Registration of ‘B2’ Connecticut Broadleaf Cigar‐Wrapper Tobacco Resistant to Fusarium Wilt, Tobacco Mosaic Virus, Cyst Nematodes, and Blue Mold

Abstract

‘B2’ Connecticut broadleaf cigar‐wrapper tobacco (Nicotiana tabacum L.) (Reg. No. CV‐124, PI 664300) is a male‐sterile hybrid released by the Connecticut Agricultural Experiment Station and is resistant to Fusarium wilt, Tobacco mosaic virus (TMV), the tobacco cyst nematode [TCN; Globodera tabacum tabacum (Lownsbery and Lownsbery 1954) Stone 1973], and blue mold [caused by Peronospora tabacina de Bary Adam 1933 (= Peronospora hyoscyami de Bary 1863 f. sp. tabacina Skalicky 1964)]. Initial crosses were made in 1987 between VA‐81 and PD4 flue‐cured tobacco and three broadleaf inbreds resistant to Fusarium wilt [caused by Fusarium oxysporum Schlechtend.:Fr. f. sp. nicotianae (J. Johnson) W.C. Snyder & H.N. Hans.] and TMV. F2 selections were backcrossed twice to broadleaf lines, inbred and selected across 12 generations using bulk modified single‐seed descent with 2% of plants (20 plants of 1000) selected most years; selection for TMV and TCN resistance was conducted in greenhouse screens with fewer plants. Lines were field selected for reduced ozone weather fleck. One F12 selection was backcrossed again to the broadleaf cultivar ‘Scantic’ and inbred via pedigree selection across 10 generations with field and greenhouse selection. Progeny testing was used to select F8 plants homozygous for resistance to TCN and for hypersensitive TMV resistance from Nicotiana glutinosa L. A superior male‐fertile inbred (MF‐2) resulting from 27 generations of selection for broadleaf characteristics with 8 cycles of selection each for Fusarium wilt, TMV and TCN resistance was identified and crossed with a male‐sterile CT broadleaf line resistant to TMV and Fusarium wilt (MS‐1) to produce the F1 male‐sterile hybrid B2.