Interactions of Ralstonia solanacearum and Pectobacterium carotovorum with Meloidogyne incognita on potato

Effect of interactions of Meloidogyne incognita with Ralstonia solanacearum and interaction of M. incognita with Pectobacterium carotovorum were studied in sequential and simultaneous inoculations on potato (Solanum tuberosum). Inoculation of M. incognita caused a lesser reduction in plant growth than caused by R. solanacearum. Inoculation of M. incognita plus R. solanacearum caused a greater reduction in plant growth than the damage caused by either pathogen. Inoculation of M. incognita prior to R. solanacearum resulted in a greater reduction in plant growth than R. solanacearum was inoculated prior to M. incognita. However, inoculation of M. incognita or P. carotovorum caused similar reduction in plant growth. Inoculation of P. carotovorum prior to M. incognita caused lesser reduction in plant growth than simultaneous inoculation of both pathogens. Inoculation of M. incognita caused galling in potato roots but the size of galls was small. Inoculation of P. carotovorum or R. solanacearum with M. incognita had adverse effect on galling and nematode multiplication. Wilting or soft rot index was 3 when R. solanacearum or P. carotovorum was inoculated alone. In other treatments, where R. solanacearum or P. carotovorum was inoculated with M. incognita, wilting or soft rot indices were 5.     

Effect of plant growth promoting rhizobacteria,nematode parasitic fungi and root-nodule bacterium on root-knot nematodes Meloidogyne javanica and growth of chickpea

Effects of plant growth promoting rhizobacteria (Pseudomonas putida MTCC No. 3604 and Pseudomonas alcaligenes MTCC No. 493) and parasitic fungi (Pochonia chlamydosporia KIA and Paecilomyces lilacinus KIA) were studied, alone and together with Rhizobium sp. (charcoal commercial culture) on the growth of chickpea and multiplication of Meloidogyne javanica. Individually, P. putida 3604, P. alcaligenes 493 and Rhizobium caused a significant increase in the growth of chickpea in both nematode inoculated and uninoculated plants. Inoculation of Rhizobium with a parasitic fungus or with plant growth promoting rhizobaterium caused a greater increase in the growth of plants inoculated with nematodes than caused by either of them singly. Individually, P. lilacinus KIA caused a greater increase in the growth of nematode inoculated plants than caused by P. putida 3604 or P. alcaligenes 493. P. lilacinus KIA caused a greater reduction in galling and nematode multiplication followed by P. chlamydosporia KIA, P. putida 3604 and P. alcaligenes 493. Combined use of P. lilacinus KIA with Rhizobium was better in reducing galling and nematode multiplication than any other treatment. P. putida 3604 caused a greater colonization of root than P. alcaligenes 493 while P. lilacinus KIA was isolated from more nematodes than P. chlamydosporia KIA.     

Biocontrol of <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> by <Emphasis Type="Italic">Rhizobium</Emphasis> and plant growth-promoting rhizobacteria on lentil

Biocontrol of the root-knot nematode Meloidogyne javanica was studied on lentil using plant growth-promoting rhizobacteria (PGPR) namely Pseudomonas putida, P. alcaligenes, Paenibacillus polymyxa and Bacillus pumilus and root nodule bacterium Rhizobium sp. Pseudomonas putida caused greater inhibitory effect on the hatching and penetration of M. javanica followed by P. alcaligenes, P. polymyxa and B. pumilus. Inoculation of any PGPR species alone or together with Rhizobium increased plant growth both in M. javanica-inoculated and -uninoculated plants. Inoculation of Rhizobum caused greater increase in plant growth than caused by any species of plant growth-promoting rhizobacteria in nematode-inoculated plants. Among PGPR, P. putida caused greater increase in plant growth and higher reduction in galling and nematode multiplication followed by P. alcaligenes, P. polymyxa and B. pumilus. Combined use of Rhizobium with any species of PGPR caused higher reduction in galling and nematode multiplication than their individual inoculation. Use of Rhizobium plus P. putida caused maximum reduction in galling and nematode multiplication followed by Rhizobium plus P. alcaligens. Pseudomonas putida caused greater root colonization and siderophore production followed by P. alcaligenes, P. polymyxa and B. pumilus. Analysis of the protein bands of these four species by SDS-PAGE revealed that P. putida had a different protein band profile compared to the protein profiles of P. alcaligenes, P. polymyxa and B. pumilus. However, the protein profiles of P. acaligenes, P. polymyxa and B. pumilus were similar.     

