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Characterization of Eight Russian Wheat Aphid (Hemiptera: Aphididae) Biotypes Using Two-Category Resistant‐Susceptible Plant Responses

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Eight biotypes of the Russian wheat aphid, Diuraphis noxia (Kurdjumov), have been discovered in the United States since 2003. Biotypes are identified by the distinct feeding damage responses they produce on wheat carrying different Russian wheat aphid resistance genes, namely, from Dn1 to Dn9. Each Russian wheat aphid biotype has been named using plant damage criteria and virulence categories that have varied between studies. The study was initiated to compare the plant damage caused by all the eight known Russian wheat aphid biotypes, and analyze the results to determine how Russian wheat aphid virulence should be classified. Each Russian wheat aphid biotype was evaluated on 16 resistant or susceptible cereal genotypes. Plant damage criteria included leaf roll, leaf chlorosis, and plant height. The distribution of chlorosis ratings followed a bimodal pattern indicating two categories of plant responses, resistant or susceptible. Correlations were significant between chlorosis ratings and leaf roll (r 2 = 0.72) and between chlorosis ratings and plant height (r 2 = 0.48). The response of 16 cereal genotypes to feeding by eight Russian wheat aphid biotypes found RWA1, RWA2, RWA6, and RWA8 to differ in virulence, while Russian wheat aphid biotypes RWA3, RWA4, RWA5, and RWA7 produced similar virulence profiles. These biotypes have accordingly been consolidated to what is hereafter referred to as RWA3/7. Our results indicated that the five main biotypes RWA1, RWA2, RWA3/7, RWA6, and RWA8 can be identified using only four wheat genotypes containing Dn3, Dn4, Dn6, and Dn9.
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PLANT RESISTANCE
Characterization of Eight Russian Wheat Aphid (Hemiptera:
Aphididae) Biotypes Using Two-Category Resistant–Susceptible
Plant Responses
G. J. PUTERKA,
1,2
S. J. NICHOLSON,
1
M. J. BROWN,
1
W. R. COOPER,
3
F. B. PEAIRS,
4
AND T. L. RANDOLPH
4
J. Econ. Entomol. 107(3): 1274Ð1283 (2014); DOI: http://dx.doi.org/10.1603/EC13408
ABSTRACT Eight biotypes of the Russian wheat aphid, Diuraphis noxia (Kurdjumov), have been
discovered in the United States since 2003. Biotypes are identiÞed by the distinct feeding damage
responses they produce on wheat carrying different Russian wheat aphid resistance genes, namely,
from Dn1 to Dn9. Each Russian wheat aphid biotype has been named using plant damage criteria and
virulence categories that have varied between studies. The study was initiated to compare the plant
damage caused by all the eight known Russian wheat aphid biotypes, and analyze the results to
determine how Russian wheat aphid virulence should be classiÞed. Each Russian wheat aphid biotype
was evaluated on 16 resistant or susceptible cereal genotypes. Plant damage criteria included leaf roll,
leaf chlorosis, and plant height. The distribution of chlorosis ratings followed a bimodal pattern
indicating two categories of plant responses, resistant or susceptible. Correlations were signiÞcant
between chlorosis ratings and leaf roll (r
2
0.72) and between chlorosis ratings and plant height (r
2
0.48). The response of 16 cereal genotypes to feeding by eight Russian wheat aphid biotypes found
RWA1, RWA2, RWA6, and RWA8 to differ in virulence, while Russian wheat aphid biotypes RWA3,
RWA4, RWA5, and RWA7 produced similar virulence proÞles. These biotypes have accordingly been
consolidated to what is hereafter referred to as RWA3/7. Our results indicated that the Þve main
biotypes RWA1, RWA2, RWA3/7, RWA6, and RWA8 can be identiÞed using only four wheat
genotypes containing Dn3,Dn4,Dn6, and Dn9.
KEY WORDS plant resistance, wheat, barley, invasive specie, plant damage
Biotypes of the Russian wheat aphid, Diuraphis noxia
(Kurdjumov), have become a serious threat to the
development and deployment of plant resistance in
cereals since the occurrence of the Þrst Russian wheat
aphid biotype (RWA2) in 2003 (Haley et al. 2004).
Previous to the appearance of RWA2, resistance genes
for wheat designated Dn1 to Dn9, Dnx, and Dny were
found to be effective against the original Russian
wheat aphid (RWA1) that invaded the United States
in 1986 (Haley et al. 2004). Six additional biotypes
(RWA3ÐRWA8) have been described (Burd et al.
