The potential of Beauveria bassiana and Metarhizium anisopliae in controlling the root-knot nematode Meloidogyne incognita in tomato and cucumber

Meloidogyne incognita is one of the most important plant parasitic nematodes. This study was conducted to determine the nematicidal potential of Beauveria bassiana and Metarhizium anisopliae against M. incognita. B. bassiana and M. anisopliae spore suspensions and bio -nematicide, Purpureocillium lilacinum were applied. B. bassiana and M. anisopliae revealed considerable nematicidal activity against M. incognita in tomato and cucumber. The gall index decreased gradually from 8.0 for control to 3.2, 2.0 and 2.2 for B. bassiana, M. anisopliae and P. lilacinum in tomato, respectively. The highest reduction (%) in gall formation (control index) was calculated as 75.2 % in M. anisopliae treated group for tomato. The gall index was 7.6 for control, but decreased to 3.6, 2.0 and 2.2 for B. bassiana, M. anisopliae and P. lilacinum in cucumber, respectively. The highest control index was 71.7 % for M. anisopliae in cucumber. The number of the second instar juveniles of M. incognita was recorded as 2240 for control. However, this value reduced to 508, 332 and 328 by B. bassiana, M. anisopliae and P. lilacinum in tomato, respectively. The highest control indexes for the second instar juveniles were 85.2 % and 85.3 % for M. anisopliae and P. lilacinum in tomato, respectively. Alike, the highest control indexes were 84.9 % and 85.7 % for the same applications in cucumber, respectively. B. bassiana and M. anisopliae displayed also positive effect on the number of leaves, dry and fresh root weights of tomato. The results showed that B. bassiana and M. anisopliae can be considered as an alternative.     

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.     

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.     

Relationships between Meloidogyne incognita resistance genes in Lycopersicon peruvianum differentiated by heat sensitivity and nematode virulence

Resistance to Meloidogyne incognita (Kofoid and White) Chitwood in clones of Lycopersicon peruvianum (L.) Mill. PI 126443-1MH, 270435-2R2 and 2704353MH, their F₁, a field-produced F₂, and their test-cross (TC₁) populations, was evaluated based on egg masses and eggs produced on root systems. Reactions to M. incognita isolates differing in virulence to gene Mi were determined at 25°C (Mi expressed) and 32°C (Mi not expressed). PI 126443-1MH, 270435-2R2, 270435-3MH, and their F₁ progenies were resistant to Mi-virulent and Mi-avirulent isolates. At 32°C with a Mi-avirulent isolate and at 25°C with a Mi-virulent isolate, four TC₁ generations segregated into resistant: susceptible (RS) ratios close to 31. These results indicated resistance to Mi-(a)virulent M. incognita isolates is conferred by different non-allelic dominant genes in PI 126443-1MH, 270435-2R2 and 270435-3MH. The F₂ progeny of PI 126443-1MH x EPP-1, challenged with Mi-avirulent M. incognita at 32°C and with Mi-virulent M. incognita at both 25°C and 32°C, segregated with a ratio of 31 (RS), indicating expression of a single dominant resistance gene in PI 126443-1MH in each case. In dual screenings on clones of the same individual plants from the TC₁ and F₂ segregating populations, some individual plants were susceptible at 32°C to a Mi-avirulent isolate but resistant to the Mi-virulent isolate, and vice versa, suggesting that different but linked genes confer heat-stable resistance to Mi-avirulent M. incognita and resistance to Mi-virulent M. incognita. We propose the symbol Mi-5 for the gene in PI 126443 clone 1MH and the symbol Mi-6 for the gene in PI 270435 clone 3MH which both confer resistance to Mi-avirulent M. incognita isolates at high temperature. We propose the symbol Mi-7 for the gene in PI 270435 clone 3MH and the symbol Mi-8 for the gene in PI 270435 clone 2R2 that both confer resistance to the Mi-virulent M. incognita isolate 557R at moderate (25°C) temperature. The novel resistance genes are linked and reside in a genomic region in each parental clone that is independent from the Mi locus.     

