Biological control of root-knot nematode,Meloidogyne incognita infesting tomato

Talc based formulations of two antagonistic fungi, Acremonium strictum W. Gams and Aspergillus terreus Thom were tested separately and together for their ability to suppress the development of root-knot disease of tomato caused by the root-knot nematode, Meloidogyne incognita Kofoid & White in two consecutive trials (2007–08). Tomato seedlings were each inoculated with M. incognita at 2 infective second stage juveniles /g of soil. M. incognita caused up to 48% reduction in plant growth parameters compared to un-inoculated control. Control efficacy achieved by combined soil application of both fungi, in terms of galls/root system and soil population/50 ml of soil, was 66 and 69% respectively at 60 days of inoculation compared to control. Soil application by individual fungus did not achieve as much effectiveness as the biocontrol agents applied together. The combined treatment was found to have antagonistic effect on M. incognita development and increased plant vigor. Incorporation of fine powder of chickpea pod waste with talc powder was beneficial in providing additional nutrients to both plant and biocontrol agents and increased the activity of the nematophagous fungi in soil. A. strictum and A. terreus were successfully established in the rhizosphere of tomato plants up to the termination of the experiment.     

Interactions between the root-knot nematode Meloidogyne incognita and Glomus mosseae in banana

The effects of the interaction between the arbuscular mycorrhizal fungus Glomus mosseae and the root-knot nematode Meloidogyne incognita on growth and nutrition of micropropagated ;Grand Naine banana (Musa AAA) cultivar was studied under greenhouse conditions. Inoculation with two G. mosseae isolates significantly increased growth of plants in relation to non-mycorrhizal plants. Response to mycorrhizae was as effective as with an optimum P fertilization in promoting plant development for most growth parameters. Meloidogyne incognita had no apparent effect on the percentage of root colonization in mycorrhizal plants. In contrast, G. mosseae suppressed root galling and nematode buildup in the roots. The percentage of mycorrhizal colonization was high (over 80%) in low P fertilized plants, but optimum P rates for bananas (four times higher than low P) significantly reduced mycorrhizal colonization. Most elements were within sufficiency levels for banana with exception of N which was low for all treatments. Mycorrhizal plants fertilized with a low P rate showed higher N, P, K, Ca, and Mg contents as compared to non-mycorrhizal plants low in P with or without the nematode. Inoculation with G. mosseae favours growth of banana plants by enhancing plant nutrition and by suppressing nematode reproduction and galling during the early stages of plant development.     

Pathogenicity of root-knot nematode,Meloidogyne incognita on Lens culinaris (Medik.)

Effects of the root-knot nematode (Meloidogyne incognita) on lentil (Lens culinaris) were studied under greenhouse conditions. The plants were inoculated with 250, 500, 1000, 2000 and 4000 J₂ per plant. Plant growth, yield, nodulation, seed weight, chlorophyll, nitrogen, phosphorus and potassium, (NPK) contents, as compared to control, were found decreased in all the nematode infected plants. The extent of reduction increased with an increase in inoculum levels. The reductions were significant at 500 J₂ and at higher inoculum levels, i.e. 1000, 2000 and 4000 J₂ per pot over the control. An increase in inoculum level caused enhancement in galling, egg mass production and nematode population. At higher inoculum levels, the population of the nematode in the root as well as in the soil increased to a greater magnitude than at lower inoculum levels. On the contrary, reproduction factor (RF) and rate of population increase (RPI) decreased with increasing inoculum levels.     

In vitro studies of antagonistic fungi against the root-knot nematode,Meloidogyne incognita

The present study was carried out in vitro to determine the efficacy of indigenous fungi isolated from egg masses of root-knot nematode, Meloidogyne incognita on egg parasitism, egg hatching, mobility and mortality against root-knot nematode, M. incognita. The tested fungi were Acremonium strictum, Aspergillus terreus, A. nidulans, A. niger, Chetomium aubense, Chladosporium oxysporum, Fusarium chlamydosporium, F. dimarum, F. oxysporum, F. solani, Paecilomyces lilacinus, Pochonia chlamydosporia, Trichoderma viride and T. harzianum. All tested fungi showed varied effects against the nematodes. Culture filtrates of A. strictum was very effective against the nematode in regards to egg parasitism (53%), egg hatching inhibition (86%) and mortality (68%) compared to controls. A. strictum was found to have an advantage over P. lilacinus, P. chlamydosporia, T. viride and T. harzianum in that it caused greater mortality of the second stage juveniles (J₂). A. terreus did not show egg parasitism but was found to be highly toxic against second stage juveniles (J₂) causing high mortality (around 68%). Thus, A. strictum and A. terreus showed good biocontrol potential against root-knot nematode, M. incognita under in vitro conditions.     

