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Anand Agricultural University, Anand
Anand Agricultural University (AAU) was established in 2004 at Anand with the support of the Government of Gujarat, Act No.(Guj 5 of 2004) dated April 29, 2004. Caved out of the erstwhile Gujarat Agricultural University (GAU), the dream institution of Sardar Vallabhbhai Patel and Dr. K. M. Munshi, the AAU was set up to provide support to the farming community in three facets namely education, research and extension activities in Agriculture, Horticulture Engineering, product Processing and Home Science. At present there seven Colleges, seventeen Research Centers and six Extension Education Institute working in nine districts of Gujarat namely Ahmedabad, Anand, Dahod, Kheda, Panchmahal, Vadodara, Mahisagar, Botad and Chhotaudepur
AAU's activities have expanded to span newer commodity sectors such as soil health card, bio-diesel, medicinal plants apart from the mandatory ones like rice, maize, tobacco, vegetable crops, fruit crops, forage crops, animal breeding, nutrition and dairy products etc. the core of AAU's operating philosophy however, continues to create the partnership between the rural people and committed academic as the basic for sustainable rural development. In pursuing its various programmes AAU's overall mission is to promote sustainable growth and economic independence in rural society. AAU aims to do this through education, research and extension education. Thus, AAU works towards the empowerment of the farmers.
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ThesisItem Open Access STUDIES ON ROOT-KNOT NEMATODE, Meloidogyne javanica (Pathotype 2) ON GROUNDNUT cv. GG 20(AAU, Anand, 1998) Patel, Somabhai Keshavlal; Patel, D. J.The experiments on root-knot nematode, MeloidoQ/ne javanica (Pathotype 2), attacking groundnut cv. GG 20 were conducted with respect to i. pathogenicity of root-knot nematode, M. javanicapt.2 on groundnut cv. GG 20 to determine threshold level in terms of plant growth character and nematode reproduction; ii. effect of M. javanica pt 2 on uptake of N, P, K, Ca, Mg and S nutrients by plant; iii. effect of M. javanica pt. 2 infection on meteorological parameters viz., leaf temperature, diffusion resistance and transpiration rate in groundnut; iv. histopathological studies to know host-parasite relationship in groundnut; v. biochemical changes induced by M. javanica pt 2 infection in groundnut; vi, effect of interaction between M. javanica pt 2 and Aspergillus niger on groundnut; vii. effect of interaction between M. javanica pt.2 and Rhizobium sp. on groundnut and viii. determination of avoidable yield losses due to M. javanica pt2 on groundnut in pots as well as field, during kharif, 1996 through kharif 1997. The saHent findings are as under : i) An inoculiun level of 100 M. javanica pt2 J2 and above/plant proved detrimental to the growth and development of groundnut cv. GG 20. The nematode population significantly increased progressively with an increase in nematode inoculum levels from 10 to 10,000 M. javanica pt.2 J2 /plant. Nematode reproduction rate was maximum of 4801.0 times in the level of 10 J2 /plant while it was minimum of 10.7 times in the highest level of 10,000 J2 /plant. ii) Uptake of various nutrients viz., N, P, K, Ca, Mg and S by groundnut cv. GG 20 was significantly reduced with an increase in inoculum levels from 10 to 10,000 J2 /plant Control plants had significantly more uptake of all the nutrients over other treatments of various nutrients, uptake of N, K and Mg was much more reduced by M javanica pt.2 infection than P, Ca and S nutrients. iii) Infection of M. javanica pt 2 induced significant increase in leaf temperature and diffusion resistance with proportionately decrease in transpiration rate with an increase in nematode inoculum levels in groundnut cv. GG 20. iv) Histopathological and cytological studies revealed that after root invasion, nematodes penetrated epidermal cells and migrated both inter and intra cellularly reaching to cortex region and anchored adjacent to the vascular tissues resulting in rupturing and degeneration of epidermic cells and cortical layers of roots. All different nematode stages were found inside infected root tissues feeding on vascular portion, while no abnormalities of root tissues were observed in healthy roots. Infected tissues exhibited hypertrophy. uneven thickening of cell walls and granular