Zaki A. Siddiqui

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.

PGPR: Prospective Biocontrol Agents of Plant Pathogens

Plant growth promoting rhizobacteria (PGPR) are indigenous to soil and the plant rhizosphere and play a major role in the biocontrol of plant pathogens. PGPR can profoundly improve seed germination, root development and water utilization by plants. These rhizobacteria can stimulate plant growth directly by producing growth hormones and improving nutrient uptake or indirectly by changing microbial balance in the rhizosphere in favour of beneficial microorganisms. They can suppress a broad spectrum of bacterial, fungal and nematode diseases. PGPR can also provide protection against viral diseases. The use of PGPR has become a common practice in many regions of the world. Although significant control of plant pathogens has been demonstrated by PGPR in laboratory and greenhouse studies, results in the field have been inconsistent. Recent progress in our understanding of their diversity, colonizing ability, mechanisms of action, formulation and application should facilitate their development as reliable biocontrol agents against plant pathogens. Some of these rhizobacteria may also be used in integrated pest management programmes. Greater application of PGPR is possible in agriculture for biocontrol of plant pathogens and biofertilization.

Mycorrhizae : sustainable agriculture and forestry

Preface 1. Mycorrhizae: An overview Z.A. Siddiqui, J. Pichtel 2. The molecular components of nutrient exchange inarbuscular mycorrhizal interactions J.H. Ruairidh, S-Y. Yang, C. Gutjahr, U. Paszkowski 3. Arbuscular mycorrhizal fungi as potential bioprotectants against plant pathogens M.S. Akthar, Z.A. Siddiqui 4. Arbuscular Mycorrhizae and alleviation of soil stresses P. Giasson, A. Karam, A. Jaouich 5. Arbuscular mycorrhizal fungi communities in major intensive North American grain productions M.S. Beauregard, C. Hamel, m. St-Arnaud 6. Arbuscular mycorrhizae: A dyanamic microsymbiont for sustainable agriculture J. Panwar, R.S. Yadav, B.K. Yadav, J.C. Tarafdar 7. Indirect contributions of AM fungi and soil aggregation to plant growth and protection K.A. Nichols 8. Arbuscular mycorrhizae and their role in plant restoration in native ecosystems K. Jayachandran, J. Fisher 9. Effects of interactions of arbuscular mycorrhizal fungi and beneficial saprophytic mycoflora on plant growth and disease protection M.G.B. Saldajeno, W.A. Chandanie, M. Kubota, M. Hyakumachi 10. The mycorrhizosphere effect: A multitrophic interaction complex improves mycorrhizal symbiosis and plant growth R. Duponnois, A. Galiana, Y. Prin 11. Ectomycorrhizae and their importance in forest ecosystems K. Futai, T. Taniguchi, R. Kataoka 12. Ectomycorrhizal associations function to maintain tropical monodominance K.L. McGuire 13. The use of mycorrhizal biotechnology in restoration of disturbed ecosystem A.M. Quoreshi 14. In vitro mycorrhization of micropropagated plants: Studies on Castanea sativa Mill A. Martins 15. Effective and flexible methods for visualizing and quantifying endorhizal fungi S.G.W. Kaminskyj Subject index

Plant Growth Promoting Rhizobacteria Formulations and its Scope in Commercialization for the Management of Pests and Diseases

The export oriented agricultural and horticultural crops depends on the export of residue free produce and has created a great potential and demand for the incorporation of biopesticides in crop protection. To ensure the sustained availability of biocontrol agent’s mass production technique and formulation development protocols has to be standardized to increase the shelf life of the formulation. It facilitates the industries to involve in commercial production of plant growth promoting rhizobacteria (PGPR). PGPR with wide scope for commercialization includes Pseudomonas fluorescens, P. putida, P. aeruginosa, Bacillus subtilis and other Bacillus spp. The potential PGPR isolates are formulated using different organic and inorganic carriers either through solid or liquid fermentation technologies. They are delivered either through seed treatment, bio-priming, seedling dip, soil application, foliar spray, fruit spray, hive insert, sucker treatment and sett treatment. Application of PGPR formulations with strain mixtures perform better than individual strains for the management of pest and diseases of crop plants, in addition to plant growth promotion. Supplementation of chitin in the formulation increases the efficacy of antagonists. More than 33 products of PGPR have been registered for commercial use in greenhouse and field in North America. Though PGPR has a potential scope in commercialization, the threat of certain PGPR (P. aeruginosa, P. cepacia and B. cereus) to infect human beings as opportunistic pathogens has to be clarified before large scale acceptance, registration and adoption of PGPR for pest and disease management.

Effects of fly ash and Helminthosporium oryzae on growth and yield of three cultivars of rice

A 120-day greenhouse experiment was conducted to study the effects of various fly ash concentrations (0%, 20%, 40%, 60%, 80% and 100% vol/vol) with normal field soil and Helminthosporium oryzae on the growth and yield of three cultivars (Pusa Basmati, Pant-4 and Pant-10) of rice, Oryza sativa L. Application of 20% and 40% fly ash with soil caused a significant increase in plant growth and yield of all the three cultivars. Forty percent fly ash caused a higher increase in growth and yield than did 20%. Sixty percent, 80% and 100% fly ash had an adverse effect on growth and yield of all the three cultivars, the maximum being with 100% fly ash. Inoculation of H. oryzae had an adverse effect on the growth and yield, Pant-10 suffered higher damage by H. oryzae than Pusa Basmati and Pant-4. Pant-10 also exhibited higher infected leaf area and greater disease symptoms of H. oryzae than did Pusa Basmati and Pant-4. Plants grown in 100% fly ash suffered higher reductions in growth and yield with H. oryzae than plants grown in pure soil or in 20% or 40% fly ash. In general, plant growth was best in Pusa Basmati followed by Pant-4 and Pant-10, while yield was higher in Pant-4 followed by Pant-10 and Pusa Basmati.

Arbuscular Mycorrhizal Fungi as Potential Bioprotectants Against Plant Pathogens

Arbuscular Mycorhizal (AM) fungi are ubiquitous and form symbiotic relationships with roots of most terrestrial plants. Their associations benefit plant nutrition, growth and survival due to their enhanced exploitation of soil nutrients. These fungi play a key role in nutrient cycling and also protect plants against environmental and cultural stresses. The establishment of AM fungi in the plant root has been shown to reduce the damage caused by soil-borne plant pathogens with the enhancement of resistance in mycorrhizal plants. The effectiveness of AM fungi in biocontrol is dependent on the AM fungus involved, as well as the substrate and host plant. However, protection offered by AM fungi is not effective against all the plant pathogens and is modulated by soil and other environmental conditions. AM fungi generally reduce the severity of plant diseases to various crops suggesting that they may be used as potential tool in disease management. AM fungi modify the quality and abundance of rhizosphere microflora and alter overall rhizosphere microbial activity. These fungi induce changes in the host root exudation pattern following host colonization which alters the microbial equilibrium in the mycorrhizosphere. Given the high cost of inorganic fertilizers and health hazards associated with chemical pesticides, AM fungi may be most suitable for sustainable agriculture and also for increasing the yield of several crops through biocontrol of plant pathogens. This chapter provides an overview of mechanisms of interaction which take place between soil-borne plant pathogens and AM fungi on different plants. The availability of new tools and techniques for the study of microbial interactions in the rhizosphere may provide a greater understanding of biocontrol processes in the near-future.

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.