BIOMANAGEMENT OF NEMATODES BY MYCORRHIZA - A REVIEW

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1 .. Agric. Rev., 26 (4) : BIOMANAGEMENT OF NEMATODES BY MYCORRHIZA - A REVIEW G. Jothi, Rajeswari Sundara Babu and G. Rajendren Department of Nematology. Tamil Nadu Agricultural University. Coimbatore India ABSTRACT Vesicular - Arbuscularmycorrhizal associationswith plantsare attributed to the growth promoting ac;pects. Plant growth is mainly due to nutrient acquisition from soil, water uptake, growth promoting substance and biological control of soil borne pathogens. The nematode control may be through improved vigour, physiological alteration of root exudates or through direct role of mycorrhiza in retarding the development and reproduction of nematode within root tissues. In an integrated management of nematodes the compatibility of VAM with other biocides and nematicides are also discussed. 1. Plant parasitic nematodes have emerged as a seriouslimiting factor, hindering crop productivity. Nematicides of chemical origin are widely used and are effective in containing the nematode menace worldwide. Large scale, indiscriminate use of such chemical nematicides poses environmental hazards, besides being costly and uneconomical. Hence, it is imperative tosearch for safer and economic alternative management strategy against plant parasitic nematodes. On these lines, a tremendous break through in research efforts on use of bid-control agents for management of plant nematodes has been made in the recent past. Though more than 200 microorganisms have been identified as nematode antagonists, very few of them are commercialized and are presently in use for farming community. Besides Vesicular Arbuscular Mycorrhizal (VAM) fungi in vermiculite formulation, Pseudomonas fjuorescens (PFI strain) and Trichoderma viride are available in commercial formulation for use and are highly effective against plant parasitic nematodes. 2. Vesicular Arbuscular Mycorrhizal (VAM) fungi Mycorrhiza, a symbiotic association of fungi and plant roots, is a universal phenomenon throughout the plant kingdom and is beneficial and even indispensable,for healthy growth of the host plants. Endomycorrhizae produced by non-septate fungi are commonly known as "Vesicular ArbuscuJar Mycorrhiza" (VAM) belonging to the Family - Endogonaceae of the class Zygomycetes. VAM fungi have a mutualistic symbiotic relationship with most agricultural crops and enhance plant growth. Interactions between fungal antagonists and nematodes have been known to occur in abricultural soils for many years. Mycorrhizal fungi and plant parasitic nematodes are commonly found inhabiting the rhizosphere and colonizing the roots of their host plants. exert an opposite effect on plant health. VAM supplies nutrients to crop, where as, nematode takes out vital nutrients from the roots resulting in reduced plant growth Habitat: Ona global scale, VAM fungi are virtually ubiquitous, being present in tropical, temperate and arctic regions. Within the different global regions VAM fungi have a broad ecological range. Theyare found in most ecosystems including dense rain forests, open woodlands, scrub, savanna, grasslands, heaths, sand dunes and semi-deserts. VAM populations of cultivated lands are affected by the various soil, plant and environmental factors in natural ecosystems plus various agricultural practices like fertilizer amendments, pesticide applications and crop rotations.

