Spiegel, Y., Department of Nematology, ARO, The Volcani Center, P. O. B. 6, Bet Dagan, Israel
Chet, I., Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot, Israel
Cohn, E., Department of Nematology, ARO, The Volcani Center, P. O. B. 6, Bet Dagan, Israel

Bean and tomato seedlings, treated with different amounts of ammonia and chitin, and inoculated with the root-knot nematode, Meloidogyne javanica, were reared in two consecutive 35-day growth of shoot and root and the condition of the root systems of both plant species and degree of infection by M. javanica were decreased by increasing amounts of ammonia. Chitin caused a relatively small reduction in gall formation but almost no changes in fresh shoot weights. The effect of chitin on plant growth and nematode attack were also compared in irradiated and non-irradiated soil. In the first cycle galling index of the chitin treated plant was similar to that of untreated plants maintained in the irradiated soil conditions, while in the non-irradiated soil, chitin treatment reduced galling index. In the second cycle, chitin treatment reduced galling index in both irradiated and non-irradiated soils, especially in the latter, where galling index greatly decreased compared with the non-treated plants. Differences in fresh shoot weight between nematode-infected and nematode-free plants amended with chitin were greater under non-irradiated than irradiated conditions, especially in the second cycle. In non-irradiated soil, a higher level of chitinolytic microorganisms, particularly actinomycetes, was found in the second cycle. © 1987 Martinus Nijhoff Publishers.