Tolerance limit of winter wheat to cereal cyst nematode,Heterodera filipjevi,in pot trials in Iran

The cereal cyst nematode,Heterodera filipjevi,is recognised as one of the most important soil-borne pathogens limiting yield in many rain-fed wheat growing areas throughout the world. It also occurs in many cereal growing regions of Iran. Two pot experiments were conducted under field conditions to evaluate the response and tolerance limit of winter wheat cv. Sardari to infestation with different population densities of H. filipjevi. Pots were artificially infested with initial population densities (Pi) of 0,2.5,5,10 and 20 eggs and second-stage juveniles (J2s)/g soil. Each treatment was replicated seven times during two successive growing seasons. Tolerance limits (T) of 0.8 and 0.6 eggs and J2/g soil for the grain yield were estimated in the first and second years respectively,with an average of 0.7 egg and J2/g soil for both years. Minimum relative yields were 0.4 at the Pi of 40 in the first year and 0.45 at the Pi of 64 in the second year for the grain yield. The final population of H. filipjevi increased with increasing the Pi levels. The maximum reproduction rates of the nematode were 4.6 and 3.9 at the lowest Pi of 2.5 eggs and J2s/g soil in the first and second years respectively.