Cross Compatibility of Intersubgeneric Hybrids of Azaleas on Backcross with Several Evergreen Species

2015

The Hortic J

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Reciprocal crosses between nine evergreen azalea species and Rhododendron uwaense were performed to clarify the pre-and post-fertilization barriers in this interspecific hybridization for the purpose of obtaining fragrant evergreen azaleas. Unilateral incompatibility appeared in this hybridization. When evergreen azalea species were used as a seed parent, many pollen tubes stopped elongating in a style and no seed could be obtained. The reverse crosses exhibited inhibition of pollen tube penetration into ovules, chlorophyll deficiency in cotyledons, and death of young seedlings in some cross combinations. These pre-and post-fertilization barriers reduced hybridization but did not arrest it completely. As a result, many putative hybrid seedlings could be obtained. RAPD analysis revealed that 10 of the putative hybrid seedlings examined (two vigorous plants selected from respective crosses of R. uwaense #1 × five evergreen azalea species) possessed specific bands derived from both parents. The plastid DNA (ptDNA) of these seedlings was inherited maternally except for seedlings of R. uwaense #1 × R. yedoense var. poukhanense, and the ptDNA of hybrid ones obtained from R. uwaense #1 × R. yedoense var. poukhanense was inherited paternally.

Section: Molecular Analysis Of Hybridity and Plastid Dna Inheritancementioning

confidence: 99%

Pre- and Post-fertilization Barriers in Interspecific Hybridization between Evergreen Azalea Species and <i>Rhododendron uwaense</i> H. Hara & T. Yamanaka

Okamoto

2015

The Hortic J

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“…To improve the semi-deciduous traits, chromosome doubling of the progenies was conducted, and the derived plants were back-crossed to evergreen azaleas. These BC 1 plants were vigorously developed with evergreen traits (Ureshino et al, 2006). In future, we will investigate their flower colors.…”

Section: Future Studymentioning

confidence: 99%

Study of Cross Incompatibility between Evergreen and Deciduous Azaleas

J. Japan. Soc. Hort. Sci.

2008

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“…The flower color of cross parents is described in Table 1. Pollen viability of JP was evaluated by the standard acetocarmine technique as described in a previous report (Ureshino et al, 2006). Capsules were harvested at 180 days after crossing, and the derived seeds were used for in vitro sowing.…”

Section: Plant Materialsmentioning

confidence: 99%

Relationship between Nuclear Genome Construction and the Plastome-genome Incompatibility of Progenies from Intra- and Inter-ploid Cross of Evergreen Azaleas × Rhododendron japonicum f. flavum

J. Japan. Soc. Hort. Sci.

Abe

Akabane³

2010

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In intersubgeneric crosses of diploid evergreen azaleas (EV) × diploid Rhododendron japonicum f. flavum (JP), many progenies become albino as a result of plastome-genome incompatibility between a plastid genome from EV and a nuclear genome from JP. To clarify the mechanism of the incompatibility, inter-and intra-ploid crosses of diploid (2x) EV × diploid (2x) JP, tetraploid (4x) EV × tetraploid (4x) JP, 2x EV × 4x JP, and 4x EV × 2x JP were conducted. Seeds were obtained in all crosses, although the number of progenies per capsule was relatively low in crosses with 4x JP as a pollen parent. Plastome-genome incompatibility between a plastid genome from EV and a nuclear genome from JP was observed in progenies from 2x EV × 2x JP, 4x EV × 4x JP, and 2x EV × 4x JP, but not in 4x EV × 2x JP. This result indicates that plastome-genome incompatibility was broken by relative increase of the genome from EV in the nuclear genome of progenies.