population genetic diversity of fusarium solani the causal agent of sugar beet root rot, using vegetative compatibility groups (vcgs) and its relationship to virulence of isolates

in the present study, vegetative compatibility groups (vcg) of 27 isolates of fusarium solani collected from root and  crown of sugar beets of different provinces in iran were determined using nitrate non– utilizing (nit) mutants. totally, 222 nit mutants were generated from 27 isolates using pdc medium. based on the weak growth on basal medium containing one of four nitrogen sources the phenotypic classes of nit mutants were determined. among them, 44%, 36% and 20% of nit mutants were belong to phenotypic classes nit1, nit3 and nitm, respectively. to determine vcgs and complementation tests, pairing were made between all nitm and nit1 or nit3. in a compatible reaction between nit m and the two other mutants, a dense growth at the line of contact between two colonies was formed which was more than those between nit1 and nit3. all isolates  belonged to 14 vcgs, of which ten were single member and four were multi member. no corelation was observed between vcgs and the geographic origin of isolates and also between the vcgs  and the type of disease symptoms.