Interaction of vesicular arbuscular mycorrhiza with root knot nematodes in tomato
ABSTRACT The interaction between the VA mycorrhizal fungus,Glomus fasciculatus and the root-knot nematodes,Meloidogyne incognita andM. javanica, and their effects on the growth and phosphorus nutrition of tomato was studied in a red sandy loam soil of pH 6.0. Inoculation of tomato roots with root-knot nematodes enhanced infection and spore production byG. fasciculatus. Inoculation of tomato plants withG. fasciculatus significantly reduced the number and size of the root-knot galls produced byM. incognita andM. javanica. Inoculation withG. fasciculatus although improved plant growth and its total phosphorus content compared to the uninoculated plants, the difference were not statistically significant.
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ABSTRACT: Pot investigations were designed to study the effect of inoculation time, phosphorus (P) and nemacur on the interaction between V AM fungi, Glomus sp, and root-knot nematode, Meloidogyne incognita, on tomato (Lycopersicon esculentum) growth. The results indicated that addition of P or Glomus sp significantly increased the shoot and The addition of P, nemacur or Glomus sp significantly root dry weight and P content. decreased the gall number in plants infected with M. incognita. Addition of P significantly decreased the mycorrhizal infection percentage, whereas, the addition of nemacur did not affect it. Shoot and root dry weight and P content were significantly increased, whereas, the gall number significantly decreased, when the mycorrhizal The results indicated that tomato growth infection preceded the nematode infection. could be improved by the addition of mycorrhiza, which could also be used as a control for root-knot nematodes.Eibuhuth Scientific Journal. 01/1996; 5:88-107.
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ABSTRACT: Plant defense responses are strongly stimulated by AM fungi in host plants by control over defense gene expression during establishment of a successful functional symbiosis. Peroxidase requiring compounds are laid down on cell wall as barrier against microbial incursion thus can be used as an indicator in plant defense responses. In the present study, activity and expression of peroxidase was monitored in Glomus geosporum (transferred from roots of Cyperus rotundus) colonized and uncolonized two-weeks-old Lycopersicon esculentum Mill seedlings for two pathogens Pseudomonas aeruginosa and Fusarium oxysporum f. sp. lycopersici separately. Mycorrhizal colonized plants without pathogen and that infected with Fusarium oxysporum f. sp. lycopersici showed increased protein and POD activity in comparison to uncolonized plants after 120 hrs. Mycorrhizal colonized plants infected with Pseudomonas aeruginosa showed less protein and POD activity than uncolonized plants; while POD activity in these plants increased from 72hrs to 120hrs. Response observed was more promising against soil borne pathogen than air borne pathogen after both 72hrs and 120hrs. Statistical analysis (Unpaired t-test) showed that an increase in total protein content in mycorrhizal than uncolonized plants and decrease in POD activity in mycorrhizal colonized plants infected with Pseudomonas aeruginosa than uncolonized plants is insignificant. Except these two sets difference in total protein content and POD activity between colonized and uncolonized plants was statistically significant at both 72hrs and 120hrs.This study concludes that Arbuscular Mycorrhizal Fungi can be transferred from one root to another and it modulates plants defense mechanism by increasing the basal level responses (priming) in the host.Biolife 10/2014; 2(4). · 4.18 Impact Factor
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ABSTRACT: Arbuscular mycorrhizal (AM) fungi colonize roots of terrestrial plants and have been hypothesized to reduce susceptibility or to improve the vigor of hosts challenged by root pathogens. Meta-analysis was used to test whether a broad pattern exists in which AM fungi not only enhance plant growth but fundamentally alter plant-pathogen interac- tions. Data were gathered from studies published between 1970 and early 1998. In these studies nonmycorrhizal or mycorrhizal plants were untreated or challenged with root-in- fecting fungal pathogens or nematodes. Effect sizes for AM fungus treatment, pathogen treatment, and their interaction were calculated based on measures of average plant growth, pathogen growth, or AM colonization as reported by authors. AM fungus had a very large positive effect, and pathogens had a very large negative effect on plant growth. However, the interaction of AM fungi and pathogen depended upon the class of pathogen. AM fungi tended to decrease the harmful effects of fungal pathogens but to exacerbate the harmful effects of nematodes. Overall, inoculation with AM fungi had a large negative effect on growth of pathogens, but the outcome for nematodes depended upon mode of feeding. AM fungi harmed sedentary endoparasitic nematodes. AM fungi improved growth of migratory endoparasitic nematodes, but this outcome was not significant in an analysis limited to independent experiments. Reduced growth of pathogens in mycorrhizal plants may indicate increased host resistance. Alternatively, reduced AM colonization in pathogen-treated plants may suggest that root- infecting organisms compete for resources. Some experiments that did not meet criteria for meta-analysis were analyzed with x 2 tests by calculating the proportion of experiments in which authors reported a significant pathogen effect in the absence vs. presence of AM fungi. AM fungi did not alter the effect of fungal pathogens but reduced the proportion of experiments in which nematodes de- pressed plant growth in a test limited to independent observations. Comparison of frequency distributions of effect sizes suggests that the difference in results for nematodes in the meta-analysis and the x 2 tests stems from differences in the AM fungus-plant-pathogen systems examined in each approach rather than a statistical artifact. AM fungi reduced pathogen growth in ;50% of studies included in x2 tests, and this effect was similar for fungal vs. nematode pathogens and sedentary vs. migratory nema- todes. Fungal pathogens reduced AM fungus growth more frequently than did nematodes. Both AM fungi and pathogens suffered reduced growth in 16% of experiments that assessed reciprocal effects. Reciprocal suppression was more common when the pathogen was a fungus, which may indicate that fungal pathogens are more likely than nematodes to compete with AM fungi. Almost all research on the effects of AM fungi on plant-pathogen relations has examined economically important species, in low-phosphorus soil, in greenhouse or microplot culture. Although these analyses revealed general patterns of the effects of AM fungi on plant- pathogen relations, research on a broader range of species over a wider range of environ- mental conditions is required to determine the domain for which these patterns apply.Ecology 11/2001; 82(11):3057-3068. · 5.00 Impact Factor