2019 ASHS Annual Conference

Somatic hybridization (protoplast fusion) has become an essential part of citrus breeding programs worldwide that helps to generate new somatic hybrids or cybrids by mixing desired traits from different parents including tolerance to abiotic and biotic stresses as well as fruit quality. In theory, it allows to combine into the same cell not only the nuclear genome of one parent, but also the cytoplasm genome of the second by producing new cytoplasmic-nuclear genome combinations at both ploidy levels (diploid and tetraploid) to enhances the diversity of gene pools in the new germplasm. Fruit quality is substantially one of the most important goals for any citrus breeding program. There are diversity of plant material extends great predictions for variety improvement, mainly for the development of new scions and rootstocks. However, Citrus is characterized by a complex reproductive system, which limits the possibilities of conventional breeding. In this study, protoplast fusion experiments were performed between ‘W. Murcott’ (Afourer) mandarin (a hybrid of ‘Murcott’ mandarin and unknown pollen parent) as an embryogenic cell suspension source for embryogenic protoplasts and five different mesophyll sources of protoplasts (‘Sugar Bell’, ‘Fallglo’, ‘Lb8-8’, ‘Bingo’, and ‘7-11’ new mandarin). To characterize regenerated plants, the regenerated plantlets were subjected to flow cytometry (FCM) to determine the ploidy level. After generating the plants, genomic DNA was extracted for molecular investigation of genomic constitutions using simple sequence repeats (SSR) markers, universal chloroplast (cp) and mitochondrial (mt) PCR markers. Ploidy analysis using flow cytometry has shown so far that 114 of the 118 regenerated plants were diploid, while two, which originated from ‘W. Murcott’ + ‘Sugar Belle’; one, which generated from ‘W. Murcott’ + ‘Fallglo’ and one, which originated ‘W. Murcott’ + ‘7-11’ were tetraploids. The nuclear SSR, cp and mt markers are underway to confirm the genetic background of the regenerated somatic hybrids and cybrids plants.