Occurrence, Morphology and Reproduction of Heterodera avenae on Wheat and Barley in Saudi Arabia

The cereal cyst nematode ( CCN ), Heterodera avenae was frequently found ( 52 - 90 % ) in wheat and barley fields in Hail, Gassim and Riyadh, the three major wheat-producing regions in Saudi Arabia. The nematode produced large number of cysts. In pot tests, with naturally infested field soil, the nematode reproduced readily on 8 wheat and barley cultivars or lines ( Rf 6.0 - 12.8 ). The highest rate of reproduction ( P = 0.05 ) was found on barley cvs. CC 89 and Beecher ( Rf = 12.8 and 10.0 ), with lowest in barley cvs. Justo and Lignee 640 ( Rf = 6.8 and 6.0 ). Wheat cvs. and lines west bread, Yocora Rojo, El 93 - 4 and L9 were relatively intermediate ( Rf = 7.0 - 7.9 ). The nematode was identified on the basis of cyst vulval cone structures and measurements, and separated from its closely relative H. mani by cyst colour, cyst vulva slit length, and shape of J2 basal knobs. Other morphometrics and morphological features of J2, gravid females, cysts, eggs and males typically fit well with H. avenae