تعيين گروه هاي سازگاري رويشي FUSARIUM OXYSPORUM F. SP. SESAMI VCGS عامل زردي و پژمردگي كنجد در استان فارس

VEGETATIVE COMPATIBILITY GROUPING IN FUSARIUM OXYSPORUM F. SP. SESAMI THE CAUSAL AGENT OF SESAME YELLOWS AND WILT IN FARS PROVINCE

One handred and twenty eight isolates of Fusarium oxysporum f.sp. sesami (Fos) were isolated from sesame plant during 2001-2002 growing season in major sesame growing areas in Fars province . Nit mutants were synthesized on minimal medium (MM) containing 3% potassium chlorate. Based on colony growth on basal medium containing nitrogen sources such as sodium nitrate, sodium nitrite, hypoxanthine , ammonium tartrate and uric acid the nit mutants were grouped. To obtain heterokaryon, nit mutants were crossed on MM. Formation of mycelia) tufts at the junction was considered as compatible and no growth as non-compatible reaction. Nit mutants were generated from all isolates. Based on the ability to use different nitrogen sources the mutants were grouped in to three phenotypic classes nit I (77.3%), nit 3(12.9%) and nitM(9.8%) . Ten compatible groups were recognized among nit mutants. The results are indicative of relationship between vegetative compatibility groups(VCGs) and geographic origin of the isolates. Since there was no sesame seeds exchange in the areas and farmers usually used their own seeds, the pathogen had limited distribution resulted in local VCGs group.