MORPHOLOGY AND ENZYME HISTOCHEMISTRY IN GERMPLASM PEA ROOTS ATTACKED BY HETERODERA GOETTINGIANA

Abstract

The host-parasite relationships between Heterodera goettingiana Liebschser and pea accessions (Pisum sativum L.) were examined through secretions of ingested rootlets. Nematode feeding stimulated formation of syncytia in both susceptible and resistant host tissues 4 days after inoculation. The size of syncytia increased with time after inoculation. At 10 days in all the susceptible accessions the multinucleate syncytium was characterized by dense, granular cytoplasm. In all of the resistant accessions the mechanism of resistance involved degeneration of the syncytial cytoplasm and the nematode failed to develop the maturity. Localization for peroxidase and esterase activity was carried out on 4 day-inoculated root tissue. Light and ultraviolet light microscope observations of tissues revealed that both enzyme activities were increased in the susceptible and the resistant accessions following nematode invasion, but with higher levels in the resistant tissues. The results are discussed in relation to the possible role of peroxidases and esterases in the response of pea root to nematode infection.