Parasitism of Beta vulgaris by Meloidogyne hapla and Heterodera schachtii alone and in combination.

Interrelationships of Meloidogyne hapla and Heterodera schachtii in combinations of several population levels and different inoculation periods were studied. Results indicated suppression of gall development of M. hapla in any treatment in which inoculations of H. schachtii preceded those of M. hapla by 10 days. This interrelationship was characterized by amensalism with M. hapla serving as an amensat and H. schachtii serving as an inhibitor. Conversely, when inoculations of M. hapla preceded H. schachtii inoculations by 10 days, there were increases in cyst development. This relationship was characterized by commensalism with H. schachtii serving as a commensal. In both interactions, the preinvading parasites acted independently and established populations equal to treatments receiving either parasite alone. When both nematodes were inoculated simultaneously, there were no effects on populations of either. Relationships of this nature were characterized by neutralism. Ratios of total soluble/reducing carbohydrates were lower in treatments when M. hapla inoculations preceded those of H. schachtii. Plants inoculated with both nematodes died earlier than those inoculated with either parasite alone. High concentrations of Al and Fe occurred in treatments wherein M. hapla or H. schachtii inoculations preceded each other by 10 days. Generally, noninoculated control plants exhibited higher concentrations of K, P, Mg, and B than other treatments.