Male Meiosis Peculiarities of Four Oat (Avena sativa L.) Varieties Cultivated in Central Yakutia

Abstract

Extreme environmental factors decrease seed setting and form unseeded or thinning panicles. Since meiosis underlies formation of gametes, it largely determines further processes associated with pollination, fertilization and development of a full-fledged seed. In this regard, studies meant to identify the peculiarities of male meiosis for plants cultivated in the severe natural and climatic conditions of Central Yakutia are relevant and of particular interest. The goal of this study was to identify the characteristics of male meiosis in oat (Avena sativa L.) varieties adapted to local conditions. We should emphasize that no studies of meiosis in common oats under the conditions of Central Yakutia have been performed earlier. We used four varieties of common oats (Pokrovsky, Vilensky, Pokrovsky 9, and Khibiny 2) as study material. All the varieties under analysis were hexaploids (2n = 6x = 42). The studies were conducted in 2020 at the Pokrovsky Department of Yakut Research Institute of Agriculture, in Khangalassky ulus of the Republic of Sakha (Yakutia) located in the middle taiga zone. The weather and climatic conditions during the growing season were characterized by an insufficient provision of soil with productive moisture at the early phases of grain and forage crop growth and development. To analyze meiosis, we used oat spikelets sampled when they were emerging into the tube. The spikelets were fixed on June 25-27, 2020 in duplicate using Carnoy’s solution. We analyzed microsporogenesis and pollen fertility on the temporary squashed preparations of meiocytes using the generally accepted method with 4% acetocarmine staining. The results were statistically processed using Statistica 7.0 (StatSoft. Inc., USA). The samples were compared through one-way ANOVA. The general cytological picture of meiosis in the oat varieties under study mostly corresponded to the conservative scenario typical of monocotyledonous plants. However, all the oat varieties showed some deviations from the general meiosis pattern. One of such deviations was cytomixis - chromatin migration as part of nuclei between microsporocytes through one or several cytomictic channels (Fig. 1, 2). As a rule, the phenomenon of cytomixis in microsporocytes was observed at middle prophase 1 at the pachytene stage (Fig. 1). Nuclei migration was also observed at late prophase 1, for example, at the diplotene stage. Chromatin movement between two adjacent microsporocytes clearly correlated with the formation of micronuclei and cytoplasts. Quite often, this process was also accompanied by nuclei pycnosis (Fig. 2). We should note that rarely we observed massive destructive cytomixis in microsporocytes and tapetum cells. When studying common oat cultivars, we also found microsporocytes with separately lying bivalents that were not included in the metaphase plate (Fig. 2), as well as chromosomal bridges (Fig. 2) at the anaphase-telophase 1 stage. The proportion of microsporocytes with meiotic deviations in all the four cultivars was small (Fig. 3) and varied from 2.99 to 3.23% (Table 1). We found no consequences of the revealed deviations at the tetrad stage. Probably, either most deviations were compensated for by intracellular mechanisms or defective microsporocytes were excluded from the microsporogenesis and eliminated. Besides, these deviations of meiosis did not significantly decrease pollen fertility (Table 1). The results indicate that the observed deviations of meiosis do not significantly contribute to seed formation in such an important grain fodder crop as common oats in the climatic conditions of Central Yakutia. The article contains 3 Figures, 2 Tables, 27References. The Authors declare no conflict of interest.