2006, Weiland et al. 2008, Randolph et al. 2009) since
the discovery of RWA2. The biotypic diversity in Rus-
sian wheat aphid has limited useful resistant germ-
plasm to 94M370 (Dn7 gene), CI2401, and STARS
2414-11. In addition, two sources of resistance in bar-
ley, STARS 9301B and STARS 9577B, still exhibit
strong resistance to all eight biotypes (Puterka et al.
2006, Mornhinweg 2012).
The appearance of RWA2 was unexpected because
the original invading population of Russian wheat
aphid (RWA1) was considered to be asexual (Butts
1992, Hammon and Peairs 1998, Burd et al. 1998) and
showed no biotypic (Puterka et al. 1992) or genetic
variation (Puterka et al. 1993, Shufran et al. 1997). In
2005, an area-wide study on Russian wheat aphid bio-
typic variation in wheat found RWA2 to have almost
completely displaced the original biotype, RWA1
(Puterka et al. 2007). Genetic variation among Russian
wheat aphid biotypes suggested a single (Shufran et al.
2007, Shufran and Payton 2009) or multiple invasions
into the United States that afterward diversiÞed into
more biotypes (Liu et al. 2010). Sexually reproducing
Russian wheat aphid have also been discovered in the
high plateau region of western Colorado, in which
40 distinct biotypes were documented when 90
progeny were screened against key sources of Russian
wheat aphid resistance (Puterka et al. 2012). The re-
cent discovery of the currently designated biotypes,
Mention of trade names or commercial products in this article is
solely for the purpose of providing speciÞc information and does not
imply recommendation or endorsement by the United States Depart-
ment of Agriculture. The authors declare no conßicts of interest.
1
USDAÐARS, Plant Science Research Laboratory, 1301 N. West-
ern, Stillwater, OK 74074.
2
Corresponding author, e-mail: gary.puterka@ars.usda.gov.
3
USDAÐARS, Fruit & Vegetable Insect Research, 5230 Konnowac
Pass Road, Wapato WA 98951.
4
Department of Bioagricultural Sciences and Pest Management,
1177 Campus Delivery, Colorado State University, Fort Collins, CO
80523-1177.
the potential for new biotype introductions, and the
production of new biotypes via sexual reproduction
present a signiÞcant challenge for breeding Russian
wheat aphid-resistant wheat with durable resistance
to a range of biotypes.
Past studies that characterized and designated the
eight Russian wheat aphid biotypes compared new
biotypes with a limited subset of already known bio-
types or with those biotypes available at the time.
Biotypes RWA3, 4, and 5 were characterized by the
mean damage ratings (1 [no damage] to 9 [dead plant
rating]) they caused on plant leaves (Burd et al. 2006),
while Russian wheat aphid biotypes RWA6, 7, and 8
were characterized by a combination of leaf damage
and leaf roll ratings (Weiland et al. 2008, Randolph et
al. 2009). Although these biotype studies categorized
plants into resistant, intermediately resistant, or sus-
ceptible damage categories, the damage rating range
for each category differed. In some cases, damage
ratings produced by Russian wheat aphid biotypes on
certain plant genotypes were statistically similar but
were assigned different damage categories. Further
complicating biotype classiÞcations were studies that
reported opposing damage responses in identical
wheat genotypes; for example, RWA3 feeding damage
on Dn7 (Burd et al. 2006, Weiland et al. 2008, Randolph
et al. 2009).
Producing reproducible biotype effects on cereal
germplasm is fundamental to the identiÞcation of Rus-
sian wheat aphid biotypes and the detection of new
more virulent biotypes. The objective of this study was
to characterize the damage caused by all the eight
Russian wheat aphid biotypes (RWA1ÐRWA8) on re-
sistant and susceptible wheat and barley genotypes.
Damage was assessed using rating scales for leaf chlo-
rosis and leaf roll, similar to those used in previous
biotype studies (Burd et al. 2006, Weiland et al. 2008,
Randolph et al. 2009). The damage rating distributions
were analyzed to determine whether a two- (resistant
and susceptible) or three (resistant, intermediately
resistant, and susceptible)-category system was most
appropriate for classifying Russian wheat aphid viru-
lence to each plant genotype. Data on plant damage
components were analyzed with the goal of develop-
ing virulence categories for biotypes that account for
the variability in damage data. Consistencies and dis-
crepancies among previously reported virulence pro-
Þles to common wheat genotypes were addressed in
light of our results to better unify the biotype concept
for Russian wheat aphid and facilitate studies on bio-
typic diversity.