2 250 AGRICULTURAL REVIEWS VAM colonization in the roots includes intra cellular unbranched hyphae, intercellular hyphae, arbuscules and vesicles. In the outer cortical ceils, hyphae spread intracellular and form characteristic hyphal coils. When the hyphae come to inner cortex they become intercellular. Here the hyphae spreads in between cells and do not penetrate host cells. They grow in the same direction of the root. They form 'H' connections and 'Y' joints, as several hyphae pass through intercellular spaces. The intercellular hyphae again become intracellular, penetrate the host cells, and become highly branched forming a structure called arbuscule. It is the site of exchange of nutrients between the host and the fungus. Essentially this transfer involves carbohydrates from plants to fungus and minerals especially phosphate from fungus to plants. Life span of arbuscules is generally 4-5 days. The formation of arbuscules was visible after 17 th day of sowing and the vesicles were seen after 25 days as round structures in the beginning and became oval shaped later on. The hyphae were noticed sticking outside the roots from 31 St day on wards indicating that the hyphae, vesicles and arbuscules occupy the space inside the roots (Jothi and Rajeswari Sundara Babu, 1997b)'vesicles are globose structures, either terminal or intercalary. Size varies from pm. They are formed between the cortical cells or occasionally inside them. They contain oil, sometime as a large single globule as in Glomus and are believed to function as storage organs. In older roots they develop a thick wall and presumably function as resting spore when the roots decay. Fungi belonging to Gigaspora and ScuteJIospora do not form vesicles. AcauJospora forms irregular vesicles. Vesicles act as storage structures and as reproductive organs Function: The mycorrhizae are vital for uptake and accumulation of ions from soil and translocation to hosts because of their high metabolic rate and strategically diffuse distribution in the upper soil layers. In fact, the fungus serves as a highly efficient extension of the host root system. Minerals like N, P, K, Ca, S, Zn, Cu and S absorbed from soils by mycorrhizal fungi are translocated to the host plant (Smith, 1987). Ions such as P, Zn, Cu do not diffuse readily through soil. Because of this poordiffusion, rootsdeplete the immobile soil nutrients from a zone immediately surrounding the root. Mycorrhizal fungal hyphae extend into the soil, penetrating the zone of nutrient depletion and can increase the effectiveness of absorption of immobile elements by as much as 60 times. Along with other mineral nutrients, phosphate enters the plant both directly from the soil and through the fungus. VAM is not only used as biofertilizer, but have also been shown to enhance water transport in plants (Safir et a/., 1971), decrease transplant injury (Menge et a/., 1978), help plants withstand high temperature (Marx and Bryan, 1971), promote establishment of plants in wasteland and in soil polluted with heavy metals (Chandra and Kheri, 1994) and reduce the wlnerability todisease causedby plant parasitic nematodes. (Hasan and Jain, 1992; Jain and Hassan, 1995) Assessment of spore density: A quantity of one ml of water was pipetted out into a nematode counting dish and the number of spores was counted. Based on this the total number of spores in the extract from the seives were calculated by multiplying the number of spores/ml. Thus total number of spores present in the soil can be calculated Assessment of root colonization: VAM fungi inoculated roots are to be examined for colonization and presence of VAM hypae, arbuscules and vesicles after cleaning and staining as suggested by Philips and Hayman (1970). Percent colonization on root segment can be computed as suggested

3 Vol. 26, No.4, by Nicholson (1955). Per cent colonization = Number of root segments colonized Total number of segments examined x VAM Fungi for bio control of plant parasitic nematodes Nematodes and VAM Fungi often occur together in the rhizosphere and roots of plants and therefore frequently encounter each other. This is especially true for VAM and endoparasitic nematodes, since both the organisms co-habit same locality In the root system. Since mycorrhizae and nematodes are active during the same periods, they overlap temporally as well as spatially, Increasing the probability of biological Interactions between them. Early evidence of possible interactions between VAM and nematodes was obtained from surveys In which spores and mycelia of VAM were found to be more abundant In fields free of cyst (Heterodera spp.) or root-knot (Meloidogyne spp.) nematodes than In fields where these nematodeswere present (Schenck andklnloch. 