The role of chitinase from Lecanicillium antillanum B-3 in parasitism to root-knot nematode Meloidogyne incognita eggs

B-3 fungal isolate was isolated from soil samples of Gwangju in Korea. Based on morphological and phylogenetic analysis, it was designated as Lecanicillium antillanum B-3 (syn. Verticillium antillanum B-3). The fungus was a chitinolytic-nematophagous microorganism. B-3 chitinase activity from 0.5% swollen chitin broth medium reached the highest level on the sixth day and then plateaued until 12 days. B-3 isolate showed the high rate of parasitism on Meloidogyne incognita eggs with more than 90% infection rate on the third day after treatment. B-3 crude chitinase damaged the eggshell structures more than 78% based on lactoglycerol staining data at a final protein concentration of 14.6 µg mL^?1 on the fourth day following treatment. Partially purified chitinase with molecular 37 kDa from DEAE-Sephadex chromatography also showed damaging effect on the eggs. These results suggested that chitinase from B-3 isolate was responsible for degradation of M. incognita eggshell structures.     

Histological response of resistant tomato cultivars to infection of virulent Tunisian root-knot nematode (Meloidogyne incognita) populations

The response of a susceptible tomato cultivar (Solanum lycopersicum cv. Rio Grande) to infection by three populations of root-knot nematode (Meloidogyne incognita) was compared histologically with that of Lycopersicon esculentum cv. Monita, L. esculentum cv. VFN8 and Solanum lycopersicum cv. Nemador possessing the Mi-1 resistance gene and accession PI126443 of L. peruvianum possessing the Mi-3 gene. The resistant cultivars showed susceptibility to the Tunisian Meloidogyne populations. Feeding sites were characterised by the development of giant cells that contained granular cytoplasm and several hypertrophied nuclei. The cytoplasm of giant cells was aggregated along their thickened cell walls and consequently the vascular tissues within galls appeared disrupted and disorganised. Feeding site formed on resistant L. esculentum lines and susceptible cultivar Rio Grande are similar according to cell and nucleus number, and the nurse superficies. Resistant accession L. peruvianum PI126443, known to possess heat-stable nematode resistance, also showed susceptible reaction to Tunisian Meloidogyne incognita populations; however, nematode development was reduced in comparison with susceptible plants and less developed feeding cells were observed.     

Bio-control activity of Purpureocillium lilacinum strains in managing root-knot disease of tomato caused by Meloidogyne incognita

The potential of 24 indigenous isolates of Purpureocillium lilacinum (Paecilomyces lilacinus) (Thom) Samson collected from different agro-climatic zones of India was investigated against the root-knot nematode, Meloidogyne incognita. The studies were conducted in vitro (larvicidal, ovicidal and egg-parasitising capacity) and under naturally infested field conditions with selected strains. Repeated field trials were conducted with talc-based preparations of fungal strains at 10 kg ha^?1, which were applied mixed in farm yard manure (FYM) at 1.5 t ha^?1. Results (in vitro) showed that all tested isolates were capable to parasitise eggs, inhibit egg hatching and cause juvenile mortality of M. incognita at various levels. Based on the performance under in vitro studies, eight isolates (NDPL-01, ANDPL-02, SHGPL-03, HYBPL-04, AHDPL-05, PTNPL-06, SNGPL-07 and VNSPL-08) were re-tested to confirm the results. HYBDPL-04 was found causing highest mortality (80%), inhibition of egg hatching (90%) as well as parasitisation of M. incognita eggs (75%). Under field trials also, the best protection of root-knot disease of tomato (Lycopersicon esculentum L.), in terms of reduction of galls (61%) and reproductive factor (P_f/P_i (RF) = 0.2) was achieved through application of HYBDPL-04 + FYM compared to control and other tested isolates. It also enhanced marketable yield of tomato up to 43%. It is concluded that the HYBDPL-04 strain of P. lilacinum is highly effective for management of root-knot disease of tomato under naturally infested field conditions. It is the isolate which produced the maximum number of metabolites which were extracted through high pressure liquid chromatography.     