Materials and Methods
The original Russian wheat aphid biotype (RWA1)
that invaded the United States was collected in Bailey
County, TX, in 1986 (Burd et al. 1993) and maintained
by the U.S. Department of AgricultureÐAgricultural
Research Service (USDAÐARS), Stillwater, OK. Bio-
types RWA3 (Floyd County, TX), RWA4 (Lubbock
County, TX), and RWA5 (Park County, WY) were
originally collected in 2002Ð2003 and described by
Burd et al. (2006). Four biotypes were obtained from
the Colorado State University, Ft. Collins, CO, namely,
RWA2 collected in Baca County, CO, in 2003 (Haley
et al. 2004) and RWA6, RWA7, and RWA8 collected
in western (RWA6 and RWA8) and eastern (RWA7)
Colorado (Weiland et al. 2008). These biotypes were
obtained by U.S. Department of AgricultureÐAgri-
cultural Research ServiceÐPlant Science Research
Laboratory (USDAÐARSÐPSRL) at Stillwater, OK,
soon after they were collected. For the 7 yr before
this study, the eight Russian wheat aphid biotypes
were maintained on ÔYumaÕ wheat grown in 8-cm-
diameter pots within cylindrical clear plastic cages
5 cm in diameter and 30 cm in length that were
topped with a Þne mesh cloth for ventilation. The
aphid colonies were held in a room with tempera-
tures of 20Ð22C on light racks with a photoperiod
of 14:10 (L:D) h provided by four 40W cool white
ßuorescent lights.
The virulence and biotypic classiÞcations for isofe-
male colonies of Russian wheat aphid biotypes 1Ð8
were determined by plant reactions of 16 Russian
wheat aphid-resistant or -susceptible wheat and bar-
ley genotypes (Table 1). Seeds of each genotype were
planted in a mini-ßat 18 cm in width by 27 cm in length
by 5 cm in depth in a completely randomized design.
The mini-ßats were placed in a 27 cm in width by 38
cm in length by 6 cm in depth tray Þlled with con-
struction grade sand that served as a bed to seat metal
frame cages (30 cm in width by 40 cm in length by 30
cm in height) covered with Þne mesh nylon screen.
The plants were watered moderately and infested at a
rate averaging 10 aphids per plant genotype when the
plants reached a height of 3Ð5 cm. The experiment was
replicated 10 times during the fall and spring of 2009Ð
2010 under variable greenhouse temperatures (12Ð
28C) and sunlight (10Ð13 h). Plant damage was as-
sessed as a percent leaf chlorosis or necrosis on a 1Ð9
rating scale of increasing damage (1 healthy; 2
1Ð5% and spotted; 3 5Ð20%; 4 21Ð35%; 5 36Ð50%;
651Ð65%; 7 66Ð80%; 8 81Ð95%; and 9
96 Ð100% or dead (Webster et al.1991, Burd et al. 2006)
when susceptible ÔYumaÕ and ÔCusterÕ plant genotypes
rated an 8Ð9 (20Ð24 d). Leaf rolling was rated using a
1Ð3 scale, where 1 ßat; 2 folded or partially rolled;
and 3 fully rolled (Burd et al. 1993). The distribution
and frequency of leaf chlorosis ratings for all 16 ge-
notypes across all aphid biotypes was tested against a
normal distribution (SAS Institute 2010) to determine
if the distribution was modally or normally distributed
across the nine damage scores to classify aphid viru-
lence. Each plant genotypeÐRussian wheat aphid bio-
type combination was classiÞed as either resistant
(R damage rating of 5) or susceptible (S damage
rating of 5) based on the bimodal distribution of the
chlorosis rating data. Categorical data from leaf chlo-
rosis, plant infestation level, and rolling for aphid bio-
types within and across cereal genotypes were sub-
jected to a one-way nonparametric analysis using a
KruskalÐWallis analysis of variance (ANOVA; PROC
NPAR1WAY) and, if signiÞcant (P
2
0.05), plant
comparisons were made using pair-wise KruskalÐWal-
June 2014 PUTERKA ET AL.: EIGHT RUSSIAN WHEAT APHID BIOTYPES CHARACTERIZATION 1275
lis tests (SAS Institute 2010). Parametric data from
plant heights were analyzed by a two-way ANOVA to
determine the effects of aphid biotype, plant geno-
type, and their interaction; means for biotypes within
genotypes were compared using the least signiÞcant
difference (LSD) analyses (P0.05).
