杨梅根结线虫病及其病原鉴定

本文报道对杨梅根结线虫病的研究及病原鉴定结果。该病症状为:病树根部形成大小不一的根结,内有乳白色囊状雌虫及棕色卵囊;后期根结腐烂,病树叶片黄化脱落,梢枯乃至死亡。病原鉴定确认,引起该病的根结线虫有3个种:爪哇根结线虫(Meloidogyne javanica)、南方根结线虫(M.incognita)和北方根结线虫(M. hapla)。爪哇根结线虫为优势种。     

丛枝菌根真菌对不同番茄品种抗根结线虫病的影响

【背景】根结线虫病害严重制约我国设施蔬菜的生产。丛枝菌根真菌(Arbuscular Mycorrhizal Fungi,AMF)作为土壤中最重要的有益真菌之一,可以促进植物生长,提高植物抗病性,减轻土传真菌和线虫病害的发生。在蔬菜保护地栽培中,AMF对于植物线虫病防治作用的研究受到了广泛关注。【目的】针对番茄生产中危害最严重的南方根结线虫(Meliodogyne incognita)病害问题,研究AMF和番茄品种不同组合的抗线虫效应,以期为菌根真菌作为生物防治剂和生物菌肥应用于实际生产提供技术基础。【方法】在灭菌土壤中,人工接种根结线虫,比较不同菌种Rhizophagus intraradices(Ri)、Acaulosporamellea(Am)及菌种组合Rhizophagusintraradices+Acaulosporamellea(Ri+Am)在不同番茄品种(感病品种蒙特卡罗和抗线虫品种仙客1号)上对南方根结线虫侵染和繁殖的影响,研究AMF对根结线虫的拮抗效应。另外,采用南方根结线虫连作发病的土壤,在感病品种蒙特卡洛上接种AMF混合菌种Ri+Am,番茄苗移栽入连作土壤中,测定各生长指标和调查根结和卵块数量,评价接种AMF处理对根结线虫病的防治效果。【结果】在灭菌土壤中,普通番茄品种蒙特卡罗的菌根效应显著优于抗线虫番茄品种仙客1号,表现为前者单位根重的根结和卵块的数量均比对照显著降低,而后者仅降低了卵块数量;蒙特卡罗上接种Ri+Am混合菌种的效果优于接种单一菌种Am和Ri;而仙客1号上接种Ri的效果更好。接种线虫也显著影响了AMF的侵染,而且对抗性品种仙客1号的影响更为明显。但除了接种Am的处理,大多数处理收获时菌根侵染率仍维持较高的水平(70%以上)。在连作土壤中,感病品种蒙特卡罗接种混合菌种Ri+Am具有较好的抗/耐线虫效应,主要表现为促进植株生长,显著降低根结和卵块数量,但菌根侵染率较灭菌土壤低,约为40%。【结论】综合以上结果,表明菌根化苗能够在一定程度上减轻根结线虫病的危害。土壤灭菌条件下,在感病和抗线虫番茄品种上接种AMF能够减轻线虫的侵染和繁殖,而且在感病品种上的防治效果更加显著。在连作土壤中,在番茄感病品种上接种AMF也表现较好的抗线虫效果。     

红麻种质资源根结线虫病抗性鉴定

为鉴定我国红麻种质资源对根结线虫病的抗病性,在对120份红麻遗传资源进行田间自然发病鉴定的基础上,选择25份有代表性(22份高抗和3份感病)的种质进行盆栽根结线虫病接种鉴定。田间自然发病鉴定结果:120份红麻遗传资源中5个高感、19个中感、25个中抗、71个高抗;其侵染的根结线虫主要为南方根结线虫(Meloidogyne incognita)、爪哇根结线虫(Meloidogyne javanica)和花生根结线虫(Meloidogyne arenria)的混合种群。进行盆栽接种鉴定的25份遗传资源中,7份为中抗,其余分别为中感和高感品种,未发现高抗或免疫品种。本研究可为红麻种质资源发掘利用提供科学依据。     

蓖麻提取物和淡紫拟青霉对南方根结线虫的防治作用

通过杀线活性测定及盆栽试验,研究了蓖麻提取物和淡紫拟青霉(Paecilomyces lilacinus)对南方根结线虫(Meloidogyne incognita)的杀线活性及防治效果.结果表明:蓖麻碱不影响淡紫拟青霉孢子的萌发.蓖麻碱和淡紫拟青霉均具有较强杀线活性,蓖麻碱处理对南方根结线虫的卵孵化抑制率和二龄幼虫死亡率分别达61.7%和59.2%,显著高于对照处理;蓖麻碱和孢子液复合处理接种南方根结线虫的番茄苗后,植株平均根结数为15±3,显著低于对照的平均根结数37±2,株高、鲜重和根长增长率分别比对照提高38.5%、44.0%和57.0%.说明蓖麻提取物和淡紫拟青霉能减轻线虫危害,对番茄南方根结线虫病控制效果明显.     

