Genetic variation in Alternaria isolates pathogenic to linseed (Linum usitatissimum) based on RAPD

Genetic variation in eight Alternaria isolates (AL1-AL8) collected from geographically diverse region of India was studied with polymerase chain reaction based random amplified polymorshic DNA (RAPD) marker. Forty decamer primers were tested for amplification of genomic DNA of Alternaria isolates which generated 1 to 14 reproducible bands with a total of 258 bands. Six primers could not produce any band whereas, 29 primers generated 100% polymorphism. RAPD markers showed substantial diversity among the different isolates with maximum of 0.65 between AL3 and AL5 collected from Berhampore and Kangra, respectively. UPGMA analysis of RAPD data showed that eight isolates collected from geographically distinct region clustered in four groups corresponding to their genetic similarity. Two isolates AL6 (Kaul) and AL7 (Ludhiana) collected from same zone formed a group with 85% similarity index. Another group of four isolates AL1 (Kanpur), AL4 (Kangra), AL2 (Kanpur) and AL8 (Raipur) formed an unresolved polytomy with 76% similarity index. The isolates AL3 (Berhampore) and AL5 (Kangra) did not share any of the groups at the similarityindexof67 and47%, respectively. Weconclude thatinter-regionalvariabilitybetweenthecollected Alternaria isolates was more apparent than the intra-regional variation and primers SBSA-09 and SBSB-18 were highly efficient in detection of intra-regional variation between the isolates.