STUDIES ON THE EFFECT OF AMINO ACIDS ON THE ROOT-KNOT NEMATODE MELOIDOGYNE INCOGNITA INFECTING TOMATO

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1 Indian I. Nematol. 5 (197S) : STUDIES ON THE EFFECT OF AMINO ACIDS ON THE ROOT-KNOT NEMATODE MELOIDOGYNE INCOGNITA INFECTING TOMATO BY P. PARVATHA REDDY, H. C. GOVINDU and K. G. H. SETTY Department of Plant Pathology, University of Agricultural Sciences, Bangalore, India Nine amino acids, viz., DL-isomers of methionine,. valine, serine, phenylalanine an~ isoleucine and L-isomers of serine, proline, cysteine HCI and histidine were evaluated for their effect on the root-knot nematode, Me/oidogyne incognita infecting tomato. DL-methionine and DL-phenylalanine inhibited larval hatching from egg masses in vitro tq the maximum extent. In general, DL-amino acids (except DL-valine) had some contact toxicity in vitro to the second-stage larvae whereas L-amino acids (except L-cysteine HCt) had no such effect. DL-isoleucine and L-cysteine HCI exhibited adverse effects on the growth of tomato plants. DL-methionine and DL-valine gave maximum reduction in root galling. Studies on the effect of amino acids against plant parasitic, nematodes have been generaliy limited (Overman & Woltz, 1962; Prasad & Webster, 1967; Setty, 1968 ; Rao & Prasad, 1969; Krishna Prasad, 1969 and Evans & TrudgilI, 1971). Nine amino acids, viz., DL-forms of methionine, valine, serine, phenylalanine and isoleucine, and L forms of serine, proline, cysteine HCl and histidine were evaluated against M. incognita infecting tomato during the period and the results of these investigations.are presented in this paper. In vitro studies MATERIALS AND METHODS Fifty egg masses of more or less uniform size, placed in 5 ml of different concentrations of the amino acids (loo, 200 and 400!Jog/mlprepared in sterile distilled water) in screw-capped test tubes and replicated thrice, were incubated, in dark at 25 C for 5 days, and the number of larvae hatched were estimated using 1 ml counting dishes. Similarly, 1000 freshly hatched larvae placed in 5 ml of the different concentrations in screw-ca.pped test tubes and replicated thrice, were incubated in dark at 25 C for 48 hours. The larval suspension in each case was Adapted from the doctoral thesis submitted to the University of Agricultural SCiences, Bangalore, by the senior author in 1974.

2 EFFECT OF AMINO ACIDS ON M. INCOGNITA 37 then transferred to a wire-gauze sieve containing 2 layers of facial tissue paper kept in a petri dish holding sufficient water to remain in contact with the bottom of the wire gauze. After 24 hours, the larvae that had passed through the tissue paper into the petri dish were counted. Pot culture studies Stock cultures of M. incognita were maintained on tomato (Lycopersicon esculentum var. Pusa Ruby) in the green-house. Five weeks-old tomato seedlings planted in 10 cm pots containing steam-sterilised soil were inoculated with 1000 freshly hatched larvae by pouring the suspension into 4 holes made around the base of the plant. After inoculation, the holes were closed by pressing the soil around the plants and watering. The nine amino acids, dissolved in 10 ml of water at the rate of their molecular weights in mg to supply equal quantity of nitrogen, were applied 3 days after nematode inoculation as soil drench. Shoot height, shoot weight and root weight were recorded 6 weeks after nematode inoculation to study the effect of amino acids on the growth of tomato plants. Gall counts were made at the same time using the method described by Setty (196lS). RESULTS AND DISCUSSION Effect of amino acids on larval hatching in vitro: It may be seen from Table I that all the nine amino acids at all the three concentrations tested inhibited larval hatching to varying degrees as compared to the control. However, DLmethionine and DL-phenylalanine inhibited hatching to the maximum extent. Wallace (1956) had found similar results with Heterodera schachtii where fewer larvae emerged in stronger solutions of amino acids. Evans & Trudgill (1971) also obtained fewer larvae from cysts of H. rostochiensis placed in solutions of DLmethionine in potato root diffusate for one week than cysts placed in root diffusate only, and greater the concentration of methionine fewer the larvae which emerged. Contact toxicity of amino acids to larvae in vitro: In general, blamino acids (except Db-valine) had some contact action on the second-stage larvae, whereas L-amioo acids (except L-cysteine HCI) had no such effect (Table 11). DL-methionine at all the concentrations tested significantly reduced the number of larvae survived, there being no significant differences between the concentrations. In the case of DL-serine, DL-phenylalanine, DL-isoleucine and L-cysteine HCI, there was significant reduction in the number of larvae survived only in the highest concentration tested indicating that there is some contact toxicity in these amino acids also at this concentration. Similar results were obtained by Setty (1968) who showed that DL-methionine could act as a contact nematicide, or at least cause

