Irshad Mahmood

Role of bacteria in the management of plant parasitic nematodes: a review

Bacteria are ubiquitous and destroy nematodes in virtually all soils because of their constant association in the rhizosphere. Bacteria like Pasteuria penetrans destroy nematodes by their parasitic behaviour while the non-parasite rhizobacteria reduce nematode populations by colonizing the rhizosphere of the host plant. A large number of rhizobacteria are known to reduce nematode populations and important genera include Agrobacterium, Alcaligenes, Bacillus, Clostridium, Desulfovibrio, Pseudomonas, Serratia and Streptomyces. Application of some of these bacteria has given very promising results. Practical control systems and formulation and mechanisms of nematode suppression are discussed. Possible uses of bacteria in nematode biocontrol are suggested.

Biological control of plant parasitic nematodes by fungi: a review

Of the microorganisms that parasitize or prey on nematodes or reduce nematode populations by their antagonistic behaviour, fungi hold important positions and some of them have shown great potential as biocontrol agents. Fungi continuously destroy nematodes in virtually all soils because of their constant association with nematodes in the rhizosphere. A large number of fungi are known to trap or prey on nematodes but the most important genera include Paecilomyces, Verticillium, Hirsutella, Nematophthora, Arthrobotrys, Drechmeria, Fusarium and Monacrosporium. Application of some of these fungi has given very interesting results. There is an urgent need to develop some easy technologies for formulation and mass production of fungi at a commercial scale for field application. Some of these fungi may be used in integrated nematode management programmes despite some obstacles.

Control of plant-parasitic nematodes with organic and inorganic amendments in agricultural soil

Abstract The effects of different application rates of oilcakes of neem ( Azadirachta indica ) and castor ( Ricinus communis ), composted manure and urea on plant-parasitic, predatory and free-living nematodes and growth of pigeonpea ( Cajanus cajan ) in field trials were studied. Amendments to soil with these materials resulted in a significant decrease of plant-parasitic nematodes, whereas predatory and free-living nematodes increased. Neem and castor oilcakes were the most effective in reducing plant-parasitic nematodes. However, amendment to soil of composted manure and urea was found to be beneficial in increasing free-living nematodes. As a consequence of suppression of plant-parasitic nematodes, plant growth parameters improved. Increasing doses of the amendments were found to be effective in further reducing plant-parasitic nematodes and increasing predatory and free-living nematodes.

Effects of rhizobacteria and root symbionts on the reproduction of Meloidogyne javanica and growth of chickpea

The effects of rhizobacteria, i.e. Pseudomonas fluorescens, Azotobacter chyroococcum and Azospirillum brasilense, alone and in combination with root symbionts, Rhizobium sp. and Glomus mosseae, on the growth of chickpea, Cicer arietinum, and reproduction of Meloidogyne jaranica were studied. When added alone G. mosseae was better at improving plant growth and reducing galling and nematode reproduction than any other tested organism. Application of P. fluorescens caused an almost similar increase in plant growth to that caused by Rhizobium sp., while use of A. chroococcum was better than A. brasilense in improving growth of nematode --infected plants. Combined use of P. fluorescens with G. mosseae was better at improving plant growth and reducing galling and nematode multiplication than any other combined treatment.

Effects of Pseudomonas fluorescens and fertilizers on the reproduction of Meloidogyne incognita and growth of tomato

A 60-day glasshouse experiment was conducted to assess the influence of two strains of Pseudomonas fluorescens (GRP3 and PRS9), organic manure, and inorganic fertilizers (urea, diammonium phosphate (DAP), muriate of potash and monocalcium phosphate) alone and in combination on the multiplication of Meloidogyne incognita and growth of tomato. Pseudomonas fluorescens GRP3 was better at improving tomato growth and reducing galling and nematode multiplication than PRS9. Organic manuring resulted in less galling and nematode multiplication than occurred with DAP. However, DAP was found better in reducing nematode multiplication and improving plant growth than urea. Muriate of potash was the inorganic fertilizer least effective in reducing galling and nematode multiplication. Pseudomonas fluorescens GRP3 with organic manure was the best combination for the management of M. incognita on tomato but improved management of M. incognita can also be obtained if DAP is used with the GRP3 strain of P. fluorescens.

