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4. Mycosphaerella pinodes and Ascochyta pinodella cause severe foot rot
while the others cause leaf, stem and pod blight. A fungus isolated from peas
in Pakistan in association with Ascochyta pisi Lab. is considered to be a
weak parasitic race of' Ascochyta pinodella Jones.
Growth Requirements of the Fungus
A comparative study of nutritional requirements, germination of conidia, pathogenicity
of Ascochyta rabieiand Ascochyta pisi did not indicate a high degree of
specialization of parasitism in the two fungi in infecting chickpea and pea plants.
Of the factors studied, any degree of specialization of parasitism that may be
shown by these two fungi could only be explained on the basis of the presence of
malic acid on the leaves of chickpea plants which was detrimental to the conidia
of Ascochyta pisi (Ahmad 1959).
Sattar and Hafiz (1952) outlined optimum, maximum and minimum temperatures
for growth of the fungus as 25°C, 32.5°C and below 10'C, respectively.
The fungus made maximum growth at about the neutral point and grew fairly
well over a ranee ef pH 4.0-8.8. The germination of spores is very meager, slow
and uncertain in pure water. Their germination is improved by the presence of
N/50 and N/25 malic acid or acidified carbon food. Very few spores germinate
and cause infection during December and January due to very low temperature.
The spores, however, remain viable during freezing temperature and cause infection
in February-March when the temperature varies between 20-27 0 C (Sattar
and Hafiz 1952).
Transmission of Disease
Luthra and Bedi (1932) supported the view that the disease is seed-borne and
suggested the use of seed grown in disease-free localities for the control of the
disease. The importance of secondary infection in widespread attacks of the
disease was recognized as early as 1930. It was pointed out by Sattar (1933) that
the rainfall in summer and in the early growth phase resulted in luxuriant growth
of chickpea and such a crop was most prone to attack. He pointed out that the
parts of Punjab where blight was serious received on average more than 150 mm
rainfall during the chickpea growing season and that blight appeared sporadically
in parts with rainfall less than 87 mm during that period.
Further studies pointed out that blighted plant debris lying in the field on the
surface of soil or threshing floor was a very important source of perpetuating the
disease from year to year as the blight fungus could remain viable in chickpea
plant debris for 2-3 years. Studies on dissemination of the fungus indicated that