Colchicine induced manifestation of abnormal male meiosis and 2n pollen in Trachyspermum ammi (L.) Sprague (Apiaceae)

Unreduced gametes are the key source for the natural polyploidization in plants, but process of its formation is very low in nature. Meiotic mutants are second source for the formation of 2n pollen. In this cytological investigation, the meiotic aberrations and its impact on post-meiotic products were analysed in autotetraploid Trachyspermum ammi (L.) Sprague (4n=36). The seedlings of T. ammi (L.) Sprague were treated with 3 different concentrations of colchicine (0.2, 0.4 and 0.5%, w/v) for 3 different durations. Six polyploid plants were induced which was confirmed on the basis of cytological analysis. Colchicine, an anti-microtubular drug induced different meiotic and post-meiotic abnormalities such as chromosomal bridges, lagging chromosomes, scattering, precocious, fragments, dyads, triads, and polyads. The formation of several abnormal sporads clearly signifies the meiotic restitution. The tendency of univalents to scattered in the cytoplasm at metaphase was identified as a peculiar aberration asynapsis. Pollen variability and fusion of pollen walls was reported and pollen fertility was calculated. The morphological analysis of the pollen allowed us to confirm the occurrence of 2n pollen.

Colchicine induction of ‘Old Blush’ 2n pollen for the hybridization and breeding of tetraploid rose

Obtaining 2n pollen from the diploid Chinese old rose ‘Old Blush’ through artificial induction is one important means of hybridizing and breeding modern tetraploid roses. We used colchicine-induced 2n pollen to assess normal viability during hybridization and fructification. The results showed that the pollen mother cell had lagging chromosomes and parallel spindles at meiosis I stage, following which the 2n pollen was produced from dyads and triads with doubled chromosomes. We obtained 4.30% viable 2n pollen, which was significantly higher than the yield of the spontaneous 2n pollen (1.00%) using an optimal treatment combination of induction for 24 h with 0.50% colchicine. There was no significant difference between the external morphology of the induced 2n pollen and the spontaneous 2n pollen, whereas both types of 2n pollen possessed finer furrows, and fewer and smaller pores than the 1n pollen, and the external morphology of 2n pollen was more evolved. In terms of in vitro germination rate and pollen tube length, the induced 2n pollen did not differ significantly from the spontaneous 2n pollen. The survival rate of the floral buds was significantly decreased with increased colchicine concentration and treatment time.

Frequency of Polyploids of Solanum tuberosum Dihaploids in 2X × 2X Crosses

When breeding diploid potatoes, tetraploid progeny can result from the union of 2n eggs and 2n pollen in 2x-2x crosses. Thirty-three crosses were made to examine tetraploid progeny frequency in 2x-2x crosses. All crosses were between S. tuberosum dihaploids and diploid self-compatible donors, M6 and DRH S6-10-4P17. Using chloroplast counting for ploidy determination, the frequency of tetraploid progeny was as high as 45% in one of the 33 crosses. Based upon single nucleotide polymorphism (SNP) genotyping, the tetraploid progeny were attributed to bilateral sexual polyploidization (BSP), which is caused by the union of 2n egg and 2n pollen. Dihaploids were identified that produce lower frequencies of 2n eggs. The results of this study suggest that S. tuberosum dihaploids with a high frequency of 2n eggs should be avoided in 2x - 2x crosses for diploid breeding programs.

High frequency 2n pollen formation in black poplar (Populus nigra L.) induced by colchicine

Populus nigra L. is one of the most important male genetic donors in populus genetic improvement and tree breeding over the world. Many excellent Populus nigra clones are identified as triploids potentially obtaining by hybridization of 2n pollen and normal oogamete. This study revealed the cytological mechanism of 2n pollen formation in Populus nigra L. for the first time and concluded the best treated combination of colchicine treatment, which obtained 2n pollen with the highest rate reaching at 87.11% (even 100% 2n pollen in some floral buds) which made the polyploid hybridization utilizing 2n pollen in section Aigeiros possible. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Colchicine did not affect the viability of induced 2n pollen in Populus tomentosa

Colchicine is widely used as a mutagen to induce production of diploid gametes in plants. However, whether colchicine affects induced pollen viability remains unclear. To clarify whether colchicine affected the viability of induced pollen, we induced production of diploid pollen by colchicine, followed by pollen germination and crossing induced pollen with normal gametes to produce triploid in Carrière. The results showed that the predominant meiotic stages and the number of colchicine injections had significant effects on the occurrence rates of induced 2n pollen. When the colchicine injection was given at diakinesis, a significant decrease in the pollen production per bud was observed ( < 0.001). The morphology of the colchicine-induced 2n pollen was similar to that of the natural 2n pollen in its ectexine structure. The pollen germination experiments revealed that there was also no significant difference in germination rates between the induced diploid pollen and natural 2n pollen grains, and 68 triploids were created by crossing colchicine-induced pollen. Our findings revealed that colchicine injection could induce to produce 2n pollen and will not lead to dysfunction of induced diploid pollen.in vitroPopulus tomentosapP. tomentosa