protoplasm with enlarged nuclei and nucleoli. Multinucleate condition of giant cells was also observed. v) Studies on biochemical changes induced by M javanica pt.2 indicated that roots inoculated with 10, 100, 1,000 and 10,000 J2 /plant had progressively more peroxidase and polyphenol oxidase activities and total phenol contents. These activities increased progressively with an increase in nematode inoculum levels over uninoculated control roots. Chlorophyll a, b and total chlorophyll contents also decreased due to increase in M.javanica pt2 infection levels. vi) Study on interaction between M javanica pl2 and Aspergillus niger indicated neutral type of effects for plant growth diaracters. When both the pathogens inoculated simultaneously, there was more depressing effects on plant growth and development than that of fungus inoculation alone. Thus, nematode inoculation @ 1,000 and 2,000 J2 /plant played a vital role in predisposing host roots to the attack and aggravation of A. niger fungus on groundnut cv. GG 20. vii) Study conducted on interaction between M javanica pt 2 and Rhizobhun sp. revealed that the presence of M. javanica pt 2 significantly recfaiced number of nodules/plant over Rhizobiiun alone and control treatments. This clearly indicated that M. javanica pt.2 infection adversely affected N fixation by Rhizobium bacteria on groundnut cv. GG 20. viii) Application of Phenamiphos @ 2 kg/ha and Dazomet @ 400 kg/ha significantly increeised plant height, fresh and dry shoot weights over control in pots. Phenamiphos was more effective than Dazomet. However, fresh and dry root weights were more in control (untreated) plants due to heavy root galling and egg sac formation on roots. RKI was minimum in Phenamiphos followed by Dazomet treatment. Nematode reproduction rate was maximum of 37.1 times in control (untreated) plants while it was minimum of 2.2 times and 2.7 times in Phenamiprfios and Dazomet treatments, respectively. Thus, it is concluded that nematicides Phenamiphos and Dazomet proved very effective in management of M. javanica pt.2. ix) Under field condition, soil application of Phenamiphos @ 2 kg/ha under the crop row at the time of seeding effectively increased dry pod and fodder yields by 42.6 and 25.7% with reduction in RKI and final nematode population by 60.7 and 63.7% respectively, incurring 30.0 and 20.4% yield loss with monetary loss of Rs. 5025=00 and Rs. 1375=00 in dry pod and fodder yields of groundnut cv. GG 20 respectively over control.ThesisItem Open Access STUNT NEMATODE, Tylenchorhynchus vulgaris, UPADHYAY et al., 1972, ON MAIZE(AAU, Anand, 1997) Singh, Uma Shankar; PATEL, D. J.The experiments on stunt nematode, Tylenchorhynchus vulgaris, affecting maize were conducted to study i, pathogenicity of stunt nematode, T. vulgaris, on maize cv. Farm Sameri to determine threshold level in terms of plant growth characters, nematode reproduction and uptake of N, P, K, Ca, Mg and S nutrients by plant; ii, biochemical changes induced by nematode infection in crop; iii, histopathological studies to know host-parasite relationship in crop; iv, effect of meteorological parameters viz. leaf temperature, diffusion resistance and transpiration rate due to stunt nematode, T.vulgaris, infection in maize cv. Farm Sameri; v, effect of stunt nematode, T.vulgaris, infection on seed germination, seedling emergence, plant growth development and nematode reproduction on maize cv. Farm Sameri in pots; vi, estimation of avoidable yield losses due to stunt nematode, T.vulgaris, in maize in pots as well as field; vii, interaction between stunt nematode, T. vulgaris and stalk rot fungus, Fusarium moniliforme, on maize cv. Farm Sameri and viii, evaluation of different maize varieties / hybrids for source (s) of resistance against stunt nematode, T. vulgaris, during 1994-95 and 1995-96. The salient findings are as under : i. An inoculum level of 1000 nematodes and above / plant proved detrimental to the growth and development of maize cv. Farm Sameri (FS). The nematode population / plant significantly increased progressively with an increase in nematode inoculum from 10 to 10,000 nematodes / plant. Nematode reproduction rate was maximum (61.7 times) in the level of 10 nematodes / plant and minimum (7.2 times) in 10,000 nematodes / plant. Uptake of various nutrients viz. N, P, K, Ca, Mg and S by maize cv. FS significantly reduced with an increase in inoculum levels from 100 to 10,000 nematodes / plant. Control plants had significantly more uptake of all the nutrients over other treatments. ii. Biochemical changes induced by stunt nematode feeding on maize roots indicated that roots inoculated with 10, 100, 1,000, 2,000, 5,000 and 10,000 nematodes / plant had progressively more peroxidase and total phenol contents, whereas polyphenol oxidase proportionately decreased with an increase in nematode inoculum levels over control (uninoculated) roots, Histopathological studies revealed that after root invasion, nematodes penetrated epidermal root cells. Due to migratory ectoparasitic feeding habit, the only apparent damage to roots due to nematode feeding was disarrangement of organisation of root cap cells. A collapse of some epidermal cells was also noticed. Roots attacked by nematodes generally appeared darken than roots from sterilized soil. No nematodes were observed inside root tissues. Observations recorded on meteorological parameters revealed that infection of T.vulgaris caused significant increase in leaf temperature and diffusion resistance with proportionately decrease in transpiration rate with an increase in nematode inoculum levels in maize cv. FS, Study on effect of stunt nematodes on seed germination, overall plant growth development, leaf chlorophyll contents and nematode reproduction on maize cv. FS indicated that there was no significant difference in seed germination at 15th day of seeding but sprouting of seeds was delayed in nematode infested soils over uninfested steam sterilized soils even after 7 days of seeding.ThesisItem Open Access INVESTIGATIONS ON ROOT-KNOT NEMATODES (Meloidogyne incognita AND M. javanica pt. 1) IN BANANA (Musa paradisiaca L.)(AAU, Anand, 1998) Patel, Ashokkumar D.; Patel, D. J.studies pertaining to the effect of root-knot nematodes (RKN), Meloidogyne incognita and M. javanica pt. 1 in banana cv. Basrai with respect to i, pathogenicity of Meloidogyne incognita and M. javanica pt. 1 on banana to determine economic threshold levels; ii, effect of M. incognita and M. javanica pt.l infection on nutrients uptake by banana; iii, biochemical changes broughtout by M. incognita and M. javanica pt.l infection in banana, iv, histopathological and cytological changes due to M. incognita and M. javanica pt.l infection in banana, v, effect on meteorological parameters viz. leaf temperature, diffusion resistance and transpiration rate due to M. incognita and M. javanica pt.l infection in banana, vi, effect of aqueous leaf extracts of various botanicals on egg hatching and larval penetration of M. incognita and M. javanica pt.l in banana and vii, effect of different oil cakes extracts on egg hatching and larval penetration of M. incognita and M. javanica pt.1 in banana were carried out during 1994-95 and 1995-96. The salient findings are : i. An inoculum levels of 10,000 J/plant of M. incognita and 50,000 J2/plant of M. javanica pt.1 proved detrimental to the growth and development of banana cv. Basrai. The root and soil nematode populations were increased but nematode reproduction rate decreased with an increase in the inoculum levels of both the nematode species. ii. The uptake of various nutrients viz. N, P, K, Ca, Mg and S by banana cv. Basrai roots decreased with an increase in inoculum levels of M. incognita and M. javanica pt.1. However, significant reduction in uptake of nutrients was recorded at 10,000 & 50,000 and above J2/plant of M. incognita and M. javanica pt.1 respectively. iii. There was an increase in peroxidase and polyphenol oxidase activities and total phenol contents with an increase in inoculum levels of M. incognita and M. javanica pt.1 the maximum being in the level of 1,00,000 J2/plant. iv. Histopathological and cytological studies indicated that the second stage larvae of both M. incognita and M. javanica pt.1 after invasion migrated inter and intra cellularly, finally anchored near vascular tissues. Hypertrophy and hyperplasia and giant cell formation were common for both the species of Meloidogyne. The root galls produced by M. incognita were larger in size than that of M. javanica pt.l. All nematode stages were noticed in banana roots. V. There was an increase in leaf temperature and transpiration rate with decrease in diffusion resistance with an increase in inoculum levels of M. incognita and M.javanica pt.l. vi, Among various botanicals tested for their effects on egg hatching and subsequent larval penetration of