RFLP Detection of 2n Pollen Formation by First and Second Division Restitution in Perennial Ryegrass

Abstract

Unreduced gametes can be used to transfer desirable traits from parent to polyploid offspring. Codominant restriction fragment length polymorphism (RFLP) markers were applied to determine the mechanism of 2n pollen formation in diploid (2n = 2x = 14) Lolium perenne L. Sixty heterologous probes were randomly chosen from a Festuca arundinacea Schreb. PstI‐genomic DNA library. A total of 30 and 33 heterozygous allelic loci were detected in two genotypes of parental L. perenne, respectively, based on segregation of RFLP loci in 13 triploid (3x) and two tetraploid (4x) hybrids, produced in 1993, between diploid L. perenne and tetraploid F. mairei St. Yves. Approximately 30 and 83% of the heterozygosity was transmitted by 2n pollen from L. perenne into two tetraploid hybrids, respectively. Both meiotic first division restitution (FDR) and second division restitution (SDR) occurred in 2n pollen formation in L. perenne. Omission of the second meiotic division (OS) and fusion of adjacent polar nuclei (FA) were found during microsporogenesis. These two mechanisms were supposedly responsible for forming 2n gametes by SDR and FDR, respectively. Formation of 2n pollen in diploid L. perenne could facilitate efficient transfer of germplasm from diploid to higher ploidy levels in Lolium and Festuca.