Evaluation of screening protocols to determine genetic variability of grain sorghum germplasm to Sporisorium sorghi under field and greenhouse conditions

Covered kernel smut caused by Sporisorium sorghi is a serious problem in gr ain sorghum (Sorghum bicolor)-growing areas in the world, particularly wher e seed dressings are unavailable or too expensive. In a screening protocol designed to eliminate the possibility of escapes, seed subjected to a telio spore suspension coupled with a partial vacuum, and seeds directly infested with dried teliospores, were equal in development of smutted sorghum panic les, inoculation with sporidia from teliospores was ineffective when plants were inoculated at the boot stage of growth and was minimally effective wh en plants were inoculated at the 10-12 leaf stage of growth. Environmental conditions were more conducive to disease incidence when sorghum was grown under greenhouse conditions or planted late in the field. Sorghum planted i n warm (>20 degrees C) soil had the greatest incidence of covered kernel sm utted panicles.