Reduction of Ploidy Level by Androgenesis in Intergeneric Lolium–Festuca Hybrids for Turf Grass Breeding

Abstract

To widen the gene pool of cool season turfgrasses, intergeneric tetraploid hybrids of Festuca pratensis Hudson with Lolium perenne L. and L. multiflorum Lam. are being screened for desirable turf characteristics. Anther culture was used to reduce their ploidy level to diploid. Of the 37557 anthers cultured, 1986 green and 904 albino plantlets were regenerated with large differences in androgenic responses among the genotypes tested. Lolium perenne regenerated only albino plants, and that with a low frequency, while in F. pratensis × L. perenne and L. multiflorum × F. pratensis hybrids 3.7 and 25.5 green plants per 100 anthers cultured were recovered, respectively. Chromosome numbers among the progeny ranged from 13 to 56, with a majority being diploid (about 14) or tetraploid (about 28). The rates of spontaneous chromosome doubling were 50% in L. multiflorum, 25.7% in L. multiflorum × F. pratensis, and 8.3% in F. pratensis × L. perenne hybrids. In situ probing with total genomic DNA (GISH) showed that all tetraploids recovered were spontaneously doubled haploids; no regeneration from somatic anther tissue took place. GISH among sets of plants originating from what appeared as single embroids showed that with one exception, all such sets were of clonal nature. The single exception was a set of plants with unique recombination patterns along chromosomes that must have regenerated from different microspores. This experiment demonstrates that large-scale production of androgenic progeny for breeding of intergeneric hybrids of grasses is feasible and that with low frequency of spontaneous chromosome doubling ploidy reduction it is highly efficient. The experiment also verifies the nature and origin of various classes of regenerants.