CROSS–FERTILIZATION BETWEEN DIPLOID AND TETRAPLOID RYEGRASSES

Preliminary studies have been undertaken to determine the degree to which diploid and tetraploid ryegrass varieties intercross under field conditions. The results obtained through the use of diploid and tetraploid non-red-base tester plants indicate that pollen from tetraploid ryegrasses constitutes little or no danger to the genetic purity of diploid seed crops, even if grown in close proximity. A small proportion of viable triploid hybrids can arise in the progenies of tetraploid plants heavily exposed to diploid pollen, but here again their frequency and incidence are not of practical consequence.