1974). In addition, several studies revealed Increased numbers of spores, arbuscules orvesicles when densities ofcertain root- parasitic nematodes were reduced by nematicide treatments (Bird eta/., 1974; Rich and Bird, 1974; Germani et ai., 1980; Rich and Schenck, 1981). Many workers have demonstrated a reduction in nematode population densities (Sikora and Schonbeck, 1975; Bagyaraj etal., 1979; Cooper and Grandison, 1986; Grandison and Cooper, 1986; Jainand Hasan, 1994; Kassab and Taha, 1990; Sharma and Trivedi, 1994; Sadasivan Nageswari and Rajeswari Sundara Babu, 1998) but cases where nematode population remain unaffected (O'Bannon et ai., 1974; Cason et al.,1983; Hasan and Jain,1987 and 1992) or even increased under the influence of mycorrhlza (Atilano etai., 1981 j Kassab and Taha, 1990) are not uncommon. The majority of interaction studies have showed that VAM decreased populations of endoparasltic nematodes. Fox and Spasoff (1972) were among the first to discover that these two organisms may be mutually Inhibitory and observed decrease of 25-35% In populations of H. so/ancearum when co-inoculated on tobacco with Endogone gigantea. Similarly, Sikora.and Schonbeck (1975) found that significantly fewer (75%) M. incognita and M. hap/a juveniles developed into adults In tobacco, oats and tomatoes pre Inoculated with G. mosseae. Bagyaraj et al. (1979) and Suresh and Bagyaraj (1984) observed that significantly fewer galls of M... incognita or M. javanica developed when tomato roots were colonized with G. fasciculatum. Galls that did develop were smaller In size than in plants without VAM. Thenumber of galls of onsoybean was also reduced by G. macrocarpus, even though rootsystems of VAM plants were larger (Kellam and Schenck, 1980). Sikora (1979) observed thatthe prior presenceofvam fungi, G. mosseae has resulted Inan.lncreaseIn plant resistance against Meloidogyne sp. and suggested that fungal symbiont may have exerted its Influence of the nematode by: 1. Altering root attractiveness 2. RedUcing larval penetration and larval development 3. Increased root growth and function 4. Alteration in root exudation 5. Competition for host photosynthesis, space and nutrition 6. Production of nematostatic compounds 7. Parasitism of eggs

4 252 AGRICULTURAL REVIEWS Table 1. Possible effects of interactions between,plant parasitic nematodes and VA Mycorrhizae (After Hussey and Roncadori, 1982) Type of interaction Neutral Positive Negative Component Fungus Host Nematode Fungus Host Nematode Fungus Host Nematode Effect on component Root infection or sporulation not altered. Mycorrhizal stimulation of vegetative growth or yield not altered, nematode suppression of vegetative growth or yield not offset. Attraction to roots, penetration, development and reproduction not altered. Root infection or sporulation increased. Nematode suppression of vegetative growth or yield offset. Attraction to roots, penetration, development and reproduction suppressed. Root infection or sporulation suppressed. Vegetative growth or yield response to mycorrhizae suppressed. Attraction to roots, penetration, development and reproduction increased. The nature of interaction between nematode and mycorrhizae may be antagonistic, neutral or synergistic (Table 1). In tomato plants, development of second stage juvenile was retarded in well colonized roots. The mycorrhizal tomato plants became resistant to root-knot nematode (Sikora, 1979). In the case of maize inoculated with VAM, the plants recorded higheryield and reduced nematode, (Pratylenchus zeae) population compared to control both in pot culture and field studies (Jothi and Rajeswari Sundara Babu, 1996 and 1997a). G. mosseae was effective in reducing the nematode population especially and R. simi/is infecting banana besides enhancing growth and bunch weight under field condition. There was an increase in number of hands and increased in fingers (Sosamma, et a/., 1998). Significantly fewer juveniles of R. reniformis penetrated tomato roots pre-inoculated with G. fasciculatum, regardless of the number of nematodes inoculated (Sitaramaiah andsikora, 1982). Pre-inoculation of tomato, tobacco. oats, brinjal and carrot with G. mosseae to allow this slow-growing symbiont to become established in the roots before introducing of resulted in fewer juveniles penetrating and developing to maturity in roots of mycorrhizal plants than in roots of nonmycorrhizal controls. (Krishna