Epidemiology of Melampsora ciliata leaf rust of poplars in India

Between six temperature ranges and five levels of relative humidity, temper ature of 20 degreesC and 100 % relative humidity were optimal for the germi nation of urediniospores of Welampsora ciliata. Low (5 degreesC) and high ( 30 degreesC) temperature and relative humidity of 90 % or less did not favo ur the germination of urediniospores. The relative rate of germination of u rediniospores revealed that maximum rate of germination occurred at 20 degr eesC and 100 % relative humidity during early hours of incubation. Inoculum production (urediniospores/uredinium and urediniospores/unit leaf area) wa s adversely affected by maximum and minimum temperature while higher relati ve humidity and rainfall favoured it. Viability of urediniospores stored at 20 degreesC or more was lost within 10 days. Temperature and/or relative h umidity adversely affected urediniospore viability and coefficient of multi ple determination indicated that 9.43 % variation in urediniospore viabilit y could be ascribed to these factors.