Indian Phytopath. 50 (2) : 294-296 (1997)

a 70 per cent formulation of thiophanate-methyl(Topsin-M) at 0.14 per cent. The seed were theninoculated with a peat based Rhizobium culture in10 per cent sucrose solution (10 ml per 25 g ofseed). The following were the treatments (i) Con-trol - without fungicide and Rhizobium, (ii) 0.14per cent thiophanate - methyl, (iii) inoculated withRhizobium 24 h before sowing, and (iv) 0.14 percent thiophanate-methyl and inoculated with Rhizo-bium 24 h before sowing. The seeds (inoculated oruninoculated) were sown in pots (10 seeds/pot)and all the treatments were replicated thrice, con-taining three pots per replicate. The data on nodulecount, dry weight of nodules, fresh and dry weightof plants was recorded after 60 days of emergence.Nodules were dried at 60°C while plants were driedat 80°C for 40 h. The leghaemoglobin content ofexcised root nodules was measured spectrophoto-metrically using Drabkin's solution. The total ni-trogen content in the dried plant samples was es-timated using an N - auto analyzer (Anon., 1971).

Effect of thiophanate-methyl and Rhizobium seedtreatment on nodulation and growth of soybean

B. SANTHA LAKSHMI* and J.P. GUPTA

Nuclear Research Laboratory, Indian Agricultural Research Institute, New Delhi J 10 OJ2*ICAR Research Complex for NEH Region, Barapani, Meghalaya 793 103

Keywords : Soybean, nodulation, seed treatment, Rhizobium thiophanate-methyl

Crop management practices, namely, seed treat-ment with chemicals are expected to playa role innodulation and production in legumes. Fungicidaltreatments of soybean. seed is found effective inimproving germination and emergence of the crop(Borelli et al., 1980; Sundaresh and Hiremath,1982). However, results on the effect of seed dress-ing chemicals on symbiosis of Rhizobium are con-troversial (Sundaresh and Hiremath, 1982;Bandyopadhyay et al., 1983). It may be because ofthe incompatibility of certain chemicals with therhizobia, variation in techniques, soil and environ-mental conditions existing at the time of experi-mentation. The present investigations were under-taken to study the effect of thiophanate-methyl onin vitro growth of Rhizobium and to correlate thefungicide seed treatment with root nodulation, ni-trogen fixation and vegetative growth characters ofsoybean plants in symbiotic relationship with Rhizo-bium.

The effect of different concentrations ofthiophanate-methyl on the in vitro growth of Rhizo-bium was studied in yeast extract mannitol brothmedium whereas on nodulation and plant growthwas studied by applying the fungicide to seed.Soybean seed of variety 'Bragg' was treated with

Thiophanate-methyl at 50-500 ug/ml stimulatedRhizobium growth in vitro. Absence of any inhibi-tory effect of thiophanate-methyl on the growth invitro indicates that the fungicide does not have anybactericidal activity.

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Table 1. Effect of thiophanate-methyl on nodulation and nitrogen fixation in soybean plants grown in symbioticrelationship with Rhizobium

Treatments Nodule number" Nodule dry Leghaemoglobin"per plant weight= (mg per plant)

(mg per plant)

Control 10.00 66.36 2.69

Thiophanate methyl 15.00 79.47 2.81

Rhizobium 19.00 116.33 4.14

Thiophanate-methyl+

Rhizobium 20.00 123.29 4.58

CD at 5% 7.23 16.42 0.74

*Average of three replicates.

