GENETICS OF MALE-STERILITY IN GYNODIOECIOUS PLANTAGO-CORONOPUS .2. NUCLEAR GENETIC-VARIATION

Inheritance of male sterility was studied in the gynodioecious species Plantago coronopus using five plants and their descendants from an ar ea of similar to 50 m(2) from each of four locations. In each location , crosses between these five plants yielded the entire array of possib le sex phenotypes. Both nuclear and cytoplasmic genes were involved. E mphasis is placed on the nuclear (restorer) genetics of two cytoplasmi c types. For both types, multiple interacting nuclear genes were demon strated. These genes carried either dominant or recessive restorer all eles. The exact number of genes involved could not be determined, beca use different genetic models could be proposed for each location and n o common genetic solution could be given. At least five genes, three w ith dominant and two with recessive restorer allele action, were invol ved with both cytoplasmic types. Segregation patterns of partially mal e sterile plants suggested that they are due to incomplete dominance a t restorer loci. Restorer genes interact in different ways. In most in stances models with independent restorer gene action were sufficient t o explain the crossing results. However, for one case we propose a mod el with epistatic restorer gene action. There was a consistent differe nce in the segregation of male sterility between plants from the two c ytoplasmic types. Hermaphrodites of cytoplasmic type 2 hardly segregat ed male steriles, in contrast to plants with cytoplasmic type 1.