根结线虫天敌真菌及其高效菌株筛选

本文报道捕食和寄生南方根结线虫(Meloidogyne incognita)和爪哇根结线虫(M.javanica)的天敌真菌6属14种。其中Arthrobotrys candida A.cladodes var.macroides,A.musiformis,Monacrosporium cionopagum,M.doedycoides,Drechmeria coniospora,Harposporium crassum,H.lilliputanum,Myzocytium humicola和Verticillum coccospora为我国新纪录种。室内测定结果表明:GACA 1B(Arthrobotrys oligospora)、GACM 102(Monacrosporium doedycoides)菌株对南方根结线虫和爪哇根结线虫均具极高的捕食率,接种线虫7天后,捕食率达98%以上,接种20天后,捕食率均达100%。     

影响四川凉山地区烟草根结线虫病发生的关键气候因子分析

烟草根结线虫病是一种由根结线虫(Meloidogyne spp.)侵染引起的重要土传病害,目前,对于影响烟草根结线虫病发生的关键因子研究相对缺乏,其监测预警和防治难度依然较大,该病的灾变机理有待进一步探索.本研究通过田间调查和室内分析相结合的方法,明确了2020年四川省凉山州主要植烟区烟草根结线虫病发生面积和为害程度,其中,以四川省会理市通安镇发病最为严重,发生面超过52%,发病烟田的烟株感病率超过46%,死棵率超过34%.同时,借助形态学鉴定的方法明确了从越西县、盐源县、德昌县、宁南县、会理市和会东县采集到的烟草根结线虫种类均为南方根结线虫(Meloidogyne incognita).进一步对会理市2010—2020年同期历史旬平均气温和旬降雨量的对比分析结果表明,烟草根结线虫发生严重的会理通安镇,1—4月平均气温均高于同期历史值,温度差为0.7～5.0℃,平均高出2.8℃, 2020年1-4月的累计降雨量较历史值高15%以上,5—8月的累计降雨量较历史值低40%以上,研究结果表明,烟苗移栽前较高的温度和较多的降雨以及移栽后较少的降雨是凉山州烟草根结线虫病严重发生的重要诱因.本研究...     

番茄‘Ls-89’和‘坂砧2号’幼苗活性氧代谢对南方根结线虫侵染的反应

为了解番茄(Lycopersicon esculentum)砧木幼苗活性氧代谢与抗南方根结线虫(Meloidogyne incognita)的关系,以高感品种‘Ls-89’与高抗品种‘坂砧2号’为材料,采用盆栽人工接种法,研究了南方根结线虫侵染对番茄砧木幼苗活性氧代谢的影响。结果表明,未接种南方根结线虫的番茄砧木幼苗,其根系与叶片活性氧水平及相关酶活性在品种间没有显著差异。接种南方根结线虫后,两品种幼苗根系与叶片的O_2·~–生成速率和H_2O_2含量均升高,且‘坂砧2号’显著高于‘Ls-89’,但‘Ls-89’的MDA含量则显著高于‘坂砧2号’。两品种幼苗根系与叶片的SOD活性均在侵染早期降低,以‘坂砧2号’降幅较大;但POD、CAT活性在侵染早期变化不大,至侵染中后期则显著升高。因此,番茄抗性品种砧木幼苗的膜脂抗氧化能力较强,活性氧水平较高,且SOD活性对南方根结线虫侵染敏感。     

根结线虫天敌真菌及其高效菌株筛选*

本文报道捕食和寄生南方根结线虫(Meloidogyne incognita)和爪哇根结线虫(M. javanica)的天敌真菌6属14种。其中 Arthrobotrys candida A．Cladodes var. macroides．A. musiformis,Monacrosporium cionopagum,M．Doedycoides Drechmeria coniospora,Hdrposporium crassum. H. lilliputanum,Myzocytlum huraicola 和 Verticillum coccospora为我国新纪录种。室内测定结果表明：GACA IB (Arthrobotrys oligospora)、GACM 102 (Monacrosporium doedycoides)菌株对南方根结线虫和爪哇根结线虫均具极高的捕食率,接种线虫7天后,捕食率达98％以上,接种20天后,捕食率均达100％。     

