Unreduced Male Gamete Formation in Cymbidium and Its Use for Developing Sexual Polyploid Cultivars

Abstract

Polyploidy plays an important role in crop improvement. Polyploid plants, particularly those produced through unreduced gametes (2n gametes), show increased organ size, improved buffering capacity for deleterious mutations, and enhanced heterozygosity and heterosis. Induced polyploidy has been widely used for improving floriculture crops, however, there are few reported sexual polyploid plants in the floriculture industry. This study evaluated nine cultivars of Cymbidium Swartz and discovered that 2n male gametes occurred in this important orchid. Depending on cultivars, 2n male gamete formation frequencies varied from 0.15 to 4.03%. Interspecific hybrids generally produced more 2n male gametes than traditional cultivars. To generate sexual polyploid plants, seven pairs of crosses were made, which produced five triploid and two tetraploid hybrids. Two triploid hybrids were evaluated for in vitro regeneration and growth characteristics. Compared to the diploid parents, the triploids were more easily regenerated through rhizomes or protocorms, and regenerated plants had improved survival rates after transplanting to the greenhouse. Furthermore, the sexual polyploid plants had more compact growth style, produced fragrant flowers, and demonstrated heterosis in plant growth. Through this study, a reliable protocol for selection of appropriate parents for 2n gamete production, ploidy level evaluation, in vitro culture of polyploid progenies, and development of new polyploid cultivars was established. Our study with Cymbidium suggests that the use of 2n gametes is a viable approach for improving floriculture crops.

Genome-wide identification and expression analysis of the ERF transcription factor family in pineapple (Ananas comosus (L.) Merr.)

“…The diversity of gene combinations may be one of the factors that make the regulatory relationship complicated ( Zhang et al, 2018 ; Zhang et al, 2020 ). Polyploidization, a widespread phenomenon among plant, is considered an important process of plant speciation and evolution, and the formation of polyploid includes hybridization and genomic doubling process before or after hybridization ( Kohler, Scheid & Erilova, 2010 ; Zeng et al, 2020 ). Various Arabidopsis and rice ERF genes have been reported to be involved in the regulation of plant stress tolerance.…”

Peer Review #1 of "Genome-wide identification and expression analysis of the ERF transcription factor family in pineapple (Ananas comosus (L.) Merr.) (v0.2)"

“…The diversity of gene combinations may be one of the factors that make the regulatory relationship complicated (Zhang et al, 2018;Zhang et al, 2020). Polyploidization, a widespread phenomenon among plant, is considered an important process of plant speciation and evolution, and the formation of polyploid includes hybridization and genomic doubling process before or after hybridization (Kohler et al, 2010;Zeng et al, 2020). Various Arabidopsis and rice ERF genes have been reported to be involved in the regulation of plant stress tolerance.…”

Cytological Study of Cypripedium japonicum Thunb. (Orchidaceae Juss.): An Endangered Species from Korea

“…The underlying reason for genome size differences among the Cypripedium species might be the differential accumulation of non-coding repetitive DNAs, as reported in other plant groups (Figure 3C; [19,40,41]). An understanding of chromosomal variation among populations concomitant with changes in genome size may provide novel insights into the ecological conservation status for the extremely endangered/threatened taxa, as reported for other genera of Orchidaceae [30,42,43]. 1.…”