M. incognita and M. javanica pt.l in banana roots, aqueous leaf extracts of argemone & lantana and NSKS treatment proved most effective in almost complete inhibition of nematode egg hatching at 48, 96 and 144 hrs indicating ovicidal effect. Ipomea and castor leaf extracts were least effective. There was no nematode larval penetration from eggmasses previously treated with argemone & lantana leaf extracts and NSKS treatment. Significantly more nematode larval penetration was recorded from eggmasses treated with castor and ipomea leaf extracts, indicating ovistatic effect. vii. Of various methods of oil cakes extraction, n-methanol extraction showed significantly more inhibitory effect on egg hatching and siibsequent larval penetration of M. incognita and M. javanica pt.1 in banana roots over hexane and distilled water extraction methods. Among various cakes, mustard cake proved most effective in reducing egg hatching and larval penetration of both the species of Meloidogyne over castor and neem cakes.ThesisItem Open Access LESION NEMATODE, Pratylenchus zeae GRAHAM, 1951 ON MAIZE(AAU, Anand, 1999) Patel, Nautam B.; Patel, D. J.Studies on lesion nematode, Pratylenchus zeae, affecting maize cv. Farm Sameri were carried out with respect to i, pathogenicity of P. zeae on maize cv. Farm Sameri to determine threshold level in terms of plant growth characters, nematode reproduction and uptake of N, P, K, Ca, Mg and S nutrients by plant; ii, biochemical changes induced by nematode infection in crop; iii, histopathological studies to know host-parasite relationship in crop; iv, effect of nematode infection on seed germination, seedling emergence, plant growth development and nematode reproduction in-crop in pots; v, estimation of avoidable yield losses due to nematode infection in crop in pots and field conditions; vi, interaction between nematode and stalk rot fungus in crop and vii, evaluation of different maize hybrids/varieties against P. zeae during 1996-97 and 1997- 98. The salient findings are as under : i, An inoculum level of 1,000 and above nematodes/plant significantly decreased plant height, fresh shoot and root weights. Soil, root and total nematode population build up/plant progressively increased with an increase in nematode inoculum levels from 0 to 10,000 nematodes/plant. Nematode reproduction rate decreased with an increase in inoculum levels. It was maximum of 66.00 times in the level of 10 nematodes/plant and minimum of 5.50 times in the level of 10,000 nematodes/plant. Uptake of various nutrients viz., nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) significantly reduced from the level of 500 to 10,000 nematodes/plant except P which significantly reduced from the levels of 1,000 to 10,000 nematodes/plant. Control (uninoculated) plants had significantly more uptake of all the nutrients over other treatments. ii. Biochemical changes induced by nem.atode infection in maize revealed that peroxidase and total phenol contents progressively increased, whereas polyphenol oxidase subsequently decreased with an increase in nematode inoculum levels from 10 to 10,000 nematodes/plant over control (uninoculated) plant roots. iii, Histopathological and cytological studies to know host-parasite relationship indicated that after invasion, nematode penetrated epidermal cells and finally reached the cortex region. Because of migratory in feeding habit, cavities were formed in the cortex region and female laid eggs within cavities. During nematode feeding, they also secreted some enzymes which might have produced brown lesions on the roots. iv, Study on effect of P. zeae on seed germination, over all plant growth development, leaf chlorophyll contents and nematode reproduction on maize cv. Farm Sameri indicated non-significant differences for seed germination/emergence ' among nematode infection and control (uninoculated/sterilized soil). Nematode infested soil significantly reduced maize plant height, fresh shoot & root weights and leaf chlorophyll a, b & total chlorophyll contents by 51.02, 47.01, 71.11, 22.32, 41.18 and 28.31 respectively over control-steam sterilized soils. Nematode population also increased from 14,080 to 1,36,5 U/8 kg soil giving reproduction rate of 9.7 times in 90 days. V, Experiment on estimation of avoidable yield losses in maize cv. Farm Sameri due to lesion nematode indicated that - a. inoculation of 3,000 nematodes/plant significantly decreased plant height, stem