M60家族肽酶参与调控蜡质芽胞杆菌AR156防治南方根结线虫病的作用机制

【背景】南方根结线虫(Meloidogyne incognita)寄主范围广泛,能侵染茄科、豆科、葫芦科等蔬菜,对世界农业生产造成了严重危害,每年造成的损失可高达数百亿美元。蜡质芽胞杆菌(Bacillus cereus) AR156是一种革兰氏阳性杆状细菌,对于南方根结线虫引起的土传病害有较好的防治效果,并且已经完成了全基因组测序。【目的】了解AR156对南方根结线虫的生防机理,寻找与生防功能相关的基因,进行遗传功能基因的分析。【方法】构建蜡质芽胞杆菌AR156 miniTn10随机插入突变体文库,通过对南方根结线虫致死率和温室防病试验进行筛选,找到与AR156生防能力相关的突变体,鉴定相关功能基因,并对产蛋白酶活性、定殖能力、生物膜形成和游动性等方面进行检测。【结果】与AR156野生型相比,转座子插入位点在M60家族肽酶的突变体BC41产蛋白酶活性下降,植物根围定殖能力减弱,生物膜形成能力和游动性受到影响,从而导致其防治南方根结线虫的能力降低。【结论】通过对生防相关功能基因的分析,初步明确M60家族肽酶在蜡质芽胞杆菌AR156防治南方根结线虫的过程中发挥重要作用。     

根结线虫对斜纹夜蛾幼虫生长及营养利用随龄期变化的研究

【目的】为明确南方根结线虫Meloidogyne incognita侵染对斜纹夜蛾Spodoptera litura幼虫的影响是否因幼虫的龄期而异。【方法】采用被南方根结线虫侵染和未被侵染的乌桕叶片饲喂斜纹夜蛾幼虫,并测定不同龄期幼虫的生长（幼虫体重、发育历期、相对生长率）和营养利用（取食量、近似消化率、食物转化率）情况。【结果】随着幼虫龄期的增加,斜纹夜蛾幼虫的取食量及发育历期呈上升趋势,幼虫体重、相对生长率和食物转化率先上升后下降,而近似消化率则先下降后上升。与饲喂未侵染南方根结线虫的乌桕叶片相比,取食线虫侵染的乌桕叶片的斜纹夜蛾2龄幼虫近似消化率（0.78±0.07）%显著增加了约30%,但斜纹夜蛾的4龄幼虫体重（0.12±0.04）g、相对生长率（0.20±0.06）g·g^(-1)·d(-1)·d^(-1)和食物转化率（0.54±0.18）%分别降低了61%、36%和73%。线虫侵染处理与龄期互作对斜纹夜蛾的发育历期和取食量无显著影响。【结论】根结线虫侵染对斜纹夜蛾幼虫生长及其营养利用的影响因龄期而异,线虫侵染处理虽显著增加了斜纹夜蛾2龄幼虫的近似消化率,但却抑制了其4龄幼虫的生长及其营养利用。     

Plant growth-promoting rhizobacteria, Paenibacillus polymyxa and Paenibacillus lentimorbus suppress disease complex caused by root-knot nematode and fusarium wilt fungus

Aim:  To screen and evaluate the biocontrol potential of Paenibacillus strains against disease complex caused by Meloidogyne incognita and Fusarium oxysporum f. sp. lycopersici interactions.
Methods and Results:  Paenibacillus strains were collected from rotten ginseng roots. The strains were tested under in vitro and pots for their inhibitory activities, and biocontrol potential against disease complex caused by M. incognita and F. oxysporum f. sp. lycopersici on tomato. In in vitro experiments, among 40 tested strains of Paenibacillus spp., 11 strains showed antifungal and nematicidal activities against F. oxysporum f. sp. lycopersici and M. incognita, respectively. Paenibacillus polymyxa GBR-462; GBR-508 and P. lentimorbus GBR-158 showed the strongest antifungal and nematicidal activities. These three strains used in pot experiment reduced the symptom development of the disease complex (wilting and plant death), and increased plant growth. The control effects were estimated to be 90–98%, and also reduced root gall formation by 64–88% compared to the untreated control.
Conclusion:  The protective properties of selected Paenibacillus strains make them as potential tool to reduce deleterious impact of disease complex plants.
Significance and Impact of the Study:  The study highlights biocontrol potential of Paenibacillus strains in management of disease complex caused by nematode-fungus interaction.     

