screened seed dr. gary palmer university of kentucky
TRANSCRIPT
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Screened SeedAndy Bailey
University of Kentucky
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Industry Issues
• Big issues in tobacco industry• anti-smoking lobby
• buyout
• TSNAs
• nornicotine
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What are TSNAs?
• Tobacco Specific NitrosAmines
• Nitrogen containing compounds known to be potentially carcinogenic
• Formed during curing
• Increase during storage of cured leaf
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Major Factors Influencing TSNA Accumulation
• Curing conditions
• Storage conditions
• Nitrogen fertilization
• Varietal differences – nornicotine• high nornicotine increases chance of
high TSNAs
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Nicotine Conversion• One gene responsible for conversion
of nicotine to nornicotine• these plants are known as converters
• plants which do not have this mutation are known as non-converters
• Conversion • varies with variety and seedlot
• can vary with site and season• occurs during curing, senescence
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Variation in Seedlots
72 96 51
KY lot 1 KY lot 2 Other Source
Unselected KY 9
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Variation in Varieties
33 2
KY 16 L8
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0
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1 190
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1 89
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1 88
Variation in Site – VA 509
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1 177
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1 166
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1 51
10 19
138 9
9
TN 1 TN 2 NC
KY 1 KY 2 KY 3
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Nornicotine – why the fuss?
• Detrimental effect on smoke• considered undesirable long before
current interest in TSNAs
• Detrimental health effects• Effect on TSNAs
• ALL THINGS BEING EQUAL, lower nornicotine = lower TSNAs
• low nornicotine no guarantee of low TSNA• curing environment over-riding effect
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NNN ppm vs % conversion
NNN = 0.38 x + 1.18R = 0.68
0
5
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0 5 10 15 20 25
% conversion
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Why focus on nornicotine?
• So many variables affect TSNAs• few can be controlled
• weather• microbial populations
• Nornicotine is the one variable which can be controlled
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What can the industry do?
• Screen seed to reduce conversion• need to identify screened seed
• by renaming screened varieties
• screened cultivars re-released as “LC” cultivars• LC = “low converter”• eg TN 90 LC
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What is Screening?
• Roguing converter plants out of seed crop (breeder & foundation seed)• number & test plants individually
• cut out all plants above limit (3%)
• Use ethephon to drive plants to full potential
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Screening (3%)
0
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0 1 2 3 4
nic + nornic %
co
nvers
ion
%
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Ethephon Treatment
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Ethephon Treatment
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Effect of screening
8 2
Unscreened Screened
TN 90
VA 50957 5
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Effect of Screening
• Lowers mean conversion • does not necessarily eliminate all
converter plants
• most dramatic with high converters
• reduced effect with low converters
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Bottom Line• Screened seed
• lower nornicotine• will HELP reduce TSNAs – no guarantee
• Industry demand• manufacturers want screened seed
• enable growers to meet requirements
• need to identify screened seedlots• can only do this by renaming screened
varieties
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“LC” Varieties• Screened varieties
• Re-released as “LC” varieties • “LC” varieties available to growers in 2005• TN 90 LC, TN 86 LC, TN 97 LC, KT 200 LC,
KY 907 LC
• NO difference except for conversion• same for yield, quality, disease
resistance• TN 90 “LC” is still TN 90
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Thank you