Results
The frequency distribution of all chlorosis ratings
for 16 plant genotypes and eight Russian wheat aphid
biotypes (n1280) indicated a bimodal distribution
in the data (Fig. 1). Therefore, the nonparametric
nature of the chlorosis rating data was best repre-
sented by a two-categoryÑresistant or susceptibleÑ
plant response to Russian wheat aphid feeding. Dam-
age ratings for the resistant plant category (n590)
ranged from 1 to 5 with an average of 2.97 0.04.
Resistant ratings primarily encompassed 2Ð4, which
represented 1Ð35% leaf chlorosis. The susceptible
damage category (n690) encompassed damage
scores ranging from 4 to 9 with a mean of 7.67 0.05.
This distribution was mainly represented by damage
scores ranging from 6 to 9 (51100% chlorosis) with
a damage rating of 9 representing 39% of the total
scores in the susceptible damage category. Compari-
son of distributions showed the susceptible damage
category slightly overlapped with the resistant damage
category for ratings 4 (n2) and 5 (n27). For this
reason, the chlorosis rating of 5 provided a reasonable
dividing point between cereal resistance (rating 1 to
5) and susceptibility (5Ð9). If an intermediate cat-
egory was added, the damage ratings would have had
a distribution frequency for ratings 4 138, 5 61, and
Table 1. List of resistant and susceptible wheat and barley genotypes used to determine Russian wheat aphid virulence
Crop Plant
genotype
Resistance source
or gene
Resistance to
Russian wheat
aphid biotype
Reference
Wheat CO03797 Dn1 1 Haley et al. (2004)
CO03804 Dn2 1 Haley et al. (2004)
CO03811 Dn3 1 Haley et al. (2004)
Yumar Dn4 1 Haley et al. (2004), Collins et al. (2005)
CO950043 Dn5 1 Haley et al. (2004)
CO960223 Dn6 1 Haley et al. (2004)
94M370 Dn7 1Ð8 Haley et al. (2004), Weiland et al. (2008), Randolph et al. (2009)
Karee-Dn8Dn8 1 Haley et al. (2004)
Betta-Dn9Dn9 1 Haley et al. (2004)
CI 2401 PI372129 1Ð8 Collins et al. (2005), Weiland et al. (2008), Randolph et al. (2009)
STARS 2414-11 PI366515 1Ð8 Collins et al. 2005, Weiland et al. 2008, Randolph et al. 2009
Custer Ð Susc. Haley et al. (2004)
Yuma Ð Susc. Haley et al. (2004)
Barley STARS 9301B Rdn1/Rdn2/Rdn3 1Ð8 Mornhinweg (2012), Mittal et al. (2009)
STARS 9577B Rdn1/Rdn2 1Ð8 Mornhinweg (2012)
Mittal et al. (2008)
Schyler Ð Susc. Mornhinweg et al. (1999)
Fig. 1. Frequency distribution for all chlorosis damage ratings from 16 plant genotypes and eight biotypes (n1280).
Mean damage ratings for each biotypeÐplant genotype combination were classiÞed as resistant or susceptible to determine
the distributions of the underlying damage rating data.
1276 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 107, no. 3
6129, which is not the expected normal distribution
that would support it as a valid category.
Analysis of chlorosis ratings for each plant genotype
pooled across all biotypes showed highly signiÞcant
differences (P0.0001) between resistant (R dam-
age rating 1Ð5) and susceptible (S damage rating
5Ð9) categories for wheat resistance genes Dn1 to
Dn6 and Dn9 (Table 2). The remaining plant geno-
types produced uniform chlorosis damage responses
that were either resistant (e.g., STARS 2414-11) or
susceptible (e.g., Yuma). Comparison among plant
genotypes within each Russian wheat aphid biotype
showed signiÞcant differences in leaf chlorosis ratings
(P
2
0.0001;
2
110.4Ð135.3, df 15; Table 3).
