Isozyme analysis of Sporisorium reilianum populations from sorghum fields in Texas

Typescript (photocopy).Isozyme analysis was used to assess the genetic variability of Sporisorium reilianum from three field populations in Texas from 1982 through 1984. An effective horizontal starch gel electrophoresis technique was developed. This is the first study to use isozyme analysis in S. reilianum. Haploid sporidia were used to yield enzymes. Twentyone enzyme-encoding loci showed in vitro activity. These loci (abbreviated): are EST, GAM, PEP-LA, PEP-LGG, PEP-LLL, PEP-PAP, GPI, MPI, AGP, GAPDH, G6PDH, GDH, IDH, LDH, MADH, MDH-2, CK, GK, HK, PGM, and NP. These enzymes were monomeric, except for MDH-2, which was a dimer. One phenotypic encoding-locus was determined for each enzyme. Nineteen additional enzyme-encoding loci were examined but unresolved. Sporidia were cultured on four different liquid media, but none affected the quantity or quality of enzymes produced. The enzymes resolved were constitutively expressed and none was shown to be inducible. The Texas subpopulations have similar genetic structures, yet each maintains its own phenotypic identity. The Beeville/Berclair subpopulation possesses the greatest genetic variability followed by the College Station and Halfway/Lubbock subpopulations. Specific enzyme variants could distinguish among the subpopulations by their presence or absence in the gene pool. When the data were pooled for all subpopulations, the genetic variability was found to be randomly distributed within each virulence group in each subpopulation. No virulence group had a distinguishing isozyme phenotype with which it could be identified. The Texas subpopulations were compared with three foreign populations. The genetic structure of the Texas and Argentina populations were identical. The populations from India and South Africa were more variable than the Texas population. The population from India contained the greatest degree of genetic variability followed closely by the South African population..