limited.Here,we describe the root attraction,gall formation and genetic analysis of the resistance to M.graminicola in the rice variety Huidao 5.A nematode attraction assay showed that second-stage juveniles(J2s)of M.graminicola were attracted at the root tip of Huaidao 5 within 8 h without a significant reduction in attraction compared to the susceptible rice variety Nanjing 9108.Microscopic observation of the infection revealed that the J2s invaded root tissues 12 h after inoculation,but their subsequent movement to the root tip was hindered in Huaidao 5,resulting in decreased nematode number compared to Nanjing 9108.Additionally,we used the soil and hydroponic culture systems to simulate upland and flooding conditions in the paddy fields respectively,and found that gall number was significantly reduced,and nematode development was clearly suppressed in Huaidao 5.To investigate the genetic basis of this resistance,cross breeding was performed between the Huaidao 5 and Nanjing 9108 varieties.There was no reduction in the resistance of the F_(1) offspring to M.graminicola in the greenhouse or field trials,suggesting that a dominant gene could control resistance in Huaidao 5.In summary,this study provides a detailed characterization of a novel source of resistance to M.graminicola in rice,which is of great potential for use in crop breeding.

The synergistic advantage of combining chloropicrin or dazomet with fosthiazate nematicide to control root-knot nematode in cucumber production

The highly-damaging root-knot nematode(Meloidogyne spp.,RKN)cannot be reliably controlled using only a nematicide such as fosthiazate because of increasing pest resistance.In laboratory and greenhouse trials,we showed that chloropicrin(CP)or dazomet(DZ)synergized the efficacy of fosthiazate against RKN.The combination significantly extended the degradation half-life of fosthiazate by an average of about 1.25 times.CP or DZ with fosthiazate reduced the time for fosthiazate to penetrate the RKN cuticle compared to fosthiazate alone.CP or DZ combined with low or medium rate of fosthiazate increased the total cucumber yield,compared to the use of each product alone.A low-dose fosthiazate with DZ improved total yield more than a low dose fosthiazate with CP.Extending the half-life of fosthiazate and reducing the time for fosthiazate or fumigant to penetrate the RKN cuticle were the two features that gave the fumigant-fosthiazate combination its synergistic advantage over these products used singularly.This synergy provides the opportunity for farmers to use a low dose of fosthiazate which lowers the risk of RKN resistance.Farmers could combine DZ at 30 g m^-2 with fosthiazate at a low rate of 0.375 g m^-2 to control RKN and adequately control two major soil-borne diseases in cucumber greenhouses.

Effects of Two Composted Plant Pesticide Residues,Incorporated with Trichoderma viride,on Root-Knot Nematode in Balloonflower

Plant pesticide residues, such as chinaberry （Melia toosendan） residue and sand cypress （Sabina vulgaris） residue, are pesticidal plant materials discarded after the bioactive ingredient has been extracted with organic solvents. The only option for botanical pesticide residue utilization has been as landfill. Chinaberry residue （CBR） and sand cypress residue （SCR） were collected and composted in Yangling, Shaanxi Province, China. We studied the effects of chinaberry residue compost （CBRC）, CBRC incorporated with Trichoderma viride （CBRCT）, sand cypress residue compost （SCRC）, and SCRC incorporated with T. viride （SCRCv） on the root-knot nematode, Meloidogyne incognita, infesting the balloonflower （Platycodon grandiflorum）. Bioassay results indicated that stock solutions of the CBRCT and SCRCT extracts significantly inhibited egg hatching and caused high larval mortality, followed in degree by the CBRC and SCRC extracts. The CBR and SCR extracts caused very low inhibition of eggs and larvae. Supplementing potting mixtures with these four composts reduced the severity of root galling and increased the proportion of marketable roots. The severity of root galling decreased and the average weight of the marketable roots increased with an increase in all the composts when supplemented at rates from 5 to 30%. CBR- and SCR-supplemented pot soils also inhibited the nematodes, but CBR and SCR applied to the soil had a phytotoxic effect and inhibited balloonflower growth. Supplementing field soil with the composts reduced the severity of root galling and the populations of southern root-knot nematodes in the soil. CBRCT and SCRCT clearly enhanced the average weight of the marketable roots by 30.45 and 26.64%, respectively. Continuous supplementation with CBRCT or SCRCT in the same field significantly enhanced the control of the root-knot nematode, and the populations of nematodes continued to decrease with second inoculations. The populations of total Trichoderma spp. were distinctly enhanced and were maintained at high levels for a long time in the supplemented soils.

