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Resistance

Resistance to Tobacco Mosaic Virus and Meloidogyne arenaria in Fusion Hybrids Between Nicotiana tabacum and an N. repanda × N. sylvestris Hybrid. Phuong T. Bui, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; Anne E. Jenns(2), Sally M. Schneider(3), and Margaret E. Daub(4). (2)(4)Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; (3)USDA-ARS, Oxford, NC 27565. Phytopathology 82:1305-1310. Accepted for publication 5 August 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992. DOI: 10.1094/Phyto-82-1305.

Nicotiana repanda has resistance to many important tobacco diseases, but no tobacco cultivars are currently available that carry resistance genes derived from this species. In order to transfer resistance genes into cultivated tobacco (N. tabacum), N. repanda was first hybridized with N. sylvestris, a species that is cross-compatible with both N. tabacum and N. repanda. This N. repanda × N. sylvestris (R × S) hybrid was then hybridized with N. tabacum cv. NC2326 by protoplast fusion. Parental lines were transformed for resistance to two antibiotics, hygromycin or kanamycin, with Agrobacterium tumefaciens transformation vectors. Fused protoplasts were selected by their ability to grow and regenerate on medium containing both antibiotics. No fusion calli were recovered from 15 different fusion experiments between NC2326 and the R × S hybrid, but calli were recovered from six of 63 fusion experiments when NC2326 was fused with a chromosome-doubled R × S hybrid. Calli appeared 4–6 mo after fusion, compared to the 8–12 wk required to obtain fusion calli between two sexually compatible N. tabacum cultivars, NC2326 and Burley 21. To date, rooted plants have only been obtained from one fusion experiment; these were designated as E fusion hybrids. A total of 69 of these fusion hybrids were established in the greenhouse 17–24 mo after fusion. All resembled NC2326 in morphology, but all had resistance to tobacco mosaic virus (TMV) derived from the R × S hybrid parent. Of 12 fusion hybrids analyzed for isozyme patterns of glutamate oxaloacetate transaminase, all demonstrated hybrid isozyme patterns. All 69 plants flowered and were male sterile, and all were successfully backcrossed to NC2326. To date, BC₁F₁ plants of 27 of the 69 E fusion hybrids have been analyzed for resistance to TMV and race 2 of Meloidogyne arenaria. Only 25 of 270 BC₁F₁ plants tested showed increased resistance to M. arenaria, four of which had resistance equivalent to that of the R × S hybrid. By contrast, 164 of 226 BC₁F₁ plants had resistance to TMV. BC₁F₁ plants also segregated for morphological traits. BC₁F₁ plants were again male sterile, but were successfully backcrossed to NC2326. The efficiency of the dual antibiotic selection system for selection of fusion hybrids in vitro is also reported.