Comparison Of Chromosome Number And Karyotype Of Chinese Cherry And Its Four Related Species (variants)

Chinese Cherry belongs to genera Cerasus, subfamily Prunoideae,Rosaceae, which is also named as Cerasus pseudocerasus Lindl. (Prunus pseudocerasus Lindl.). With a long history of cultivation, it becomes one of the most widely cultivated cherry species, widely distributing in China, especially in western and southwestern of China. Based on the eco-environment and man-made interference factors, Chinese cherry was divided into cultivated germplasms and wild populations. Over the past few years, Chinese cherry became very popular due to the characteristics of its earlyblossom, high ornament, high yield and convenient management, attracting scientists to research them. The studies mainly focused on the genetic diversity of Chinese cherry, the genetic relationship between the wild population and cultivated germplasm, and so on. However, few scientists had studied the chromosomes and the karyotypes of the Chinese cherry and its relative species (varieties). Previous studies had showed that there were two kind of ploidylevels in Chinese cherry, including diploid and tetraploid. Thus, was Chinese cherry diploid orteraploid, or two kinds co-exist? Besides the two kinds, whether there was other ploidy level or not? How about the chromosome number and karyotype of its relatives? These questions were all worthy to explore.In this study, we used the root tip chromosome tabletting method to observe the apical cell mitosis on the Chinese cherry which was collected from Sichuan, Chongqing, Shanxi, Henan and other areas and its 4 relative species (varieties). Our aims are to investigate their chromosome number and karyotype characteristic, and provide certain reference in hybrid breeding and the phylogenetic relationship. The results were summarized as follows.1. The chromosome numbers and karyotypes characteristics in Chinese cherry16 Chinese cherry materials, including 4 wild populations and 12 cultivated germplasms, were used in this study. The material collected from Yingjingcounty, Sichuan province, and Fenxian county, Shanxi province was pentaploid and hexaploid respectively.Their karyotype formulae was 2n=5x=40=35m+5sm and 2n=6x= 48=42m (2SAT)+6sm. Other materials were all tetraploid, while no diploid has been found. The chromosome was mainly composed of median chromosome (m) and submedian chromosome (sm), which was accounted for 89.37% and 10.63%. In tetraploid, the composition of karyotype mainly revealed two patterns, one of which was 2n=4x=32=28m+4sm and the other was 2n=4x=32=30m+2sm. The length of chromosome was between 0.84 and2.81μm, and the Lc/Sc was 2.05 to 2.32 and the average arm ratio was 1.13 to 1.32. However, all these materials exhibited a karyotype asymmetry of type "2B", whose karyotype asymmetrical coefficient ranged from 53.09% to 57.05%. According to these data from the high value to low could be arranged as follows:Luding 1> Jianyang> Luoyang> Pengzhou> Qingxi > district Yucheng 2> Beichuan> Yingjing> Shimian> Fuling> district Yuchengl> Luding 2>Foping> district Yucheng 2> Miyi> Fengxian. There were 2-4 satellites in 7 Chinese cherries, distributing different position. No relationship between the number of satellite and asymmetrical karyotype coefficient was found. Meanwhile, we also found that the satellite located in the long arm of chromosome.2. The chromosome number and karyotype in 4 relative species (varieties)C. tomentosa (Thunb.) Wall., C. serrulata var. lannesiana, C. avium and C. campanulata Maxim. were all diploid, whose karyotype formulae was 2n=2x=16= 16m、2n=2x=16=14m+2 sm (SAT)、2n=2x=16=12m+4sm、2n=2x=16= 16m,respectively. They consisted of median chromosome (m) (about 90.63%), and a few submedian chromosome (sm) (only 9.37%). C. serrulata var. lannesiana has a pair of satellite, which was located on the short arm of chromosome 1. The absolute length of chromosome rangedfrom 0.81μm to 2.51μm. The longest and shortest relative length is C. tomentosa (Thunb.) Wall. The ratio between longest chromosome and shortest chromosome was from 1.67 to 2.11 and the average arm ratio was 1.13 to 1.30. The karyotype asymmetrical coefficient of C. avium,C. serrulata var. lannesiana, C. tomentosa (Thunb.) Wall., and C. campanulata Maxim. was57.34%,57.10%,53.68% and 52.84%, respectively. Their karyotype type were "2A", "2B", "1B" and "1A".3. The relationship between Chinese cherry and its 4 relative species (varieties)The karyotype asymmetry of type ranged from 1A to 2B among these 5 species (varieties), which were primitive. The asymmetrical karyotype coefficient can be listed as follows:C. avium (57.34%), C. serrulata var. lannesiana (57.10%), Chinese cherry (average 54.47%), C. tomentosa (Thunb.) Wall (53.68%) and C. campanulata Maxim. (52.84%). The basic trend of karyotype evolution in higher plants was from symmetrical to asymmetrical type.According to that, C. campanulata Maxim is more ancient than sweet cherry. Duncan’s testing showed that the karyotype asymmetry coefficient, the Lc/Sc and the arm ratio had differences, C. campanulata Maxim, of (As.K%) and Lc/Sc was minimum,52.84%,1.67, respectively.