Control of Southern Root-knot Nematodes on Tomato and Regulation of Soil Bacterial Community by Biofumigation with Zanthoxylum bungeanum Seed

Biofumigation is an environmentally friendly strategy used to control nematodes and plant diseases.The volatile oil of Zanthoxylum bungeanum has high insecticidal and antibacterial activity.However,it is not known if the seed of Z.bungeanum is a suitable material for biofumigation to control southern root-knot nematodes(SRKN)on tomato,and how it may regulate the soil bacterial community structure.We used pot experiments in the greenhouse to determine the effects of Z.bungeanum seeds on SRKN,plant growth parameters,soil physicochemical and microbial characteristics.A total of 26 volatile components,including nematicidally active substances,were identified from Z.bungeanum seeds.Z.bungeanum seed biofumigation significantly reduced the SRKN population by 88.89%and 81.55%on the 50th and 100th day after transplanting,respectively.Compared to the control,the total soluble sugar,soluble solids,soluble protein,titratable acid,root activity and the fruit yield per tomato plant increased significantly.The content of soil alkali-hydrolyzed nitrogen,available potassium and the soil enzyme activities were also significantly increased.The soil bacterial diversity and the co-occurrence network complexity were increased by Z.bungeanum seed biofumigation.Relativelymore keystone OTUs in biofumigation soil had potential plant growth-promoting capabilities.The function of Z.bungeanum seed increasing tomato production in SRKN-infected soil depends on directly killing SRKN and improving soil properties.These results indicate that Z.bungeanum seed can be used as both a nematicide and a high quality organic fertilizer in tomato production.

Preparation and efficacy evaluation of Paenibacillus polymyxa KM2501-1 microbial organic fertilizer against root-knot nematodes

Root-knot nematodes(RKNs) cause huge yield losses to agricultural crops worldwide. Meanwhile, livestock manure is often improperly managed by farmers, which leads to serious environmental pollution. To resolve these two problems, this study developed a procedure for the conversion of chicken manure to organic fertilizer by larvae of Hermetia illucens L. and Bacillus subtilis BSF-CL. Chicken manure organic fertilizer was then mixed thoroughly with Paenibacillus polymyxa KM2501-1 to a final concentration of 1.5×10^(8)CFU g^(-1). The efficacy of KM2501-1 microbial organic fertilizer in controlling root-knot nematodes was evaluated in pot and field experiments. In pot experiments, applying KM2501-1 microbial organic fertilizer either as a base fertilizer or as a fumigant at the dose of 40 g/pot suppressed root-knot disease by 61.76 and 69.05% compared to the corresponding control treatments, respectively. When applied as a fumigant at the dose of 1 kg m;in field experiments, KM2501-1 microbial organic fertilizer enhanced the growth of tomato plants, suppressed root-knot disease by 49.97%, and reduced second stage juveniles of RKN in soil by 88.68%. KM2501-1 microbial organic fertilizer controlled RKNs better than commercial bio-organic fertilizer in both pot and field experiments. These results demonstrate that this co-conversion process efficiently transforms chicken manure into high value-added larvae biomass and KM2501-1 microbial organic fertilizer with potential application as a novel nematode control agent.

Toxicity Test of Different Pesticides on Tobacco Root-knot Nematodes

[Objectives]This study was conducted to quickly screen out effective and safe agents for controlling tobacco root knot nematode disease.[Methods]Six pesticides were tested and screened indoors at five different concentrations.[Results]The six pesticides all had toxic effects on the second-instar larvae of tobacco root-knot nematode,and the corrected mortality was positively correlated with the concentration and time of the pesticides,with the correlation coefficients above 0.8.From the perspective of inhibitory activity,the order was fosthiazate>abamectin>emamectin benzoate>cadusafos>ethoprophos>carbosulfan.Four pesticides that can be used in the field were selected.[Conclusions]This study provides a theoretical basis for field pesticide selection.

