Meiotic chromosome behaviour in an allotriploid derived from an amphidiploid × diploid mating in Cucumis

Abstract

A synthetic amphidiploid species Cucumis hyriviis Chen & Kirkbride (2n -4x -38; genome designated as HHCC) has recently been created from an interspecific mating between C. saiivtis L. (2n -2x = 14: genome designated as CC) and C. hyslri.\ Chakr. (2n -2x -24; genome designated as HH). This amphidiploid is resistant to root knot nematode. tolerant io low irradiance. and has higher nutritional value than standard processing cucumber cultivars. An allotriploid (2n 3 x -26; HCC) was derived frotii a cross between C. stiiivu.s L. and C. hvfivus Chen & Kirkbride. Diploid meiotic behaviour in C. saliviis and C. hysni.x involves the development of seven and 12 metaphase bivalents respectively. In the derived allotriploid. univalents. bivalents, and trivalents (at relatively low frequency) were observed at metaphase I indicating that some homeologues from the C and H genomes can synapse. Based on a comparative karyotype analysis of cucumber (i.e. chromosome size and pairing behaviour) and aliotriploid plants, ihe seven bivalents observed at metaphase I were ascertained to be cucumber homologtics. while the !2 univalents were of C. hystrix origin thus confirming the allotriploid karyotypic constitution to be HCC. On average, the frequency of trivalent.s was 0.24 at diakinesis and 0.22 in 100 meiocyles at metaphase I. indicating the possibility of genetic exchange due to the homoeology between the C and H genomes. After simultaneous cytokinesis, only polyads were observed in pollen mother cells (PMCs) at telophase II, which led to the production of sterile pollen grains. Multi-polarization of chrotnosomes was dominant at anaphase II. However, in about 20% PMCs. chromosotnes separated to form a 7C + I 2H complement, suggesting a possible method for the production of alien addition cucumbcr-C hvstrix hnes through fnrther backcrossing of the allotriploid to diploid cucumber.

Implications of polyploidy events on the phenotype, microstructure, and proteome of Paulownia australis

“…Based on parental genome differences, polyploidy is generally classified as either autopolyploid (the duplicated genome from the same species) or allopolyploid (the duplicated genome from the different species). Moreover, plant polyploids generally have large leaves and fruits, as well as other superior traits that make them attractive to breeders; for example, autotetraploid mulberry [ 6 ] and allotriploid cucumber [ 7 ]. In natural populations, after genomic merging and/or doubling, some genetic combinations may generate new morphological, ecological, physiological, and/or cytological characteristics that may be associated with speciation and biodiversification.…”

Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.)

“…sativus) matings as well as diploid derivatives (2n=2x= 14), which are fully fertile with C. sativus var. sativus (Chen et al 2004a;Qian et al 2005). The amphidiploid and its allotriploid and diploid derivatives provide a species bridge in Cucumis, and a source for broadening the genetic base of C. s. var.…”

“…The amphidiploid and its allotriploid and diploid derivatives provide a species bridge in Cucumis, and a source for broadening the genetic base of C. s. var. sativus and perhaps eventually also of C. melo (Chen et al 2003a;Zhuang et al 2004;Qian et al 2005). …”