title: The transmission of rye B chromosomes in natural pollination.
abstract: This paper examines the transmission of B chromosomes in natural (but controlled) pollination, in order to obtain results which can be applied to natural populations of rye. The frequencies of the female gametes in both 2n= 14+1 and 2n=14+2 rye plants have been estimated with reference to their chromatid constitution. From the results obtained on the offspring, it seems that preferential distribution takes place during female meiosis of 2n= 14+2 plants. It has been demonstrated that pollen carrying B chromosomes formed in plants of 2n=14+2 was more competitive than normal pollen. On the contrary, when it was formed from plants 2n=14+1, B chromosome elimination by pollen was total. This process may be considered as sporophytic determination. The genetic significance of the presence of B chromosomes in natural populations is discussed. It is proposed that B chromosomes may be the cytological expression of a complex evolutionary system which results in conservation of population genetic variability.
authors.affiliation: Departamento de Genética, Facultad de Biologia, Universidad Complutense, Madrid, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Puertas
authors.forename: J R
authors.initials: JR
authors.lastname: Lacadena