Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Ploidy level and their relationship with vegetative traits of mulberry (Morus spp.) species in Taiwan Lan-Yen Chang a , Kuo-Tan Li b,1 , Wen-Ju Yang b,1 , Mei-Chu Chung c,1 , Jer-Chia Chang d, ⁎ , Ming-Wen Chang e a Tainan District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan, No. 70, Muchang, Tainan 71246, Taiwan, ROC b Department of Horticulture and Landscape Architecture, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, ROC c Institute of Plant and Microbial Biology, Academia Sinica, No. 128, Sec. 2, Academia Road, Taipei 11529, Taiwan, ROC d Department of Horticulture, National Chung Hsing University, No. 145, Xingda Road, Taichung 40227, Taiwan, ROC e Miaoli District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan, No. 261, Guannan, Miaoli 36346, Taiwan, ROC ARTICLE INFO Keywords: Mulberry Genome size Polyploidy Vegetative characters Binary regression ABSTRACT To accelerate the mulberry breeding program and examine the genome size and ploidy levels of 27 mulberry accessions of promising lines in Taiwan, nuclei suspensions were prepared from unfolded young leaves and analyzed by a flow cytometer. The genome size of each accession was estimated by referring to the standard genome size of chicken erythrocyte nuclei (CEN, 2.5 pg). Our results indicated that 25 among 27 investigated accessions in M. bombycis, M. alba, M. latifolia, M. australis, M. formosnensis, and M. atropurpurea are diploids with genome sizes ranging from 0.61 to 0.71 pg. ‘Elongated mulberry No. 1’ (M. laevigata) with a genome size of 1.06 pg is a triploid. Two populations were identified in the accession ‘67C001’ (M. australis Poir.) with a genome size of either 0.63 pg or 0.98 pg. Due to their similarity in appearance, we suspected that they are probably from the same origin, thus warranting further investigations. Several important vegetative characters of diploids and triploids have been estimated, including leaf length, leaf width, petiole length, petiole width, leaf thickness, and internode length, to document their correlation using the unpaired t-test. Subsequently, the statistical re- lationship between diploid and triploid species on some of these important characters, including leaf width, petiole width and internode length, was determined through binary regression analysis. We suggested that the internode length could provide a beneficial index to distinguish individuals with different ploidy levels in the field. Results of this study provide useful information to clarify the taxonomy of Morus and improve breeding programs aiming to advance horticulture and sericulture. 1. Introduction Mulberry (Morus spp.) is an important economical crop that has versatile utilizations. In traditional folks, it provides forage for rearing silkworm (Bombyx mori) and has implications in the pharmaceutical industry (Asano et al., 1994), cosmetic industry (Wang et al., 2016), dye, wood, and for landscaping (Chang, 2006; Aroonpong and Chang, 2015). Besides, the production and economic value of mulberry has increased as it now is recognized for the nutritional and healthy value due to its abundance in phytochemicals which imparts oxidative properties to the fruits (Chen et al., 2004; Lee and Hwang, 2017; Vijayan et al., 2011). Hence, in addition to being cultivated for fresh or process consumption, it also has a high demand for use in the agri-food industry. Mulberry varies greatly in its appearance and adapts well to various environments due to its dioecious and cross-pollination nature (Chang, 2006; Vijayan et al., 2011). Some wild mulberry species, i.e., M. serrata and M. laevigata, are quite different from domesticated varieties and have better resistance to biotic and abiotic stresses (Tikader and Dandin, 2007). It is essential to preserve and utilize these wild species for breeding program because these can sustain drastic climate changes. Seven mulberry species, including the introduced (M. alba, M. latifolia, M. laevigata, M. atropurpurea, and M. bombycis) and the indigenous (M. australis, and M. formosensis) can be found in Taiwan (Chang, 2006). Numerous varieties have been selected from these species. Within these varieties, some are distinctive in their vegetative size, inability of fruiting, suspicious polyploidy level (Chang, 2006). Polyploid plants differ from diploids usually in morphological https://doi.org/10.1016/j.scienta.2018.01.029 Received 17 October 2017; Received in revised form 8 January 2018; Accepted 14 January 2018 ⁎ Corresponding author. 1 Contributed equally. E-mail address: jerchiachang@dragon.nchu.edu.tw (J.-C. Chang). Scientia Horticulturae 235 (2018) 78–85 0304-4238/ © 2018 Elsevier B.V. All rights reserved. T