Prasad, 1991, Jain and Gupta, 1991; Rao et a/., 1998). Earlier introduction of G. fasciculatum by 15 days adversely affected H. cajani root penetration to a greater extent in cowpea than simultaneous inoculations. Over 60 per cent colonization of root system by VAM considerably hampered root invasion (Jain and Sethi, 1988). Umesh et al. (1988) studied the interaction of R. similis with G. fasciculatum in banana and found that mycorrhizal plants contained fewer nematodes, supported lower number of nematodes in soil and had fewer nematode induced root lesions than nonmycorrhizal plants if G. fasciculatum was added simultaneously with or seven days before R. simi/is. Inoculation of G. fasciculatum 15 and 20 days earlier than the nematode had controlled the root - knot nematode population and also increased the biomass production in blackgram. VAM sporulation was affected when the nematodes were inoculated earlier (Sankaranarayanan and Rajeswari Sundara Babu, 1997i. When the VAM fungus, G. fasciculatum was inoculated 15 days earlier than M. javanica on tomato, VAM prevented the multiplication of nematode and offset the deleterious effects of nematode on the plant

5 growth (Rajeswari Sundara Babu et aj., 1993). Prior inoculation of VAM was found to be more effective against R. similis than simultaneous inoculation of VAM and nematode in coconut seedlings (Koshy et al., 1998). Cooper and Grandison (1987) reported that infection and development were less in the plants, (TamariJIo) pre-infected with mycorrhizal fungi and in plants inoculated simultaneously with both the organisms. Glomus mosseae inoculation stimulated growth of Citrus jambhiri seedlings while the nematode decreased growth in pot experiment. When the two organisms were inoculated simultaneously the adverse effects of the nematode was partly neutralized and the fungus limited the development of the nematode (O'Bannon et al, 1979a). ""Glomus intraradices decreased nematode development and egg production more when inoculated 28 days before nematodes than when both organisms were added atthe sametime. When pre-inoculated, VAM reduced totaleggs produced and number of eggs g-l of root but numbers of eggs per female was not affected (Smith et al., 1986a). Cooper and Grandison (1986) also found that the numbers of M. hapla on tomato or clover was decreased appreciably more when VAM fungi were Inoculated 4 weeks before the nematode. Presence of the fungal symbionts substantially reduced orcompletely suppressed adult development. Similarly, G. mosseae reduced the number of adult female R. reniformis by 87 and 63% on two cotton cultivars (Sikora and Sitaramaiah, 1980). Suresh et al. (1985) found that significantly fewer giant cells developed in each gall of. Average cell size was also less than in non-mycorrhizal roots but this result was not statistically significant. Kellam and Schenck (1980) also suggested that VAM decreased giant-cell development. Vol. 26, No.4, Rajeswari Sundara Babu and Sankaranarayanan, 1995) incorporated VAM into nursery beds of tomato allowing the fungus to colonize the root before it was transplanted to main field thereby preventing the penetration and development of the nematode in the VAM infected plants. Thus the VAM was able to offset the adverse effect of nematodes and increase the yield by 91 per cent over control. Rajeswari Sundara Babu et aj. (1996) and Jothi and Rajeswari Sundara Babu (1998) observed that with VAM application contained the ill-effects induced by the nematode, R. reniformis and gave higher yield compared to control. Different doses of G. fasciculatum inoculum viz., 5, 10, 15 and 20 g/kg of soil were tried on tomato and bhendl for control of. All thedoseswereeffective in suppressing nematode population, but 10g/ kg soil was found to be the effective optimum dose for the management of the nematode (Rajeswari Sundara Babu etal., 1998andJothi and Rajeswarl Sundara Babu, 2001 a). 4. Mechanism involved in nematode management through VAM fungi Many mechanisms operate simultaneously during interaction of VAM and plant parasitic nematode on a particular host. Following factors play significant role in reducing nematode population and in enhancing plant growth. 1. VAM fungi may increase root growth, expand the absorptive capacity of the root system for nutrient and water and enhance cellular processes in roots (Hayman, 1982). 2. VAM fungi improve plant nutrition and by doing so may aid the host In compensating for damage caused by parasitic nematodes, thereby increasing plant tolerance to these pathogens. 3. Mycorrhizal root colonization has been shown to affect root exudation (Gerdemann, 1968; Hayman, 1982). These changes could alter chemotactic attraction of nematodes to