girth, fresh shoot and root weights by 46.43, 29.55, 67.28 and 56.01 % giving cent percent grain yield loss respectively over control-no nematode inoculation. Nematode population increased from 3,000 to 45,299/4 kg soil giving reproduction rate of 15.10 times. b. application of phenamiphos @ 2 kg/ha in two equal splits at the time of seeding and 30 DAS significantly increased plant height, fresh shoot & root weights, cob length, grain, stover and straw yields to the extent of 17.95, 39.19, 46.60, 25.45, 32.16, 33.90 and 24.69 % respectively with significant reduction in RLI, final soil and root nematode population by 30.96, 49.60 and 48.72 % respectively over control. vi. Study on interaction between P. zeae (N) and F. moniliforme (F) on maize cv. Farm Sameri revealed that plant height, fresh shoot and root weights were significantly less in N-F treatment followed by N+F, N alone treatments. N alone treatment produced maximum number of soil, root and total nematode population with reproduction rate of 10.27 times followed by N-F and N+F treatments having 7.57 and 6.29 times reproduction rates respectively. The N-F treatment recorded maximum plant mortality of 42.86 % due to stalk rot disease over other treatments and disease appeared one week earlier than N+F treatment. Similarly, N+F and F-N treatments also recorded 35.71 and 14.29 % plant mortality respectively. The treatment of F alone had no plant mortality possibly due to weak parasitism of fungus on the host. vii. Evaluation of different maize hybrids/varieties for locating source(s) of resistance against lesion nematode revealed that all 13 hybrids/varieties viz., IC 9001, 9002, 9004, 9005, 9010 & 9011; composite 74; Gujarat Maize 1 & 2; Cargill 633, 501 & 520 A and Farm Sameri recorded susceptible reaction to P. zeae.ThesisItem Open Access INVESTIGATIONS ON ROOT-KNOT NEMATODES (Meloidogyne spp.) AND WILT FUNGUS (Fus rium oxysporum f. sp. ciceri) ON CHICKPEA(AAU, Anand, 1997) Patel, Bhagabhai Ambaram; Patel, D. J.Studies pertaining to the effects of root-knot nematodes (RKN), Meloidogyne spp. on chickpea cv. Dahod Yellow with respect to i. pathogenicity of Meloidogyne incognita and M. Javanica pathotype (pt.) 1 & 2 on chickpea to determine threshold levels; ii. biochemical changes brought out by Meloidogyne spp. infection in chickpea, iii. effect of M. incognita and M. Javanica pt. 1 & 2 on nutrients uptake by chickpea, iv. histopathological and cytological changes due to infection of Meloidogyne spp. in chickpea to study host - . parasite relationship, v. interaction between M. incognita and M. Javanica pt. 1 & 2 and wilt inducing fungus, Fusarium oxysporum f. sp. ciceri on chickpea, vi. interaction between M. incognita and M. Javanica pt. 1 and 2 on chickpea, vii. effect of seed treatment with chemical coupled with soil application of granular nematicides in management of root-knot nematodes in chickpea field, viii. effect of seed treatment with chemical coupled with soil application of different organic amendments in management of root-knot nematodes in chickpea field, and ix. effect of root-knot nematodes-wilt complex on chickpea yield in field were carried out during 1995-96 and 1996-97. The salient findings are : i. In a study on pathogenicity of M. incognita and M. javanica pathotypes 1 & 2, an inoculum level of 100 M, incognita juveniles and 500 juveniles of M. Javanica pathotype 1 & 2/plant and above was detrimental to the growth and development of chickpea cv. Dahod Yellow, indicating more pathogenic effect of M, incognita. Roots, soil and total populations of the three Meloidogyne popns./plant increased progressively with an increase in inoculum levels from 10 to 10,000 J2/plant. Nematode reproduction rate decreased with an increase in inoculum levels and it was maximum in the level of 10 J2/plant and minimum in 10,000 Jz/plant for all three RKN populations, ii. Studies on biochemical changes broughtout by Meloidogyne spp. on chickpea cv. Dahod Yellow indicated increase in activities of peroxidase and polyphenol oxidase enzymes, total phenol contents of roots and reduction in chlorophyll a, b & total chlorophyll content of leaves due to inoculation of 1,000 and 10,000 J2/plant of either M. incognita or M. Javanica pathotype 1 & 2. The increase was more in 10,000 J2/plant than that of 1,000 J2/plant. Among three RKN populations, M. incognita had maximum effect on enzymatic activities and phenol contents as well as chlorophyll a, b & total chlorophyll content followed by M. Javanica pathotype 2 and pathotype 1. iii. M. incognita and M. Javanica pathotypos 1 & 2 reduced uptake of N, P, K, Ca, Mg and S in chickpea cv. Dahod Yellow significantly at 1,000 and 10,000 J2/plant. However, the reduction was more with higher inoculum level. The reduction in nutrients uptake was maximum by infection of M. incognita while it was more or less similar by both the pathotypes of M. Javanica. iv. Experiments on interaction of Fusarium oxysporum f. sp'. ciceri with M. incognita as well as with M. Javanica pathotypes 1 &. 