Role of plant symbionts in nematode management: a review

Mycorrhizal fungi increase soil nutrient and water absorption as plant symbionts. Root nodule bacteria, beside fixing atmospheric nitrogen, have the ability to produce antibiotics and phytoalexins, etc. The use of these two symbionts together appears to be more beneficial for plant growth than their use individually. The results of most studies indicate that mycorrhizal fungi and root-nodule bacteria generally reduce the severity of nematode diseases of various crops. There are possibilities for biological control of nematodes by selecting effective strains of mycorrhizal fungi and root-nodule bacteria, despite some obstacles.

Potentiality of phytochemicals in nematode control: A review

Abstract In the search for alternatives to chemical control of nematodes and with consideration for resource-poor farmers, the potential nematicidal value of a number of plant parts, by-products, and residues, and plant interculture with other crop plants, have been studied. In order to find out their nematicidal properties, the plant materials have been tested by in-vitro, pot and field trials by extracting or incorporating the materials as soil amendments, seed treatments and/or bare-root dip treatments. Root exudates of certain plants have also exhibited nematicidal activity. However, the mode of action of the materials on nematodes is not understood. The beneficial effects of natural phytochemicals reveals a promising area of non-chemical nematode management, but further work on the plant-based nematicides is needed.

BIOLOGICAL CONTROL OF HETERODERA CAJANI AND FUSARIUM UDUM ON PIGEONPEA BY GLOMUS MOSSEAE, TRICHODERMA HARZIANUM, AND VERTICILLIUM CHLAMYDOSPORIUM

Glomus mosseae, Trichoderma harzianum, and Verticillium chlamydosporium were used alone and in combination for the management of wilt disease complex of pigeonpea caused by the nematode Heterodera cajani and the fungus Fusarium udum. Treatment of plants inoculated with pathogens increased plant length, shoot dry weight, number of nodules, and reduced nematode multiplication and wilting index. Simultaneous use of biocontrol agents against pathogens gave better control than their individual application. T. harzianum had an adverse effect on root colonizaiton by G. mosseae. Parasitism of nematodes by V. chlamydosporium was also reduced in the presence of T. harzianum. The highest reduction in nematode multiplication was observed when all three biocontrol agents were used together.

Effect of a plant growth promoting bacterium, an AM fungus and soil types on the morphometrics and reproduction of Meloidogyne javanica on tomato

Abstract The effects of a plant growth promoting bacterium Pseudomonas fluorescens , an AM fungus Glomus mosseae and different soil types (having a mixture of clay:sand into 4:0, 3:1, 2:2, 1:3 and 0:4) were studied on the growth of tomato plants and on the reproduction of Meloidogyne javanica and morphometrics of nematode females. Combination of clay and sand of 3:1 gave best plant growth response followed by combination of 4:0 and 2:2 of clay:sand. Use of G. mosseae or P. fluorescens in different soil types caused significant increase in plant growth except in plants grown in pure sand. Use of G. mosseae or P. fluorescens both in uninoculated and nematode inoculated plants caused almost similar increase in plant growth but the combined use of both organisms caused greater increase in plant growth than when used singly. Plants grown in pure sand had the least galling and nematode reproduction. Moreover, plants grown in a mixture of clay and sand of 1:3 supported highest galling and nematode reproduction, followed by 2:2 and 3:1 clay:sand ratio. Applications of G. mosseae or P. fluorescens caused reduction in galling, nematode reproduction and morphometric parameters of females. Combined use of both organisms caused higher reduction in galling, nematode reproduction and morphometrics than their individual application. All the parameters of morphometrics observed showed reduction in their size except stylet length and stylet knob width. AM colonization was best in plant roots grown in 3:1 clay:sand ratio and least when grown in pure sand.

Some observations on the management of the wilt disease complex of pigeonpea by treatment with a vesicular arbuscular fungus and biocontrol agents for nematodes.

A vesicular arbuscular fungus Gigaspora margarita and two biocontrol agents for nematodes, Paecilomyces lilacinus and Verticillium chlamydosporium, were used for the management of the wilt disease complex of pigeonpea caused by the nematode Heterodera cajani and the fungus Fusarium udum. All the three management agents, alone or in combination, applied to plants inoculated with pathogens increased shoot dry weight, number of nodules, phosphorus content and reduced nematode multiplication and wilting index. Simultaneous use of the biocontrol agents and the vesicular arbuscular fungus gave better control of the disease complex than did their individual applications.