新生物杀线虫剂对线虫致死力室内测定

室内测定了新研制的3种生物杀线虫剂及其复配剂对根结线虫(Meloidogyen spp.)和松材线虫(Bursaphelenchusxy Lophilus)致死力,在25℃恒温、60%RH恒湿条件下4种杀线虫剂,杀线剂1、杀线剂2、杀线剂3对两种线虫的致死力都较强,药后72h根结线虫死亡率达98%,松材线虫死亡率达80%。杀线剂复配效果好于单一效果。     

日本曲霉ZW1发酵滤液的杀线虫活性和发酵条件优化

根结线虫是一类严重为害作物的寄生线虫，分布于世界各地，且寄主范围广。前期试验表明，日本曲霉Aspergillus japonicus ZW1发酵滤液对南方根结线虫Meloidogyne incognita 2龄幼虫（J2）具有毒杀作用，发酵过程中产生表面光滑球形菌丝体和表面辐射状球形菌丝体，且两种菌丝体发酵滤液的杀线虫效果具有显著差异。表面光滑球形菌丝体的发酵滤液处理南方根结线虫J2的校正死亡率在24 h达100%，显著高于表面辐射状球形菌丝体发酵滤液处理的死亡率（12.7%）。本研究通过对菌株ZW1发酵的温度、转速、培养基、光照和黑暗等条件优化表明，菌株ZW1的最优培养温度25℃和转速150 r/min，以Czapek培养基为基础培养基的最优碳源为蔗糖30 g/L和氮源KNO₃3 g/L，光照和黑暗条件下培养不影响菌株ZW1杀线虫活性；评价煮沸和4℃保存发酵滤液的杀虫效果结果表明，发酵液杀线虫活性随着贮藏时间发生变化，发酵液煮沸对菌株ZW1发酵液的杀线虫活性无影响，4℃保存1年的发酵滤液处理J2的校正死亡率仍保持87.8%。菌株ZW1代谢产物对南方根结线虫J2具有良好的毒杀作用，值得进一步研究和开发利用。     

水稻干尖线虫室内人工培养条件研究

在室内同一培养基质上研究了温度、光照、湿度对水稻干尖线虫繁殖量的影响。结果表明:在不同温度、光照、湿度下水稻干尖线虫的繁殖量差异明显,在温度30℃,光照6h,湿度90%条件下水稻干尖线虫的繁殖量最高。     

温度和湿度对南方根结线虫存活的影响

在实验室条件下,测试了不同温度处理对离体南方根结线虫存活的影响,结果表明,在25、30、35℃和40℃下,杀死90%以上离体南方根结线虫分别需要30d(100%)、26d(96.6%)、24d(94.1%)和9d(99.6%),而45、50℃下则需要15min和2.3min。同时测试了不同温湿度处理对土壤中南方根结线虫存活的影响,结果表明,25、30℃是土壤中根结线虫的适宜温度,当土壤含水量为14%时,40d死亡率分别为91.1%、90.4%;35℃线虫处于抑制状态,40d死亡率为85.3%;而线虫对40℃以上的高温敏感,随着处理温度升高,杀死线虫所需时间缩短。根结线虫在不同温湿度下的死亡情况不同,土壤温度为25～35℃,土壤含水量为6%是线虫的适宜湿度;土壤温度达到40℃且含水量为6%和14%时,杀死100%根结线虫仅需4d,不利于其存活;而50℃的高温和含水量达18%的高湿更不利于其存活。     

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,但不能确定南方根结线虫不同群体的分子进化与其寄主来源和地理分布之间的相关性。     

温湿度对南方根结线虫卵孵化和二龄幼虫的影响

根结线虫病害是世界上最难防治的蔬菜病害之一,是否可以通过控制生态条件经济有效地防治根结线虫病害值得深入研究。本文利用室内纯培养技术研究了温湿度单因素和双因素对南方根结线虫（Meloidogyne incognita）2龄幼虫(J2)的致死率和卵囊中卵孵化率的影响。试验结果表明,该线虫对温度敏感,40 ℃以上高温和5 ℃以下低温即可抑制J2存活和卵囊中卵孵化,15～30 ℃是线虫的适宜温度;该线虫对湿度不十分敏感,只有干旱（含水量低于1%）和高湿（含水量高于30%）时,对线虫才有一定抑制作用。低温（5 ℃以下低温、含水量5%以上湿度）和高温高湿（35 ℃以上温度和30%含水量）抑制卵囊中卵孵化和J2的存活。本数据的获得将为设施园艺中生态控制南方根结线虫病害提供理论指导和数据支持。     

