Identity and Pathogenicity of Fungi Associated with Root and Crown Rot of Soft Red Winter Wheat Grown on the Upper Coastal Plain Land Resource Area of Mississippi

Seedling stand\ disease severity and fungal incidence were determined from untreated {Wake_eld| soft red winter wheat planted on a Leeper silty clay loam in _eld tests conducted at the Mississippi Agricultural and Forestry Experiment Station\ Plant Science Research Center\ Mis! sissippi State University\ Starkville\ Mississippi during the 0885 86 and 0886 87 growing seasons[ Seedling stand was reduced by 39) each year in plots established with untreated seed[ Cochliobolus sativus was the most fre! quently isolated fungus[ Fusarium acuminatum\ Fusarium equiseti and Fusarium solani were the most prevalent Fus! arium spp[ Seven other Fusarium spp[ and 12 species of other fungal genera were isolated[ Pathogenicity tests with three isolates each of C[ sativus\ Cochliobolus spic! ifer\ F[ acuminatum\ F[ solani\ F[ equiseti\ Fusarium com! pactum\ Embellisia chlamydospora and Microdochium bolleyi were performed in test tube culture and two iso! lates each of C[ sativus\ C[ spicifer\ F[ acuminatum\ E[ chlamydospora and M[ bolleyi under greenhouse conditions[ In test tubes and in the greenhouse\ seedlings infected with isolates of C[ sativus developed seedling blight\ discoloration and necrosis\ primarily in seminal roots and crowns[ In the greenhouse\ C[ sativus induced lesions on the lower leaf sheath and reduced seedling height\ seedling emergence\ dry and fresh weight of roots and shoots[ Isolates of F[ acuminatum\ F[ solani\ F[ equi! seti\ F[ compactum\ E[ chlamydospora and M[ bolleyi induced slight to moderate orange to light!brown dis! coloration of crown and seminal roots in test tubes[ Coch! liobolus spicifer isolates had the most pre!emergence activity\ inducing black root discoloration and root prun! ing of wheat seedlings and reducing seedling emergenceroot fresh weight and shoot dry weight[ In the green! house\ F[ acuminatum reduced seedling height\ seedling emergence and root and shoot dry weights[ Mic! U[ S[ Copyright Clearance Center Code Statement] 9820 0674:1999:3791 9966 , 04[99:9 rodochium bolleyi and E[ chlamydospora reduced fresh and dry weight of roots\ plant emergence and shoot dry weight[ Fusarium acuminatum and C[ spicifer reduced the growth rate of wheat seedlings[ All fungi evaluated showed increased disease severity compared to the untre! ated control[ The high frequency of isolation of C[ sativus from crown and root tissues can be partially explained by the dry\ warm conditions during the early stages of wheat seedling development in the Upper Coastal Plain Land Resource Area of Mississippi