Abstract
Field experimental details are the same as those outlined in Paper 1. Data on chocolate spot (Botrytis fabae) in faba bean and Aschochyta blight (Mycosphaerella pinodes) in field pea were recorded based on a 1-9 scale and analyzed. The result showed highly significant differences among the treatments, between years and locations and their interaction effects in most of the cases. Mixed-cropping did not exclude the occurrence of both diseases, the incidences of which were relatively higher at Holetta than at Denbi. Chocolate spot at Denbi and Ascochyta blight in field pea at both locations also significantly differed between the systems. Faba bean varieties Mesay and NC 58 were more affected by chocolate spot under both systems. However, mixed production of the two crops favored incidence of chocolate spot in faba bean and disfavored Ascochyta blight maybe due to changes in the microenvironment associated with changes in the cropping systems. Field pea as an intercrop may reduce free air circulation and create a humid microenvironment, that favor chocolate spot. Field pea in a mixed culture with faba bean is supported in an erect position that facilitates free air circulation providing a drier microenvironment unfavorable for the development of Ascochyta blight. Therefore, any breeding effort anticipated to develop faba bean and field pea varieties suitable for mixed-cropping should give greater priority to chocolate spot resistance in faba bean than Ascochyta blight resistance in field pea. There was a strong positive interrelationship (r = 0.96) between varietal reactions to chocolate spot incidence under the two systems, indicating that selection of better genotypes for lower disease incidence under sole culture could identify better genotypes for mixed as well and separate evaluation under the two systems may not be necessary. The interrelationship between varietal reactions to Ascochyta blight under the two systems in field pea was very weak, indicating that reactions to Ascochyta blight under the two systems were governed by different set of genes and, hence, separate selection for resistance under both systems maybe necessary.
