CYTOPLASMIC MALE-STERILITY (CMS) IN LOLIUM-PERENNE L .1. DEVELOPMENT OF A DIAGNOSTIC PROBE FOR THE MALE-STERILE CYTOPLASM

Analysis of reciprocal crosses between nonrestoring fertile genotypes and restored male-sterile genotypes of Lolium perenne confirmed the cy toplasmic nature of the sterility trait. This prompted a search for a molecular probe that could be used to distinguish between fertile and cytoplasmic male-sterile (CMS) cytoplasms. We describe the identificat ion and cloning of a 4.5-kb BamHI-HindIII restriction fragment from th e mtDNA of the CMS line. The cloned fragment (pCMS45) failed to hybrid ise to sequences in the mtDNA of fertile lines and was thus capable of unambiguously distinguishing between fertile and CMS cytoplasms. The use of pCMS45 as a diagnostic probe provided a simple test for positiv e identification of young non-flowering plants carrying the CMS cytopl asm and also permitted confirmation at the molecular level of the mate rnal transmission of the CMS trait suggested by the genetic data.