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Great care must be exercised in the movement of chickpea seed for research
and commercial purposes from ascochyta blight infested areas to prevent the
inadvertent introduction of the pathogen into new areas, or more virulent isolates
or strains of A. rabiei into already infested regions.
Survival in Infected Seed
Ascochyta rabieisurvives adverse environmental conditions for extended periods
on internally or externally infected chickpea seeds, which may give rise to
infected plants under favorable blight conditions. In Iran, the fungus survived
117 weeks in naturally infected chickpea seeds in a weather station shelter where
temperatures rose to 45+°C during the summer (Kaiser 1972; Kaiser 1973a).
The pathogen was still viable in over 50% of infected seed stored for 5 years at 2­
5OC (W.J. Kaiser, unpublished data).
On the Indian subcontient, A. rabieisurvived over 2 years on infested chickpea
debris left in the field after harvest (Luthra et al 1935). However, the pathogen
lost its viability rapidly when the infested refuse was buried (Kaiser 1973a;
Luthra et al. 1935). Ascochyta spores survived on the surface of chickpea seeds
after 5 months at 25-35°C (Sattar 1933), while one-third of those washed from
heavily infected seeds germinated after 14 months at about 3°C (Maden et al.
1975). In nature, infected seed is thought to be the primary source of infection in
many countries, e.g., Canada (Morall and McKenzie 1974), Greece (Zachos et
al. 1963), India (Sattar 1933), Iran (Kaiser 1972; Kaiser 1973a) and Israel
(Halfon-Meiri 1970). However, in some countries, infested trash may play an
important role in local spread of the pathogen (Luthra et al. 1935; Zachos et al.
1963).
Site of Infection in Seed
Research by Halfon-Meiri (1970), Luthra and Bedi (1932) and Maden et al.
(1975) has provided valuable information on the localization of the pathogen in
chickpea seed.
Infection of seed may occur
during cool, wet weather while immature or
mature seeds are still in the pod, or during the harvesting and thrashing operations.
Halfon-Meiri (1970) observed that 50-80% cf the seed from chickpea pods
with Ascochyta lesions were infected with A. rabiei,but that the pathogen could
not be detected in seeds from apparently healthy pods collected from diseased
plants.
Infected seeds may not show signs of fungal infection (Halfon-Meiri 1970;
Luthra and Bedi 1932; Luthra et al. 1935; Maden et al. 1975). On seeds of white­