Cytogenetic Analysis For Taxanomy And Reproduction Of Atractylodes Lancea (Thunb.) DC SSP. Luotianensis

The plants belonging to the genus Atractylodes in the Asteraceae family produces the atractylodes rhizome which is widely used as a traditional medicine in China. These plants can be reproduced and cultivated by seeds, division propagation and rhizome. Five species, one subspecies and one variety were identified on the basis of their phenotypes. The types distributed in mountainous Luotian and Yingshan regions in Hubei Province presented distinct morphology and superior medicinal quality, which were classified as one subspecies A. lancea (Thunb.) DC ssp. Luotianensis. In this study, the chromosome karyotype and meiotic divisions of this subspecies were investigated by the methods of cytology and fluorescent in situ hybridization, to provide the cytological evidence for the taxonomic unit and reproductive pattern. The main results are given as follows:1. The phenotypes of plants, leaves, flowers, fruits and rhizomes for Aatractylodes lancea from Luotian region were observed during flowering period at native place. The plant heights varied greatly among fields of different fertility. The flowering plants had multibranches, serrated leaves at middle and basal parts and non-serrated leaves at top part. The capitulum inflorescence at top of main stem and branches produced the female florets or bisexual florets. Each achene contained a number of seeds. The growth process of the potted plants derived from the rhizomes was also investigated in the nonheated green house in our University campus at Wuhan.2. The karyotype was 2n=24=12m+12sm (2SAT). A single locus of 5S rDNA and two loci of 45S rDNA loci were identified and separated on different chromosomes. Its one pair of the satellited chromosomes rather than two pairs in other Atractylodes species still with 2n=24 occurred likely after its occupation of this geographic location. The evidence of karyotype differentiation of this subspecies native to the area is useful for elucidating the genome structure and identifying chromosomes. Its karyotype was 2A, the most symmetric and also primitive one, but the other Atractylodes types had more asymmetric 2B, suggesting the primary evolution stage of this plant with no obvious structural changes of its chromosomes. A single locus of 5S rDNA also revealed the dipoidy nature of this species. The cytological differentiation of plant type from this region supported its taxanomic unit as one subspecies.3. During the meiotic divisions of pollen mother cells (PMCs) for this plant, thenormal chromosome pairing and segregation were performed and thus no laggards and micronuclei were formed. The pollen grains with high stainability were produced, which provided the cytological explanations for the high seed-sets and good seed viability of this plant type. The normal meiosis also ensured the stable chromosome number (2n=24) for different types of this plant which reproduced sexually and asexually.