Pathotoxin‐Induced Alteration in Protein Synthesis Associated with Susceptibility of Sorghum to Milo Disease

Abstract

Symptoms of milo disease of sorghum, Sorghum bicolor (L.) Moench, caused by the fungus, Periconia circinata (Mangin) Sacc., can be elicited selectively in susceptible genotypes by treatment with the host‐specific toxin produced by the fungus. Sorghum lines with diverse genetic backgrounds were examined to determine whether disease susceptibility is correlated with an enhanced rate of synthesis of 16‐kilo dalton proteins induced by the toxin. Test materials included near‐isogenic susceptible and resistant lines of grain sorghum ‘Colby’, susceptible and resistant selections of shattercane, toxin‐sensitive selections from China and Nigeria, and spontaneous resistant mutants of Colby. Protein synthesized in root tips after treatment with the toxin were labeled in vivo with [3H]‐leucine, separated by polyacrylamide gel electrophoresis, and detected by fluorography. Toxin treatment enhanced the rate of synthesis of the 16 kD proteins in all susceptible selections but not in any of the resistant selections. These results establish a correlation between susceptibility of sorghum to P. circinata and an increased rate of synthesis of 16 kD proteins induced by the host‐specific toxin from P. circinata.