3 38 P. P. REDDY, H. C. G0VINDU AND K. G. H. SETTY TABLE I Effect of amino acids on /arlla/ hatching of M. incognita in vitro (mean of 3 replicates) tions acids. D. at 5% level Treatment Number of larvae hatched/50 egg masses (in hundreds) in different concentrations S Mean [Lg/ml S [Lg/ml inactivation of the larvae on contact, whereas L-methionine is not nematicidal in vitro. The contact action of DL-serine, DL-phenylalanine, DL-isoleucine and L cysteine HCI to root-knot larvae is being reported for the first time. Effect of amino acids on growth and root galling in tomato plants infected with M. incognita: Tomato plants treated with DL-isoleucine showed yellow strapleaf (YSL) symptoms such as stunting, chlorosis of new growth, green netting of leaves and narrow strap-shaped leaves that hook at the distal ends. A similar disorder has been reported in chrysanthemum by the application of D and L isoleucine, DL-alIoisoleucine and L-Ieucine to the soil (Woltz, 1963) and in tobacco by the application of L-isoleucine (Steinberg, 1952). Production of YSL symptoms in plants may be due to amino acids acting as growth inhibitors causing subnormal plant growth. The plants which received L-cysteine HCI died one week after its

4 EFFECT OF AMINO ACIDS ON M. INCOGNITA 39 TABLE II Contact toxicity of amino acids to larvae ofm. incognita in vitro (mean of 3 replicates) C. D. at 5% level Mean llg/ml Number concentrations 100 llg/ml of116.0 larvae survived/looo after 48 hours in different application, indicating that this amino acid is phytotoxic at the dosage tested. This sulphur-containing amino acid needs to be tested further at lower dosages. The results presented in Table In indicate that the maximum shoot height was observed in tomato plants treated with DL-phenylalanine which was on par with L-proline, L-serine, L-histidine and control. Even though the least shoot height was noticed with DL-isoleucine, it did not differ significantly from DL-serine. The shoot heights were moderate in tomato plants treated with DLmethionine and DL-valine. The maximum shoot weight was observed in plants treated with DLphenylalanine though it did not differ significantly from L-serine, L-proline, DLmethionine, DL-serine and control (Table HI). DL-isoleucine treated plants gave the least shoot weight, differing significantly from aij the other treatments. Shoot weights recorded were moderate in plants treated with DL-valine and L-histidine.

5 40 P. P. REDDY, H. C. GOVINDU AND K. G. H. SETTY TABLE III Effect of amino acids on plant growth and root galling 6 weeks after M. incognita inoculation (mean of 5 replicates) Dose/plant Treatment in All in galls/plant 1.62 Shoot 4.67 incm Root Number g/plant plants height weight of died a week after amino acid application C. D. at 5% level 9.80 Not included for statistical analysis "Each amino acid was applied at the rate of quantity of N per plant its molecular weight in mg so as to supply equal The maximum root weight was noticed in plants treated with DLphenylalanine which was however on par with L-proline, L-serine, DL-serine, L histidine, DL-valine and control (Table Ill). The plants treated with DL-isoleucine showed the least root weight, differing significantly from the other treatments. DL-methionine treated plants showed moderate root weight. In general, DL-amino acids were effective in reducing root-galling, whereas L-amino acids (L-proline being exception) had no such effect (Table Ill). The maximum reduction in root galling was noticed in plants treated with DL-. methionine, this however not differing significantly from DL-valine. L-histidine did not show any effect on root galling and was on par with control. DL-serine, DL-phenylalanine and L-proline gave moderate control of the nematode. Reduction in root galling on tomato through application of certain amino acids has been reported earlier by Overman & Woltz (1962), Setty (1968) and Krishna Prasad (1969). Effect of some amino acids in decreasing the numbers of other plant parasitic nematodes has also been reported by few other investigators (Overman & Woltz, 1962; Prasad & Webster, 1967; Rao & Prasad, 1969 and Evans & Trudgill, 1971). Results of further studies on the action of DL-methionine on

6 EFFECT OF AMINO ACIDS ON M. INCOGNITA 41 M. incognita infecting tomato carried out by the present authors are being reported separately. The authors are grateful to Dr. K. Ramakrishnan, Dean, University of Agricultural Sciences, Bangalore, for his keen interest and encouragement during the course of these investigations. REFERENCES EVANS,K. &. TRUDGILL,D. L. (1971). Effects of amino acids on the reproduction of Heterodera rostochiensis. Nematologica 17 : 4' KRISHNAPRASAD,K. S. (1969). Effect of amino acids and plant growth subtances on tomato and its root-knot nematode, Meloidogyne incognita Chit wood. M. Sc. (Agri.) thesis. Univ. Agri. Sci.. Bangalore. 73 pp. OVERMAN.A. J. &. Woltz. S. S. (1962). Effect of amino acid antimetabolites upon nematodes and tomatoes. Proc. Fla. Sta. Hort. Soc 75: PRASAD, S. K. &. WEBSTER,J. M. (1967). The effect of amino acid antimetabolites on tour nematode species and their host plants. Nematologica 13 : RAO,B. H. K. &. PRASAD,S. K. (1969). The effect of amino acid antimetabolites on Rotylenchulus reniformis Linford &. Oliveira. Indian J. Ent. 31 : SETTY, K. G. H. (1968). Studies on the biology and host-parasite relationships of root-knot nematodes (Meloidogyne spp.) on tomatoes. Ph. D. thesis, Univ. Lond. 293 pp. STEINBERG,R. A. (1952). Frenching symptoms produced in Nicotiana tabacum and N. rustlea with optical Isomers of isoleucine and leucine and witb Bacillus cereus toxin. Plant Physiol. 17 : WALLACE,H. R. (1956). The emergence of larvae from cysts of the beet eelworm, Heterodera schacht ii Schmidt, in aqueous solutions of organic and IDorganicsolutions. Ann. Appl. Bioi. 44 : WOLTZ,S. S. (1963). Growth modifying and antimetabolite effects ofamino acids on Chrysanthemum. Plant Physiol. 38 : Accepted/or publication: 13April, 1976