Screened Seed - Dark Tobaccodarktobacco.ca.uky.edu/files/lcvarieties_-_2.pdf · • Increase during storage of cured leaf . Major Factors Influencing TSNA Accumulation • ... •

Screened Seed Dr. Gary Palmer

University of Kentucky

Screened Seed Anne Jack

University of Kentucky

Screened Seed Letha Tomes

Kentucky Seed Improvement

Screened Seed Paul Denton

University of Tennessee

Screened Seed Andy Bailey

University of Kentucky

Industry Issues

• Big issues in tobacco industry •  anti-smoking lobby •  buyout •  TSNAs •  nornicotine

What are TSNAs? •  Tobacco Specific NitrosAmines •  Nitrogen containing compounds

known to be potentially carcinogenic •  Formed during curing •  Increase during storage of cured leaf

Major Factors Influencing TSNA Accumulation

•  Curing conditions •  Storage conditions •  Nitrogen fertilization •  Varietal differences – nornicotine

•  high nornicotine increases chance of high TSNAs

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

Variation in Seedlots

72 96 51

KY lot 1 KY lot 2 Other Source

Unselected KY 9

Variation in Varieties

33 2

KY 16 L8

0

10

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 19 0

0

10

2 0

3 0

4 0

50

6 0

70

8 0

9 0

1 8 9

0

10

2 0

3 0

4 0

50

6 0

70

8 0

9 0

1 8 8

Variation in Site – VA 509

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 1 7 7

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 1 6 6

0

10

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 5 1

10 19

13 8 9

9

TN 1 TN 2 NC

KY 1 KY 2 KY 3

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

NNN ppm vs % conversion NNN = 0.38 x + 1.18R = 0.68

0

5

10

15

0 5 10 15 20 25

% conversion

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

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

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

Screening (3%)

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4

nic + nornic %

conv

ersio

n %

Ethephon Treatment

Ethephon Treatment

Effect of screening

8 2

Unscreened Screened

TN 90

VA 509 57 5

Effect of Screening

•  Lowers mean conversion •  does not necessarily eliminate all

converter plants • most dramatic with high converters •  reduced effect with low converters

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

“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

Thank you