Interaction between Meloidogyne incognita and Rhizoctonia solani on green beans

The interaction between Meloidogyne incognita (race 2) and Rhizoctonia solani (AG 4) in a root rot disease complex of green beans (Phaseolus vulgaris) was examined in a greenhouse pot experiment. Three week-old seedlings (cv. Contender) were inoculated with the nematode and/or the fungus in different combinations and sequences. Two months after last nematode inoculation, the test was terminated and data were recorded. The synchronized inoculation by both pathogens (N + F) increased the index of Rhizoctonia root rot and the number of root galls; and suppressed plant growth, compared to controls. However, the severity of root rot and suppression of plant growth were greater and more evident when inoculation by the nematode preceded the fungus (N → F) by two weeks. Nematode reproduction (eggs/g root) was adversely affected by the presence of the fungus except by the synchronized inoculation. When inoculation by nematode preceded the fungus, plant growth was severely suppressed and roots were highly damaged and rotted leading to a decrease of root galls and eggs.     

Response of five lettuce cultivars to root-knot nematode, Meloidogyne incognita

The root-knot nematode, Meloidogyne incognito (Kofoid et White) Chitwood is an important pathogen of vegetables. Five commercial cultivars of lettuce (Lactuca sativa L.) were evaluated under greenhouse conditions for resistance to Meloidogyne incognita, Benguet population. Plants were inoculated with 1000 eggs collected from 'Apollo' tomato (Lycopersicon esculentum) roots. The degree of galling and number of egg masses were assessed 4 and 8 weeks after inoculation. Host plant response was classified as immune, highly resistant, resistant, moderately resistant, intermediate, moderately susceptible, and highly susceptible based on the resistance index of Kouamè et at., 1998 [RI = (gall2 + egg2)]. Inoculation of 1000 eggs/plant significantly affected the growth and yield of the five lettuce cultivars 4 and 8 weeks after inoculation. A significant interaction was observed between treatment and cultivar during the two evaluation periods in terms of marketable and non-marketable yield, plant height, root weight, number of galls and number of egg masses. A reduction in growth and yield was observed in the cultivars Ballon, Lollo Rosa and Red Wave. Significant differences were noted in the number of galls and egg masses among the different cultivars tested. The highest average number of galls was obtained from the cultivars Red Wave, Ballon and Lollo Rosa. Cultivar Ballon had the highest average number of recovered nematode while Gilaben had the lowest with 15 and 4 per roots, respectively after 4 weeks inoculation. After 8 weeks, nematode was highest in cultivar Red Wave (615) and lowest in Great Lakes (70). Based on the host response, cultivars Great Lakes and Gilaben were rated highly resistant and resistant, respectively, while Red Wave, Ballon and Lollo Rosa were rated intermediate.     

Comparative analysis of two 14-3-3 homologues and their expression pattern in the root-knot nematode Meloidogyne incognita

14-3-3 proteins are highly conserved ubiquitous proteins found in all eukaryotic organisms. They are involved in various cellular processes including signal transduction, cell-cycle control, apoptosis, stress response and cytoskeleton organisation. We report here the cloning of two genes encoding 14-3-3 isoforms from the plant parasitic root-knot nematode Meloidogyne incognita, together with an analysis of their expression. Both genes were shown to be transcribed in unhatched second stage larvae, infective second stage larvae, adult males and females. The Mi-14-3-3-a gene was shown to be specifically transcribed in the germinal primordium of infective larvae, whereas Mi-14-3-3-b was transcribed in the dorsal oesophageal gland in larvae of this stage. The MI-14-3-3-B protein was identified by mass spectrometry in in vitro-induced stylet secretions from infective larvae. The stability and distribution of MI-14-3-3 proteins in host plant cells was assessed after stable expression of the corresponding genes in tobacco BY2 cells.     