Interaction between Pseudomonas fluorescens and Meloidogyne incognita on tomato plant as influenced by the different levels of phosphorus

A pot experiment was conducted on tomato (Solanum lycopersicum cv. Pusa Ruby) to assess the effect of different phosphorus (P) levels (0, 125, 250 and 500 mg/pot) and the plant growth promoting rhizobacterium, Pseudomonas fluorescens, on the growth of tomato and on the reproduction of Meloidogyne incognita. Maximum growth of tomato occurred at P rates of 125 mg/kg soil, irrespective of whether plants were uninoculated or inoculated with P. fluorescens or M. incognita or inoculated with both the agents. Nematodes per gram of roots, egg masses per root, eggs per egg mass and galls per root significantly increased by increasing levels of P. P. fluorescens performed better than other treatments and different P levels in improving tomato growth and reducing galling and multiplication of M. incognita.     

Studies on interaction of Meloidogyne incognita (Kofoid and White) Chitwood and Fusarium solani (Mart.) Sacc forming a disease complex in lentil (Lens culinaris Medik.)

Abstract

An experiment was conducted to study the effects of interaction between Meloidogyne incognita and Fusarium solani on plant length, fresh and dry weights, number of pods, chlorophyll, carotenoid, nitrogen and phosphorus contents and nitrate reductase activity in lentil plants. The results reveal a maximum damage occurring in all the plant growth, biochemical and nutrient parameters, in plants inoculated with M. incognita 10 days prior to F. solani (Mi?→?Fs). This was followed by simultaneous (Mi?+?Fs) inoculations, fungus inoculation 10 days prior to nematode (Fs?→?Mi), M. incognita alone and F. solani alone treatments. Nematode reproduction factor and root galling were highest in individual inoculation of M. incognita, while root rotting percentage was highest when nematode was inoculated 10 days prior to fungus followed by simultaneous inoculation with both nematode and fungus.     

Der Besatz von Beta-Rüubensaatgut rait Wurzelbranderregern und der Einfluß von Umweltfaktoren auf das Auftreten des samenbüurtigen Wurzelbrandes

The root knot nematode Meloidogyne incognita was controlled more effectively when P. lilacinus and G. mosseae were applied together in a pot experiment than either was applied alone. Inoculation of tomato plant with G. mosseae did not markedly increase the growth of plant infected with M. incognita. Inoculation of plant with G. mosseae and P. lilacinus together or alone resulted in a similar shoot and plant height. The highest root development was achieved when mycorrhizal plant were inoculated with P. lilacinus to combat root knot nematode. Inoculation of tomato plant with P. lilacinus suppressed galls/root system and eggs/egg masses, compared to seedling inoculated with M. incognita alone. The mycorrhizal colonization was not affected by inoculation of P. lilacinus.     

Pseudomonas fluorescens mediated suppression of Meloidogyne incognita infection of cowpea and tomato

Plant growth-promoting rhizobacterium, Pseudomonas fluorescens strain BICC602 suppresses root-knot nematode (Meloidogyne incognita) by enhancing defence mechanism leading to induced systemic resistance in cowpea (Vigna unguiculata) cv. L.Walp. and tomato (Solanum lycopersicum) cv. Pusa Ruby. In cowpea, the soil treatment proved more effective than foliar spray on root galling and eggs in roots. However, which factors are necessary in the induction of resistance response in plants against nematodes by BICC602 is not yet known. Salicylic acid (SA) production by some bacteria acts as endogenous signal for the activation of certain plant defence responses. In a split-root trial with tomato as a host plant and M. incognita as challenging parasite, BICC602 induces systemic resistance in tomato plants. Based on the results, it is assumed that P. fluorescens-induced resistance against M. incognita in cowpea and tomato is made either through SA-dependent or SA-independent transduction pathway.     

