Abstract: In the natural population of burley tobacco, some plants have the ability converting nicotine to nornicotine due to gene mutation, resulting in the abnormal increase of nornicotine content, which has negative effect on tobacco safety and flavor quality. Burley tobacco hybrids Dabai 1 and Eyan 1 were used to investigate the relationship between principle alkaloid contents in bulk and individual samples from natural and purified populations. The results showed that in the purified populations nicotine content accounted for 92–95% of total alkaloid; the proportion of anatabine was higher than that of nornicotine, they were 3.2–5.0% and 1.6–2.8% respectively; the proportion of anabasine was the lowest. In the natural population contained large amount of converted plants, the nicotine content decreased and the nornicotine content increased, and the nornicotine content was higher than anatabine content. In the purified populations, as the increase of total alkaloids, all the principle individual alkaloids increased linearly, with the order of correlation coefficients with total alkaloids as nicotine > anatabine or anabasine > nornicotine, and with the order of slope for alkaloid increasing as nicotine > nornicotine > anatabine > anabasine. In natural populations, the correlation of total alkaloid with nicotine and nornicotine decreased, and that with anabasine and anatabine did not change. The nicotine and nornico-tine were positively correlated in purified populations, but negatively or not correlated in natural populations. Anatabine was sig-nificantly and positively correlated with anabasine in both populations.

Key words: Alkaloid, Nicotine, Nornicotine, Conversion rate, Converted plants, Natural population, Purified population, Relationship