A comparative study of the black stem fungi on lucerne and red clover and the footrot fungus on pea

North American (U.S.A., Canada) and Dutch strains of the black stem and footrot organisms were comparedin vitro and some amplifying inoculation experiments were made. It appears that black stem of lucerne is associated in nearly all cases with one relatively uniform pycnidial fungus. From comparison withPhoma herbarum, the type species of the form-genusPhoma, it is concluded that the fungus, although quite different fromP. herbarum, belongs toPhoma and not toAscochyta. The correct name is therefore considered to bePhoma medicaginis Malbr. & Roum. and notAscochyta imperfecta orP. herbarum f.medicaginum. Black stem of red clover is in general caused by a similar pycnidial fungus which, however,in vitro can always be distinguished from the lucerne fungus by its greater variability. This organism, the current name of which isPhoma trifolii, appears to be identical with the well-known footrot fungus of pea:Ascochyta pinodella. It is proposed to designate it asPhoma medicaginis var.pinodella (Jones) Boerema comb. nov. IncidentallyP. medicaginis can be associated with black stem of red clover andP. medicaginis var.pinodella with black stem of lucerne. Inoculation experiments confirmed the pathogenicity of both organisms to lucerne and red clover. On pea only the varietypinodella has been found, although inoculation experiments proved thatP. medicaginis can also attack pea.