Influence of cadmium on penetration of the root-knot nematode,Meloidogyne incognita and plant growth parameters of tomato

The results of experiment clearly reveal that cadmium inhibited root penetration by the second stage juveniles (J₂) of Meloidogyne incognita which subsequently affected the development of root galls in tomato. The heavy metal was highly injurious to tomato plants at all the concentrations tested for (7.5, 15.0, 30.0 and 60.0?ppm). The inhibitory effect on plant growth and other parameters (fresh and dry weight of plant, chlorophyll content of leaves, water absorption capability of roots) significantly increased with an increase in the concentration of the metal. It was further increased in the presence of the nematode.     

Effects of Eclipta alba on the morphometrics of root-knot nematode,Meloidogyne incognita as influenced by fly ash amended soil

An experiment in a complete randomised design was conducted with the aim of investigating the impact of graded quantities (10, 20, 30, 40 and 50%) of fly ash on the morphometrics of root-knot nematode, Meloidogyne incognita (2000 J₂/pot) in Eclipta alba. The application of fly ash brought about deleterious effects on the development of the nematode which were reflected on dimensions of the mature females in all the fly ash concentrations over the inoculated control (IC). Significant reductions in length and width of body, neck, stylet and median bulbs of the mature females were recorded at higher (40 and 50%) fly ash levels, when compared with inoculated control (IC). The severity of root-knot disease was found to be decreased with increasing fly ash concentrations.     

Pathogenic potential of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on chilli (Capsicum annuum L.)

Damaging threshold levels of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on plant growth parameters, viz., plant length, fresh and dry weight of chilli were determined by conducting their pathogenicity trials in pot experiments. The results revealed a significant reduction in the plant growth parameters at and above the inoculum level of about 1000?J₂ per plant of M. incognita and the highest reduction was recorded at 8000?J₂ per plant. Significant reduction in plant growth parameters was recorded at 1.00?g mycelial mat of F. solani per plant, while the highest reduction was observed at 8.00?g mycelial mat per plant. The damaging threshold level was 1000?J₂ per plant of M. incognita and 1.00?g mycelial mat of F. solani.     

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.     

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。     

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.     

Effect of organic fertiliser and Chromolaena odorata residue on the pathogenicity of Meloidogyne incognita on maize

Pot experiments laid out in a complete randomised design were conducted in the screen house of the Department of Crop Protection, University of Agriculture, Abeokuta, Ogun State, Nigeria to determine the effects of organic fertiliser and Chromolaena odorata residue at 1% w/w on the pathogenicity of Meloidogyne incognita infecting maize. M. incognita significantly reduced the plant height, number of leaves per plant, leaf area, cob weight and grain yield of maize by 6.89, 15.18, 20, 63.92 and 56.16% respectively. C. odorata residue and organic fertiliser significantly suppressed M. incognita galling, inhibited the nematode fecundity and reduced the number of eggs and juveniles on maize. A remarkable increase in plant height, number of leaves per plant, leaf area, cob weight and grain yield were observed on maize plants treated with the mixture of C. odorata and organic fertiliser despite the nematode infection. The observation from this study suggests that C. odorata in combination with organic fertiliser is a viable option for the control of M. incognita on maize.     

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.     