花生茎线虫 Ditylenchus arachis 在真菌上的培养条件研究

花生茎线虫Ditylenchus arachis是危害花生的重要病原线虫。本研究通过测试不同真菌和培养温度对花生茎线虫繁殖力的影响,以探讨该线虫在室内的培养条件。研究结果表明:花生茎线虫在长柄链格孢、茄镰孢、尖镰孢和灰葡萄孢上均能完成生活史并进行繁殖,但不同真菌上培养线虫的效果不同。其中长柄链格孢的培养效果最好,培养30d后的总虫量和繁殖系数分别为37 292条和1 243倍;灰葡萄孢的培养效果最差,30d后的总虫量和繁殖系数仅为1 514条和50倍。25~30℃是花生茎线虫的适宜培养温度,30℃时为最佳温度;当温度低于20℃或高于35℃时线虫繁殖效果差。此方法繁殖的线虫可用于花生茎线虫生物学、遗传学等方面的研究。     

和田鞘氨醇杆菌AMCC 100218菌株的筛选、鉴定及杀线虫特性

为筛选对南方根结线虫具有致死效果的生防细菌,从山东省10个县市蔬菜主产区番茄根际土壤中分离可培养细菌,采用离体杀线虫试验测定分离菌株对南方根结线虫Meloidogyne incognita的致死活性,结合生理生化特征及分子生物学方法对高效杀线虫菌株进行分类鉴定,同时对其杀线虫特性进行表征,并通过盆栽试验进一步验证其生防潜力。结果显示,从山东省蔬菜主产区番茄根际土中分离到1株高效杀线虫菌株AMCC 100218,结合生理生化试验与16S rRNA序列分析,鉴定此菌株为和田鞘氨醇杆菌Sphingobacterium hotanense;该菌株对南方根结线虫2龄幼虫的致死效果可达88.87%,其杀线虫活性物质具有较好的热稳定性和储存稳定性,且耐碱不耐酸;盆栽试验结果表明,该菌能够显著减少土壤中的虫口密度,降低番茄发病率。表明和田鞘氨醇杆菌AMCC 100218菌株是1株具有防治根结线虫病潜力的生防细菌。     

生物熏蒸用于治理蔬菜根结线虫病的研究

将甘蓝(Brassica oleracea)、芥菜(B.juncea)和雪里蕻(B.junceavar.multiceps)的叶及芥菜疙瘩(B.napifor-mis)的块根组织以3.5 kg/m²的量分别施入密封于棉纱缸中的严重感染根结线虫(Meloidogyne incognita)的土壤中,在25℃和32℃下熏蒸6 d后对活体线虫的测定结果表明,在25℃下用上述4种材料熏蒸后活体线虫数量分别比对照减少80%、85%、87%和91%。32℃下的熏蒸效果明显优于25℃下的熏蒸效果,各处理土壤中均未发现活体线虫,而无处理对照土壤中的活体线虫数量为1 540条/kg土壤。对各类添加物增效作用的调查结果表明,添加麦麸的增效作用最明显。田间试验结果表明,植物材料单独或与添加物混合使用对根结线虫病的防效均显著高于太阳能和土壤还原消毒法的防效。其中芥菜添加麦麸在开花期和盛果期的防效分别为65.2%和66.0%,与对照药剂98%棉隆可湿性粉剂的防效无显著差异;各植物材料熏蒸效果大小依次为芥菜>雪里蕻>芥菜疙瘩>甘蓝。     

