Effects of Citrus ( Citrus spp. ) Genotype and Carbohydrate Source Composition on Callus Growth and Somatic Embryogenesis and Recovery of the Plant Regeneration Ability

Citrus, a globally cultivated tropical fruit crop, belongs to the family Rutaceae, which comprises Citrus and other genera, including Fortunella and Poncirus (Kim et al. 2020;Praveen et al. 2003).Citrus spp.are divided into oranges, mandarins, lemons, lime, grapefruit, and pomelo (Richa et al. 2023).Among these, mandarins (C.reticulata) are popular for their flavor and nutritional benefits.Mandarins comprise several varieties, including satsuma mandarin (C.unshiu Marc.; Swingle 1943), one of the most popular types of mandarin globally.Satsuma mandarins are predominantly cultivated in Japan and Korea (Jin et al. 2007;Ling et al. 1990) and exhibit polyploidy and male sterility, which hinders their improvement through crossbreeding (An et al. 2008;Jin et al. 2020).Consequently, the enhancement of this cultivar relies on selecting bud-sport mutants (Park et al. 2013) and seed reproduction via embryos from nucellar cell tissues around the embryo sac (Jin et al. 2020;Kepiro et al. 2007;Kim et al. 2016;Zhang et al. 2018).Furthermore, variants with low citric acid and high sugar contents show genetic similarity to the maternal plants (Liu et al. 2009;Zhang et al. 2006), thereby complicating mutant identification based solely on morphological characteristics (Jin et al. 2020), exhibit lower efficiency in callus formation and plant regeneration than other citrus varieties (Han et al. 2002;Ling et al.