Table 2. Effect of thiophanate-methyl on germination, plant fresh and dry weight and total nitrogen content ofsoybean plants grown in symbiotic relationship with Rhizobium

Treatment Germination Plant fresh Plant dry Total(%) weight (g) weight (g) nitrogen

content(mg/plant)

60 D 120 D 60 D 120 D 60 D 120 D

Control 72.00 (58.08) 9.10 27.99 1.05 6.32 13.76 103.06

Thiophanate-

methyl 79.00 (62.79) 9.58 29.55 1.97 6.96 15.31 108.73

Rhizobium 86.00 (68.05) 16.16 42.55 3.25 11.'08 38.58 175.38

Thiophanate-

methyl+

Rhizobium 89.00 (70.77) 18.68 51.09 3.79 16.85 51.91 2J8.38

CD at 5% 4.49 1.12 4.16 0.58 0.75 3.59 6.86

Average of three replicates.

It is evident from Table 1 that there was asignificant increase in the number, dry weight ofnodules collected from plants raised from seedtreated with thiophanate-methyl in combinationwith Rhizobium as compared to untreated controland in treatment where seed was treated with fun-gicide alone. Thiophanate-methyl seed treatment

has no advers effect on symbiotic nitrogen fixa-tion in soybean. Moreover, there was significantincrease in the leghaemoglobin content of nodulesin treatment where seed was inoculated with Rhizo-bium in combination with thiophanate-methyl ascompared to control.

The results (Table 2) reveal that the treat-

296 Indian Phytopathology

ment of soybean seed with Rhizobium andthiophanate-methyl prior to sowing has signifi-cant effect on the growth of the plant.

The stimulation in nodulation and growth ofthe plant raised from seeds inoculated with Rhi-zobium as compared to uninoculated ones showsthe efficiency of the strain of Rhizobium in estab-lishing an effective symbiotic relationship.

A significant increase in nodulation, nitrogenfixation and growth characters of plants grownfrom seed treated with fungicide in combinationwith Rhizobium compared to control indicates asynergistic effect. It is possible that the fungicidewhich ultimately reaches the soil may reduce thenumber of soil fungi and their colonisation ofnodules and root. The soil fungi are known tocompete with rhizobial population resulting in theinhibition of growth and nitrogen fixation of hostplant (Wildin and Kennedy, 1983). Secondly,cytokinin like activity of carbendazim (Thomas,1974) can be attributed to increased nodulation asapplication of kinetin had resulted in increasednumber of nodules, fresh/dry weight,leghaemoglobin and total nitrogen content of peaplants (Nandwal et al., 1981). Similar results ofincrease in fresh weight, dry weight and totalnitrogen content of plants was observed byRadhakrishnan and Chatrath (1991) incarbendazim treated groundnut, Saxena et al.(1994) in metalaxyl, triforine, captafol, captan andcarbendazim treated soybean plants. The present

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results on the interaction of thiophanate-methylused as seed treatment on soybean are of practicalsignificance because they show not only theircompatibility but also a synergistic effect. There-fore, the fungicide can be recommended as seedtreatment in combination with Rhizobium on soy-bean.

REFERENCES

Anonymous (1971). Technican Monograph I. TechnicanPrivate Ltd., Tarry Town, New York.

Bandyopadhyay, S., Bhattacharjee, P. andMukherjee, N. (1983). Pesticides 17 : 27-28.

Borelli, A., Carvalho, N.M., Barrelo, M., FarnandesN.G. and Kronka, S.N. (1980). Phytopathologica,6: 123-129.

Nandwal, A.S., Bharti, S., Garg, O.P. and Ram, P.c.(1981). Indian J. Plant Physiol. 24: 47-52.

Radhakrishnan, P. and Chatrath, M.S. (1991). In-dian Phytopath. 44 : 206-213.

Saxena, M., Saxena, D.R. and Vyas, S.c. (1994).Indian J. Mycol. Plant Pathol. 24 : 151-154.

Sundaresh, H.N. and Hiremath, P.C. (1982). Pesti-cides 16 : 22.

Thomas, T.H. (1974). Ann. appl. Bioi. 76: 237-241.

Wildin, K.D. and Kennedy, B.W. (1983). Phytopa-thology 73: 429-434.

Received for publication August 9, 1996.