Daiki Mizuta

Chimeric inheritance of organelle DNA in variegated leaf seedlings from inter-subgeneric crossing of azalea

The inheritance of organelle DNA was investigated using PCR–RFLP markers in reciprocal cross combinations of inter-subgeneric azalea hybrids between evergreen azaleas (Rhododendron nakaharai and its hybrids) and fragrant deciduous azaleas (R. arborescens and R. viscosum) for the purpose of breeding fragrant evergreen azaleas. The hybrid progenies included green leaf, pale green leaf, variegated leaf and albino seedlings. Most viable green leaf seedlings had inherited ptDNA from the deciduous parent and non-viable albino and pale green leaf seedlings had inherited ptDNA from the evergreen parent. On the other hand, variegated leaf seedlings had chimerically inherited ptDNA from both parents. Their green leaf segments had ptDNA from the deciduous parent, and the pale green and white segments had biparental or maternal ptDNA depending on the progeny. In this study, we obtained interesting inter-subgeneric azalea hybrid progenies that had chimerically inherited organelle DNA and had different colored leaf segments corresponding to the composition of ptDNA from each parent. These results suggest that variegated leaf progenies with chimeric ptDNA from both parents can be subsistent, whereas albino seedlings resulting from plastome–genome incompatibility between the plastid genome from evergreen azalea and the nuclear genome from deciduous azalea are non-viable.

Association of putative viral RNA sequences to flower colour variegation in Japanese primrose (Primula sieboldii E. Morren)

Flower colour variegation is characteristic symptom of viral infections in ornamentals such in the case of camellia, tulip, petunia, and daffodil. This is also seen in different cultivars of Japanese primrose like ‘Shichikenjin’, ‘Sotorihime’ and ‘Isaribi’, signifying a possible viral origin. Putative viral RNA sequences were first identified in the Primula sieboldii databases. Total RNA was then isolated and reverse transcriptase polymerase chain reaction was done using virus-specific primers to identify the association between the presence of putative viral RNA sequences and flower colour variegation. Five putative viral RNA homologous sequence groups were identified, with a possible virus identity of Cycas necrotic stunt virus, Lettuce big-vein associated virus and Rosa multiflora cryptic virus. Results showed that instances of amplifications were seen in both variegated and non-variegated within and across cultivars denoting the presence of putative viral RNA and a possible viral morbidity in the amplified cultivars. Instances wherein amplification of non-variegated flowers, while no amplification of variegated flowers within the same cultivar were also observed. Variegated plants of cultivars which had variegated and non-variegated flowers had a weak correlation. Thus, no definite association could be deduced from the presence of putative viral RNA and flower colour variegation. It is also recommended that flower tissue should be used for gene expression analysis to avoid error in differential gene expression.

Presence of putative Cycas necrotic stunt virus RNAs in Japanese primrose (Primula sieboldii E. Morren)

Abstract The study screened the putative viral RNA sequences in the cDNA library of Japanese primrose, and conducted a molecular approach in determining its presence in selected Primula sieboldii accessions showing characteristic viral symptoms. Three putatively viral non-homologous sequence groups of RNA were identified; however, coding for different proteins representing a complete virus structure, it was determined to be singly originating from Cycas necrotic stunt virus (CNSV). Subsequently, sequence-specific primers were customised based from the non-homologous-sequence groups; however, amplification data showed no association between the presence of the putative viral RNA sequences and the identified characteristic virus symptoms. Despite this, amplification of the three non-homologous sequences is fully correlated. Thus, Japanese primrose was potentially identified as an alternate host of CNSV.