I - --ii

India and Iran were highly sporulating as compared with those from Turkey and
West Pakistan. He also observed differences in virulence of the isolates on
differential chickpea lir-... However, he did not make any attempt to correlate
sporulating capacity of an isolate to its pathogenicity.
To reduce losses by ascochyta blight disease, resistant cultivars were released
from time to time. These have subsequently been found to succumb to the
pathogen (FAO 1963; Grewal 1969) indicating the possible appearance of new
virulent strains of the pathogen. The fact that a given cultivar performed well for
some years before it succumbed to the pathogen indicates the slow appearance of
new strains. This may be due to the absence of the perfect state of the pathogen
in the main chickpea-growing regions of the world. Attempts to establish races of
the pathogen were made by Aujla (1964). Pathogenic variation among isolates of
the pathogen has also been reported by Kaiser (1973).
The studies carried out at New Delhi indicate that the 13 morphological forms
of the pathogen could be distinguished as two pathogenic races on the basis of
disease reaction produced on three chickpea cultivars. Resistant type of disease
reaction was produced by cultivars 1-13, EC 26435 and C 235 against race I
represented oy fast-growing and less-sporulating isolates mentioned above. These
cultivars were, however, moderately susceptible to susceptible to slow-growing
and more-sporulating isolates representing race 2, except isolate J-101 which
incited resistant type of infection (disease grade 3) on cultivars 1-13 and C'235,
and was distinguished as a biotype of race 2.
Pathogenicity tests with 15 well known blight-resistant lines from all over the
world against race 2 of the pathogen showed that all of them except the highly
resistant line 1528-1-1 from Morocco were moderately susceptible to susceptible
to race 2. The observation that cultivar C 235, previously thought to be resistant
in India, was susceptible to race 2 indicates that race 2 is a newly evolved or
introduced race of the pathogen. It is also probable that the highly slorulating
isolate of A. rabiei reported by Kaiser (1973) from Iran may belong to race 2 of
the pathogen. Some new blight-resistant lines have been identified in Bulgaria
(Geneva and Matsov 1977; Radkov 1978) and Syria (Eingh et al. 1981).
Summary
Occurrence of Ascochyta rabiei and its variations have been reported from
chickpea-growing countries. In view of the breakdown of resistance in known
ascochyta blight resistant cultivars of chickpea in Ildia, studies were undertaken
to find out physiologic specialization in the pathogen. Two hundred and sixtyeight
isolates of A. rabiei were collected, purified and grouped into 13 forms.
One representative isolate of each form was used for further studies. Six fastgrowing
and low-sporulating isolates gave a resistant type of reaction on cultivars
1-13, EC 26435 and C 235 and ':onstituted race I of the pathogen. Six other slow­
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