Molecular and Cultural Characterization of Alternaria brassicae Infecting Cauliflower in Uttar Pradesh, India

Abstract

The Alternaria blight or leaf blight (Alternaria brassicae) causes severe damage to cauliflower at curd formation and seed setting stage. Roving survey revealed that the disease incidence on cauliflower in different farmer’s fields ranged from 10 to 40 % with an average incidence of 20 % in Uttar Pradesh. Twenty-three (23) isolates of A. brassicae were collected from different cultivars in Uttar Pradesh and characterized for cultural, morphological, pathogenic and molecular variations. Based on the pathogenicity, isolates of A. brassicae were rated as virulent or less virulent based on the percentage disease incidence on cv. Hajipur local. Most of the isolates showed smooth mycelial growth with circular, irregular margin and without concentric zonation. The colony colour is white, dark brown to light brown and pinkish in white. Significant morphological variations in conidial length, conidial width, and number of horizontal septa were observed in all the isolates. The maximum length of conidia ranged from 150 to 122 lm with 8 to 9 transverse and 2 vertical septation. Further the genetic diversity of isolates based on RAPDPCR using sixteen random primers were produced on clarity, repeatability and the number of polymorphic bands in all the isolates. Cluster analysis of DNA fragments was performed using NTSYSpc V2.2 based on UPGMA method and Jacard coefficient. Based on the analysis the isolates represented four major groups with 75 % similarity.