Integration of Glomus mosseae with Chromolaena odorata powder for suppression of Meloidogyne incognita on maize (Zea mays L.)

Meloidogyne incognita infestation on maize results in heavy yield loss in farmers’ field. Most of the varieties adopted by subsistence farmers in Nigeria are susceptible to M. incognita. Beside these, the cost of control exceeding the profit from the crop using nematicides and the pollution risk they pose to the environment has necessitated the need for alternatives. Pot and field experiments were, therefore, conducted to investigate the effects of Chromolaena odorata powder and Glomus mosseae (a mycorrhizal fungus) on M. incognita pathogenicity on maize. Hybrid Oba super II improved maize variety adopted by local farmers was selected for the study. Maize plants were grown with G. mosseae (5 spores/g of soil) and soil amended with C. odorata powder (1% w/w) singly and in combination. Two weeks after emergence, Test plants were inoculated with 5000 M. incognita eggs. Sixty days after planting, destructive samples were assessed for root gall symptom and severity, and nematode population. Results show that G. mosseae and C. odorata powder were effective in controlling the population of M. incognita and the root knot nematode symptom and gave the highest yield parameters in combination. Single application of G. mosseae and C. odorata powder was similar in the effect on M. incognita and maize yield. Combination of G. mosseae and C. odorata powder may become a viable alternative to nematicide in managing M. incognita pathogenicity on maize as C. odorata powder may serve as a carrier medium for G. mosseae.     

Effect of certain organic materials in controlling Meloidogyne incognita root-knot nematode infesting banana

Efficacy of certain plant wastes as onion bulb envelope, dry leaves of sugar beet, fleabane and jojoba, filter cake or mud as sugar cane industrial residue and nile fertile mineral bio-fertilisers were studied under field conditions for managing Meloidogyne incognita on banana Cv. Williams. All the tested treatments significantly (P ≤ 0.05 and 0.01) proved to be effective in reducing the studied nematode criteria during the growing season of banana. The highest percentage reductions of 87.5 and 85.5% were recorded in the number of second-stage juveniles caused by fleabane at vegetative and harvest stages, respectively. As for galls, the highest percentage reductions of 80.4 and 79.6% were achieved at harvest stage by sugar beet waste and filter cake residue, respectively. Also, sugar beet waste was the best at increasing banana fruit yield per feddan (77.0%), followed by jojoba (53.1%) and fleabane (50.4%). The number of fingers and hands per bunch increased by the different materials at various degrees.     

Differential expression of root-knot nematode resistance genes in tomato and pepper: evidence with Meloidogyne incognita virulent and avirulent near-isogenic lineages

Reproduction of artificially selected near isogenic Meloidogyne incognita lineages virulent and avirulent against the Mi resistance gene of tomato was assessed on host and resistant lines and cultivars of pepper. Egg mass production following inoculation of individual potted seedlings with second-stage juveniles was studied in experiments conducted in controlled environment. Artificially selected Mi-virulent nematode populations were unable to develop on resistant pepper lines PM 217 and PM 687. This suggests that the genetic systems governing resistance to root-knot nematodes are differently expressed in tomato and pepper, in spite of the very close phylogenetic relationships and structural genomic homologies occurring between these two vegetable crops. Moreover, these artificially selected nematode populations were also found unable to develop on the susceptible pepper cultivars California Wonder and Doux Long des Landes, while their pathogenicity was not significantly affected on susceptible tomatoes. Due to the existence of naturally virulent Meloidogyne populations, these results enhance the need for a better understanding of the mechanisms involved, in order to develop new forms of management of plant resistance to root-knot nematodes.     

Efficacy of Ricinus communis Fruit Meal with and without Bacillus Species on Suppression of Meloidogyne incognita and Growth of Tomato

The efficacy of ground Ricinus communis fruit, with and without Bacillus species, was tested on suppression of Meloidogyne incognita, growth of tomato, soil electrical conductivity (EC) and soil pH. At harvest, 85 days after applying Ricinus organic amendment, Ricinus and initial population nematode density (P_i), accounted for 64–74% of the total treatment variation (TTV) in final population nematode density (P_f) and 53–89% of the TTV in dry shoot weight. Ricinus, P_i and electrical conductivity accounted for 49–69% of the TTV in fresh fruit weight, whereas Ricinus, P_i and Bacillus accounted for 65–82% of the TTV in plant height. Because Bacillus×Ricinus interaction was not significant (P > 0.05) for any variable measured, the efficacy of Ricinus fruit meal was independent of microbial activities.     

