Genome size and chromosome ploidy identification in pear germplasm represented by Asian pears - Local pear varieties

Pear (Pyrus) germplasm resources in Xinjiang were rich, most of which were diploid. Including dozens of varieties such as Pyrus bretschneideri Rehd. (P-br), Pyrus pyrifolia Nakai. (P-py), Pyrus ussuriensis Maxim. (P-us), Pyrus communis L. (P-co), Pyrus betulifolia Bunge. (P-be), Pyrus sinkiangensis Yü. (P-si). The P-si was mainly distributed in Shanshan, Turpan, Korla, Aksu and other places. The genetic background of the main varietieswas not completely clear.The genome size and chromosome ploidy of main pear varieties in Xinjiang were identified by flow cytometry (FCM) and the traditional chromosome pressing method. The results showed that, the genome size of P-xj was 566.54 ± 125.17 Mb, slightly larger than that of the introduced varieties, with a 2C values of 1.16 ± 0.26 pg and a ploidy value (DI) of 1.1 ± 0.24. Twenty-four P-xj were diploid with 34 chromosome numbers. The genome sizes of introduced P-br, P-py, P-us, P-be, and P-co were 485.44 ± 10.05∼567.94 ± 44.40 Mb, and the 2C values was 0.99 ± 0.02∼1.16 ± 0.10 pg. The DI was 0.9 ± 0.06∼1.0 ± 0.09, the FCM detection indicated that they were diploid; the number of chromosomes was 34.There were differences in genome size between pear with the same ploidy. The genome size of all diploid pear was 480.95 ± 16.24∼599.14 ± 38.36 Mb, the 2C values was 0.98 ± 0.03 pg ∼1.23 ± 0.08 pg, and the DI was 0.9 ± 0.00∼1.2 ± 0.06. A total of 5 polyploid materials were found in this study: ‘Yilikamut’, ‘Kotoamut’, ‘Aiwenqieke’, ‘Heisuanli’ and ‘Sha01′, it can provide materials for the innovation and utilization of pear germplasm resources. The results of this study can provide technical support for Pyrus plant on ploidy breeding and omics study, and also a reference for other plants.