Effects of dual inoculation of mycorrhiza and endophytic,rhizospheric or parasitic bacteria on the root-knot nematode disease of tomato

The effects of mycorrhisation and inoculation with soil bacteria on the disease caused by Meloidogyne incognita on tomato were studied in pots under greenhouse conditions. Efficacy in promoting plant growth and reducing disease severity and final nematode densities were evaluated for two arbuscular mycorrhizal fungi (AMF; Funneliformis mosseae and Rhizophagus irregularis), three soil bacteria with different living strategies (the endophyte Bacillus megaterium, a rhizospheric Pseudomonas putida and the hyperparasite of nematodes Pasteuria penetrans) and combinations of the fungi and bacteria. In M. incognita-infested plants, F. mosseae increased tomato growth more than R. irregularis, and plants inoculated with B. megaterium presented higher shoot fresh weight than with P. putida or P. penetrans, but dual inoculation did not improve tomato growth more than single inoculations. Disease severity and final nematode densities were reduced by F. mosseae compared to non-mycorrhizal plants. B. megaterium and P. penetrans reduced both the root galling and the final nematode densities compared to treatments without bacteria. P. penetrans reduced final nematode densities more than B. megaterium or P. putida. Dual inoculation of AMF and P. penetrans showed the highest efficacy in reducing the final nematode densities in tomato.     

Effect of Meloidogyne incognita,M. hapla,and M. javanica on the Severity of Fusarium Wilt of Chrysanthemum

Rooted cuttings of Chrysanthemum morifolium ''Yellow Delaware'' (Fusarium-susceptible) and ''White Iceberg'' (Fusarium-resistant) were greenhouse-grown in: (i) non-infested soil; (ii) soil infested with Fusarium oxysporum alone; (iii) soil infested with Meloidogyne incognita, M. javanica or M. hapla; and (iv) each nematode separately plus the fungus. All nematode species infected roots of both cultivars and caused characteristic root-knot symptoms but did not appreciably affect growth meassured by plant weight. Nematodes did not break Fusarium wilt resistance of ''White Iceberg''; however, wilt symptoms appeared earlier and were more severe among ''Yellow Delaware'' plants inoculated with Meloidogyne javanica and F. oxysporum than with similar combinations of the fungus and M. incognita or M. hapla or with the fungus alone.     

Interaction of Population Levels of Fusarium oxysporum f. sp. vasinfectum and Meloidogyne incognita on Cotton

In autoclaved greenhouse soil without Fusarium oxysporum f. sp. vasinfectum, Meloidogyne incognita did not cause leaf or vascular discoloration of 59-day-old cotton plants. Plants had root galls with as few as 50 Meloidogyne larvae per plant. Root galling was directly proportional to the initial nematode population level. Fusarium wilt symptoms occurred without nematodes with 77,000 fungus propagules or more per gram of soil. As few as 50 Meloidogyne larvae accompanying 650 fungus propagules caused Fusarium wilt. With few exceptions, leaf symptoms appeared sooner as numbers of either or both organisms increased. In soils infested with both organisms, the extent of fungal invasion and colonization was well correlated with the extent of nematode galling and other indications of the Fusarium wilt syndrome.     

Biological control of root-rot disease complex of chickpea by AM fungi

Abstract

Six species AM fungi, namely Glomus fasciculatum, G. constrictum, G. intraradices sp., Gigaspora margarita, Acaulospora sp. and Sclerocystis sp., were used for the biological control of root-rot disease complex of chickpea caused by Meloidogyne incognita and Macrophomina phaseolina. Application of these AM fungi increase plant growth, pod number, chlorophyll, nitrogen, phosphorus and potassium contents in diseased plants and also reduced nematode multiplication and root-rot index. G. fasciculatum caused greater increase in plant growth, pod number, chlorophyll, nitrogen, phosphorus and potassium contents of pathogen inoculated plants followed by G. intaradices, G. constrictum, Sclerocystis, G. margarita and Acaulospora sp. Percent root colonization caused by G. fasciculatum was high followed by G. intaradices, G. constrictum, Sclerocystis sp., G. margarita and Acaulospora sp. Glomus fasciculatum also caused higher reduction in root-rot index, galling and nematodes multiplication while Acaulospora sp. produced the least.     

