New Intergeneric Somatic Hybrids Combining Amblycarpa Mandarin with Six Trifoliate/Trifoliate Hybrid Selections for Lime Rootstock Improvement

Abstract

<jats:p>No presently available rootstock combines all the available rootstock attributes necessary for efficient long-term citriculture (production and harvesting) of Mexican limes and other commercially important scions. In the present study, somatic hybridization techniques were used to combine the widely adapted Amblycarpa mandarin (also known as Nasnaran mandarin) with six different trifoliate/trifoliate hybrid selections: Benton, Carrizo, and C-35 citranges; Flying Dragon and Rubidoux trifoliate oranges; and a somatic hybrid of sour orange + Flying Dragon. The ultimate goal of this research is to generate polyploid somatic hybrids that express the complementary horticultural and disease resistance attributes of the corresponding parents, and have direct potential as improved tree-size controlling rootstocks. Somatic hybrids from all six parental combinations were confirmed by a combination of leaf morphology, flow cytometry, and randomly amplified polymorphic DNA (RAPD) (for nuclear hybridity) and cleaved amplified polymorphic sequence (CAPS) analyses (for mtDNA and cpDNA). This is the first report of citrus somatic hybridization using Amblycarpa mandarin. Unexpected hexaploid somatic hybrid plants were recovered from the fusion of Amblycarpa mandarin + C-35 citrange. Hexaploid hybrids should be very dwarfing and may have potential for producing potted ornamental citrus. Resulting somatic hybrid plants from all six combinations have been propagated by tissue culture and/or rooted cuttings and are being prepared for commercial field evaluation for their potential as improved rootstocks for Mexican lime and other important scions.</jats:p>

Bifunctional selection–reporter systems for genetic transformation of citrus: mannose- and kanamycin-based systems

“…Therefore, it is important to evaluate progeny to determine if regenerated transgenic lines are indeed true to type or of zygotic origin. RAPD-PCR analysis was carried out using primer C-11 as described by Medina-Urrutia et al (2004) to confirm the nucellar (non-zygotic) state of the regenerated transgenics. In our results, we observed a banding pattern from transgenic lines equivalent to that obtained with DNA of the non-transgenic seed source Carrizo tree, indicating the nucellar origin of all regenerated transgenic plants (Fig.…”

“…Genomic DNA from transgenic and non-transgenic control plants was isolated using GenElute plant genomic DNA Kit (Sigma-Aldrich, St. Louis, MO) according to manufacturer supplied protocol. PCR was performed using primer C-11 (5′AGGTACGCCCGA3′) as described byMedina-Urrutia et al (2004).…”

Inter-generic mitochondrial genome recombination in somatic hybrids betweenCitrusandPoncirus

“…To date, numerous artificial Citrus hybrids have been produced by protoplast fusion, with considerable potential both for theoretical studies and genetic improvement (Grosser et al, 2005;Wu et al, 2005). Genetic diversity analyses using molecular markers such as restriction fragment length polymorphisms (RFLP; Moriguchi et al, 1997;Olivares-Fuster et al, 2005), random amplified polymorphic DNA (RAPD; Medina-Urrutia et al, 2004;Takami et al, 2005), amplified fragment length polymorphisms (AFLPs;Fu et al, 2004), cleaved amplified polymorphic sequences (CAPS;Cheng et al, 2003a;Lotfy et al, 2003;Medina-Urrutia et al, 2004), simple sequence repeats (SSRs; Guo and Grosser, 2005;Xu et al, 2006;Guo et al, 2006), and genomic in situ hybridisation (GISH;Fu et al, 2004) provide powerful approaches for hybrid identification and further genetic analyses. Molecular evidence strongly suggests that the nuclear genome was inherited from both fusion parents in somatic hybrids, and from the mesophyll parent in cybrids; however, the cytoplasmic inheritance pathway is understood only in some cases (reviewed by Cabasson et al, 2001).…”

“…20 inter-generic somatic hybrids were created between Citrus + Poncirus (reviewed by Grosser et al, 2000;Medina-Urrutia et al, 2004), incorporating complementary traits from Poncirus and Citrus, and displaying a high potential for wider adaptability, better yields of high quality fruit, and a more desirable canopy size (Grosser et al, 2000). Meanwhile, genetic characterisation of nuclear genomes in tetraploid somatic hybrids showed integration of both fusion parents, whereas the chloroplast genomes segregated uniparentally, and mitochondrial genomes were obtained from the suspension embryogenic parent with rearrangements in some cases (Medina-Urrutia et al, 2004;Liu et al, 2005). However, most of the above conclusions were based on a small sample population and/or on limited numbers of marker loci.…”

“…Detailed genetic analyses of somatic hybrids could facilitate further applications of artificial hybrids for the improvement of Citrus scions and rootstock (Medina-Urrutia et al, 2004). In the present investigation, detailed genetic analyses of fusion-derived plants were performed between 'Page' tangelo and trifoliate orange by a combination of flow cytometry and marker methods such as nuclear SSR, CAPS, RFLP, and cpSSR.…”