穿刺巴斯德菌活体大量繁殖体系的优化

穿刺巴斯德菌Pasteuria penetrans专性寄生于根结线虫Meloidogyne spp.,具有很好的生防潜力。为了进一步提高其产量,本研究比较了5个对南方根结线虫敏感的番茄栽培品种繁殖穿刺巴斯德菌的效率。结果表明,佳粉18和毛粉802繁殖效率最高,单株番茄上的产孢量分别为1.54×108孢子.株-1和1.47×108孢子.株-1。以佳粉18为根结线虫的寄主植物,研究线虫接种量、接种次数、线虫接入时的苗龄及接种后第1周的培养温度对穿刺巴斯德菌活体繁殖量的影响。研究表明,在番茄9片真叶时,每株番茄接种7500条线虫,分3次接入,根粉的产孢量可提高至1.86×108孢子g-1。在18～31℃温度范围内,温度越高,穿刺巴斯德菌对线虫的侵染率越高;31℃时,其孢子侵染率平均达44.57%。     

Greenhouse and field evaluations of commonly occurring weed species for their host suitability to Meloidogyne species

Since weeds serve as hosts for nematode pests, the host status of 20 weed species (commonly occurring in fields of developing farmers) to Meloidogyne incognita and M. javanica, respectively, were investigated. Greenhouse studies showed that seven weed species had Rf values >1 for both nematode species indicating susceptibility, while 13 had Rf values ≤ 1 indicating resistance. Greenhouse results showed that Hibiscus trionum and Amaranthus tricolor were identified as the most susceptible and Chenopodium carinatum and Datura ferox the poorest hosts for M. incognita and M. javanica. For field experiments at Kuruman, Solanum retroflexum was the most susceptible weed to a M. javanica population, while the same was evident for H. trionum at Nelspruit, where a mixed population of M. incognita and M. javanica occurred and at Potchefstroom, where a population of M. incognita was present. Results from this study indicated that certain weed species are highly susceptible to root-knot nematodes and should be removed timely and effectively to prevent population level increases of root-knot nematode pests in the fields of farmers.     

PIN1 auxin efflux carrier absence in Meloidogyne incognita-induced root-knots of tomato plants

The nematode species Meloidogyne incognita infects a large variety of cultivated crops and is one of nature’s most notorious pests. One cultivated plant which is prone to M. incognita infestation is the tomato. Knowing that in A. thaliana the PIN auxin efflux transporters distribution is being altered upon early invasion by M. incognita, the PIN1 allocation patterns in the giant cells of tomato plants after 15 and 25 days of infection were investigated. PIN1 was absent from the giant cells’ membrane in both assessment timings examined, indicating the maintenance of a local auxin maxima, which was also supported by IAA immunodetection. PIN1 distribution pattern could be attributed on either the nematodes nutritional needs throughout its life cycle or due to the tomato plants differential responses upon M. incognita infection.

     

Nematicidal potential of materials from <Emphasis Type="Italic">Medicago</Emphasis> spp.

The nematicidal effect of soil amendments with dry top and root material from Medicago sativa and/or Medicago arborea was evaluated on the root-knot nematode Meloidogyne incognita and on the cyst nematode Globodera rostochiensis in potting mixes. All amendments suppressed root and soil population densities of both nematode species compared to non-treated and chemical controls. The suppressiveness of M. sativa differed between top and root material and among the amendment rates. In field conditions soil amendments with 20 or 40 t ha⁻¹ of a pelleted M. sativa meal increased tomato crop yield and reduced soil population densities and root galling by M. incognita. It is suggested that saponins were at least partly responsible for the nematicidal activity.     

长枝木霉菌株TL16防治南方根结线虫的作用机理

为探明长枝木霉Trichoderma longibrachiatum菌株TL16防治南方根结线虫Meloidogyne incognita的作用机理,采用原生质体转化法获得绿色荧光蛋白(green fluorescent protein,GFP)标记菌株GFP-TL16,通过测定菌株TL16和GFP-TL16对南方根结线虫卵和2龄幼虫(2nd-stage juvenile,J2)的寄生与致死作用,其发酵液对卵孵化的抑制作用和对J2的致死作用,以及菌株GFP-TL16在黄瓜根系的定殖情况和菌株TL16对番茄根结形成的抑制作用来综合分析其作用机理。结果显示:菌株TL16菌丝对南方根结线虫卵无寄生作用,处理19 d后卵降解率为26.33%,致死作用较低;菌株TL16分生孢子悬浮液处理南方根结线虫J2后72 h的致死率为1.65%,且无寄生作用。菌株TL16发酵液处理南方根结线虫J2后48 h的校正死亡率为10.71%,处理卵15 d后对卵孵化的相对抑制率为77.11%。菌株GFP-TL16可定殖于黄瓜根系中,经菌株TL16处理后接种南方根结线虫J2,番茄根结减退率为55.88%。表明长枝木霉菌株TL16可通过抑制根结线虫卵孵化和诱导番茄产生抗病性来防治根结线虫病。     