Management of Root-Knot Nematode,Meloidogyne Incognita,by integration of Paecilomyces Lilacinus with organic materials in Chilli

Studies were made to determine the efficacy of Paecilomyces lilacinus in management of root-knot nematode (Meloidogyne incognita) in soil amended with various organic matters. The soil amendments with organic additives except gram and rice husks significantly reduced the multiplication of M. incognita and the root galling caused by root-knot nematode which consequently increased the plant growth. The greatest improvement in plant growth and reduced reproduction factor and root galling was recorded in soil amendment with leaves of Calotropis procera while the least was in kail saw dust. The best protection against M. incognita was observed on the integration of organic additives with P. lilacinus, which resulted increased plant growth and reduced population build-up of nematodes and root gallings. The leaves of C. procera with P. lilacinus were most effective than all other organic materials used among the different integrated approaches. The organic amendments also increased the parasitism of P. lilacinus on M. incognita.     

Induction of defense-related proteins in tomato roots treated with Pseudomonas fluorescens Pf1 and Fusarium oxysporum f. sp. lycopersici

Pseudomonas fluorescens isolate Pf1 was found to protect tomato plants from wilt disease caused by Fusarium oxysporum f. sp. lycopersici. Induction of defense proteins and chemicals by P. fluorescens isolate Pf1 against challenge inoculation with F. oxysporum f. sp. lycopersici in tomato was studied. Phenolics were found to accumulate in bacterized tomato root tissues challenged with F. oxysporum f. sp. lycopersici at one day after pathogen challenge. The accumulation of phenolics reached maximum at the 5^th day after pathogen challenge. In pathogen-inoculated plants, the accumulation started at the 2^nd day and drastically decreased 4 days after the pathogen inoculation. Activities of phenylalanine ammonia-lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) increased in bacterized tomato root tissues challenged with the pathogen at one day after pathogen challenge and activities of PAL and PO reached maximum at the 4^th day while activity of PPO reached maximum at the 5^th day after challenge inoculation. Isoform analysis revealed that a unique PPO1 isoform was induced and PO1 and PPO2 isoforms were expressed at higher levels in bacterized tomato root tissues challenge inoculated with the pathogen. Similarly, -1,3 glucanase, chitinase and thaumatin-like proteins (TLP) were induced to accumulate at higher levels at 3-5 days of challenge inoculation in bacterized plants. Western blot analysis showed that chitinase isoform Chi2 with a molecular weight of 46 kDa was newly induced due to P. fluorescens isolate Pf1 treatment challenged with the pathogen. TLP isoform with molecular weight of 33 kDa was induced not only in P. fluorescens isolate Pf1-treated root tissues challenged with the pathogen but also in roots treated with P. fluorescens isolate Pf1 alone and roots inoculated with the pathogen. These results suggest that induction of defense enzymes involved in phenylpropanoid pathway and accumulation of phenolics and PR-proteins might have contributed to restriction of invasion of F. oxysporum f. sp. lycopersici in tomato roots.     

