The structure of sterile cytoplasm types within a maize genebank collection

Maize Research Institute (MRI) gene bank maintains a collection of 6000 maize accessions. Within this collection over 100 sources of cytoplasmic male sterility (CMS) were found in field trials, i.e. more than 2% of the total accession numbers. These sources are distributed among Yugoslav open-pollinated varieties (4.56% of them contain CMS), as well as introduced heterozygous genotypes and inbred lines. In order to identify cytoplasm types the gene-bank sources of CMS were screened using a PCR assay with specific primers for C, T and S cytoplasms. Predominant cytoplasmic male sterility type among the analyzed accessions was CMS-S. Results were inconclusive for three accessions, i.e. different results for the progenies of two ears per accession were obtained. For another two accessions a new PCR product profile was identified, consisting of one band characteristic for CMS-S and one unspecific for any of the three CMS types. The PCR approach enabled a simple, fast and reliable large scale screening of maize cytoplasm among MRI gene bank accessions, significantly reducing time for cytoplasm characterizations compared to classical method of testing with restorers for each known type of CMS.