The susceptible standards Yuma, Custer, and ÔSchylerÕ
were among the highest damaged of the cereal geno-
types within each biotype. The wheat genotypes
94M370 (Dn7), CI2401, and STARS 2414-11, and the
barley genotypes STARS 9301B and STARS 9577B,
were highly resistant to all eight Russian wheat aphid
biotypes, as indicated by low chlorosis ratings. Signif-
icant differences in chlorosis ratings were found
among Russian wheat aphid biotypes within most
cereal genotypes (range, P
2
0.006 to 0.0001;
2
19.2Ð45.8; df 7) with the exception of suscep-
tible Custer and highly resistant STARS 2414-11 (P
2
0.055Ð0.70;
2
4.613.2; df 7, respectively).
RWA2 was the most virulent to RWA1-resistant cereal
genotypes followed by a group with lesser virulent
biotypes RWA3, 4, 5, and 7. Least virulent to the
RWA1-resistant cereal genotypes was RWA1 followed
by slightly more virulent RWA6 and RWA8.
The leaf roll ratings produced by Russian wheat
aphid biotypes signiÞcantly differed for cereal geno-
types containing Dn1 to Dn6 genes, Dn9, and STARS
9577B (P
2
0.0001;
2
87.4 Ð137.1; df 15; Table
4). No signiÞcant differences in leaf roll ratings were
found among Russian wheat aphid biotypes within
cereal genotypes that were highly susceptible (e.g.,
ÔYumarÕ) or highly resistant (e.g., 94M370 [Dn7]) in
Table 4. There was a moderate correlation between
increasing chlorosis damage ratings and an increase in
leaf roll damage ratings (P0.0001; r
2
0.72).
Plant height was signiÞcantly impacted by cereal
genotype (F129.08; df 15, 1438; P0.0001),
Russian wheat aphid biotype (plus uninfested control;
F450.96; df 8, 1438; P0.0001), and their inter-
action (F125.93; df 120, 1438; P0.0001; Table
5). In general, feeding by the Russian wheat aphid
biotypes reduced plant height of cereal genotypes by
50Ð75% in comparison to the uninfested controls.
There was a signiÞcant yet inconsistent inverse linear
relationship between chlorosis ratings and plant
height (F1343.47; df 1439; P0.0001; r
2
0.48).
Virulence patterns of each Russian wheat aphid
biotype were categorized into resistant (R) and sus-
ceptible (S) plant responses for the 16 cereal geno-
types (Table 6) based on chlorosis ratings in Table 3.
Wheat genotypes containing the Russian wheat aphid
resistance genes Dn1, Dn2, Dn3, Dn5, Dn7, and Dn8
responded similarly to all Russian wheat aphid bio-
types. In contrast, Dn4, Dn6, and Dn9 showed vari-
ability in plant responses to feeding by Russian wheat
aphid biotypes. The wheat germplasm sources, CI2401
and STARS 2414-11, were highly resistant to all Rus-
sian wheat aphid biotypes. The wheat (Custer and
Yuma) and barley (Schyler) varieties that were used
as positive controls conÞrmed uniform susceptibility
to all Russian wheat aphid biotypes. The barley lines
STARS 9301B and STARS 9577B displayed strong re-
sistance to the all Russian wheat aphid biotypes. Over-
all, variable damage responses in four wheat geno-
types containing Dn3, Dn4, Dn6, and Dn9 identiÞed
RWA1, RWA2, RWA6, and RWA8, respectively, as
unique biotypes, whereas RWA3, 4, 5, and 7 did not
differ in their responses (Table 7).
