Genetic variability of Bipolaris sorokiniana isolates using URP-PCR

Spot blotch disease, caused by Bipolaris sorokiniana, is one of the major diseases of wheat and is responsible for large losses of wheat crops worldwide. We used polymerase chain reaction (PCR) with universal rice primers (URP) for molecular characterization of 60 monosporic B. sorokiniana isolates from Brazil and other countries, and evaluated the diversity of the samples. PCR amplification generated 232 different DNA fragments ranging in size from 100 to 2018 bp. The primers URP-4R, URP-2R, and URP-1F generated greater numbers of amplified fragments ( 36, 30, and 25, respectively) from the single-spore isolates, and some diversity was observed among the isolates generated using these primers. The primers URP-2F, URP-6R, URP-17R, URP-30F, and URP-38F produced a pattern of monomorphic fragments and 73% of the isolates showed an average of 44 different DNA-amplified fragments. Primer URP-2F generated a 578-bp fragment that was common to 83.7% of the isolates; primer URP-6R generated a 548-bp fragment and primer URP-38F generated a 650-bp product that was common to 89.1% and 80% of the isolates, respectively. The URP-PCR primers provided important information about the genetic profiles of the monosporic cultures, which showed intraspecific variability among the monoconidial isolates and among the monosporic cultures that originated from the same polysporic strain. Our results indicate that URP's are sensitive and give reproducible results for assaying the genetic variability of B. sorokiniana.