6 254 AGRICULTURAL REVIEWS roots or directly retarded nematode development within root tissues. 4. VAM fungi have reduced nematode infection and development on several hosts in spite of larger root systems on mycorrhizal plants (Cooper and Grandison, 1986; Grandison and Cooper, 1986; Smith et a/., 1986a; Sharma, 1992, 1993, 1994). It may be due to unfavourable conditions for nematodes developed on root system due to VAM colonization. Changes in hormones, amino acids and cell permeability in roots have been attributed to mycorrhizal symbiosis (Hayman, 1982). 5. VAM fungi maycause change in the postinfectional nematode - host interaction by altering nematode reproduction and development. 6. Direct competition for space may account for reduced nematode infection on mycorrhizal root system since endoparasitic nematodes occupy similar root tissues as VAM fungi. However, results of several studies do not support this hypothesis. In addition to above given factors, increased tolerance or resistance to nematodes by VAM fungi may be due to competition for host photosynthates, production of nematostatic compound and parasitism of eggs. It may be concluded from observations that VAM fungi do not directly interact with plant parasitic nematodes in spite of their proximity in roottissue. More likely, VAM fungi alter the host either physical~ or physiologically, and thus indirectly affect the host nematode relationship (Smith, 1987). 5. Bio chemical basis for nematode management though VAM fungi Disease incidence was observed to be greater when the level of sugars in host plants was low. It was noted that resistant plants had higher total and reducing sugar content. Compared to uninoculated control plants, those inoculated with mycorrhiza or with mycorrhiza and nematodes simultaneously showed increases in the reducing sugar content lower amounts reducing sugar were recorded from plants with nematode only. Total sugars were highest in plants inoculated with nematodes first followed by mycorrhiza (Suresh and Bagyaraj, 1984; Jothi, 1999). Mycorrhizal plants had high concentrations of phenylalanine and serine which are known to reduce the growth and reproduction of the root-knot nematode (Krishnaprasad, 1991; Parvatha Reddy et a/., 1975). Graham et aj. (1981) reported that aminoacids and reducing sugars were greater from root exudation of mycorrhizal sudan grass grown in phosphorus deficient soils than from non-mycorrhizal plants. Mycorrhizal plants had increased quantities of phosphorus, potassium, calcium, amino acid, phenylalanine and serine than nonmycorrhizal plants (Suresh and Bagyaraj, 1984). Total phenols, total free ami:1o acids and acid phosphates activity were found to be higher in VAM inoculated plants (O'Bannon and Nemec, 1979). Plants inoculated with mycorrhiza contained larger amounts of amino acids specifically phenylalanine, isoleucine, threonine and serine than in uninoculated plants. Plants inoculated with mycorrhiza plus nematodes generally showed an increase in amino acids, especially glutamic acid and aspartic acids compared with plants inoculated with nematodes only. Plants with nematodes only had more tyrosine and phenylalanine and less proline, aspartic acid and histidine than did uninoculated control plants (Nemec and Meredith, 1981). Further, the mycorrhizal plants had higher concentration of phenylalanine and serine which are known to reduce the growth and reproduction of root knot nematodes (Krishnaprasad, 1991; Parvatha Reddy et a/., 1975). The presence of increased quantities of aminoacids like phenylalanine and serine play a role in

7 suppressing the development of in mycorrhizal tomato plants (Suresh and Bagyaraj, 1984). Studies conducted at Pant University indicated that preoccupation of tomato cv. Pusa Ruby roots with G. fascicu/atum coupled with biochemical changes such as increase in lignins and phenols made Pusa Ruby resistant to root-knot nematode, (Singh et a/., 1990). Various biochemical changes occur due to the presence of VAM, like increase in the contents of lignins, total phenolics, protein, total sugars, reducing suga~ and aminoacids like arginin and phenylalanine. Reproduction of nematode or recovery of second stage juveniles from soil supporting mycorrhizal plants were significantly less than soil containing non-mycorrhizal plants. This difference could be justified on the basis of higher counts of females without eggs or less number of eggs per egg-sac