2 individually on chickpea cv. Dahod Yellow revealed that all the organisms either individually or in combinations reduced plant height and fresh shoot and root weights significantly but the reduction was more by root-knot nematodes as compared to fungus. Among combined inoculations of nematodes and fungus, simultaneous inoculation of both the pathogens had maximum suppressive effect on growth of chickpea plants as compared to preceding or succeeding inoculations of fungus and nematodes at 2 weeks interval. Among three RKN populations, M. incognita had more suppressive effect than both pathotypes of M. Javanica. Root galling and nematode multiplication on chickpea were maximum when nematodes were inoculated alone but it was reduced in the presence of fungus. The fungus alone was able to produce wilt disease but the incubation period for disease development and severity of the disease increased when root-knot nematodes were present with fungus. Maximum wilting of plants was observed when the fungus and either of the nematodes species were inoculated simultaneously followed by fungus inoculation 2 weeks after nematode inoculation and nematode inoculation 2 weeks after fungus inoculation. Among three populations of root-knot nematodes, M, incognita was more aggressive in inciting wilt disease followed by M. Javanica pt. 2 and pt. 1. V. Study on interaction of M. incognita with pathotypes 1 & 2 of M. javanica indicated that all three populations either individually or in combinations reduced plant height and fresh shoot & root weights of chickpea but the suppressive effect was more by M. incognita. Based on the no. of mature females developed, it was found that M. incognita was most dominant followed by M, Javanica pt, 2 and pt. 1. vi. An experiment to study efficacy of chickpea seed treatment with chemical coupled with soil application of different granular nematicides in varying doses for management of root-knot nematodes, M. incognita and M. Javanica pathotype 1 in chickpea field indicated seed treatment with carbosulfan @ 0.75% (w/w) alone to be effective in improving final plant stand, plant height, grain &. fodder yields and reducing root-knot disease. Among granular nematicides, sebufos was most effective followed by phenamiphos and carbofuran. Of the nematicidal doses tested, higher dose of 2.0 kg was moat effective followed by lower doses of 1.5 and 1.0 kg/ha. vii„ In an experiment on efficacy of seed treatment with chemical and soil application of different organic amendments for management of root-knot nematodes, M. incognita and M. Javanica pathotype 1 in chickpea under field conditions, seed treatment with carbosulfan @ 0.75 % (w/w) alone reduced root-knot disease and improved final plant stand, increased plant height and grain &. fodder yields. All organic amendments viz. pressmud (3.0 t/ha), poultry manure (3,0 t/ha), neem cake (1.0 t/ha) and mustard cake (1.0 t/ha) proved effective but neem cake was most effective followed by mustard cake while poultry manure was found least effective. Soil application of organic amendments was more effective than seed treatment with carbosulfan. viii.An experiment on management of root-knot nematodes {M, incognita and M. Javanica pathotype 1) - wilt complex in chickpea field using seed treatment of carbosulfan @ 0.75 % (w/w) + carbendazim ® 0,1% (w/w) coupled with soil application of carbofuran @ 2.0 kg/ha + carbendazim granules ® 0.5 kg/ha revealed that there was significant reduction in wilt and root-knot disease and thereby improved seeding emergence and plant growth which ultimately .increased grain and fodder yields. Chickpea cv. Dahod Yellow (wilt susceptible) produced more grain yield than Avrodhi (wilt resistant) whereas Avrodhi had higher fodder production than Dahod Yellow. Chickpea cv. Avrodhi resistant to wilt disease became susceptible to disease