Megaspore Chromosome Doubling in Eucalyptus urophylla S.T. Blake Induced by Colchicine Treatment to Produce Triploids

Abstract

Triploids generally provide an advantage in vegetative growth in forest trees. However, the technique of triploid breeding is still an open field in the Eucalyptus tree species. This study aims to explore the colchicine treatment technique for megaspore chromosome doubling to establish triploids in this tree species. Cytological observation on microsporogenesis and megasporogenesis was carried out to guide megaspore chromosome doubling induced by colchicine treatment. Ploidy level in progenies was detected by flow cytometry and somatic chromosome counting. A relationship between microsporogenesis and megasporogenesis was established to guide the colchicine treatment. Seven triploids were obtained in the progenies, and the highest efficiency of triploid production was 6.25% when the flower buds underwent a 0.25% colchicine solution treatment for 6 h using an aspiration method seven days after the first observation of leptotene during microsporogenesis on the floral branch. Cytological analysis showed that the megasporocyte from leptotene to diakinesis may be the optimal period for megaspore chromosome doubling by colchicine treatment. Plant height, ground diameter, leaf area, and the photosynthetic parameter of triploid eucalypt were significantly higher than those of the diploid plant at 6 months old. Hybridization with 2n megaspores induced by colchicine treatment is an effective way for Eucalyptus triploid breeding. These results should accelerate the development of advanced germplasms in this tree species.

POLYPLOIDY INDUCED BY COLCHICINE IN Robinia pseudoacacia L. AND IT'S EFFECTS ON MORPHOLOGICAL, PHYSIOLOGICAL AND ANATOMICAL SEEDLING TRAITS

“…The results suggested that stomata in tetraploid plants were larger but fewer (in area unit of leaf) compared to the control plants. These results are consistent with other studies (6,8,17,24,34,35,40). The increased cell size as exemplified by enlarged stomata size in triploid may play an important role in increasing the size of the leaves, which was also observed in this study.…”

“…Roy et al, (29) was suggested that the length and diameter of the stomata were set to be standard parameters for identification of tetraploid plants. Other reports on stomata size in the guard cells indicated that these cells are more dependent on genetic than environmental factors as compared to other cells in plant (40). The results suggested that stomata in tetraploid plants were larger but fewer (in area unit of leaf) compared to the control plants.…”

Effects of Colchicine on Populus canescens Ectexine Structure and 2n Pollen Production

“…It inhibits microtubule polymerization by binding to tubulin, and thus it inhibits the mitotic spindle formation resulting in the development of a polyploid cell. Colchicine has been successfully used to induce 2n female gametes by treating embryo sacs, zygotes, and somatic cells, furthermore, a large number of triploids and tetraploids have been generated in Populus (Li et al, 2001;Kang et al, 2004;Wang et al, 2010a,b;Cai and Kang, 2011;Xu et al, 2016), Robinia pseudoacacia (Ewald et al, 2009), Eucommia ulmoides (Zhang et al, 2008), and Eucalyptus urophylla (Yang et al, 2018). Colchicine has also been applied to induce 2n pollen production in Populus (Li et al, 2014;Zhao et al, 2017Zhao et al, , 2019, Eucommia ulmoides , and Eucalyptus (Yang et al, 2016).…”

Hybrid Triploid Induced by Megaspore Chromosome Doubling in Jujube (Ziziphus jujuba Mill.) ‘Maya’ and Its Characteristics

“…Consequently, polyploids have been widely used in fruit tree production [4][5][6]. The use of colchicine [7,8] or high temperature [9,10] to induce the formation of 2n gametes and their use in controlled pollinations is an important approach to obtain triploid progeny [11]. As a polyploidization agent, colchicine treatment is the most common and effective method applied to produce diploid gametes and triploids, as has been reported for poplar [12], cassava [13], Eucalyptus [14], and Cymbidium [15].…”

“…During fertilization, the induced 2n pollen usually exhibits weaker development and competitiveness compared with haploid pollen [18], whereas 2n female gametes show greater efficiency for formation of triploids by hybridization [19]. Induction of 2n female gametes by chromosome doubling in the megaspore or embryo sac has been Forests 2021, 12, 112 2 of 16 successfully used to obtain triploid plants in poplar [20], mulberry [21], Eucalyptus [8], Eucommia [9]. However, few studies have investigated artificial induction of unreduced gametes to induce polyploidy in fruit trees.…”