in mycorrhizal roots. Lignin and phenols were found significantly more in the mycorrhizal roots. Both the chemicals are known for their role in host resistance (Bhatia et a/., 1972; Krishna and Bagyaraj, 1984). Suresh and Bagyaraj (1984) noted that elevated levels of amino acids and sugars observed in VAM roots are associated with increased plant resistance, each singly or collectively playing a role in suppressing nematode development. Significant difference was observed in total phenol contents in mycorrhizal and non mycorrhizal plants. In nematode infested plants the phenolic content was less. The phenolics are associated with disease resisting compounds responsible for hypersensitivity of plants and increased percentage was observed in resistant cultivar (Suresh and Bagyaraj, 1984; Umesh et aj., 1988; Sharma, 1994). Some phenols are known to form complexes of amino acid, chlorogenic acid complex which is highly toxic to the parasite. The phenolics stimulate IAA oxidase which favours auxin Vol. 26, No.4, decomposition and formation of necrosis in plants resisting sedentary parasites. The phenols in mycorrhizal roots are associated in the reduced reproduction of nematodes, M. javanica reproduction in tomato (Singh et a/. 1990). Suresh et aj. (1985) found that 50% of juveniles exposed to extracts of mycorrhizal tomato roots died after 4 days. Only 32% of juveniles exposed to either clean tap water or extracts of non-mycorrhizal plants died during the same period. Suresh and Bagyaraj (1984) suggested that the presence of nematicidal substances in VAM roots may result from improved plant vigor owing to enhancedp uptakeorincreased concentrations of phenylalanine and/or serine which are known to be nematicidal. Thickening of the cell walls through lignification and production of their polysaccharides in mycorrhizal plants prevented the penetration by the nematodes (Dehne and Schonbeck, 1979; Jothi, 1999). This phenomenon was the result of increased phenol synthesis in the plants brought about by an increase in phenyl propanes which is a lignin precursors. 6. Histopathological changes in plants due to VAM fungi mediated nematode suppression VAM hyphae penetrated the epidermis and invaded the cortex which resulted in the formation of vesicles and arbuscules. In the citrus seedling infested by Tylenchu/us semipenetrans, G. mosseae was found in 50 per cent of the cortical cells. In the cortex, vesicles, were formed along the pericycle. The fungus rapidly invaded the roots and produced vesicles as well as arbuscles before nematode invasion (O'Bannan et a/., 1979a, Sankaranarayanan, 1995). VAM infected roots gave rise to vesicles and arbuscules. The cytoplasmic granules and nuclei were condensed in the centre leaving clear space in the giant cells. The xylem and phloem vessels were pushed

8 256 AGRICULTURAL REVIEWS Table 2. VAM fungi in r:ematode management Host plant Nematode VAM fungus Reference Tomato Tomato Tomato Egg plant Citrus Banana Grape Peach Cotton Soybean Chickpea Pigeonpea Phaseolus vulgaris Cowpea Onion Tobacco Pepper Coffee Beachgrass M incognita Rotylenchu/us reniformis Tylenchu/us semipenetrans Radopholus simi/is M. arenaria Pratylenchus brachyurus H. glycines H. glycines M. javanica H. cajani Pratylenchus penetrans H. cajani M. hapla Pratylenchus coffeae Pratylenchus sp Heterodera spp. G. fascicu/atus G. mosseae G. fascicujatum G. fasciculatum Glomus mosseae G. fascicu/atum G. fasciculatum G.margari~.G.&unkatus G intraradices Gigaspora margarita G. margarita G. margarita G. mosseae G. intraradices Mixed species Entrophospora colombiana G. Margarita G. fascicujatum G. fasciculatum G. fascicujatum G. mosseae G. fasiculatum G. etunicatum G. darum, AcauJospora meljea Mixed species Bagyaraj et al., 1979; Suresh et al., 198.5; Suresh and Bagyaraj, 1984; Rajeswari Sundara Babu et al., 1996; Rajeswari Sundara Babu and Sankaranarayanan, 1998 Rao et a/., 1995; Sikora, 1979; Thomas Cason et al., 1983 Sitaramaiah and Sikora, 1982 Rao et al., 1998 O'Bannon eta/., 1979 Umesh et al., 1988 Atilano et al Strobel et a/., 1982 Smith et al., 1986 Roncadori and Hussay, 1977 Hussey and Roncadori, 1978 Carling et al., 1989 Kellam and Schenck, 1980 Price et al Winkler et ai., 1994 Diederichs, 1987 Siddiqi and Mahmood, 1995 Elliot et al Jain and Sethi, 1987 MacGuicfwin et al., 1985 Krishnaprasad, 1991 Sivaprasad and Sheela, 1998 Vaast et al., 1998 Uttle and Maun, 1996 to one side of the root cortex and the space was occupied by the giant cells. In VAM inoculated plants, the wall thickening in the cortex cells of root prevented the penetration of pathogen. Increased Iignins in mycorrhizal roots were associated with reduced reproduction of M. javanica on tomato (Singh et ai., 1990). 