Shin-ichi Masuzaki

Direct comparison between genomic constitution and flavonoid contents in Allium multiple alien addition lines reveals chromosomal locations of genes related to biosynthesis from dihydrokaempferol to quercetin glucosides in scaly leaf of shallot (Allium cepa L.)

The extrachromosome 5A of shallot (Allium cepa L., genomes AA) has an important role in flavonoid biosynthesis in the scaly leaf of Allium fistulosum–shallot monosomic addition lines (FF+nA). This study deals with the production and biochemical characterisation of A. fistulosum–shallot multiple alien addition lines carrying at least 5A to determine the chromosomal locations of genes for quercetin formation. The multiple alien additions were selected from the crossing between allotriploid FFA (♀) and A. fistulosum (♂). The 113 plants obtained from this cross were analysed by a chromosome 5A-specific PGI isozyme marker of shallot. Thirty plants were preliminarily selected for an alien addition carrying 5A. The chromosome numbers of the 30 plants varied from 18 to 23. The other extrachromosomes in 19 plants were completely identified by using seven other chromosome markers of shallot. High-performance liquid chromatography analyses of the 19 multiple additions were conducted to identify the flavonoid compounds produced in the scaly leaves. Direct comparisons between the chromosomal constitution and the flavonoid contents of the multiple alien additions revealed that a flavonoid 3′-hydroxylase (F3′H) gene for the synthesis of quercetin from kaempferol was located on 7A and that an anonymous gene involved in the glucosidation of quercetin was on 3A or 4A. As a result of supplemental SCAR analyses by using genomic DNAs from two complete sets of A. fistulosum–shallot monosomic additions, we have assigned F3′H to 7A and flavonol synthase to 4A.

Development of microsatellite markers in cultivated and wild species of sections Cepa and Phyllodolon in Allium

The potential of microsatellite markers for use in genetic studies has been evaluated in Allium cultivated species (Allium cepa, A. fistulosum) and its allied species (A. altaicum, A. galanthum, A. roylei, A. vavilovii). A total of 77 polymerase chain reaction (PCR) primer pairs were employed, 76 of which amplified a single product or several products in either of the species. The 29 AMS primer pairs derived from A. cepa and 46 microsatellites primer pairs from A. fistulosum revealed a lot of polymorphic amplicons between seven Allium species. Some of the microsatellite markers were effective not only for identifying an intraspecific F1 hybrid between shallot and bulb onion but also for applying to segregation analyses in its F2 population. All of the microsatellite markers can be used for interspecific taxonomic analyses among two cultivated and four wild species of sections Cepa and Phyllodolon in Allium. Generally, our data support the results obtained from recently performed analyses using molecular and morphological markers. However, the phylogeny of A. roylei, a threatened species with several favorable genes, was still ambiguous due to its different positions in each dendrogram generated from the two primer sets originated from A. cepa and A. fistulosum.

Morphological characterisation of multiple alien addition lines of Allium reveals the chromosomal locations of gene(s) related to bulb formation in Allium cepa L.

Summary Japanese bunching onion (Allium fistulosum L.) shallot (Allium cepa L. Aggregatum group) alien chromosome addition lines were used to determine the chromosomal locations of genes related to bulb formation in shallot. The morphological characteristics of 17 multiple alien addition lines were investigated by measuring maximum bulb diameter, calculating the bulbing ratio, and counting the number of shoots. Of the 17 multiple addition lines, four (U138, U154, U4, and U87), in which chromosome 2A was deleted and which also contained five or more additional chromosomes from shallot, showed significantly higher values of maximum bulb diameter and bulbing ratio than multiple addition lines carrying 2A. Moreover, the number of shoots in these four plants was fewer than in plants with multiple addition lines carrying 2A, and in the allotriploid between A. fistulosum and shallot. A sucrose transporter gene of shallot was allocated to chromosome 5A through sequence-characterised amplified region analysis using two sets of the monosomic addition lines. These results indicate that a gene, or genes, inhibiting bulb formation and stimulating side-shoot formation in shallot may be located on chromosome 2A, and that the sucrose transporter gene is located on chromosome 5A of shallot.