Disease Resistance: Incorporation into Sexually Incompatible Somatic Hybrids of the Genus Nicotiana

Abstract

Somatic hybrid plants of Nicotiana nesophila and N. stocktonii with N. tabacum (cultivated tobacco) were produced by protoplast fusion. These combinations cannot be achieved with conventional sexual hybridization, yet are important in that the wild Nicotiana species are resistant to numerous diseases. Hybridity was verified by chromosome number, isoenzyme analysis, morphological characteristics, and genetic behavior. Local lesion-type resistance to tobacco mosaic virus has been observed in leaves of these somatic hybrid plants.

Somatic Hybridization BetweenN.tabacum(NR−, Km+) andN.sanderae.Hybrid Genome Constitution and Expression of Resistance toTomato Spotted Wilt Virus

“…Parental genomes function normally together within hybrid cells without spontaneously elimination of parental nuclear genetic material. A similar genome constitution was reported also for other interspecific somatic hybrids in Nicotiana, obtained after selection by using nuclear encoded traits (4,5). Test for resistance to Tomato Spotted Wilt Virus In vitro propagated and greenhouse adapted plants from 13 fusion lines were tested for resistance to Tomato Spotted Wilt Virus.…”

“…The wild Nicotiana species often carry resistance to diseases (11). The transmission of resistance to tobacco mosaic virus into interspesific somatic hybrids has been reported (1,4). N.sanderae is wild Nicotiana species, which is resistant to Tomato Spotted Wilt Virus (TSWV) (8).…”

The potential of somatic hybridization in crop breeding

“…The transfer of TMV resistance into fertile tobacco somatic hybrids from N . nesophila or N. stocktonii has also been achieved (Evans et al ., 1981) . The above-mentioned hybrids can be produced by sexual crossings although special techniques such as ovule culture in vitro are necessary .…”

In vitro regeneration of Didymopanax morototoni

“…This is critical, in some species, for explants that in spite of friable calli, root and leaf explants do not complete embryogenesis, and for other species might be due to not only to physiological differences among explant sources, but also to conditions under which development took place (Harry & Thorpe, 1991;Jimenez, 2001). Cytokinin presence can stimulate somatic embryo maturation (Evans et al, 1981) and make plantlet regeneration feasible, as was the case for Myrtus comunis (Canhoto et al, 1999). But absence of plant growth regulators generally yielded better developmental responses for Eucalyptus (Muralidharam & Mascarenhas, 1995), Juglans cinerea (Pijut, 1993), and Simarouba glauca (Rout & Das, 1994).…”