The Potential of Five Winter-grown Crops to Reduce Root-knot Nematode Damage and Increase Yield of Tomato

Broccoli (Brassica oleracea), carrot (Daucus carota), marigold (Tagetes patula), nematode-resistant tomato (Solanum lycopersicum), and strawberry (Fragaria ananassa) were grown for three years during the winter in a root-knot nematode (Meloidogyne incognita) infested field in Southern California. Each year in the spring, the tops of all crops were shredded and incorporated in the soil. Amendment with poultry litter was included as a sub-treatment. The soil was then covered with clear plastic for six weeks and M. incognita-susceptible tomato was grown during the summer season. Plastic tarping raised the average soil temperature at 13 cm depth by 7°C.The different winter-grown crops or the poultry litter did not affect M. incognita soil population levels. However, root galling on summer tomato was reduced by 36%, and tomato yields increased by 19% after incorporating broccoli compared to the fallow control. This crop also produced the highest amount of biomass of the five winter-grown crops. Over the three-year trial period, poultry litter increased tomato yields, but did not affect root galling caused by M. incognita. We conclude that cultivation followed by soil incorporation of broccoli reduced M. incognita damage to tomato. This effect is possibly due to delaying or preventing a portion of the nematodes to reach the host roots. We also observed that M. incognita populations did not increase under a host crop during the cool season when soil temperatures remained low (< 18°C).     

钾素营养对防治番木瓜叶枯病的影响

对番木瓜叶枯病与植株营养、土壤相关养分的关系等进行研究,结果表明,番木瓜叶枯病是由于土壤有效钾缺乏而导致的一种生理性缺钾症;施用钾肥能有效控制该症的发生并获得较高产量。在发生缺钾叶枯病的番木瓜根、茎、叶片、叶柄等器官中镁含量均明显升高,说明番木瓜植株钾镁间存在拮抗作用。     

The multi-year effects of repeatedly growing cotton with moderate resistance to Meloidogyne incognita

Meloidogyne incognita causes more damage to cotton in the US than any other pathogen. The objective of this study was to document the cumulative effect of moderate resistance on M. incognita population density, root galling, and yield suppression in the southern United States on a moderately resistant cotton genotype grown continuously for three years. Cotton genotypes were Phytogen PH98-3196 (77% suppression of M. incognita), Acala NemX (85% suppression of M. incognita), and Delta and Pine Land DP458 B/R (susceptible standard, 0% suppression). Cotton was grown in fumigated and non-fumigated plots to measure yield loss. Each genotype and nematicide combination was planted in the same place for three years at two sites to document cumulative effects. In 2006, following three years of the different genotypes, all plots at one site were planted with susceptible cotton to document residual effects of planting resistant genotypes. Root galling and nematode population densities in the soil were significantly lower, and percentage yield suppression was numerically lower, when moderately resistant cotton was grown compared to the susceptible standard in both fields in all three years. Differences between susceptible and moderately resistant genotypes are established quickly (after only one season) and then either maintained at similar levels or slightly increased in subsequent years depending on initial nematode levels. However, when susceptible cotton was grown following three years of the moderately resistant genotypes, the nematode suppression provided by moderate resistance was undetectable by the end of the first season. Moderately resistant cotton genotypes are more beneficial than previously reported and should be pursued for nematode management. Rotation of moderately resistant and susceptible cotton could be used along with nematicides to manage root-knot nematodes in a continuous cotton cropping system and reduce selection pressure on the nematodes.     

