Author(s):

Srujani Behera and Srikanta Das

Abstract: The effect of temperature and Relative humidity on spore germination of Alternaria porri isolates were studied under controlled environmental condition (growth chamber). The growth rate experiment was conducted according to the virulence of the isolate through pathogenicity. Among the 15 isolates, three isolates (AP₁, AP₈ and AP₁₅) were selected according to their aggressiveness towards disease production. The effect of temperatures on A. porri was investigated to study their influence on the conidial germination, length of germ tube (μm) and number of germ tube /conidia. The result showed that the germination % and length of germ tube (μm) were greatly influenced by different temperatures. Maximum conidial germination (71.60%) was observed at 20⁰C at 6 hr after incubation period followed by 25⁰C (65.55%). Moderate conidial germination (57.57%) was observed at 30⁰C and minimum conidial germination was recorded at 35⁰C (48.64%) and their difference was statistically significant. Maximum growth rate was observed at 25⁰C for all these 3 isolates (10.00, 11.02 and 9.72 mm/day) followed by 30⁰C (9.70, 9.96 and 8.91 mm/day respectively). According to the maximum growth rate on 25⁰C one isolate (AP₈) was selected for study on spore germination, length of germ tube and no. of germ tube/conidium on 4 different Relative Humidity i.e. 65, 75, 85 and 95% and it was observed that maximum conidial germination was observed at 95% RH (97.42%) followed by 85 %RH (93.77%) and minimum conidial germination was observed at 75% RH (9.50%).

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