Chimerism Evaluation of 'Hongrou Huyou', a Grafted Chimera between Citrus changshan-huyou and Citrus unshiu

Chimeras occur spontaneously or artificially and are valuable in horticultural crop breeding. A new diploid citrus chimera, named `Hongrou Huyou' (abbreviated HH) (Citrus changshan-huyou + C. unshiu), was found during a bud sports investigation in China. The morphology, flesh carotenoid content, and molecular markers were evaluated in HH and the two grafted donors. The results showed that characteristics derived from L2/L3, such as the fruit size, winged leaf, seed, pollen, and rind aroma, were similar to those of C. changshan-huyou (CH), whereas the juice sac and stomatal characteristics originating from L1 were the same as those of the satsuma mandarin. High-performance liquid chromatography analysis of carotenes from the flesh of HH showed that the content was the same as that of the satsuma mandarin, with beta-cryptoxanthin producing the main carotenoid spectrum, whereas lutein and violaxanthin were the main carotenoids in CH. Nuclear simple sequence repeat, chloroplast simple sequence repeat, and mitochondria' simple sequence repeat analyses showed that the leaves, outer pericarp (epidermis and flavedo), segment wall, and juice sac of HH contained the nuclear, chloroplast, and mitochondria' genomes of both donors; however, the albedo of HH only contained the genetic material of CH. Thus, HH is confirmed to be a periclinal chimera that consists of L1 from C. unshiu and L2/L3 from CH.