Analysis of Cytoplasmic Genomes in Somatic Hybrids between 'Hazzara (Abohar)' (Citrus reticulata Blanco) and Microcitrus australis (Planch.) Swingle

Abstract

Somatic hybrids were produced by protoplast fusion between embryogenic callus cells of 'Hazzara (Abohar)' (Citrus reticulata Blanco) and mesophyll cells of Microcitrus australis (Planch.) Swingle, in an attempt to expand genetic diversity that might be valuable for Citrus breeding. Among the 40 plants acclimatized, 37 plants were intermediate in leaf morphology, whereas, the remaining 3 had leaves quite different from those of both parents. Ten plants among those with intermediate leaf morphology were selected for analysis of genome composition. These plants proved to be somatic hybrids by nuclear rDNA analysis. Mitochondrial DNA (mtDNA) analysis showed that all 10 hybrids contained 'Hazzara (Abohar)' plastome. Analysis of chloroplast DNA (cpDNA) showed that most of them carried specific fragments derived from 'Hazzara (Abohar)'. Others, however, carried specific fragments derived from both parents. Possible causes for such band patterns are discussed from a genetical viewpoint.

Homologous recombination and retention of a single form of most genes shape the highly chimeric mitochondrial genome of a cybrid plant

“…Previous studies on somatic hybrids and cybrids showed a similar pattern of single-allele retention, although only one or a few genes per hybrid were analyzed in most of these studies (Temple et al, 1992; Bonnema et al, 1995; Motomura et al, 1996; Kanno et al, 1997; Moriguchi et al, 1997; Cardi et al, 1999; Lossl et al, 1999; Rasmussen et al 2000; Bastia et al, 2001; Scotti et al 2004). Also, a genomic study (Wang et al, 2012) on a Brassica cybrid showed that its mitochondrial genome contained only 59 genes, very similar to the gene content in each parental mtDNA (Tanaka et al, 2012), although the parental origin of the cybrid genes was not determined.…”

Maternal inheritance of chloroplast DNA in intergeneric sexual hybrids of “true citrus fruit trees” revealed by PCR-RFLP analysis

“…In citrus, analysis of chloroplast DNA (cpDNA) have been used for many purposes such as phylogenetic study (Yamamoto et al, 1993;Nicolosi et al, 2000;Gulsen and Roose, 2001) and characterization of somatic hybrids and cybrids (Motomura et al, 1996;Moreira et al, 2000aMoreira et al, , 2000bGuo et al, 2002;Liu et al, 2002), however, only a few reports describe the inheritance pattern of cpDNA in sexual hybrids of citrus. Moreira et al (1996; studied cpDNA inheritance in only one kind of intergeneric hybrids between Citrus and Poncirus.…”

Intergeneric somatic hybridization and its application to crop genetic improvement

“…In comparison to symmetric fusions, in asymmetric fusions, cpDNA of the recipient is predominant in the hybrids, as has been shown in hybrids of Brassica and Arabidopsis (Bauer-Weston et al, 1993), N. tabacum and D. carota (Smith et al, 1989), T. aestivum and Z. mays or L. multiflorum (Xu et al, 2003;. Co-existence of chloroplasts from both fusion parents has been found in a few somatic hybrids (Primard et al, 1988;Motomura et al, 1996;Mohapatra et al, 1998;Moreira et al, 2000;. Kumar and Cocking (1987) ascribed such phenomenon to parental chloroplast genomic similarity or absence of any selection advantage to either of the two plastid genomes in the heterokaryonic cells and their regeneration into plants.…”