Inducing triploids and tetraploids with high temperatures in Populus sect. Tacamahaca

Abstract

This study is the first to report that triploids and tetraploids have been successfully produced through embryo sac and zygotic embryo chromosome doubling with high temperatures in P. simonii Carr. and its hybrid. A new synthetic polyploid induced by hybridization with unreduced gametes and heterozygotic embryo chromosome doubling can effectively combine polyploidy and heterosis, which can provide two major breeding advantages. In Populus, successfully creating and cultivating new polyploid varieties have economic and ecological production value. This was the first successful study in which embryo sac and zygotic embryo chromosome doubling was induced using high temperatures to produce triploids and tetraploids in Populus simonii Carr. and its hybrid, P. simonii × P. nigra var. Italica, of Populus sect. Tacamahaca. The relationship between flower bud morphological characteristics (time after pollination) and female meiotic stage (embryo sac and zygotic embryo development) was established to guide the induction treatment period. In the resulting progeny, 37 triploids and 12 tetraploids were obtained and identified using flow cytometry. The optimal temperatures for embryo sac and zygotic embryo chromosome doubling were 38 and 41 °C, respectively. Cytogenetic analysis revealed that 66-72 h after pollination (HAP), a period characterized by a high proportion of one-nucleate and two-nucleate embryo sacs, was the optimal period for embryo sac chromosome doubling. For zygotic embryo chromosome doubling, 168 HAP was the optimal induction period, as there was a high proportion of two-cell and four-cell proembryos. The results indicate that inducing embryo sac and zygotic embryo chromosome doubling is an ideal method for producing polyploids. The methods for inducing polyploids and for evaluating ploidy and offspring with different ploidies and heterozygosity in this study will be useful for genetic research and Populus breeding programmes.

In Support of Winge's Theory of “Hybridization Followed by Chromosome Doubling”

“…In this context, it is interesting to note that chromosome doubling at the zygote level can be artificially induced. For example, high temperatures induced the formation of synthetic triploids and tetraploids through embryo sac and zygote embryo chromosome doubling in Populus simonii and its hybrids (Guo et al, 2017). Similarly, corn plants exposed to high temperatures after pollination produced diploid, tetraploid, and octoploid seedlings (Randolph, 1932).…”

An improved method for high-temperature induced embryo sac chromosome doubling in Populus simonii Carr. × P. nigra var. italica (Moench.) Kochne, an interspecific hybrid of Tacamahaca and Aigeiros poplars

“…simonii , as a protospecies of sect. Tacamahaca , completed its embryo sac development at 144 HAP 13 . In Populus simonii × P .…”

“…Aigeiros are especially significant for forestation in the northeast of China because of their excellent stress resistance and growth characteristics. Our research group has focused on chromosome doubling during hybridization between the two sections for several years and has established a technical system for high-temperature polyploidy induction 13 . The development of the female gamete and zygotic embryo in P .…”

“…The development of the female gamete and zygotic embryo in P . simonii was observed to confirm the time required for the induction treatment, and cross compatibility was used to determine the parents and cross combinations 13 . Finally, we chose P .…”

Comparative mitochondrial proteomic, physiological, biochemical and ultrastructural profiling reveal factors underpinning salt tolerance in tetraploid black locust (Robinia pseudoacacia L.)

“…Polyploid plants play important roles in agricultural production due to their specific traits such as longer leaves [ 10 ], morphological enlargements in seeds and corolla limbs [ 11 ] and delayed flowering [ 12 ]. Additionally, some polyploidy forest species also showed a lot of advantages over their diploid counterparts, including larger leaves, greater growth vigour, better timber quality and higher stress resistance [ 13 , 14 ]. However, empirical data supporting this hypothesis are scarce, especially for forest species [ 15 ].…”