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Reproduction of M. arenaria on flue-cured tobacco homozygous for Rk1 and/or Rk2 resistance genes, and possible effects of soil temperature on resistance
Jill Pollok, Virginia Tech University 20
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Nematodes in Tobacco
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Nematodes in Tobacco
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Root-Knot Nematode Damage
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Root-Knot Nematode Damage
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Crop rotation
Nematicides
Resistant varieties
Current Control Options
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M. incognita 22%
M. arenaria 41%
M. javanica 5%
M. hapla 32%
2004 VA Nematode Survey, Flue-Cured Tobacco
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M. incognita
8%
M. arenaria
58%
M. javanica
9%
M. hapla 25%
2010 VA Nematode Survey, Flue-Cured Tobacco
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Reproduction Experiment
• Genes Rk1 and Rk2 are
responsible for root knot
resistance in tobacco
– Rk1: resistance to races 1 and 3 of
M. incognita
– Rk2: resistance mostly
uncharacterized
• Objective: Does having both
resistance genes (Rk1Rk1 and
Rk2Rk2) give more resistance in
tobacco to M. arenaria than just
one or the other?
TOBACCO ENTRY RESISTANCE GENES
Coker 371 Gold Susceptible
SC 72 Rk1Rk1
NC 95 Rk1Rk1
T-15-11 Rk2Rk2
STNCB-2-28 Rk1Rk1 Rk2Rk2
NOD 8 Rk1Rk1 Rk2Rk2
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Methods
• 6 tobacco entries
• 6 replications
• Inoculated each plant with
5,000 root-knot eggs
• 60 days after inoculation, cut
plant tops off, rinsed roots,
and collected data
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1. Gall Rating
• Weight of galled roots/total root
weight
2. # of females per gram root
• Sub-divided root system in half
by weight
• Stained ½ red with Phloxine B,
collected three 1-g samples
from stained roots, counted the
number of egg masses to
estimate females
Root-knot egg masses protruding from roots.
Methods: Data Collected
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McGawley, via Nemapix
Methods: Data Collected
3. # of eggs per gram root
• Bleach-extracted eggs from the root
surface of the other half of the root
system
• Suspended eggs in 500 ml water and
counted two 10-ml aliquots
• Averaged the counts and calculated
eggs for 500 ml/0.5 root weight to
estimate eggs/gram roots
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Host Plant Reaction: Galling
Mean data from 5 trials, each with 6 replications. Data presented are non-transformed means of 6 observations. Means followed by the same letter(s) are not significantly different according to statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP Pro 11.
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Egg masses/g root by trial
Mean data from 5 trials, each with 6 replications. Data presented are non-transformed means of 6 observations. Means followed by the same letter(s) are not significantly different according to statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP Pro 11.
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Eggs/g root by trial
Mean data from 5 trials, each with 6 replications. Data presented are non-transformed means of 6 observations. Means followed by the same letter(s) are not significantly different according to statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP Pro 11.
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Reproduction Experiment Conclusions
• Galling, egg masses per g of root, and eggs per g of root were significantly lower when entries possessed Rk1 alone versus the control.
• Combining Rk1 and Rk2 genes further reduced galling (in 1 of 5 trials), egg masses (in 4 of 5 trials), and eggs (in 3 of 5 trials). Entries containing both Rk1 and Rk2 genes exhibited the largest reduction in nematode reproduction.
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Soil Temperature Experiment
• Objective: to determine if
temperature plays a role in
resistance gene efficacy
• Previous student noted that
resistance seemed to break down
at temps above 30°C (with M.
javanica)
• Tested at 25°, 30°, and 35°C
• Inoculated with 3,000 RK eggs,
took down after 35 days
• Soil moisture was standardized
between chambers based on soil
moisture deficit in designated pot
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a
c
b
cd d d
a
a
b b
b b
a
b b
bc bc c
Host Plant Reaction: Galling
Mean data from 1 trial with 4 replications. Data presented are non-transformed means of 4 observations. Means followed by the same letter(s) are not significantly different according to
statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP Pro 11.
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a
b
c c c c
a a
b b
c
b
a
a
a a
a a
Mean data from 1 trial with 4 replications. Data presented are non-transformed means of 4 observations. Means followed by the same letter(s) are not significantly
different according to statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP
Pro 11.
Egg masses/g root by temp
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a
bc
ab
c c c
a a
bc bc
ab
c
a a a a
a
a
Mean data from 1 trial with 4 replications. Data presented are non-transformed means of 4 observations. Means followed by the same letter(s) are not significantly different according to
statistical analysis of transformed [log10(x+1)] data and the Tukey-Kramer honest significant difference (HSD) test. Data were analyzed in JMP Pro 11.
Eggs/g root by temp
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Temp Experiment Conclusions
• At 25°C, galling, egg masses/g root, and eggs/g root followed trends
shown in previous reproduction experiments
• Plants with Rk1, or Rk1 and Rk2, almost always had significantly
fewer egg masses/g root and eggs/g root than the control and Rk2
plants at 30°C
• At 35°C there were no significant differences between any cultivars
for the number of egg masses/g root or the number of eggs/g root
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What Am I?
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Thank You
Dr. Chuck Johnson
Dr. Jon Eisenback
Dr. David Reed
VT Southern Piedmont summer help
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