Effect of Fusarium oxysporum f. sp. glycines and Sclerotium rolfsii on the pathogenicity of Meloidogyne incognita race 2 to soybean

Screenhouse studies were conducted to investigate the effects of Fusarium oxysporum f. sp. glycines and Sclerotium rolfsii on the pathogenicity of Meloidogyne incognita race 2 on soybean and the influence of the nematode on wilt incidence and growth of soybean. The interaction of each fungus with the nematode resulted in reduced shoot and root growth. Final nematode population was also reduced with concomitant inoculation of nematode and fungus or inoculation of fungus before nematode. While M. incognita suppressed wilt incidence in two nematode-susceptible cultivars of soybean (TGX 1485-2D and TGX 1440-IE), it had limited effect on wilt incidence in the nematode resistant cultivar of soybean (TGX 1448-2E). When F. oxysporumwas inoculated with the nematode, the mean number of nematodes that penetrated soybean roots decreased by 75% in TGX 1448-2E, 68% in TGX 1485-1D and 65% in TGX 1440-1E. Similarly when the soil was treated with S. rolfsii, the number decreased by 78% in TGX 1448-2E, 77% in TGX 1485-1D and 68% in TGX 1440-1E. The nematode did not develop beyond second-stage juvenile in TGX-1448-2E.     

The effect of root-knot nematode on vascular resistance to Fusarium oxysporum f. sp. vasinfectum in the stems of cotton plants

The effect of root-knot nematode (Meloidogyne incognita) on external wilt symptoms and on the cotton plant's vascular response to stem-inoculation with Fusarium oxysporum f. sp. vasinfectum was investigated. Wilt symptoms were more severe in all plants inoculated with both organisms than with the fungus alone but relative wilt resistance of the cultivars was maintained. Greater symptom severity was associated with greater fungal proliferation in the stele and this was related to the ability of the nematode to reduce the efficiency of vascular occlusion. The nematode had no effect on the accumulation of infection-induced terpenoid aldehyde compounds.     

The Influence of Trichoderma harzianum on the Root-knot Fusarium Wilt Complex in Cotton

Wilt-susceptible cultivar ''Rowden'' cotton was inoculated wilh Meloidogyne incognita (N), Trichoderma harzianum (T), and Fusarium oxysporum f. sp. vasinfectum (F) alone and in all combinations in various time sequences. Plants inoculated with F alone or in combination with T did not develop wilt, Simultaneous inoculation of 7-day-old seedlings with all three organisms (NTF) produced earliest wilt. However, plants receiving nematodes at 7 days and Fusarium and Trichoderma at 2 or 4 weeks later (N-T-F, N-TF) developed the greatest wilt between 49-84 days after initial nematode inoculation. During the same period, Fusarium added 4 weeks after initial nematode inoculation (N-F) and Fusarium added 4 weeks after initial simultaneous inoculation of nematode and Trichoderma (NT-F) produced the least wilt. The addition of Fusarium inhibited nematode reproduction. Simultaneous inoculation with nematodes and Trichoderma (NT-) resulted in the greatest root gall development, whereas nematodes alone produced the greatest number of larvae. In comparison with noninoculated controls (CK), treatments involving all three organisms inhibited plant growth, plants inoculated with the nematode alone (N-) or with nematodes and Trichoderma (NT-) simultaneously had greatest root weight. Any treatment involving the nematode resulted in fewer bolls per plant and greater necrosis on roots than the noninoculated checks.     

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.     

Association of Criconemella xenoplax and Fusarium spp. with Root Necrosis and Growth of Peach

Criconemella xenoplax, Fusarium solani, and F. oxysporum caused necrosis of Nemaguard peach feeder roots in greenhouse tests. Root necrosis was more extensive in the presence of either fungus than wtih C. xenoplax alone. Shoot growth and plant height were less for plants inoculated with F. oxysporum or F. solani than for plants inoculated with the fungi plus C. xenoplax. Neither synergistic nor additive effects on root necrosis or plant growth occurred between C. xenoplax and the fungal pathogens.     

Effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the phytoremediation potential of Catharanthus roseus (L.) in Cu and Pb-contaminated soils

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the growth and phytoremediation potential of Catharanthus roseus in Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. The P. fluorescens RB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly, B. subtilis 189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation of P. fluorescens RB4, B. subtilis 189, and P. fluorescens RB4 + B. subtilis 189 resulted in higher accumulation of Cu and Pb in shoots of the C. roseus grown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability of C. roseus was improved by inoculation of P. fluorescens RB4 and B. subtilis 189.     

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.