Novel diploids following chromosome elimination and somatic recombination in Lolium multiflorum × Festuca arundinacea hybrids

Crosses were made between diploid Lolium multiflorum (2n = 2x = 14) and hexaploid Festuca arundinacea (2n = 6x = 42) in order to produce new forage hybrids. The F1 were treated with colchicine to double the chromosome number and to restore fertility in the amphidiploids (2n = 8x = 56). Chromosome counting in fertile hybrids revealed some unexpected diploid plants (2n = 14), as well as the expected amphiploids with 2n = 56. The phenotype of the diploids showed Festuca-like inflorescences which indicated they were not selfs of the L. multiflorum parent. Chromosome painting with a L. multiflorum genomic DNA probe showed the diploid complements to be recombinant and to carry some whole chromosomes, and some chromosome segments of L. multiflorum together with other chromosome parts which originated from the F. arundinacea genome. Meiotic behaviour of the diploids was regular, with seven bivalents. The results are discussed in terms of the segregation and recombination of different genomic components in the F1 hybrids during diploidization.