Reproduction of Meloidogyne marylandi and M. incognita on several Poaceae

The susceptibility of 22 plant species to Meloidogyne marylandi and M. incognita was examined in three greenhouse experiments. Inoculum of M. marylandi was eggs from cultures maintained on Zoysia matrella "Cavalier" or Cynodon dactylon x C. trasvaalensis "Tifdwarf". Inoculum of M. incognita was eggs from cultures maintained on Solanum lycopersicum 'Rutgers'. In each host test the inoculum density was 2,000 nematode eggs/pot. None of the three dicot species tested (Gossypium hirsutum, Arachis hypogaea, and S. lycopersicum) were hosts for M. marylandi but, as expected, M. incognita had high levels of reproduction on G. hirsutum and S. lycopersicum. Meloidogyne marylandi reproduced on all of the 19 grass species (Poaceae) tested but reproduction varied greatly (P = 0.05) among these hosts. The following grasses were identified for the first time as hosts for M. marylandi: Buchloe dactyloides (buffalograss), Echinochloa colona (jungle rice), Eragostis curvula (weeping lovegrass), Paspalum dilatatum (dallisgrass), P. notatum (bahiagrass), Sorghastrum, nutans (indiangrass), Tripsacum dactyloides (eastern gamagrass), and Zoysia matrella (zoysiagrass). No reproduction of M. incognita was observed on B. dactyloides, Cyndon dactylon (common bermudagrass), E. curvula, P. vaginatum (seashore paspalum), S. nutans, T. dactyloides, Z. matrella or Z. japonica. Reproduction of M. incognita was less than reproduction of M. marylandi on the other grass species, except for the Zea mays inbred line B73 on which M. incognita had greater reproduction than did M. marylandi (P = 0.05) and Stenotaphrum secundatum (St. Augustinegrass) on which M. incognita and M. marylandi had similar levels of reproduction.     

Arabidopsis thaliana genes expressed in the early compatible interaction with root-knot nematodes

In the compatible interaction between Arabidopsis thaliana and the endoparasitic nematode Meloidogyne incognita, galls are formed on the roots of the host plant. Differential display was used to identify alterations of gene expression in young A. thaliana root galls caused by M. incognita. Six genes were confirmed as plant genes by DNA gel blot hybridizations. Significant homology was found with a trypsin inhibitor, peroxidase, mitochondrial uncoupling protein, endomembrane protein, 20S proteasome alpha-subunit, and diaminopimelate decarboxylase. The cellular and temporal expression of each of the six genes was analyzed by mRNA in situ hybridizations.     

Host Status of Endophyte-Infected and Noninfected Tall Fescue Grass to Meloidogyne spp

Tall fescue grass cultivars with or without endophytes were evaluated for their susceptibility to Meloidogyne incognita in the greenhouse. Tall fescue cultivars evaluated included, i) wild-type Jesup (E+, ergot-producing endophyte present), ii) endophyte-free Jesup (E-, no endophyte present), iii) Jesup (Max-Q, non-ergot producing endophyte) and iv) Georgia 5 (E+). Peach was included as the control. Peach supported greater (P ≤ 0.05) reproduction of M. incognita than all tall fescue cultivars. Differences in reproduction were not detected among the tall fescue cultivars and all cultivars were rated as either poor or nonhosts for M. incognita. Suppression of M. incognita reproduction was not influenced by endophyte status. In two other greenhouse experiments, host susceptibility of tall fescue grasses to two M. incognita isolates (BY-peach isolate and GA-peach isolate) did not appear to be related to fungal endophyte strain [i.e., Jesup (Max-Q; nontoxic endophyte strain) vs. Bulldog 51 (toxic endophyte strain)]. Host status of tall fescue varied with species of root-knot nematode. Jesup (Max-Q) was rated as a nonhost for M. incognita (BY-peach isolate and GA-peach isolate) and M. hapla, a poor host for M. javanica and a good host for M. arenaria. Bulldog 51 tall fescue was also a good host for M. arenaria and M. javanica, but not M. incognita. Jesup (Max-Q) tall fescue may have potential as a preplant control strategy for M. incognita and M. hapla in southeastern and northeastern United States, respectively.     

蓖麻提取物对南方根结线虫的防治作用

通过毒力测定及盆栽试验,研究了蓖麻提取物对南方根结线虫的杀线活性及防治效果.结果表明:蓖麻碱及蓖麻水提液均具有较强毒杀线虫活性,蓖麻碱浓度为2g·L-1、处理48 h杀线虫活性最强,线虫校正死亡率达91.5％,LC50为0.6 g·L-1;蓖麻水提液浓度为100g·L-1、处理48 h杀线虫活性最强,线虫校正死亡率达83.5％,LC50为18.3 g·L-1;蓖麻碱、蓖麻水提液和蓖麻叶植物粉处理接种南方根结线虫的番茄苗后,植株平均根结数分别为(17.6±1.7)、(20.6±1.5)和(22.8±3.7),均显著低于对照(37.4±2.3),根长分别比对照提高46.8％、34.5％和33.8％,株高分别比对照提高33.5％、22.6％和15.8％,植株鲜质量分别比对照增加41.4％、18.9％和10.1％.蓖麻提取物能减轻线虫危害,对盆栽番茄南方根结线虫病控制效果明显.