Isozyme, protein, and RAPD markers within a half-sib family of buffelgrass segregating for apospory

Isolation of genes controlling apomixis would be useful to plant breeders for fixing hybrid vigor. A single gene codes for aposporous apomixis in buffelgrass [Pennisetum ciliare (L.) Link]. This study was undertaken to assess the feasibility of using isozyme, protein, and random amplified polymorphic DNA (RAPD) markers to detect apospory-linked sequences within a segregating half-sib population. Sexual plant B-2s, five sexual and three aposporous progeny of sexual B-2s, and cultivar Higgins were studied. Floret and leaf proteins were separated by starch gel electrophoresis, and enzymes in the gel were stained to detect isozyme polymorphisms. Of 22 isozyme systems tested, 12 showed polymorphisms but none cozegregated with apomixis. Two-dimensional polyacrylamide gel electrophoresis was used to separate steady state proteins of pistils at meiotic and post-meiotic stages. This technique revealed ≃12% polymorphism within 308 spots, but none of the spots cosegregated with reproductive mode. Genomic DNA was screened for RAPD markers with 111 10-mer random primers and polymerase chain reaction. Of 569 markers identified, 87% were polymorphic. One marker cosegregated with sexual lines, but none cosegregated with aposporous lines. Analysis of molecular variance examination of the B-2s parent and the eight half-sib progeny (Higgins excluded) showed that on the basis of 404 RAPD markers, the apasporous and sexual groups were not significantly different. No RAPD markers were tightly linked with apospory. Additional screening of new primers will allow identification of markers for the gene in full-sib families.