Interspecific transfer of cytoplasmic male sterility by fusion between protoplasts of normal nicotiana sylvestris and x ray irradiated protoplasts of male sterile nicotiana tabacum

Zelcer, A.; Aviv, D.; Galun, E.

Zeitschrift fuer Pflanzenphysiologie 90(5): 397-408


Accession: 005734664

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X-irradiated protoplasts from plants of a cytoplasmic male-sterile (CMS) cultivar of N. tabacum (N. suaveolens cytoplasm) were fused with protoplasts of N. sylvestris plants. The selection of fusion products was based on the suppression of cell division by X-irradiation of the CMS parent protoplasts and on the use of mannitol medium, which is unfavorable to protoplasts of N. sylvestris. The protoplast feeder-layer technique was utilized in order to resuce the low frequency of fusion products which withstood the selection procedure. Thirty-one nature plants, regenerated from 7 calli, were obtained. Of these, 21 plants (Type A) had the shoot, leaf and perianth morphologies of N. sylvestris but their anthers resembled the anthers of the CMS N. tabacum parent and in fact all were male-sterile. Of these, 7 plants had 2n = 24 chromosomes and 14 plants had 2n = 48 chromosomes. Six plants (Type B) grew as rosettes and bore flowers with white corollas, i.e., similar to N. sylvestris, but had deformed leaves and during further growth were similar to N. tabacum; their anthers were sterile but normal, or almost normal in structure of these, 4 plants had 2n = 48 chromosomes and 2 plants had 2n = 76 to 80 chromosomes. Five plants (Type C), all resulting from 1 callus, were identical in shoot, leaf and floral morphology to the cytoplasmic male-sterile N. tabacum parent. These plants are considered to be the results of a cytoplasmic male-sterile N. tabacum protoplast which escaped the X-irradiation effect. These results led to the conclusion that Type A plants bore the genome of N. sylvestris wile their plastome was partially or entirely of the CMS parent (i.e., of N. suaveolens). These Type A plants, which are the majority among the fusion products, are therefore considered somatic hybrids resulting from the transfer of male-sterility-causing cytoplasm into N. sylvestris cells. The genetic composition of Type B plants is uncertain. They probably have a mostly N. sylvestris genome but also some N. tabacum genes; their cytoplasm is probably not pure N. sylvestris. This protoplast fusion procedure may have a general applicability for interspecific transfer of cytoplasmic male-sterility, as well as other cytoplasmic factors which are hard, if not impossible, to transfer by classical genetic techniques.