Near-Hexaploid and Near-Tetraploid Aneuploid Progenies Derived from Backcrossing Tetraploid Parents Hibiscus syriacus × (H. syriacus × H. paramutabilis)

Abstract

Hibiscus syriacus, azalea, is an important woody ornamental shrub planted throughout many temperate and subtropical regions of the world. However, flower size is smaller in this species than some of its relatives. To increase flower size, interspecific hybridization has been used, and such hybrid cultivars are usually characterized by larger flowers, increased vigor, diverse leaf shapes, and reduced fertility. Our earlier studies have shown that these hybrid cultivars could backcross with H. syriacus when used as male parents. To understand the breeding potential of these hybrid cultivars, two popular tetraploid hybrid cultivars, ‘Lohengrin’ and ‘Resi’, were used as pollen parents to backcross several tetraploid H. syriacus cultivars. As a result, 28.76% and 64.4% of ‘Lohengrin’ and ‘Resi’ progenies exhibited larger flowers than both of their parents. Interestingly, 14 of 18 progenies of ‘Resi’ were putative hexaploids, whereas 19 tested ‘Lohengrin’ progenies were tetraploid. Because putative hexaploid progenies were only observed among progenies of ‘Resi’, this hybrid cultivar appears to produce unreduced gametes. In addition, among the 14 putative hexaploids derived from ‘Resi’, 11 had larger flowers than both of their parents and their tetraploid siblings (p < 0.05). The 45S rDNA and 5S rDNA locus segregation among those BC1F1 progenies was tested by fluorescent in situ hybridization (FISH), and the wide range of 45S rDNA signal numbers among siblings indicated that these aneuploids resulted from unequal segregation or chromosome rearrangement. Chromosome counting confirmed aneuploidy among BC1F1 progenies. Ploidy diversity and aneuploidy have been known to contribute to various elements of morphological diversity, such as larger flower size and reduced fertility, which are important in ornamental plant breeding. The present study demonstrated the breeding potential of interspecific Hibiscus cultivars for increasing ploidy level and flower size.

Autotetraploid Induction of Three A-Genome Wild Peanut Species, Arachis cardenasii, A. correntina, and A. diogoi

“…In addition, the study’s Arachis tetraploid plants all showed obvious morphological differences. Usually, plants with higher ploidy show significantly different morphologies, including increased leaf and flower sizes [ 15 , 17 , 31 ]. However, the morphological differences are usually not immediately visible in most plant species.…”

Genome Doubling of Northern Spicebush, Lindera benzoin L.

“…Shorter internode or more compact plant shapes are commonly observed [52]. However, in some cases, genomedoubled plants show a similar internode length to their original ploidy plant [21,36,53], and some even have longer internodes [42]. Ploidy's impact on growth vigor can vary in different situations.…”

“…Increasing ploidy frequently results in morphological changes such as "thicker, darker-colored leaves; larger, longer-lasting flowers and thicker petals; enhanced vigor; improved tolerances to environmental stresses, pests, and pathogens; increased metabolite production" [19]. In many ornamental plants, larger flower size was reported to correlate to higher ploidy levels, including Hibiscus [20,21], hybrid Euphorbia [22], Lagerstroemia indica [23], and Impatiens spp. [24].…”

“…Thicker and darker foliage was also a common trait of induced polyploid plants, for example, Lagerstroemia indica [23,28], petunia [29], and Taraxacum kok-saghyz [30]. Enlarged flowers were also frequently reported in polyploidy induction research, including Cyclamen [31], Plectranthus × hybrida [32], and Hibiscus × hybrida [21]. Fruit size changed through ploidy manipulation is rarely discussed in ornamental plants; however, enlarged fruit at higher ploidy was reported in many fruit crops, ex, Malus × domestica [33], Actinidia arguta [34], and Olea europaea [35].…”