Table 2. Chi-square analysis of chlorosis damage ratings (n80) produced by all Russian wheat aphid biotypes within each cereal
genotype after categorizing each rating as resistant (R 1to<5) or susceptible (>5–9)
Cereal
genotype Resistance gene
a
Mean SE damage rating per category
(observations per category)
2
P
2
(df 1)
Resistant Susceptible
Wheat
CO03797 Dn1 3.65 0.31 (20) 6.18 0.17 (60) 19.1 0.0001
CO03804 Dn2 4.05 0.20 (20) 7.11 0.21 (60) 20.7 0.0001
CO03811 Dn3 3.80 0.13 (20) 7.48 0.19 (30) 41.7 0.0001
Yumar Dn4 4.06 0.15 (30) 6.80 0.21 (50) 40.5 0.0001
CO9500043 Dn5 4.06 0.24 (20) 7.00 0.18 (60) 35.0 0.0001
CO960223 Dn6 3.18 0.14 (70) 6.50 0.22 (10) 23.8 0.0001
94M370 Dn7 2.85 0.10 (80) Ð Ð Ð
Karee-Dn8 Dn8 Ð 7.16 0.17 (80) Ð Ð
Betta-Dn9 Dn9 3.50 0.16 (10) 6.11 0.19 (70) 15.8 0.0001
CI2401 New 3.10 0.14 (80) Ð Ð 0.0001
STARS 2414-11 New 2.31 0.01 (80) Ð Ð Ð
Yuma Sus. Ð 8.85 0.05 (80) Ð Ð
Custer Sus. Ð 8.85 0.04 (80) Ð Ð
Barley
STARS 9301B Rdn1/Rdn2/Rdn3 2.37 0.06 (80) Ð Ð Ð
STARS 9577B Rdn1/Rdn2 2.61 0.08 (80) Ð Ð Ð
Schyler Sus. 8.48 0.09 (80) Ð Ð
a
Sus., susceptible to all Russian wheat aphid biotypes; new, new resistant germplasm.
June 2014 PUTERKA ET AL.: EIGHT RUSSIAN WHEAT APHID BIOTYPES CHARACTERIZATION 1277
Table 3. Mean leaf chlorosis damage ratings taken 20 –24 d after cereal genotypes were infested by Russian wheat aphid biotypes
Cereal
genotype Resistance gene
a
Biotype
b
RWA1 RWA2 RWA3 RWA4 RWA5 RWA6 RWA7 RWA8
Wheat
CO03797 Dn1 3.9 0.2deC 6.0 0.3fB 5.9 0.2dB 5.8 0.3eB 6.2 0.3cdAB 6.3 0.3cAB 6.9 0.4cdA 3.4 0.2efgBC
CO03804 Dn2 4.2 0.3deC 7.0 0.4deB 8.2 0.4abA 7.8 0.4cA 7.0 0.4bcB 6.9 0.5cB 7.1 0.5cdAB 3.9 0.2cdeC
CO03811 Dn3 3.5 0.2efgC 7.9 0.3bcdA 8.0 0.4bA 8.0 0.3bcA 6.9 0.3bcB 7.7 0.4bAB 7.8 0.4bcA 4.1 0.2cdC
Yumar Dn4 4.0 0.3deC 7.3 0.5cdeAB 7.6 0.4bA 6.7 0.2dAB 7.0 0.2bcAB 3.8 0.2deC 6.5 0.5dB 4.2 0.2cC
CO9500043 Dn5 4.4 0.3dC 7.3 0.4cdeAB 7.9 0.4bA 7.0 0.2dAB 6.8 0.2bcB 7.0 0.2cAB 7.7 0.4bcAB 3.3 0.3efgD
CO960223 Dn6 3.6 0.2efB 6.8 0.2efA 3.9 0.2eB 3.1 0.2fB 3.1 0.4dB 3.9 0.3dB 3.6 0.2eB 3.5 0.3defB
94M370 Dn7 2.8 0.2gABC 2.5 0.2dBC 2.2 0.1gfC 2.4 0.2ghBC 3.2 0.4dA 3.4 0.3defA 3.0 0.2eAB 2.9 0.2fghAB
Karee-Dn8 Dn8 7.4 0.5bBC 7.1 0.4cdeCD 6.4 0.3cdD 6.6 0.3dCD 7.3 0.3bBC 8.0 0.2bAB 8.5 0.2abA 8.3 0.3bA
Betta-Dn9 Dn9 6.6 0.4cAB 6.6 0.2efAB 6.8 0.3cAB 6.4 0.3dBC 6.9 0.2bcAB 6.8 0.3cAB 7.3 0.4cdA 3.4 0.2efgC
CI2401 New 2.8 0.2gA 2.8 0.3gA 2.9 0.3fA 2.7 0.3fgA 2.9 0.3deA 3.4 0.2defA 3.3 0.2efA 3.1 0.2fgA
STARS 2414-11 New 2.2 0.2gA 2.2 0.2gA 2.0 0.2gA 2.2 0.1ghA 2.5 0.3deA 2.7 0.3fgA 2.4 0.2fA 2.3 0.2hA
Yuma Sus. 8.9 0.1aAB 8.9 0.1aAB 8.8 0.1aAB 8.5 0.2abB 8.6 0.2aAB 9.0 0.0aA 9.0 0.0aA 9.0 0.0aA
Custer Sus. 8.9 0.1aA 8.7 0.3abA 8.8 0.1aA 8.9 0.1aA 8.8 0.1aA 8.8 0.1aA 9.0 0.0aA 8.9 0.1abA
Barley
STARS 9301B Rdn1/Rdn2/Rdn3 2.9 0.1gfA 2.4 0.2gBC 2.0 0.0gB 2.0 0.0gB 2.2 0.1eAB 2.6 0.2gAB 2.5 0.2fAB 2.4 0.2hBC
STARS 9577B Rdn1/Rdn2 3.0 0.31fgAB 2.4 0.3gBC 2.1 0.2gC 2.4 0.2ghBC 2.7 0.2deABC 3.1 0.1efgA 2.4 0.2fBC 2.8 0.2ghAB
Schyler Sus. 8.8 0.1aA 8.0 0.3bcB 7.9 0.1bB 8.2 0.3bcAB 8.4 0.3aAB 8.9 0.1aA 8.9 0.1aA 8.8 0.1abA
Chlorosis ratings ranged from 1 no damage to 9 95Ð100% chlorotic of necrotic leaf.