外来入侵植物飞机草的研究进展与展望

飞机草(Chromolaena odorata)是世界公认的多年生入侵性杂草, 原产于中、南美洲, 现已扩散至非洲、亚洲、大洋洲和西太平洋群岛的大部分热带及亚热带地区, 严重威胁着入侵地本地植物的生长、生物多样性和生态安全。由于其蔓延速度快, 及其对农、林、牧业等的巨大危害, 引起了社会各界的广泛关注。揭示飞机草的入侵机制, 对于遏制其扩散速度, 最终消除或降低其危害, 恢复生态系统平衡, 具有十分重要的现实意义和科学价值。该文介绍了飞机草的生物学特性、地理分布、入侵后果及防治措施等。鉴于目前对飞机草的入侵路线和入侵机制还没有全面系统的认识, 该文重点介绍了其在世界范围内的传播路线及其成功入侵机制, 旨在为飞机草的防治工作提供科学依据。最后提出有关飞机草生理生态学和分子生物学方面的一些展望, 并强调对其适应性进化遗传基础的研究可能为探讨其成功的入侵机制带来新突破。     

飞机草地上部分化学成分及其抑菌活性研究

为探究飞机草地上部分化学成分及其抑菌作用.采用正相硅胶、Sephadex LH-20等色谱方法,从飞机草乙酸乙酯提取物中得到10个化合物,根据1H NMR、13C NMR、MS波谱数据,分别鉴定为:5,6,7,4'-四甲氧基黄烷酮(1)、圣草素-7,4'-二甲醚(2)、5,7-二羟基-6,4'-二甲氧基黄酮(3)、二氢...     

Enhancement of the efficiency of Cd phytoextraction using bacterial endophytes isolated from Chromolaena odorata,a Cd hyperaccumulator

Phytoextraction is a technique using a hyperaccumulator to remove heavy metals from soil. The efficiency of heavy metal uptake can be enhanced by the inoculation of endophytes. In this study, we isolated and identified 23 endophytes from Chromolaena odorata, a cadmium (Cd) hyperaccumulator that consisted of 19 bacteria, 2 actinomycetes and 2 fungi. All bacteria and fungi could produce at least 1 plant growth promoting factors. However, only 4 bacterial isolates; Paenibacillus sp. SB12, Bacillus sp. SB31, Bacillus sp. LB51, and Alcaligenes sp. RB54 showed the highest minimum inhibitory concentration (MIC) value (2.9 mM), followed by Exiguobacterium sp.RB51 (1.7 mM). Then, these 5 high-MIC bacteria and 1 low-MIC bacterium, Bacillus sp. LB15 were inoculated onto sunflower grown in soil supplemented with 250 mg/kg of Cd. After 60 days, all inoculated plants accumulated significantly higher Cd concentration than the non-inoculated counterparts, and those inoculated with strain LB51 showed the highest Cd accumulation and growth. Interestingly, strain LB15 with low MIC also enhanced Cd accumulation in plants. The results suggest that these bacteria, particularly strain LB51, could be applied to improve Cd accumulation in plants, and that bacteria with low MIC also have the potential to enhance the efficiency of phytoextraction.     

Effect of bark extract of different plant species on the hatching of Meloidogyne incognita

An in vitro experiment was conducted to evaluate the effect of bark extract of different plant species viz., Azadirachta indica, Acacia nilotica, Emblica officinalis, Eucalyptus citriodora, Mangifera indica and Terminalia arjuna at varying concentration levels S, S/2, S/10 and S/100 on the hatching of Meloidogyne incognita. One hundred per cent inhibition was observed with Azadirachta indica under both un-decomposed and decomposed conditions. The effect was decreased with Acacia nilotica, Emblica officinalis, Eucalyptus citriodora, Mangifera indica and Terminalia arjuna, respectively. Effect of decomposed bark extract on hatching was more pronounced as compared to un-decomposed bark extract.     

Interactive effect of root-knot nematode,Meloidogyne incognita and root-rot fungus,Rhizoctonia solani,on okra [Abelmoschus esculentus L.]

The individual, concomitant and sequential inoculation of second stage juveniles (at 2000 J₂/kg soil) of Meloidogyne incognita and Rhizoctonia solani (at 2 g mycelial mat/kg soil) showed significant reduction in plant growth parameters viz. plant length, fresh weight and dry weight as compared to control. The greatest reduction in plant growth parameters was recorded in the plants simultaneously inoculated with M. incognita and R. solani followed by sequential and individual inoculation. In sequential inoculation, plant inoculated with M. incognita 15 days prior to R. solani shows more reduction in comparison to plant inoculated with R. solani 15 days prior to M. incognita. Moreover, the multiplication of nematode and number of galls/root system were significantly reduced in concomitant and sequential inoculation as compared to individual inoculation, whereas the intensity of root-rot/root system caused by R. solani was increased in the presence of root-knot nematode M. incognita as compared to when R. solani was inoculated individually.     

