With possible future regulation of nicotine levels, scientists are searching for ways to lower nicotine in ways acceptable to the tobacco industry. The conventionally bred nic1nic2 low alkaloid (LA) mutants lower nicotine to only about 10 % of the normal high alkaloid (HA) levels. We discovered a spontaneous low alkaloid mutation in a selection of the Burley breeding line L8, which reduced nicotine to 37 % of wild type sister lines. The objective of this preparatory work was to establish the nature of this mutation.

The study included a stable selection of this low alkaloid L8 line (L8-2), a sister line with normal alkaloid levels (L8-1) and the appropriate checks. Leaves of individual plants were sampled for molecular marker analysis, roots and leaves for alkaloid analysis, and roots for gene expression analysis. Molecular marker analysis revealed that both L8 lines were the same high-intermediate (HI) AAbb genotype. Nicotine + nornicotine (% DM) for L8-1 and L8-2, respectively, was 3.19 % and 0.87 % in the leaves, and 0.56 % and 0.59 % in the roots. Comparing the two lines, similar levels in the roots but different levels in the leaves suggest that the low alkaloids in L8-2 are a function of nicotine transport rather than synthesis. This is not the case when comparing LA and HA Burley 21 plants, which differ in both root and leaf alkaloid levels. Gene expression analysis also suggested the involvement of a nicotine transport mechanism behind the differential accumulation pattern of nicotine in the two L8 lines.

The mode of action of this novel gene appears to be different from that of the nic1nic2 mutants, and it is probably not allelic to nic1. If so, stacking this gene with nic1 and nic2 might lower nicotine beyond the 10 % level of the LA lines.