EFFECT OF PLANT-DENSITY ON GRAIN-YIELD, ROOT-LENGTH DENSITY AND OROBANCHE CRENATA INFESTATION IN 2 FABA BEAN GENOTYPES

The effect of host plant cultivar and sowing density on Orobanche cren ata Forsk. L. infestation in Vicia faba was studied in a field experim ent in north-west Syria. Two faba bean genotypes, ILB 1814 (Syrian Loc al Large) and 402/29/84 (new breeding line from Egypt), were planted a t four sowing densities. Whereas ILB 1814 was severely affected by O. crenata, 402/29/84 proved to be highly resistant. Sowing density did n ot have a significant effect on O. crenata dry weight in either genoty pe. However, the number of O. crenata attachments in ILB 1814 was posi tively correlated with plant density. The resistance of faba bean geno type 402/29/84 to O. crenata is due to: (a) less plant vigour and root -length density; (b) necrosis of host cells preventing O. crenata atta ck either before or just after penetration into the host root, or deve loping a barrier in the host root after the formation of a small tuber cle; (c) early flowering and pod setting.