Intergeneric asymmetric hybrids between Nicotiana plumbaginifolia and Atropa belladonna obtained by ?gamma-fusion?

Abstract

Asymmetric nuclear hybrids have been obtained by fusion of cells from a nitrate-reductase deficient mutant of Nicotiana plumbaginifolia (cnx20) and gamma irradiated protoplasts of Atropa belladonna (irradiation doses tested were 10, 30, 50 and 100 krad). The hybrid formation frequency following selection for genotypic complementation in the NR function was in the range of 0.7%-3.7%. Cytogenetic studies demonstrated that all hybrid plants tested possessed multiple (generally tetra- or hexaploid) sets of N. plumbaginifolia (n = 10) chromosomes along with 6-29 Atropa chromosomes (n = 36), some of which were greatly deleted. Besides the cnxA gene (the selection marker), additional material of the irradiated partner was expressed in some of the lines, as shown by analyses of multiple molecular forms of enzymes. Surprisingly, rDNA genes of both parental species were present and amplified in the majority of the hybrids. Whenever studied, the chloroplast DNA in the hybrids was derived from the Nicotiana parent. Regenerants from some lines flowered and were partially fertile. It is concluded that irradiation of cells of the donor parent before fusion can be used to produce highly asymmetric nuclear hybrid plants, although within the dose range tested, the treatment determined the direction of the elimination but not the degree of elimination of the irradiated genome.

Pigment Deficiency in Nightshade/Tobacco Cybrids Is Caused by the Failure to Edit the Plastid ATPase α-Subunit mRNA

“…Species-specific polymorphic markers of nuclear genomes, such as isoenzymes of peroxidases, catalase, malate dehydrogenase, and genes encoding plant tubulins, were assayed in somatic hybrids as described (Kushnir et al, 1991). Karyotypes of somatic hybrids were analyzed by acetoorceine staining of chromosome spreads from dividing cells in root tips (Gleba et al, 1988). Plastome types were identified by RFLP analysis of purified chloroplast DNA or by direct DNA sequencing of relevant PCR-amplified DNA fragments.…”

Somatic Hybridization for Plant Improvement

“…Intergeneric somatic hybrids are usually highly unstable due to spontaneous elimination of parental chromosomes, and the hybrid cells are often non-morphogenic or, once regenerated, infertile (Negrutiu et al, 1989a & b). It is therefore assumed that a directed elimination of the donor chromosomes may help overcome the regeneration and fertility problems in combinations between phylogenetically distant species (Gupta et al, 1984;Bates et al, 1987;Gleba et al, 1988). From a number of recent studies some general conclusions may be made:…”

The potential of somatic hybridization in crop breeding

“…Preliminary evidence of hybridity can be obtained by scoring the morphology which is often intermediate between the parents . More direct proof can be obtained by biochemical analysis using the isoenzyme pattern (Scandalios & Sorenson, 1977 ;Gleba & Sytnik, 1984) or various types of molecular probes such as species-specific repetitive DNA sequences (Saul & Potrykus, 1984;Imamura et al ., 1987 ;Schweizer et al ., 1988), rDNA (Gleba et al ., 1988) and other RFLP markers Melzer & O'Connell, 1990) . Recently, the use of PCR technology has also been utilized for hybrid identification (Baird et al ., 1992 ;Xu et al ., 1993b) .…”

“…To date, asymmetric hybridization has met with mixed results . In general, irradiation reduced the amount of transferred donor DNA but the fraction may vary from a few traits (Dudits et al ., 1987), one or a few chromosomes (Gupta et al ., 1984 ;Bates et al ., 1987a;Melzer & O'Connell, 1992) to numerous chromosomes (Gleba et al ., 1988 ;Famelaer et al ., 1989;Sacristan et al ., 1989 ;Sjodin & Glimelius, 1989b ;Yamashita et al ., 1989 ;Wijbrandi et al ., 1990a, b, c, Wolters et al ., 1991Derks et al ., 1992) the latter result being obtained in the majority of cases . Furthermore, chromosome elimination is random and it is not possible to predict which of the chromosomes will be lost .…”