7. Compatibility of VAM with other management practices 7.1. Organic amendments: The organic amendments like sawdust, neem cake, poultry manure effectively reduced the galls, final nematode population and increased the yield (Devi and Das, 1998), The neem cake extract is found to trigger the resistance mechanism in plants (Siddiqi and Alam, 1988). Release of certain fatty acids during the decomposition of botanicals (Sitaramaiah, 1990) and development of antagonistic fungi by application of botanicals (Bhattacharya and Goswami, 1987) were responsible for the reduced nematode infestation. Integrating eco-friendly compounds such as oil cakes with endo-mycorrhiza effectively reduced the nematode population both in soil and roots. Integrating G. mosseae with karanj cake was most effective in

9 Vol. 26. No increasing plant growth parameters and banana yield, while G. mosseae in combination with neem cake was highly effective in reducing the burrowing nematode population and increased the root colonization and the number of chlamydospores in soil (Parvatha Reddy et ai., 1997). When brinjal seedlings were transplanted in castor cake amended soil, the nematode population densities both in soil and root significantly reduced and plant growth parameters were increased. Favourable effect was observed by castor cake amendment on the growth of G. fascicuiatum in the rhizosphere of brinjal plant. The combined effect of colonization of G. fascicuiatum on roots and castor cake amendment in the soil was responsible for the significant reduction of infestation on transplanted brinjal plants (Rao et ai., 1998). Similarly Santhi and Rajeswari Sundara Babu (1998) reported that soil amendment with chopped leaves of Prosopis julif/ora, Catharanthus roseus, Ca/otropis procera and Azadirachta indica in combination with G. fasciculatum gave the highest growth of plants and high degree control. Application of oilcakes as amendments to the soil increased the root colonization of G. mosseae and the additive effects of both oil cakes and mycorrhiza significantly reduced R. similis population. Colonization was increased in citrus and tomato by G. mosseae and G. fascicuiatum in neem cake/caiotropis procera leaf amended soil which resulted in the reduction of TyIenchuIus semipenetrans and population respectively (Pal vatha Reddy et a/., 1995; Rao et al., 1995 and 1996) Bio-control agents: Pasteuria penetrans (Thorne) Sayre and Starr is a potential biocontrol agent of root knot nematodes as it parasitizes females and prevents their reproduction (Sayre, 1980). Integration of P penetrans and G. mosseae for the management of infecting tomato revealed significant increase in plant growth parameters and reduction in root galling, nematode population in roots, egg mass production and fecundity of the nematodes. Combination of these eco-friendly components has also significantly increased the parasitisation of nematode female by P. penetrans. Bacterial bioagents had not affected the root colonization of endomycorrhiza after transplanting (Rao et a/., 1999). PaeciIomyces lilacinus (Thorn) Samson is an effective parasite on eggs of plant parasitic nematodes. The combinat:on effect of P. lilacinus and VAM is one of the best opportunities for integrated nematode management (Widhi Sharma and Trivedi, 1997). Integration of these two components hadan additive effect in reducing the nematode infestation by reducing the root-knot index, final nematode populationdensity and number of eggs per egg mass of on brinjal when both the components were integrated. Mycorrhizal presence had not affected the colonization of P. Ii/acinus on the roots of brinjal or the densities of P. IiIacinus. Similarly, the presence of P. lilacinus did not affect the colonization of G. mosseae indicating that the integration of these componentsdid not affect each other (Rao et al., 1998) Nematicides: Chemicals both fumigants and non-volatile granular nematicides give -;ontrol of nematodes and higher yield. Nematicides and insecticides decrease mycorrhizal infection and spore numbers (Tommerup and Briggs, 1981). Majority of the pesticides, adversely affected the plant mycorrhizal symbiosis (Menge, 1982). In black gram, the management of root-knot nematode was tested with leaf extracts and nematicides. There was a greatest reduction in mycorrhizal spore population and mycorrhizal colonization in nematicidal

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