Abstract
Two pot experiments, in consecutive years, were conducted under outdoor conditions during the wheat growing season to examine the relationship between increasing initial population densities (Pi: 0-3,000 cysts/pot) of
Heterodera avenae
and corresponding responses of wheat cv. Yecora Rojo. Results of both experiments were very similar. The nematode suppressed plant height, root and biomass dry weights, and grain yield at all Pi's studied. The suppression of these parameters, as well as the final nematode population densities (Pf), increased with increasing Pi levels. The reproduction factor (Pf/Pi) decreased as Pi increased but was always greater than 1.0. When data from both experiments were combined for regression analyses, inverse relationships were found between log
10
(Pi + 1) and both plant growth and yield. These negative relationships were highly significant and adequately described by linear models. Final population (Pf) increased linearly with Pi. The wheat cultivar cv. Yecora Rojo was found to be highly vulnerable to damage and a good host for H. avenae.