Morphological and Genetic Variability of Alternaria alternata isolates of Sunflower

Sunflower (Helianthus annuus L.) is one of the important oilseed crops in the world and it ranks third in the area of cultivation after groundnut, mustard and rapeseed. Thirty isolates of Alternaria alternata causing leaf blight disease of sunflower during rabi season were collected from different conventional sunflower growing areas of India. All the isolates produced light brown obpyriform to ovate to obclavate conidia, which varied in the size (length, width and septa).Based on the variation in pigmentation, color of aerial mycelium the isolates were categorized into five types. Thirty isolates were studied for length, width of conidia and clustering was performed using the Unweighted Pair Group Mean Average which showed 3 major groups. Group I consisted of 16 isolates; Group II includes 12 isolates and Group III contains 2 isolates. Genetic variability and phylogenetic relationships among the collected isolates were studied by employing the Inter Simple Sequence Repeats (ISSR) markers. Thirty two ISSR primers were used to study the genetic relationship among the 30 isolates of A. alternata, out of these twelve primers were selected as polymorphic based on their banding pattern. The genomic DNA isolated from A. alternata isolates a total of 185 bands were amplified with 12 ISSR primers among which 142 bands were showing polymorphism (76%). The maximum genetic similarity observed with ISSR was 0.98 % between A a1 and A a16, while the lowest genetic similarity of 0.22 % was observed between Aa1 and Aa5. Based on the literature cited, this was the first report on morphological and genetic analysis (ISSR analysis) of A. alternata isolates from different sunflower cultivating areas of India.