Morphological characteristics of pollen grains of zizyphus (Zizyphus jujuba Mill.) cultivars bred in the Nikita Botanical Gardens

Abstract

This article presents the studying results of the pollen of three zizyphus cultivars (Zizyphus jujuba Mill.) Konfetny, Koktebel and Yalita, growing in the gene collection of the Nikita Botanical Gardens. The studies were carried out during 2019-2020. The control was zizyphus cultivar Konfetny, included in the register of protected breeding achievements of the Russian Federation. The morphological characteristics of pollen were studied. The size of pollen grains, depending on the cultivar, varied within 7-24 μm. It was revealed that the form of pollen grains in the equatorial projection is rounded for zizyphus cultivars Koktebel and Konfetny and oblong-rounded for the cultivar Yalita. The shape of the grains is spheroidal (Konfetny, Koktebel) and ellipsoidal (Yalita). By the nature of the apertures, the pollen grains of zizyphus are meridional-3-furrow-aperture. Ripe pollen grains are single, very small. To obtain a more complete understanding of the properties of pollen, its ability to germinate on an artificial nutrient medium was determined in two versions: in an aqueous solution of sucrose with a concentration of 15 and 20% and in a solution of sucrose with a concentration of 15 and 20 % with the addition of a stimulator of pollen tube growth - boric acid. Pollen on artificial nutrient medium does not germinate in both variants. The amount of abnormal pollen is relatively high in all analyzed varieties: Konfetny and Yalita 54,2- 60,5%, Koktebel – 65,7%. It is inappropriate to use these genotypes as initial parental forms in the breeding process.