Bacterial artificial chromosome library construction of root-knot nematode resistant pepper genotype HDA149 and identification of clones linked to Me3 resistant locus

Pepper （Capsicum annuum. L.） is a widely cultivated vegetable crop worldwide and has the second largest planting area and the first largest vegetable output and value in China. Pepper root-knot nematode （Meloidogyne spp.） is one of the most serious pests of pepper, which caused huge losses every year. Previous studies showed that the Me3 gene is resistant to a wide range of Meloidogyne species, including M. arenaria, M. javanica, and M. incognita. HDA149, a double haploid pepper genotype, harboring the root-knot nematode resistance gene Me3, was used to construct bacterial artificial chro- mosome library （BAC） via the vector of CopyControFM pCC1 in this study. The library consists of 210 200 BAC clones and is equivalent to 5.3 pepper genomes. The average insert size is 95 kb, and most of them are 90-120 kb; but the empty clones are less than 3%. In order to screen the BAC library easily, 550 super pools with 384 BAC clones of each pool were further developed in this study. Specific primers from Me3 gene locus were used for BAC library screening, and more than 20 positive BAC clones were obtained. Then the selected positive BAC clones were analyzed by restriction enzyme digestion, BAC-end sequencing, marker development, and new positive BAC clones exploration, respectively. Finally, the contig with total length of about 300 kb linked to the Me3 locus was constructed based on chromosome walking strategy, which made a solid foundation for the cloning of the important root-knot nematode resistance gene Me3.

Morphology and Molecular Identification of Root-knot Nematode in Partial Tobacco-growing Areas in Yunnan Province

[Objectives]The species and distribution of root-knot nematodes in tobacco growing regions of Yunnan were investigated,in order to provide reference for comprehensive prevention of root-knot nematodes disease and tobacco variety layout. [Methods]Fifty-four samples of root-knot nematode host on tobacco crops were collected from Kunming,Qujing and Yuxi cities in Yunnan from August to October in 2015. The species of root-knot nematodes were identified by observing perineal patterns and molecular biological testing（ PCR of ribosomal DNA of ITS region and sequence characterized amplified region,SCAR）. [Results] There were 24 samples belonging to Meloidogyne arenaria,accounting for 44. 44%; seven M. incognita samples,accounting for 12. 96%; one M. javanica sample,accounting for 1. 85%. Eleven samples were compound populations of M. javanica and M. arenaria,accounting for 20. 37%. Five were compound populations of M. incognita and M. arenaria,accounting for 9. 26%. Three were compound populations of M. incognita and M. javanica,accounting for 5. 56%. Three belonged to compound population of M. incognita,M. javanica and M. arenaria,accounting for 5. 56%. [Conclusions] The species of root-knot nematodes in tobacco growing areas of Yunnan mainly include M. incognita,M. javanica and M. arenaria. M. arenaria is the dominant population.

Preliminary Study on Mixed Use of Agaricus bisporus Residue and Microbial Agent to Control Cucumber Root-knot Nematode

Single or mixed use ofAgaricus bisporus residue and microbial agent had better control effect on cucumber root-knot nematode disease in greenhouse. The results showed that the control effect of single use of A. b/sporus residue was 32.9% - 34.7%, and the yield increasing rate was 2.1% - 8.7% ; the control effect of mixed use ofA. b/sporus residue and microbial agent was 59. 1% - 63. 6%, and yield increasing rate was 2.6% - 3.5%. The experimental dose had no ad- verse effects on soil physical and chemical properties. The mixed use of A. b/sporus residue and microbial agent was one of the effective ways to control root-knot nematode disease.

Occurrence of Root-Knot and Reniform Nematodes in Ornamental Plants Grown in Aligarh Muslim University Campus, India

An extensive survey of about 50 ornamental plants growing in A.M.U. campus were carried out to find out the infection of root-knot (Meloidogyne spp.) and reniform nematodes (Rotylenchulus reniformis). Out of 50 species of ornamental plants studied, 29 species of these plants were found to be infected with root-knot nematodes (Meloidogyne spp.) and 15 species were infected with reniform nematode (Rotylenchulus reniformis). The highest percentage of infection of root-knot nematodes was observed in Impatiens balsamina (100%) and reniform nematode was observed in Hibiscus rosa-sinensis (56%). Among the Meloidogyne spp. the highest percentage of infection of M. incognita was observed in Pseuderanthemum atropurpureum (80%) whereas, the highest percentage of infection of M. javanica and M. arenaria was observed in Mirabilis jalapa (72%) and Celosis cristata (28%).

