nornicotine conversion in Chinese burley tobacco and genetic
improvement for low conversion hybrids
Huihui DI1, Zifa XIE2, Lowell BUSH3
and Guoshun LIU1
University, Zhengzhou, 450002, China.
2Dazhou Tobacco Research
Institute of Sichuan, Dazhou, 635000, China.
3University of Kentucky,
Lexington, KY 40546, U.S.A.
*Corresponding author. E-mail:
Accepted 16 August, 2011
Nicotine conversion results in abnormally high levels of
nornicotine which lead to high nitrosonornicotine (NNN)
content and off-taste of smoke. Nicotine conversion is a
worldwide problem in burley tobacco production and has been
the focus in burley research in recent years. Nicotine
conversion level in Sichuan burley tobacco was the highest
with the percent nicotine conversion being 62.4%, followed
by Chongqing, Hubei and Yunnan. The leading variety
Xuanhan-5NL had serious problem of nicotine conversion, with
the proportion of converters being 96% of the total plants.
In the populations of hybrid Dabai 1, Dabai 2 and Eyan 1, a
substantial amount of converters were also found. Newly
developed hybrids Dabai 3 and Dasuo 24 had serious problems
of nicotine conversion with almost 100% of the plants being
converters. Further study using ethylene early
identification method was conducted to investigate the
contribution of different parental lines to nicotine
conversion in Dabai series hybrids. Both parents of Dabai 1
contributed to the conversion level in the hybrid. The male
parent of Dabai 2 was the main contributor of conversion
gene to the hybrid. The male parent of Dabai 3, had
extremely high converter proportion and conversion level,
and was almost the exclusive contributor of conversion gene
to Dabai 3. Improved Dabai series hybrids developed by
selecting and crossing non-converter parent plants, showed
significantly reduced converters in next populations.
Genetic improvement for low conversion trait by early
non-converter parent selections was very effective.
Burley, tobacco, nicotine to nornicotine conversion,