Stimulation of respiratory pathways in tomato roots infested by Meloidogyne incognita

Respiration of tomato roots susceptible and resistant to Meloidogyne incognita was measured during infestation. No significant changes in respiratory rate occurred in susceptible tomato roots, during infestation by M. incognita. In resistant tomato roots, a pronounced increase of both cyanide-sensitive and cyanide-resistant oxidases, was observed during nematode attack. The time-course of the respiration during 12 days, after nematode inoculation, showed that resistant tomato roots responded with a rapid increase in cyanide-sensitive and cyanide-resistant respiration as invading nematodes progressed; no changes were observed in the susceptible tomato roots.Change in the rate of oxygen uptake paralleled an increase in nematode density in resistant tomato roots; oxygen uptake rose linearly to an infestation level of 50 juveniles for each seedling, above which value it declined. The physiological significance of the alternative respiratory pathway is discussed.     

Diversity of Meloidogyne incognita populations from cotton and aggressiveness to Gossypium spp. accessions

The root-knot nematode (RKN) Meloidogyne incognita is the main nematode causing losses to the cotton crop in Brazil. In order to implement control strategies within integrated management, an accurate identification of the nematode populations prevailing in the cotton production areas is necessary. This study aimed to assess the genetic variability and aggressiveness of RKN populations from cotton production areas in Bahia state, Brazil. All populations were characterized biochemically and molecularly and identified as M. incognita. RAPD and AFLP markers detected 44% of polymorphic fragments among the 13 populations of this species. The 10 M. incognita populations collected in Bahia presented 33.7% of diversity when compared to each other, and 25% when the population from Barreiras (the most polymorphic) was excluded. This polymorphism increased when populations from other Brazilian states were included. The aggressiveness and virulence among populations from Bahia towards different cotton accessions (susceptible/resistant) was also studied. None of the populations showed virulence against the moderately resistant (Clevewilt 6, Wild Mexican Jack Jones and LA 887) and highly resistant (CIR1348 and M-315 RNR) cultivars. Two M. incognita populations from Barreiras were the most aggressive, reaching reproduction factors of 539 and 218, respectively, in the susceptible cultivar FiberMax 966. The most aggressive population (8) was also the most genetically divergent in phylogenetic analyses. These results demonstrate that diversity of M. incognita populations from cotton farms in Bahia is not related to virulence against resistant accessions, which suggests that cultivars containing one or two resistance genes with good agronomic characteristics could be used in infested commercial areas in Bahia state, Brazil.     

Root‐knot nematodes do not affect black root rot disease severity on watermelon and bottle gourd

The effects of root‐knot nematodes on black root rot of watermelon and bottle gourd were studied using field surveys and co‐inoculation tests with Meloidogyne incognita (southern root‐knot nematode) and Diaporthe sclerotioides. The results of the field survey suggested that root‐knot nematodes had little effect on either the severity of black root rot or infection with D. sclerotioides. None of the three fields showed a significant positive correlation between disease severity and nematode gall index, with low correlation coefficients. Co‐inoculation experiments under controlled conditions found no significant effect of root‐knot nematodes on black root rot of watermelon and bottle gourd based on area under disease progress curves (AUDPC). These results were supported by the quantities of DNA of the two agents in root tissues because no significant difference was found between dual‐ and single‐inoculation treatments with M. incognita and/or D. sclerotioides. These findings suggest that root‐knot nematodes probably do not affect the infection of watermelon or bottle gourd roots by D. sclerotioides or the incidence of black root rot in these crops caused by this fungus.