Regeneration and molecular characterization of interspecific somatic hybrids between Satsuma mandarin and two seedy sweet oranges for scion improvement

Abstract

With 2 figures Abstract In an effort to produce novel and elite tetraploid germplasm for citrus seedless scion cultivar improvement, symmetric fusions were conducted between embryogenic suspension protoplasts of Citrus unshiu Marc. cv. ‘Guoqing No. 1’ (G1) and mesophyll protoplasts isolated from the leaves of ‘Red Anliu’ (Citrus sinensis Osbeck cv. ‘Red Anliu’) or ‘Taoye’ sweet oranges (C. sinensis Osb. cv. ‘Taoye’). Eight plants from G1+ ‘Red Anliu’ and 20 plants from G1+ ‘Taoye’ were regenerated, respectively. Flow cytometry analysis showed that all five randomly selected plants from G1+ ‘Taoye’ were tetraploid, and for four randomly selected plants recovered from G1+ ‘Red Anliu’, three were tetraploid and the remaining one was diploid. Genetic compositions of regenerated plants were determined by nuclear simple sequence repeat (SSR), chloroplast-SSR and mitochondrial cleaved amplified polymorphic sequence analysis. It was confirmed that all tetraploid plants from both fusions were true somatic hybrids, with chloroplast DNA and mitochondrial DNA from embryogenic callus parent. The diploid from G1+ ‘Red Anliu’ was identified to be originated from G1 protoplast, the callus parent. The potential of these novel allotetraploid somatic hybrids in citrus scion breeding was discussed.