Genetic diversity analysis of fungal pathogen Bipolaris sorghicola infecting Sorghum bicolor in India.

Bipolaris sorghicola (Lefebvre and Sherwin) is a well known and economically important seed-borne pathogen with the specific species of sorghum (Sorghum bicolor [L] Moench) as host. Thirty-two strains were obtained from different geographical area of sorghum growing places in India. Molecular characterization using three marker systems i.e., universal rice primers (URP), inter simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) was carried out. Molecular marker work revealed differences along with geographical origin clustering of various B. sorghicola strains which could not be revealed through conventional method of characterization. Out of 13 URPs, 20 ISSR and 50 RAPD primers screened, 8 primers each from URP and ISSR, and 10 primers from RAPD marker were found to result in reproducible banding pattern. One hundred per cent of polymorphic bands was recorded in all three molecular markers. Total number of bands was recorded 1986 with average of 248.25 in URP marker, and 2026 bands with average of 253.25 in ISSR marker and 2158 bands with average of 215.80 in RAPD markers. Maximum heterozygosity (Hn) was revealed by URP 17R (0.40), ISSR 10 (0.41) and RAPD marker OPC-5 (0.34). The polymorphism information content (PIC) values ranged between 5.89 to 8.28 in URP, 4.57 to 8.79 in ISSR and 4.44 to 9.64 in RAPD marker profiles. Maximum cophenetic correlation was found in URP (r = 0.910) followed by ISSR (r = 0.904) and RAPD (r = 0.870). The combined analysis of all three marker systems showed high cophenetic correlation (r = 0.911), which indicated a very good fit of the data for genetic diversity analysis. To best of our knowledge, this is a first report of genetic characterization of B. sorghicola. Hence, combined use of three marker systems would be more sensitive and reliable in characterizing genetic variability in B. sorghicola strains.