Formation of Rice Tetraploids in In Vitro Androgenesis
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RODUCTION
Formation of Rice Tetraploids in In Vitro Androgenesis M. V. Ilyushkoa, * and M. V. Romashovaa aFederal
Scientific Center of Agrobiotechnology of the Far East, Timiryasevskiy, Primorskiy krai, 692539 Russia *e-mail: [email protected] Received November 26, 2019; revised December 5, 2019; accepted January 15, 2020
Abstract—Creating tetraploid rice is a promising field in increasing crop yields. There are currently no commercial rice varieties due to poor panicle grazing, which is caused by low pollen fertility. It is stated in the scientific literature that tetraploid plants are obtained in vitro androgenesis as an additional starting material. The aim of the study was to study the characteristics of callus in anther culture of rice in vitro, on which tetraploid plants are formed, and the characteristics of rice tetraploid regenerants. Studies were performed on 15 F2 hybrids of Oryza sativa L. subsp. japonica Kato of three hybrid combinations. In vitro androgenesis is a reliable way to obtain polyploid regenerants in the majority of genotypes: 59 plants (1.9% of all green regenerants) are tetraploid. The proportion of calli with tetraploids is 17.6%. Calli on which tetraploid plants were formed are characterized by a decreased number of haploids and an increased number of seedless plants of nonhaploid origin. The maximum number of tetraploids per callus aggregate is 12 pcs. Tetraploids obtained in vitro androgenesis have a slight grazing of the main panicle (on average 1.0–6.0 pcs.), which is typical for polyploid rice. Keywords: Oryza sativa, in vitro androgenesis, callus, tetraploid DOI: 10.3103/S1068367420040084
INTRODUCTION Polyploidy played a crucial role in the evolution of plants and crop breeding [1, 2]. Many polyploids are successfully used in agricultural production and floriculture, as they provide a higher yield and better decorative qualities in comparison with diploid species [2, 3]. Rice Oryza sativa L. is a widespread diploid crop (the main number of chromosomes is 2n = 24), which is grown on five continents; half of humanity feeds on rice cereal [4]. Polyploid, in particular tetraploid rice, is considered as one of the sources for increasing the yield of the species [5–7]. Tetraploid rice was first obtained in 1933; it has been included since 1953 in the breeding process in China [8]. However, a small number of seeds are formed on panicles because of a low pollen fertility, which is caused by deviations in meiotic cell division [8–10]. Therefore, tetraploid rice has not yet been used commercially [7]. Modern studies of tetraploid rice are scarce. The genetic and morphological variability of O. sativa was studied using 99 SSR markers and agronomic traits. It turned out that the variability of tetraploid rice is higher than that of diploid rice, and a heterosis was obtained from interspecific hybridization of polyploid rice [11]. The transfer of rice hybrids of O. sativa from the diploid level to the tetraploid level by treatment with colchicine contributes to the formation of awned form
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