Assessment of variability among the isolates of Bipolarissorokiniana
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Date
2014
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Rajendra Agricultural University, Pusa (Samastipur)
Abstract
Assessment of variability was carried on 32 isolates of Bipolarissorokiniana. These isolates were grouped in five categories, i.e. black, brown, grey, greenish grey and white on the basis of colony colour. Greenish grey group had maximum frequency (31.25), while the brown isolates displayed the lowest frequency (6.25) in natural population. Radial growth at 10th day on PDA media was maximum in RAU-GTL-34 (40.66mm) having cottony growth pattern and dull white with rings like marking, while minimum was recorded for RAU-GTL-35 (25.0mm) having suppressed blackish grey with whitish fluffy region. Pathogenicity and aggressiveness test were carried out on two wheat varieties namely,Sonalika (susceptible) and Chirya-3 (resistant). Pathogenicity test was conducted by test tube cotton swab method. The mean pathogenicity value showed that isolates were more pathogenic on Sonalika (3.7) than Chirya-3 (2.5). The isolates were categorized into five virulent groups on the basis of pathogenic value i.e. non-virulent, slightly virulent, moderately virulent, virulent and highly virulent. Colony colour and level of exudations were also observed to be related with level of pathogenicity and aggressiveness. Area under disease progress curve of isolates on Chirya-3 varied from 198.77 (white group) to 730.25 (black group) in both natural and polyhouse condition, while for Sonalika it varied from 458.02 (white group) to 1343.83 (black group) in natural condition, whereas from 458.02 (white group) to 1374.07 (black group) in polyhouse condition. Fungus specific primer CosA_F/R identified all isolates as B. sorokiniana. Two ITS primers gave a total of 22 alleles out of which 12 were monomorphic and 10 were polymorphic with an average of 11 alleles per locus. The PIC values varied from 0.884 to 0.915 with an average of 0.889. Cluster analysis of PCR products using the UPGMA method, based on Dice coefficients with 20 similarity unit, clustered eighteen fungal isolates into six groups. PCR-RFLP analysis gave a total 66 alleles out of which 30 unique alleles and 36 shared alleles with an average of 7.3 alleles per locus in both the region. The PIC values varied from 0.331 (ITS-2 and Hinf-I) to 0.809 (ITS-2 and HindIII). Cluster analysis of PCR-RFLP data using the UPGMA method, based on Dice coefficients with 25 similarity unit, clustered eighteen fungal isolates into four groups. Pair-wise genetic similarity (GSDice) coefficient widely varied from 0.54 to 1.0 indicating similarity among the isolates.
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