Somatic hybridization through protoplast fusion has proven to be a valuable technique in citrus for producing unique allotetraploid breeding parents that combine elite diploid selections. Many citrus somatic hybrids are now flowering and being used in interploid crosses to generate triploid hybrids that produce seedless fruit, a primary objective of citrus breeding programs. Most of the early somatic hybrids produced for mandarin improvement combined sweet oranges with mandarins, because the performance of sweet oranges in tissue/protoplast culture generally exceeds that of most mandarin selections. However, a high percentage of triploid progeny from interploid crosses using sweet orange + mandarin somatic hybrids as the tetraploid parent produce fruit that are difficult to peel. We report nine new allotetraploid somatic hybrids and five new autotetraploids from somatic fusion experiments involving easy-peel mandarin parents. These tetraploids can be used in interploid crosses to increase the percentage of seedless triploid progeny producing easy-to-peel fruit. Ploidy level of the new tetraploids was determined by flow cytometry and their genetic origin by expressed sequence tag–simple sequence repeat marker analysis.

is an economically important fruit on Jeju Island, Korea, but byproducts are a major source of agricultural waste. The aim of this study is to examine changes in phytochemical, antioxidant, and antibacterial activities of four byproducts: citrus flesh byproduct (CFB), fermented citrus flesh byproduct (FCFB), citrus peel byproduct (CPB), and fermented citrus peel byproduct (FCPB). Fermented citrus byproducts (FCFB and FCPB) exhibited greater inhibition effect on radical scavenging abilities of 2,2-diphenyl-1-picrylhtdrazyl, 2,2'-azinobis(3-ethylbenzothiazolin-6-sulfonic acid)-diammonium salt, and superoxide anion compared with those of CFB and CPB. Total polyphenol contents of FCFB and FCPB were significantly increased compared to those of CFB and CPB. Significant bioconversion of the flavonoid glucosides into corresponding bioactive aglycones during citrus byproduct fermentation was observed. Fermented citrus byproducts exhibited antibacterial activity against and suggesting that FCFB and FCPB are potent antioxidant and antibacterial sources due to the remarkable contents of bioactive compounds in them.

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We have regenerated allotetraploid plants that are interspecific somatic hybrids between Citrus sinensis Osbeck cv. Yoshida navel orange and Citrus unshiu Marc cv. Okitsu satsuma mandarin. Protoplasts isolated from 'Yoshida' leaves were chemically fused with callus-derived protoplasts from 'Okitsu'. After 6 months of culture, 102 plants were obtained. These hybrids were identified by differential leaf morphology, DNA fluorescence intensity, and DNA analysis. Ploidy analysis via the flow cytometry revealed that 15 of the 102 plants were tetraploids, with the rest being diploids that morphologically resembled their mesophyll parent. SRAP analysis confirmed that 9 of the tetraploid plants were allotetraploid somatic hybrids. These will be utilized as a possible pollen parents for improving seedy citrus cultivars, e.g., ponkan, mandarin, lemon and kumquat, in order to produce triploid seedless hybrids.

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