Variation among Sorghum Mutants Resistant to Periconia circinata (Mang.) Sacc. 1

Mutations at certain loci in sorghum [ Sorghum bicolor (L.) Moench] are known to occur at high frequencies. Although mutation frequencies have been recorded and lines have been established from the mutants resistant to Periconia circinata (Mang.) Sacc., the cause of milo disease, little is known about the nature of these mutations. This study was conducted to determine if mutants with resistance to P. circinata differed from the susceptible source, ‘Colby’, in characteristics other than resistance. Field studies of 16 lines, 15 of which were from naturally occurring resistant mutants, were conducted in 2 years at College Station, TX to determine height, days to anthesis, and kernel weight characteristics. In addition to being resistant, two mutant lines were consistently different from their susceptible source in other characteristics. They were shorter, required more days from planting to anthesis, and had smaller kernels than Colby. Other resistant mutant lines differed from their source in fewer characteristics, and all except one line differed from the source in some observed characteristic. One of the two most diverse lines had yellow stripes in leaf blades and sterility. Possible explanations for these differences that occurred concurrently with mutations in disease response include pleiotropic effects of different mutant alleles and mutations at loci other than the one controlling reaction to P. circinata . These alternative hypotheses have not been tested.