Vector 21-41

Tobacco

Variety Description

Variety used for comparison: 'Burley 21'

Summary: 'Vector 21-41' is a transgenic tobacco that was developed for very low nicotine content and has significantly lower levels than the parent and reference variety 'Burley 21'. Plants of 'Vector 21-41' also mature later than 'Burley 21'.

Description:

'Vector 21-41' is a transgenic burley tobacco variety which produces conical shaped plants with a moderate number of leaves. The plant has very little or no tendency to produce suckers. The leaves are sessile and the angle of insertion is very acute. The leaf blade is narrow elliptic and light green in colour, with a whitish green midrib on the lower side. The leaf tip is strongly pointed. Blistering of the leaf blade is moderate, and the margins are moderately undulating. Leaf auricles are medium to strong. In cross section the leaf of 'Vector 21-41' is concave, and the longitudinal profile is slightly to moderately recurved. At the leaf base the blade is narrow in width. 'Vector 21-41' has thick leaf veins.

The inflorescence of 'Vector 21-41' is moderately compact and double conical in shape and it is located above the upper leaves. 'Vector 21-41' flowers mid-season and the florets have a pink corolla. The stamens are fully developed and are slightly taller than the pistil.

The leaves of 'Vector 21-41' have very low nicotine levels.

Origin & Breeding History: The low nicotine tobacco variety 'Vector 21-41' was developed by transforming the variety 'Burley 21 LA' with the binary Agrobacterium vector pYTY32. 'Burley 21 LA' is a variety of 'Burley 21' with substantially reduced levels of nicotine as compared with 'Burley 21'. The binary vector pYTY32 carries the 2.0kb NtQPT1 root cortex specific promoter driving the antisense expression of the NtQPT1 cDNA terminated by the nopaline synthase (nos) 3' termination sequences from Agrobacterium tumefaciens T-DNA. (NtQPT1 is a tobacco gene that encodes quinolinate phosphoribosyl transferase, an enzyme involved in nicotine biosynthesis.) The selectable marker for this construct was neomycin phosphotransferase (nptII) from E. coli Tn5, the expression of which is directed by the nos promoter from Agrobacterium tumefaciens T-DNA. nptII confers resistance to kanamycin. Transformed cells, tissues and seedlings were selected by their ability to grow on MS medium containing 300 g/ml kanamycin.

One hundred independent pYTY32 transformants of 'Burley 21LA' (T0) were allowed to self. Progeny of the selfed plants (T1) were germinated on medium containing kanamycin and the segregation of kanamycin resistance was scored. Nicotine levels of T1 progeny segregating 3:1 were measured qualitatively using a micro-assay. T1 progeny that had less than 10% of the nicotine levels of the 'Burley 21 LA' parent were allowed to self to produce T2 progeny. Homozygous T2 progeny were identified by germinating seeds on a medium containing kanamycin and selecting clones in which 100% of the progeny were resistant to kanamycin. Nicotine levels in homozygous and heterozygous T2 progeny were qualitatively determined using the micro-assay and again showed levels less than 10% of the 'Burley 21 LA' parent. The transformant was designated 'Vector 21-41'.

'Vector 21-41' plants were allowed to self, producing T3 progeny, which were, in turn, allowed to self to produce T4 progeny. Samples of the bulked seeds of the T4 progeny were grown and nicotine levels were tested.

Tests & Trials: Tests and trials for 'Vector 21-41' were conducted during 2003 and 2004 at Emerson Tobacco Company, Eden, Ontario. The field trials consisted of two replicated blocks, with each replicate containing one plot each of 'Vector 21-41' and 'Burley 21', for a total of two plots per replicate. Each plot consisted of 8 rows, with 20 plants per row, for a total of 160 plants per plot. For each plot, the plant spacing within rows was 18 inches. Inter-row spacing was 42 inches. Measured morphological characteristics were based on 20 measurements. In addition to the observation of morphological characteristics of the plants, the 5th, 10th and 15th leaf from 6 plants each of 'Vector 21-41' and 'Burley 21' were collected (total of 18 leaves per variety). The leaves were dried at 105 C for 24 hours. Nicotine analysis was then conducted according to the standard operating procedure for nicotine determination using the gas chromatograph method.

Comparison table for 'Vector 21-41' with reference variety 'Burley 21'

Nicotine level