Cytological characteristics of birch and alder pollen (different breeding forms) used in hybridization

Abstract

Hybrids of some species of birch trees form completely sterile seeds (laboratory germination is zero in some hybrids, such as Karelian birch × Chinese white birch of inbred and outbred origin). It was noted analyzing the size distribution of birch pollen. Six size classes of pollen grains were identified, the modal values of which are arranged in increasing order as follows: 17 µm, 22 µm, 28 µm, 33 µm, 39 µm and 44 µm. The process of development of the male generative sphere proceeds without significant deviations in the studied black and gray alder trees. It ends with the formation of high-quality, aligned pollen. The obtained data indicate that one group of trees show normal formation of the reproductive sphere. It indicates the reasonableness of including them in the breeding process