Effect of different inoculum densities of root-knot nematode, Meloidogyne javanica on progress of disease and production of secondary compounds in pot marigold, Calendula officinalis

Marigold, Calendula officinalis, due to having various medicinal compounds is of high importance in pharmaceutical industry. In the present research, the influence of different initial inoculum levels of Meloidogyne javanica (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 5.0 eggs and second stage juveniles/g. soil) on growth parameters of pot marigold and nematode reproduction was investigated. 90 days after nematode inoculation, the chemical compounds quercetin, kaempferol and ursolic acid were measured in infected plants. The results showed that with increasing the initial nematode population, the means of plant growth factors significantly decreased. In addition, nematode reproduction factor was inversely related to the levels of population and the highest reproduction factor was observed with the lowest nematode population. Results of analysis and comparison of chemical compounds of infected and healthy plants, showed that flavonoid and triterpenoid compounds namely quercetin and ursolic acid were increased in the nematode infected plants.