in the presence of root-knot nematodes.ThesisItem Open Access STUDIES ON RENIFORM NEMATODE, Rotylenchulus reniformis LINFORD AND OLIVEIRA, 1940, ON CASTOR(AAU, Anand, 1995) Patel, Dasharathbhai Bhagabhai; PATEL, D. J.Studies pertaining to the effects of reniform nematode, R. reniformis. on castor cvs. GAUCH 1 and GCH 4 with respect to i, interaction between R. reniformis and Fusarium oxyspoum f. ricini on castor cv. GAUCH 1 and GCH 4; ii, interaction between R. reniformis and Macrophomina phaseolina on castor cv. GCH 4; iii, assessment of quantitative and qualitative losses due to R. reniformis in castor cv. GCH 4 and iv, determination of susceptible crop stage for R. reniformis infectin on castor were carried out during 1992-93 and 1993-94. The salient findings are : A. i, Study on interaction between R. reniformis (N) and F. oxysporum f. ricini (Fo) on castor cv. GAUCH 1 indicated that plant height was significantly reduced in N - Fo treatment, whereas fresh shoot and root weight of plant were minimum in N + Fo treatment followed by N - Fo and Fo - N treatments. The treatment of N alone produced maximum (469 times) reproduction rate as compared to other treatments. ii, Wilt disease appeared three weeks earlier in different combinations of N and Fo than Fo alone. Among the combinations, N inoculated 4 wksprior to Fo inoculation (N - Fo) proved highly detrimental inducing 66.6 % wilt disease in castor cv. GAUCH 1. B. i, Experiment on interaction between R. reniformis and F. oxysporum f. ricini on castor cv. GCH 4 indicated that plant height, fresh shoot and root weights were significantly less in N alone treatment followed by N + Fo and N - Fo treatments. This treatment also produced maximum nematodes population build up/plant and had higher reproduction rate of 523 times as well over other treatments. ii, Castor wilt disease incited by F. oxvsporum f. ricini was not' observed in the treatment of Fo alone, because of resistance against wilt disease in castor cv. GCH 4. However, wilt disease appeared in the plants inoculated with nematodes 4 wks prior to fungus inoculated (N - Fo) and inoculation of both the pathogens together (N + Fo). This indicated that nematode played a vital role to break down the wilt resistance nature of castor cv. GCH 4. C. i, Study on interaction between R. reniformis and M. phaseolina on castor cv. GCH 4 indicated that the plant height and fresh root weight were significantly reduced in the treatment of N+Mp followed by N-Mp, Mp-N, N alone and Mp alone treatments. With regards to fresh shoot weight, significantly less fresh shoot weight was observed in the treatment of N alone followed by N+Mp and N-Mp treatments. The treatment of N alone produced maximum nematode population build up/plant and had higher reproduction rate of 528 times over other treatments. ii, The root-rot disease appeared earlier in different combinations of N and Mp over Mp alone. The maximum plant mortality of 41.7 % was recorded in the treatment of plants inoculated with nematode and fungus concomitantly (N + Mp) over other treatments. D. i. Experiment on assessment of quantitative and qualitative losses indicated significant reduction in plant height, fresh shoot and root weights due to R. reniformis inoculation over control treatment. ii, Seed yield and test weight of castor seed reduced significantly at 1000 and 500 inoculum levels/kg soil over control. Nematode inoculated plants (both levels) had 20.08 % reduced yields over uninoculated plants. Nematode inoculation also affected the oil content of castor seeds. There were 3.14 and 6.60 % reduction in oil contents of castor seeds due to nematodes infection at 500 and 1000 J4/kg soil respectively. iii,Chlorophyll content was also significantly reduced due to nematode inoculations. iv, Observations recorded on meteorological parameters revealed that nematodes infected plants had the 35.2 and 57.0 % reduction in diffusion resistance and 52.3 and 42.0 % increased in transpiration rate at the inoculum level of 500 and 1000 J4/kg soil respectively over control. E. Determination of susceptible crop stage of castor cv. GCH 4 to R. reniformis infection indicated that maximum nematode females penetration was recorded on 150 days old plants followed by 135 days old plants. Penetration of nematode females in castor roots progressively increased with an increase in plant age, indicating positive correlation between nematode infection and plant age.