PJB-2019-617
Cultural, Morphological and Pathogenic Variability in Isolates of Alternaria alternata Causing Alternaria Blight of Tomato
RATAN LAL SHARMA
Abstract
Alternaria blight disease caused by Alternaria alternata has been a serious problem in tomato growing areas particularly at temperate subtropical, humid tropical regions of the world. To know the variability among the isolates of Alternaria alternata diseased plants of tomato were collected from four districts (Jaipur, Alwar, Dausa and tonk) of Rajasthan. All the isolates of Alternaria alternata differed in their colony characters and colony diameter. All the isolates produced initially white mycelium later turned grey, dark grey and black or remained in white colour with regular or irregular margins. Most of the isolates were black to grey in colour. Isolates (AlltJp1 and AltJp2) from Jaipur district showed maximum mycelial growth with a colony diameter 90.00 mm and 88.00 mm, respectively. Morphological observations recorded on each isolate revealed that isolates differ in their conidial length and width. In general, conidial length and width were observed in between 22.69 to 36.15 µm and 9.92 to 18.65 µm, respectively. Number of horizontal and vertical septa varied between 3 to 4 and 1 to 3, respectively. All the isolates were pathogenic to tomato and produced characteristics symptoms of disease. The per cent disease intensity was with Jaipur isolates AltJp1 (70.25 %) and AltJp2 (67.42 %).
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