Effect of Meloidogyne incognita on Selected Forest Tree Species

Four or five growth stages of 14 forest tree species were tested for susceptibility to Meloidogyne incognita at five inoculum levels. Responses ranged from the highly susceptible ''China fir'' to immune ''Taiwania''. Even highly susceptible species became increasingly tolerant at later growth stages, thus root-knot appears to be a greater problem in nurseries than in established forests. Heavily suberized cells which restricted nematode development was the predominant host response in Norway spruce, and in the jack, scotch, and Virginia pines. Adult females in jack and scotch pine, which elicited a minimum of suberized tissue, were found adjacent to infection sites showing maximum suberization which indicates that resistance can be highly localized and variable within an individual host. A few gravid females, but no giant cells, were observed in these two species.     

Preferred Temperature of Meloidogyne incognita

In laboratory thermal gradients, newly hatched infective juveniles of the plant-parasitic root-knot nematode Meloidogyne incognita migrated toward a preferred temperature that was several degrees above the temperature to which they were acclimated. After shifting egg masses to a new temperature, the preferred temperature was reset in less than a day. Possible functions of this type of thermotaxis are discussed, including the use of thermal gradients around plant roots to locate hosts and to maintain a relatively straight path while ranging in the absence of other cues (a collimating stimulus).     

Studies on the disease complex incidence by Meloidogyne incognita and Fusarium solani on Poi,Basella rubra

A survey of Poi crop in Ghaziabad (UP) exhibited a disease complex incidence by Meloidogyne incognita and Fusarium solani causing synergistic effect on the host. Paecilomyces lilacinus was found from the egg masses of M. incognita and Aspergillus niger and Aspergillus terreus from the rhizosphere of root-knot infected Poi crop. Paecilomyces lilacinus parasitised the eggs to a greater extent. The level of parasitism was highest (65%) by P. lilacinus while Aspergillus spp. did not colonise the eggs. Fusarium solani which in the present investigation has been established to be pathogenic to Poi plant.     

Comparison of Reproduction by Meloidogyne graminicola and M. incognita on Trifolium Species

The reproductive potential of Meloidogyne graminicola was compared with that of M. incognita on Trifolium species in greenhouse studies. Twenty-five Trifolium plant introductions, cultivars, or populations representing 23 species were evaluated for nematode reproduction and root galling 45 days after inoculation with 3,000 eggs of M. graminicola or M. incognita. Root galling and egg production by the two root-knot nematode species was similar on most of the Trifolium species. In a separate study, the effect of initial population densities (Pi) of M. graminicola and M. incognita on the growth of white clover (T. repens) was determined. Reproductive and pathogenic capabilities of M. graminicola and M. incognita on Trifolium spp. were similar. Pi levels of both root-knot nematode species as low as 125 eggs per 10-cm-d pots severely galled white clover plants after 90 days. Meloidogyne graminicola has the potential to be a major pest of Trifolium species in the southeastern United States.     

Extraction of Root-associated Meloidogyne incognita and Rotylenchulus reniformis

A technique based on physical maceration of root tissue was developed to extract vermiform and swollen stages of Meloidogyne incognita and Rotylenchulus reniformis. Experiments conducted on soybean and tomato evaluated the efficiency of method (stir, grind), NaOC1 concentration (0%, 0.5%), and duration (lx, 2x) on extraction of nematodes and eggs from 60-day-old populations. Root-associated populations of R. reniformis were considerably lower than those of M. incognita, so development of the method focused on the latter. Grinding liberated more nematodes than stirring, but the reverse was true for egg extraction. Among grinding treatments, a duration of 10 seconds in 0.5% NaOCl provided the most efficient extraction of nematodes and eggs. Among stirring treatments, a duration of 10 minutes in 0.5% NaOCl provided the most efficient extraction of eggs. These techniques were compared on soybean roots 30 days older than those on which the procedures were first evaluated, with consistent results.     

Nematicidal activity of powder and extracts of Melia azedarach fruits against Meloidogyne incognita

Pulverised lyophilised (dehydrated) Melia azedarach (Meliaceae) fruits (PMF) were tested in a dose–response pot experiment against juveniles (J2) of the root-knot nematode Meloidogyne incognita. Successively, with different extraction procedures, a polar (melia methanol extract, MME) and a non-polar (melia oil, MO) fragments were obtained and their effects were tested on nematode motility and development, in dose and time response bioassays and pot experiments. An EC₅₀ value was calculated for all experiments. A dose–response effect was found in pot bioassays using PMF and, after an incubation period of 24 and 48 h, the EC₅₀ values were calculated at 0.41% and 0.34% w/w, respectively. Motility bioassays revealed a dose and time dependent response effect, after exposure to MME, but not to MO. Doses of MME higher than 0.08% were nematicidal, whereas lower ones were nematostatic (the loss of motility as a result of the presence of the substance was reversible). In a pot experiment, MME doses higher than 2.5% w/w caused 100% nematode control with EC₅₀ value of 0.916% w/w.     