Biological Control of Root-Knot Nematode Meloidogyne incognita in Psoralea corylifolia Plant by Enhancing the Biocontrol Efficacy of Trichoderma harzianum Using Press Mud

Meloidogyne incognita is a plant pathogen causing root-knot disease and loss of crop yield.The present study aimed to use Trichoderma harzianum as a biocontrol agent against plant-parasitic nematodes and used press mud,which is a solid waste by-product of sugarcane,as a biocontrol agent and biofertilizer.Therefore,the combined application of T.harzianum and press mud may enhance nematode control and plant growth.Elemental analysis of press mud using scanning electron microscopy(SEM)integrated with an Energy Dispersive X-ray(EDX)analyzer revealed the presence of different elements such as C,O,Mg,Si,P,K,Ca,Cu and Zn.In addition,a greenhouse study was conducted to investigate the combined effects of press mud and T.harzianum on M.incognita reproduction and growth and the biochemical features of Psoralea corylifolia.The results showed that plant length,dry biomass,leaf area,the number of seeds per plant,chlorophyll a,chl b,carotenoid content,nitrate reductase,carbonic anhydrase,and nitrogen content were significantly increased(P≤0.05)in the T2 plants(plants were treated with 100 g of press mud+50 mL T.harzianum before one week of M.incognita inoculation),over inoculated plants(IC).Antioxidant enzyme activity of ascorbate peroxidase(APX),catalase(CAT),peroxidase(POD),and superoxide dismutase(SOD)in the foliage of P.corylifolia was significantly increased when plants were treated with press mud+T.harzianum.A significant reduction in the number of egg masses,nematode population,and root-knot index(RKI)was found in plants with T2 plants.These results suggest that the combined application of T.harzianum and press mud has the potential to control the M.incognita infection and can be used as an environmentally safe alternative to chemical nematicides and also help in the removal of sugarcane waste that causes environmental pollution.

Genetic Mapping of Root-knot Nematode Resistance Genes in Solanaceous Vegetables

Root-knot nematodes are becoming more and more harmful to solanaceous vegetables. The most economical and effective way to deal with root-knot nematode disease is to breed varieties with disease resistance. This paper reviewed the recent research progress and achievements of tomato, pepper, eggplant and potato on root-knot nematode disease resistance gene characteristics, disease resistance gene mapping and disease resistance gene molecular markers, and prospects for future research directions.

中国北方稻田及其周边环境中根结线虫种类鉴定

【目的】了解我国北方稻田及其周边环境中根结线虫的种类,为进一步制定水稻根结线虫病的防治策略提供参考。【方法】2020和2021年春季从我国河南、山东、宁夏、北京、吉林、黑龙江、新疆、甘肃、河北、辽宁、山西、陕西和内蒙古13个省(直辖市/自治区)的连片稻田、周围田埂、旱地等采集了1032份土样,每份土样与灭菌河沙混合后平均分成3等份分别放入花盆中,盆中一半播水稻一半播番茄,50 d后检测水稻或番茄根系是否有根结产生。挑取阳性样品根结中的雌成虫,制作会阴花纹玻片,对根结线虫种类进行形态鉴定;同时利用我国常见6种根结线虫特异性引物对土样中的根结线虫种类进行分子鉴定。【结果】生物测定结果显示,有119份土样能够引起水稻或番茄幼苗产生根结,总检出率为11.53%,其中宁夏回族自治区土样检出率最高,为33.33%。在根结线虫种类鉴定中发现,拟禾谷根结线虫(Meloidogyne graminicola)为北方水稻产区优势种,占鉴定样品的96.83%;花生根结线虫(M.arenaria)、北方根结线虫(M.hapla)、南方根结线虫(M.incognita)、象耳豆根结线虫(M.enterolobii)和爪哇根结线虫(M.javanica)分别占鉴定样品的84.13%,52.38%,31.75%,15.87%和3.17%。受1,2,3,4,5和6种根结线虫侵染的土样比例分别为11.11%,28.57%,28.57%,28.57%,3.18%和0%。其中最常见的为拟禾谷根结线虫、南方根结线虫、花生根结线虫和北方根结线虫混合侵染(23.81%),其次为拟禾谷根结线虫和花生根结线虫混合侵染(22.22%),再次为拟禾谷根结线虫、花生根结线虫和北方根结线虫混合侵染(15.87%),其他不同种类根结线虫混合侵染的田块比例不超过10.00%。【结论】根结线虫广泛分布于我国北方稻田及其周边环境中,其中拟禾谷根结线虫为优势种,象耳豆根结线虫也已适应低温由南向北扩散,今后应加大研究根结线虫在北方露地低温环境下的适应能力及扩散和危害风险,制定相应的防治措施。

