163 K. SITARAMAIAH. R. S. SINGH & K. P. SINGH 1): Induction of ovoviviparity in Meloidogyne javanica by fatty acids. During a study to understand the mechanism involved in the control of root-knot of okra and tomatoes in soils amended with oil-cakes small quantities of butyric acid were chromatographically detected in the soil-extracts. In further studies to determine the effect of pure butyric and other fatty acids on egg laying and subsequent hatching the authors observed several cases of ovovivi- parity (hatching of eggs within the uterus) in Meloidogyne javanica (Treub) in 10-3 to 10-8 M solutions. Molar solutions of butyric, propionic, formic, and acetic acids and of sodium oleate, varying from 10-1 M to 10-10 M, were prepared in sterilized distilled water. The pH of pure acid solutions varied from 2.4 to 6.1 and that of sodium oleate from 6.1 to 10.0. Plain sterilized distilled water as well as distilled water adjusted to pH values comparable to those obtained for various concen- trations of the fatty acid solutions served as controls. Fully developed females of M. javanica of uniform size extracted from roots of Marglobe tomato plants were rinsed in sterile distilled water and 20 individuals transferred to each of the 40 X 40 mm glass cavity blocks containing 2 ml of solution. There were four replications of each treatment and they were kept at room tempe- rature (28°-30° C). Observations were recorded daily for 42 days. Whenever necessary, fresh solu- tions were added to the cavity blocks. Solutions of butyric, propionic, formic and acetic acids at 10-1 M and of sodium oleate at 10-1 M and 10-2 M completely inhibited egg sac production and egg laying for 42 days. The few eggs which were laid at 10-2 M of butyric and propionic acids and at 10-3 M of sodium oleate failed to hatch when observed for 8 weeks in distilled water. In 10-2 M solutions of formic and acetic acids also, egg laying was very slow as compared to plain water of the same pH. In distilled water egg laying and hatching occurred at all pH values although they were very slow at pH 3.0 but normal or above normal at pH 4 to pH 9. In the lower concentrations of the fatty acids 6 to 8% of the females showed ovoviviparity contrary to the usual method of reproduction in this species, i.e., deposition of eggs in a gelatinous egg sac outside the vulva. An average of 3 to 6 larvae were found inside each female body. In these diluted solutions ( 10.3 M to 10-8 M) of butyric and propionic acids the exudation of eggs from the female body was much higher than in plain water of the same pH values. The rate of hatch was also higher and to such an extent that eggs retained inside the body hatched in The hatched larvae moved vigorously inside the female body but they did not emerge from the female even after 10 days in distilled water. The larvae within the females survived for 8 weeks when the latter were kept in distilled water and for 5-6 weeks when retained in the respective fatty acid solutions. No such phenomenon was noticed in the water controls. Ovoviviparity as a natural phenomenon is known in animal parasitic nematodes and in some of the saprophagous nematodes such as Rhabditis sp. (Hirschmann, 1960). Recently, Walker & Tsui (1968) have reported induction of ovoviviparity in Rhabditis sp. by sulphur dioxide. Although the larviparous (presence of larvae inside the female body) nature of a plant parasitic nematode, Anguina tritici, has been reported by Gupta and Swarup (1968), ovoviviparity has not been reported in plant parasitic nematodes such as M. javanica. There is good evidence from the present study that fatty acids while suppressing egg laying at higher concentrations caused stimulation at high dilutions and ovoviviparity seems to have been caused by the chemical nature of the fatty acids rather than by the pH of the solution since no such phenomenon could be seen in water controls of the same pH. The role of this phenomenon in the ecology of root knot infestations in organically amended soils is not yet understood and is being further studied. The authors express their thanks to Dr. D. J. Raski of the University of California, U.S.A. for confirming the phenomenon and to the United States Department of Agriculture for partly finan- cing this work through a grant under PL 480 (A7-CR-223). GUPTA, PRAMILA & SWARUP, G. (1968). Occurrence of living adult males and second stage larvae inside live adult females of Anguina tritici. Nematologica 14, 157. HIRSCHMANN, H. (1960). Reproduction of nematodes. In: Nematology, pp. 140-146. Eds. J. N. SASSER & W. R. JENKINS. University of North Carolina Press, Chapel Hill, N.C. 1) Departments of Plant Pathology and Bio-Sciences, Agricultural University, Pantnagar, Naini Tal, India. Journal Series Paper No. 137 from Experiment Station.
Nematologica – Brill
Published: Jan 1, 1969
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