I - --ii

seeded chickpea lines, lesions were light dark brown (Halfon-Meiri 1970; Maden
et al. 1975) and ranged in size from 1-4 mm in diameter (Halfon-Meiri 1970;
Sattar 1933). Black pycnidia containing mature spores of the fungus were observed
in many lesions, some of which formed concentric zones (Hialfon-Meiri
1970; Luthra and Bedi 1932; Maden et al. 1975; Sattar 1933). In seeds with
lesions, the fungus frequently penetrated the seed coat and could be isolated
from cotyledoihary tissues (Halfon-Meiri 1970; Luthra and Bedi 1932; Maden et
al. 1975). The pathogen was detected also in embryos (Maden et al. 1975).
Controfling Ascochyta Blight Tiwough Clean Seed
The production and use of Ascoch ta-free seed is essental to prevent introduction
of the pathogen into disease-free areas where environmental conditions may
favor spread and development of blight. It may be necessary to use a combination
of' pro 'tices, like crop rotation, field sanitation and chemical seed treatments to
prodt,:e blight-free seed. These measures should also be effective in controlling
other pathogens that are seed-borne in chickpea (Cother 1977a; Cother 1977b;
Kaiser 1972; Singh and Chohan 1976; Suhag 1973).
The following five factors are critical to the production of chickpea seed free
from A. rabiei:
Arid Environment
Ascochyta blight of chickpea is dependent on cool, wet weather for its greatest
spread and development (Kaiser 1973a; Luthra et al. 1935; Sattar 1933; Zachos
et al. 1963). Surface-contaminated or internally infected seed is the most important
metthod of spreading and perpetuating the disease (Kaiser 1973a; Luthra et
a!. 1935; Maden et al. 1975; Sattar 1933). Dry, warm weather impedes disease
development and spread. It is preferable to locate seed production fields in arid
areas where little or no rainfall occurs during the flowering and fruiting periods,
or at harvest. If plants are watered during the growing season, this should be done
by furrow irrigation, rather than overhead sprinkling.
Several seed-borne diseases of different food crops in the United States are
controlled by producing seed in arid western areas (Snyder et al. 1965). For
example, most of the bush sna p bean (Phaseolusvulgaris)seed used for planting
in the United States is produced in an arid region of southern Idaho (Zaumeyer
and Meiners !975).
Crop Rotaion
It is highly desirable to grow chickpeas in rotation with other crops such as
cereals, to prevent the buildup of A. rabieion any infested trash that may be left
in the field after harvest. Only chickpeas are susceptible to ascochyta blight in
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