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.     

Control of root-knot nematode,Meloidogyne incognita and reniform nematode,Rotylenchulus reniformis on pigeonpea and linseed

Abstract

Pigeonpea (Cajanus cajan) and linseed (Linum usitatissimum) are susceptible to Meloidogyne incognita and Rotylenchulus reniformis nematodes. Reduction in different growth parameters (length and weight of plant, number of pods), bulk density of pigeonpea stem, oil content of linseed, chlorophyll content of leaf and water absorption of roots caused by M. incognita and R. reniformis were statistically significant. Similar effects were also observed in plants raised from seeds soaked in different concentrations of water soluble fractions (WSF) of rice polish and pyridoxine solutions, however, the reductions were of a comparatively lesser extent. Higher concentrations of the solutions were more effective when compared to lower ones and pyridoxine was more beneficial than WSF for improving plant growth and reducing disease incidence.     

南方根结线虫初始接种密度对生姜生长的影响

在盆栽条件下,研究了南方根结线虫不同初始接种密度对生姜生长的影响.结果表明,南方根结线虫的侵染,降低生姜株高、茎粗、分枝数、茎叶鲜重和根系鲜重,最终降低生姜的产量,且随着接种密度的增加,生姜生长所受到的危害也随之增加.每100 g干土接种0、100和200个卵,可使生姜分别减产27.91%、37.73%和42.14%.初始接种密度对南方根结线虫繁殖速率也有很大影响.一般初始接种密度低时繁殖速率高,接种密度高时繁殖速率低,其在生姜上的平衡密度为每100 g干土746.20个.     

Relationships Between Tolerance and Resistance to Meloidogyne incognita in Cotton

The southern root-knot nematode, Meloidogyne incognita, is the most damaging pathogen of cotton in the United States, and both resistance and tolerance to M. incognita could be valuable management approaches. Our objectives were to evaluate advanced cotton breeding lines for resistance and tolerance to M. incognita and to determine if a relationship between resistance and tolerance exists. Reproduction of M. incognita was evaluated on 17 breeding lines, a susceptible control (Delta and Pine Land DP5415), and a resistant control (M-120) in two greenhouse trials with six replications in a randomized complete block design. Two-week-old seedlings were inoculated with 8,000 M. incognita eggs and assessed for egg production 8 weeks later. Reproduction on the resistant control was only 10% of that on the susceptible control. Eight breeding lines supported 45% to 57% less (P <= 0.05) nematode reproduction than the susceptible control, and none of them were as resistant as M-120. Yield was determined in 2001 and 2002 in fumigated (1,3-dichloropropene at 56 liters/ha) and nonfumigated plots in a strip-plot design with three replications in a field naturally infested with M. incognita. Yield suppression caused by nematode infection differed among genotypes (P ≤ 0.05 for genotype × fumigation interaction). Six genotypes in 2001 and nine in 2002 were tolerant to M. incognita based on no difference in yield between the fumigated and nonfumigated plots (P ≥ 0.10). However, only three genotypes had no significant yield suppression in both years, of which two also were resistant to M. incognita. Regression analysis indicated that yield suppression decreased linearly as nematode resistance increased.     

Overwintering Stages of Meloidogyne incognita in Vitis vinifera

The overwintering of Meloidogyne incognita in and around Vitis vinifera cv. French Colombard roots was studied in a naturally infested vineyard at the Kearney Agricultural Center, in a growth chamber, in inoculated vines in microplots at the University of California, Davis, and in a greenhouse. Infected roots were sampled at intervals from onset of vine dormancy until plants accumulated about 800 degree days (DD - base 10 C). Embryogenesis within eggs, classified as less than or more than 16 cells and fully differentiated, and numbers of juveniles (second to fourth stage) and preovipositional and mature (egg-laying) adult stages in roots were determined. All stages were present at the onset of dormancy. Juveniles and immature females were not recovered during the dormant period. Mature females and eggs were always present in roots, although the number of mature females generally decreased with time after onset of dormancy. In contrast, in a greenhouse experiment that accumulated comparable DD without the host plant going through dormancy, the number of mature females increased. After bud break, the number of eggs per female increased and all nematode stages were found in host roots. Eggs in all stages of embryogenesis were observed at all times of sampling, indicating that females overwinter and are capable of laying eggs when conditions improve in the spring and need to be considered in nematode management decisions.