Induction of 2n pollen with colchicine during microsporogenesis in Eucalyptus

Abstract

Artificially inducing 2n gametes through chromosome doubling is an effective way to obtain polyploids. In this study, Eucalyptus urophylla microsporogenesis and flower development were investigated to guide 2n pollen induction. We also investigated suitable conditions for colchicine treatment. Our results showed that E. urophylla 2n pollen was spherical and had a large volume (mean diameter 28.57 ± 0.46 lm), while normal untreated pollen (mean diameter 19.68 ± 0.11 lm) was tetrahedron. The highest rate of 2n pollen production was 28.71 % when the flower buds, which ranged in size from 3.5 to 4.0 mm, underwent treatment with 0.5 % colchicine solution for 6 h. Further studies suggested that diplotene to diakinesis and metaphase I to telophase I were suitable meiotic stages for chromosomes doubling, due to asynchronous development of microsporogenesis between the anthers in a single flower bud. These data help to illuminate research in other areas, such as triploid eucalyptus production by chromosome doubling of female gametes.

Microsporogenesis and Induction of Unreduced Pollen with High Temperatures in Rubber Tree Clone RRIM 600

“…In this study, higher yields of unreduced pollen were obtained in morphology 3 MFBs, which have higher ratios of diplotene to metaphase I (37.12%) and anaphase I to telophase II (29.84%) ( Table 2), and unreduced pollen could also be obtained in MFBs of morphology 2 and morphology 4, both of which have certain ratios of diplotene to metaphase I (6.14% and 9.31%, respectively; see Table 2), again confirming that diplotene to metaphase I is probably the most suitable period for induction of unreduced pollen. The results presented here are similar to those from previous studies of Populus and Eucalyptus [16,17,19]. In Populus, water culture period and flower external morphology were used to estimate PMCs development [19].…”

“…These results suggest that treated male flower buds probably contain reduced pollen grains (n = x), 2n pollen grains (n = 2x), and giant pollen grains, confirming that different mechanisms of unreduced pollen induction occurred by exposure to high temperatures. In some species, unreduced pollen can also be identified by its shape; for example, unreduced pollen grains are spherical in both lily and Eucalyptus, while normal pollen grains are elliptical and tetrahedral, respectively [3,16]. In A. borealis, reduced grains have three pores and are more triangular in shape, while unreduced grains typically have four pores and are round [35].…”

“…In natural conditions, unreduced pollen has been discovered in many trees such as poplar, conifer, Chinese jujube, and Japanese persimmons [12][13][14][15]. Many efforts have also been made to induce unreduced pollen in many trees such as Eucalyptus, Eucommia ulmoides, and Ginkgo biloba [16][17][18]. There are no efforts of unreduced pollen induction in rubber trees.…”

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

“…Eucalyptus flowers were observed in a cluster in an inflorescence born in the axil of a leaf, and the unit inflorescence was generally a simple umble with 5-7 single flower buds [2]. According to previous studies [39,40], the development of flower buds at different locations on a floral branch was generally asynchronous, and the relationship between microsporogenesis and flower development could be used to estimate the period of meiosis [38]. In this study, flower buds were sampled every 12 h when the flower bud grew to 3.0 mm in diameter in the selected floral branches until fertilization from June to August in 2016.…”

“…We previously reported a method to obtain 2n pollen via colchicine treatment during microsporogenesis in Eucalyptus urophylla S.T. Blake with an expectation to produce triploids [38], but major problems, such as low yield and the purity of 2n pollen, limited its uses. Fortunately, these attempts uncovered some basic technical requirements, such as potential suitable periods for gamete chromosome doubling, which laid some foundation and gave some hope for further developments in eucalypt triploid breeding.…”