广西水稻产区稻-菜轮作田水稻根结线虫病发生情况调查及病原鉴定

为了明确广西水稻产区稻-菜轮作田根结线虫发生情况及其病原分类地位,在广西14个市27个乡(镇)的171块水稻产区稻-菜轮作田进行了采样调查,并进行致病线虫分离,根据2龄幼虫形态、雌虫会阴花纹特征等,结合核糖体ITS区和28S rDNA D2D3区序列分析方法对病原线虫种类进行鉴定。结果表明,共有64个田块发生根结线虫为害,水稻种植季根结线虫检出率为37.4%,蔬菜轮作季根结线虫检出率为25.7%。广西水稻根结线虫病病原为拟禾本科根结线虫Meloidogyne graminicola。说明拟禾本科根结线虫病在广西稻-菜轮作田发生已经相当普遍,应当引起重视。

海南火龙果园土壤肥力与根结线虫数量调查

为了明确海南岛火龙果园土壤肥力状况和根结线虫危害情况,采集了海南岛68家火龙果园的土壤样品共204份,分析测定了土壤氮、磷、钾、钙、镁等矿质营养元素含量及根结线虫的数量,并采用模糊综合评判法对果园土壤综合肥力状况进行评价,分析了根结线虫数量与土壤养分状况的相关性。结果表明:海南岛火龙果园土壤pH为6.4,整体呈中性或弱酸性;有机质含量为19.9 g·kg^(-1),碱解氮含量为63.9 mg·kg^(-1),速效钾含量为95.8 mg·kg^(-1),均处于缺乏状态,而有效磷、交换性钙含量为丰富及以上等级,交换性镁处于中量水平;土壤pH与有机质、交换性钙、镁含量呈显著正相关,表明维持中性的pH水平有利于土壤有机质的积累,对钙、镁的有效性有重要意义;土壤有机质含量与碱解氮、有效磷、速效钾、交换性钙、镁含量呈显著正相关,说明土壤有机质的提高有助于提升土壤基础矿质养分的含量;各火龙果园根结线虫数量差异较大,其中,每100克干中土根结线虫2龄幼虫(J2)数量最多的可达736条,而较少的仅有14条;根结线虫发生轻重情况南北差异较大,整体上北部地区的火龙果园根结线虫数量低于南部地区;土壤pH、有机质、有效磷、交换性钙与根结线虫数量呈正相关。调查结果显示,海南岛火龙果园土壤综合肥力指数处于较高水平。

生物炭肥对易感根结线虫病烤烟根际菌群和理化性质的影响

为明确生物炭肥对烟草根结线虫病及根际土壤的影响,通过田间试验研究拌塘施用不同量生物炭肥对烟草根结线虫病株根际土壤的影响。结果表明,常规施肥减量10%拌塘施用酵素生物炭肥能够显著降低烟草根结线虫病的病情指数,其中酵素生物炭肥施用量为350 g·株^(-1)时,根结线虫病防治效果较好,防治效果达23.98%,且烟株农艺性状表现较好;根际土壤中过氧化氢酶、脲酶和磷酸酶活性较高,酚酸物质含量降低,化感自毒作用减弱。各处理土壤真菌数量均随生育期的推进呈先增高后降低趋势,其中酵素生物炭肥施用量为350 g·株^(-1)时,根际土壤中的细菌量随生育期推进逐步降低。各生育期土壤中均表现为真菌数量较高,细菌数量较低,真菌/细菌值较高,说明在烟草种植中,减量施肥10%同时拌塘施用酵素生物炭肥350 g·株^(-1)能提高土壤中真菌数量,降低土壤中细菌数量,显著提高土壤肥力及土壤酶活性,为生物炭肥对易感根结线虫病根际微生态调控提供了科学依据。

生防菌Y26的鉴定、发酵优化及其杀线虫活性测定

为防治黄瓜根结线虫病,本实验室前期从黄瓜根际土壤分离出的一株细菌Y26,测定其发酵液对根结线虫的生物活性,经发酵液处理后的根结线虫校正死亡率为95.12%,卵孵化的相对抑制率为83.51%,故菌株Y26可作为根结线虫生防菌资源;通过形态学观察及分子生物学方法鉴定菌株Y26为短小芽胞杆菌Bacillus pumilus;通过Plackett-Burma法和响应面分析试验得到菌株Y26发酵优化的条件是:玉米粉2.14%,豆饼粉3%,K_(2)HPO_(4)0.57%,MgSO_(4)·7H_(2)O 0.21%,种龄12 h,pH为7.2,接种量2%,培养温度28℃,装瓶量为50 mL/250 mL,发酵优化后,菌液中芽胞浓度提高25.69%,10%发酵液对根结线虫的校正死亡率从优化前的78.03%提高到93.32%。研究结果表明,经发酵优化后的Y26菌液杀线虫活性显著提高,可作为杀线生物菌剂开发应用。