Assessment of mycelial compatibility of Sclerotinia sclerotiorum isolates,causal agent of canola stem white rot and evaluation of their genetic diversity using RAPD marker

Sclerotinia stem white rot is one of the most important diseases of canola in many regions under cultivation of this valuable crop plant. The extent of infected plants in some fields reaches to 80% and sometimes the severe infection damages 50% of the crop yield. The disease caused by Sclerotinia sclerotiorum, is casual agent of stem white rot and ring in canola, sunflower and other plants such as cabbage, lettuce, tobacco etc. The casual fungus is one of the main plant polyphagous pathogens that has a wide host rang. In this study 33 samples of canola, sunflower and cabbage were collected from different areas of Golestan province in 2008-2009 and cultured on PDA medium. Nineteen mycelial compatibility groups (MCG) were obtained for studying compatibility reaction between cultured isolates (couple or single). From 171 crosses between isolates, 21 (12.3%) showed mycellial compatibility and 150 (87.7%) showed incompatibility. Furthermore, in order to study molecular diversity of obtained isolates, 8 RAPD primers were used in PCR. Totally, 136 ploymorphic markers were obtained in agarose gel electerophoresis. Analysis of molecular data using PopGene32 software indicated that there was a high genetic diversity among studied isolates. Furthermore, results showed that similarities were not associated to spatial distribution of collected isolates. On the basis of Hardy–Wineberg test it can be concluded that studied population is in equilibrium at all studied loci. This status may be due to being young the canola culture in Golestan province, existence of many hosts (particularly among weeds) and low variation of canola varieties cultivated in recent years in the region. Results indicate the efficiency of RAPD marker for studying genetic variation in Sclerotinia sclerotiorum fungus.