Introduction
The continued intensive cultivation of faba bean (Vicia faba L.), over the past several hundred years, in Egypt, Sudan, and North Africa, has increased the vulnerability of the crop to diseases. Important heavy losses from these diseases make breeding for disease resistance imperative. In most crops, disease resistant cultivars have been the least expensive and the most practical method of combating important disease problems.

    The basic principles of breeding for disease resistance are much the same as for any agronomical character. In breeding for disease resistance however, there are two different biological systems involved: (1) the host and (2) the pathogen. A thorough understanding of the biology of both systems is essential for successful resistance breeding programs.

    The discovery of suitable parent materials in. the host is among the most important steps in breeding for disease resistance. Progress in breeding programs can be accomplished only as rapidly as adequate sources of resistance to major diseases are identified. This requires exhaustive searching and screening, which can be done only when the host and pathogen are brought together into a disease- inducive environment.

    Screening for disease resistance is normally done in humid areas where natural disease epiphytotics are known to occur. This is why screening is done by ICARDA at Lattakia in northern Syria, where favorable weather conditions usually prevail. The most important advantage of natural epiphytotics is that disease nurseries are exposed to as many pathogenic variations of the pathogen as possible. It is unwise however, to rely solely on natural epiphytotics, because unsuitable weather conditions and disease failures might lead to the loss of a complete season of screening and selection.

    Large germplasm collections may vary for both specific and non-specific resistance. Therefore, selection for each of these types of resistance requires certain procedures to differentiate between the two. Although the use of mixtures with wide variation in virulence tends to detect all possible types of resistance that might occur in germplasm collections. The two types of resistance can be distinguished by studying the presence or absence of differential interactions between the genotype of the host and that of the pathogen (5).

    Faba beans are affected by several diseases. Laboratory and field techniques are given here for specific diseases which are of special interest to the Nile Valley, the Middle East, and North African regions. These diseases are: chocolate spot (Botrytis fabae), ascochyta blight, (Ascochyta fabae), rust (Uromyces fabae), stem nematodes (Ditylenchus dipsac), alternaria spot (Alternaria tenuis), bean yellow mosaic virus (BYMV), and bean leaf roll virus (BLRV).
 
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