Tetraploid Festuca apennina is Prone to Produce Triploid Hybrid Progeny When Crossed with Diploid Festuca pratensis

Abstract

Festuca apennina De Not. is a species growing at altitudes of 1100 to 2000 m a.s.l. in different regions of Europe. To test cross fertility of different cytotypes of F. apennina, pairwise crosses were made with tetraploid and triploid F. apennina, as well as diploid and colchicine-induced tetraploid Festuca pratensis Huds. Tetraploid F. apennina appeared to be quite cross-fertile with diploid F. pratensis and produced triploid progeny in both cross directions. When F. apennina plants were pollinated with diploid F. pratensis, they yielded even more seed per inflorescence than those pollinated with another F. apennina plant. About 25% of the progeny of this cross were triploids; the remaining 75% were tetraploid, presumably resulting from self-pollination. Much less seeds were obtained on diploid F. pratensis pollinated with F. apennina, but the progeny consisted of as much (52%) triploid hybrids as of diploid selfs (48%). Seeds harvested on F. apennina giving rise to triploid progeny appeared to have no cold requirement for germination, as opposed to tetraploid progeny from self-pollination or crosses among F. apennina. Colchicine-induced tetraploids and diploids of F. pratensis were much less cross-fertile. Few viable seeds were obtained, with a great majority (91%) resulting from self-pollination, with only 9% triploid hybrids. The surprisingly high cross fertility of tetraploid F. apennina with diploid F. pratensis, the apparent absence of a triploid block in their progeny, and the fact that seeds of F. apennina giving rise to triploid progeny have no cold requirement, probably contribute to the frequent occurrence of triploid forms at the low end of F. apennina altitudinal distribution.