Genetic dissection of resistance to root-knot nematodes Meloidogyne spp. in plum, peach, almond, and apricot from various segregating interspecific Prunus progenies

Sources of resistance in Prunus spp. exhibit different spectra to the root-knot nematodes (RKN) Meloidogyne incognita, Meloidogyne javanica and Meloidogyne floridensis. In this Prunus genus, two dominant genes, Ma with a complete spectrum from the heterozygous Myrobalan plums P.2175 and P.2980 (section Euprunus; subgenus Prunophora) and RMia with a more restricted spectrum from the peaches Nemared and Shalil (subgenus Amygdalus), have been identified. This study characterizes the resistance spectra of interspecific crosses involving (1) previous Myrobalan and peach sources, (2) two Alnem almonds (subgenus Amygdalus) resistant to M. javanica, and (3) the apricot A.3923, representing a species considered RKN-resistant (section Armeniaca; Prunophora). For both latter species, genetic data could be obtained through F1 crosses with genetically characterized Myrobalans that conferred their rooting ability for clonal multiplication of the hybrids and permitted their simultaneous evaluation to the three RKN. Crosses involving either Ma or RMia or both generated the expected resistance spectra. Nemared confirmed the species-specific resistance to M. incognita conferred by RMia. This rootstock, also previously considered resistant to M. javanica, was susceptible to the M. javanica isolate used, what illustrates an isolate-specific resistance to this species. Alnem accessions were shown homozygous resistant to M. javanica. In the progeny P.2980 × A.3923, Ma markers allowed to distinguish resistant individuals carrying that gene from resistant individuals lacking it. Distribution of non-Ma individuals in this cross suggested, in the apricot parent, (1) the absence of a major gene allelic to Ma and (2) the presence of a non RKN specific polygenic resistance.     

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.     

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.     

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.     

植物提取物对萝卜蚜的室内毒力研究

采用浸叶法和Potter喷雾法测定七种植物提取物对萝卜蚜 (Lipaphiserysim)的室内毒力效果。研究结果显示 :巴豆、博落回和醉鱼草提取物对萝卜蚜的致死中浓度LC50 分别为 1 86.94mg/L、2 0 0 .75mg/L和 1 5 7.73mg/L。     

Low-level herbivory by root-knot nematodes (Meloidogyne incognita) modifies root hair morphology and rhizodeposition in host plants (Hordeum vulgare)

Low amounts of root infestation by plant parasitic nematodes are suggested to increase nutrient supply and in turn enhance microbial activity and net mineralization rate in the rhizosphere. These effects are generally related to “leakage” of plant-derived metabolites from damaged roots. Besides leakage, the present study examines other nematode–host interactions such as alterations in root exudation and morphology, which were almost not considered yet. This includes undamaged root parts in order to assess systemic plant response. The root-knot nematode Meloidogyne incognita (Kofoid and White 1919; Chitwood 1949) and barley (Hordeum vulgare L. cv. Europa) was used as model system. Host plants were grown in mini-rhizotrons inoculated with 0, 2,000, 4,000 or 8,000 M. incognita for 4 weeks. Root morphology, rhizodeposition (sugars, carboxylates, amino acids), and rhizosphere microbial communities (PLFAs) were assessed. In treatments with 4,000 nematodes, shoot biomass, total N and P content increased by the end of the experiment. Generally, an enhanced release of plant metabolites (sugars, carboxylates, amino acids) from the apical root zone occurred 1 week after inoculation with 4,000 and 8,000 M. incognita, indicating root leakage. Low levels of root herbivory stimulated root hair elongation in both infected and uninfected roots. These systemic changes in root morphology likely contributed to the increased sugar exudation in uninfected roots in all nematode treatments at 3 weeks after inoculation. Root-knots formed a separate microhabitat within the root-system. They were characterised by decreased rhizodeposition and increased fungal to bacterial ratio in the adhering rhizosphere soil. The present study provides the first evidence that, apart from leakage, nematode root herbivory at background levels induces local and systemic effects on root morphology and exudation, which in turn may affect plant performance.     

