Identification and frequency of tetraploid progeny from 2x–4x and 4x–2x crosses in Dactylis

The utilization of diploid germ plasm in the improvement of tetraploid orchard grass (Dactylis glomerata L. ssp. glomerata Hayek) requires some means of polyploidization. Studies in several different crop species have shown that sexual polyploidization has the advantage of transmitting a large proportion of heterozygosity from the parent to the offspring. In tetrasomic tetraploids, maximum heterozygosity is a necessary requirement for maximum heterosis. The objective of this research was to investigate the occurrence of 2n eggs and 2n pollen in several sources of wild diploid germ plasm, by quantifying the frequency of 4x genotypes among the progeny of interploidy crosses. Pollen diameter was determined in 110 diploid genotypes. These genotypes were then ranked for five descriptive statistics based on diameter (maximum, 75th percentile, median, arithmetic mean, mode). The eight top-ranking genotypes in four of the five categories were crossed to male-sterile 4x seed parents. Randomly selected diploid geno...