Comparison of concomitant and sequential inoculation of Steinernema sp. in the management of root-knot (Meloidogyne incognita) nematode infecting eggplant (Solanum melongena)

Culture of Steinernema sp. was maintained on Corcyra cephalonica larvae. Steinernema sp. (at 50, 500, 1000, 2500, 5000, 10,000 and 20,000 ij’s /500?g soil) was concomitantly inoculated with 500 J₂ of Meloidogyne incognita/500?g soil to the eggplant seedlings in the pots filled with 4?kg sterilised soil. The simultaneous inoculation of M. incognita with either of the inoculum levels (1000, 2500, 5000 and 10,000 J₃/500?g soil) of Steinernema sp. significantly reduced the damage caused by M. incognita in terms of plant growth parameters, viz. plant length, dry weight, number of flowers and weight of fruits. Moreover, the highest improvement in plant growth parameters, viz. plant length, dry weight, number of flowers and weight of fruits, was recorded in plants inoculated with 5000 J₃ of Steinernema sp./500?g soil followed by 2500, 1000 and 10,000 J₃/500?g soil. The highest reduction in the reproduction factor and number of galls/root system was recorded in the plants treated with 5000 J₃ Steinernema sp./500?g soil followed by 2500, 1000 and 10,000 J₃/500?g soil. Comparison of concomitant and sequential inoculations showed that the sequential inoculation (both prior and after) of Steinernema sp. at different inoculum levels (1000, 2500, 5000, 10,000 and 20,000 ij’s/500?g soil) was more effective in the management of root-knot nematode than the concomitant inoculation. Therefore, the application of Steinernema sp. might be useful for suppression of nematode pest on eggplant and may be used as an alternative for chemicals.     

Root-knot development in mulberry infested with Meloidogyne incognita

Healthy mulberry roots were inoculated with second stage juveniles of the root-knot nematode, Meloidogyne incognita and the sequential anatomical changes in the root concurrent with the development of the nematode were studied with light and scanning electron microscopes. Visible anatomical changes occurred four weeks post-inoculation when the pear-shaped adult female nematodes appeared in the tissues. The infected roots lost their circular outline and increased in thickness as traumatic parenchyma was induced in the root. The stele was disorganised with reduced and deformed vascular elements. Many giant cells developed in the traumatic tissue, adjacent to the adult females. Eight weeks after the inoculation, cavities developed around the adult females by tissue disintegration, and the galls became discernable on the roots. The number and size of thegalls increased in the next three weeks, corresponding to the development of more traumatic tissues and the enlargement of the adult female nematodes. The majority of the nematodes were settled towards the gall periphery, with their posterior oriented outwards for the release of their eggs into soil by the disintegration of the outer root layers. But many were settled deep inside the gall tissue without a channel to release their eggs to soil. The inner cavities enlarged in large proportions, sometimes occupying the major volume of the gall. The conductive tissues of the root were totally disorganised or were nonexistent.     

13种植物源化合物对南方根结线虫的毒力比较

利用离体生物测定法比较了13种植物源化合物对南方根结线虫(Meloidogyne incognita Chitwood)的毒力,并探讨了紫外光照射对这些化合物杀虫活性的影响。结果表明,对苯二酚、DL-薄荷醇、丁子香酚和苦豆碱对南方根结线虫的毒杀活性最强,邻苯二酚等6种化合物的毒杀活性次之,野靛碱、毒扁豆碱和间苯二酚的毒力较低。紫外光照射可明显降低苦豆碱和柠檬酸对南方根结线虫的毒杀活性,而其他11种化合物的毒杀活性则基本不受紫外光照射的影响。     

Influence of rock dust-based soil re-mineralisation on root-knot disease of organic watermelon plants

Deplorable soil fertility characterising resource-poor agrarian communities remain a major constraint for sustainable global food security. Re-mineralisation through application of rock dust encourages maintainable productivity of degraded soils. This study was planned to appraise the effect of rock dust on root-knot disease of Citrullus lanatus caused by Meloidogyne incognita (Mi). The experiment was laid out in Randomised Complete Block Design with three replications. Soil and root populations of the nematode were estimated and galling damage of the crop was diagnosed and censured at 60?days after inoculation. Additional data were collected on vine length, number of leaves, days to 50% flowering and dry matter content. Data collected were subjected to analysis of variance and the means were separated using least significant difference. The treated watermelon plants were low in root-knot disease, significantly reduced Mi nematode populations and flowered far much earlier (p?=?0.05) than the untreated organic watermelon plants.