Biocontrol of root-knot nematode Meloidogyne incognita by the isolates of Bacillus on tomato

Fifteen isolates of Bacillus, isolated from the root-knot nematode suppressive soils, were used for the biocontrol of Meloidogyne incognita on tomato. Bacillus isolates B1, B4, B5 and B11 caused greater inhibitory effect on hatching of M. incognita than caused by other isolates. In addition, these isolates (B1, B4, B5 and B11) caused greater colonisation of tomato roots and also caused greater increase in the growth of tomato seedling than caused by other isolates. All the isolates of Bacillus were able to increase growth of tomato and caused reduction in galling and nematode multiplication in green house tests. Isolates B1, B4, B5 and B11 caused a greater increase in growth of tomato and higher reduction in galling and nematode multiplication than other isolates in a green house test. These isolates were also tested for hydrogen cyanide (HCN) and indole acetic acid productions. Only one isolate (B13) produced HCN out of 15 tested. On the other hand, isolates B5, B11, B4 and B1 showed greater production of IAA than the other 11 isolates tested. This study suggests that Bacillus isolates B5, B11, B4 and B1 may be used for the biocontrol of M. incognita on tomato.     

Biocontrol of root-knot nematode Meloidogyne incognita by the isolates of Pseudomonas on tomato

Biocontrol of root-knot nematode Meloidogyne incognita was studied on tomato using 15 isolates of fluorescent Pseudomonads isolated from pathogen suppressive soils. Pseudomonas aeruginosa (isolates Pa8, Pa9 and Pa3) caused greater inhibitory effect on hatching of M. incognita than other isolates. In addition, isolates Pa8, Pa9 and Pa3 caused greater colonisation of tomato roots and also caused a greater increase in the growth of tomato seedlings. These isolates also caused a greater increase in growth of tomato and higher reduction in galling and nematode multiplication in a green house test than is caused by other isolates. Isolates Pf1, Pf5, Pf6 and Pa13 were unable to increase growth of tomato and caused less reduction in galling and nematode multiplication compared to other isolates. Only 10 isolates produced siderophores on chromo-azurol sulfonate (CAS) agar medium and isolate Pa12 showed greater production of siderophore followed by Pa11, Pa9, Pf10, Pa3 and Pf5. Similarly, isolates Pa14, Pa12, Pf10, Pa9, Pa8, Pa7 and Pa6 produced greater amount of HCN than the other isolates tested. Isolates Pa8 and Pa9 showed greater production of IAA than the other 13 isolates tested. This study suggests that P. aeruginosa isolates Pa8 and Pa9 may be used for the biocontrol of M. incognita on tomato.     

Peroxiredoxins from the plant parasitic root-knot nematode, Meloidogyne incognita, are required for successful development within the host

Root-knot nematodes, Meloidogyne spp., are sedentary biotrophic parasites which are able to infest > 2000 plant species. After root invasion they settle sedentarily inside the vascular cylinder and maintain a compatible interaction for up to 8 weeks. Plant cells respond to pathogen attacks by producing reactive oxygen species (ROS). These ROS, in particular hydroperoxides, are important regulators of host-parasite interactions and partly govern the success or failure of disease. ROS producing and ROS scavenging enzymes from both the pathogen and the host finely tune the redox state at the host-pathogen interface. We have analysed the gene structure and organization of peroxiredoxins (prx) in Meloidogyne incognita and analysed their role in the establishment of the nematode in its host. Meloidogyne incognita has seven prx genes that can be grouped with other nematode prx into three clades. Clade B prx genes are more actively transcribed in parasitic stages compared with free-living pre-parasitic juveniles. We confirmed in vitro the activity of one of these, Mi-prx2.1, on hydrogen peroxide and butylhydroperoxide. We showed by ultrastructural immunocytochemistry the expression of clade B PRX proteins in the hypodermis and pseudocoelum beneath the tissues directly in contact with the environment, both in free-living and parasitic stages. Finally, knock-down of clade B prx genes led to a significant reduction in the ability of the nematodes to complete their life cycle in the host. The expression of clade B PRX proteins in the tissues in close contact with plant cells during parasitism and the impaired development of nematodes inside the host after clade B prx knock-down suggest an important role for these genes during infection.