a
Sus., Russian wheat aphid susceptible control; new, new RWA2 resistant germplasm.
b
Means within a column followed by the same lower-case letter, or within a row followed by the same upper-case letter, are not signiÞcantly different (P0.05, KruskalÐWallis test).
1278 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 107, no. 3
Table 4. Comparisons of mean leaf roll damage ratings taken 20 –24d after cereal genotypes were infested by Russian wheat aphid biotypes
Cereal
genotype Resistance gene
a
Biotype
b
RWA1 RWA2 RWA3 RWA4 RWA5 RWA6 RWA7 RWA8
Wheat
CO03797 Dn1 1.1 0.1deB 2.3 0.6bcA 2.1 0.2bcA 2.1 0.2cA 2.0 0.0cA 2.1 0.4cA 2.1 0.4cA 1.7 0.4cA
CO03804 Dn2 1.6 0.4cdB 2.4 0.3bcA 2.6 0.4aA 2.4 0.2bcA 2.8 0.2abA 2.9 0.1aA 2.9 0.1aA 2.2 0.2abA
CO03811 Dn3 1.7 0.4bcCD 2.4 0.4bcAB 2.8 0.2aAB 2.8 0.2aAB 2.8 0.2abAB 2.2 0.2cBC 3.0 0.0aA 1.4 0.1aD
Yumar Dn4 1.6 0.2cdBC 2.3 0.4bcA 2.9 0.2aA 2.9 0.2aA 3.0 0.0aA 1.1 0.1abC 2.6 0.4abA 1.8 0.3abB
CO9500043 Dn5 1.5 0.2edC 2.4 0.4bcB 3.0 0.0aA 2.9 0.1aAB 2.6 0.2bAB 2.4 0.4bcB 2.7 0.3abAB 2.8 0.2aAB
CO960223 Dn6 1.2 0.2edB 2.6 0.3abA 1.5 0.3dAB 1.5 0.3dAB 1.0 0.0dB 1.3 0.3dAB 1.3 0.3dAB 1.2 0.2cdB
94M370 Dn7 1.0 0.0eA 1.0 0.6eA 1.0 0.0eA 1.0 0.0eA 1.0 0.0dA 1.0 0.0dA 1.0 0.0dA 1.1 0.1eA
Karee-Dn8 Dn8 2.7 0.4aAB 2.4 0.4aB 2.5 0.2abAB 2.6 0.2abAB 2.5 0.2bAB 2.9 0.1aAB 3.0 0.0aA 2.9 0.1aAB
Betta-Dn9 Dn9 2.2 0.3bB 2.9 0.1aA 2.3 0.3bcB 2.3 0.6bcB 2.6 0.2abB 2.4 0.2bcB 2.6 0.2abB 1.4 0.1aC
CI2401 New 1.0 0.0eA 1.0 0.0eA 1.0 0.0eA 1.2 0.2edA 1.0 0.0dA 1.2 0.2dA 1.0 0.0dA 1.4 0.4cdeA
STARS 2414-11 New 1.0 0.0eA 1.1 0.1eA 1.1 0.1deA 1.1 0.1edA 1.0 0.0dA 1.0 0.0dA 1.2 0.2dA 1.2 0.2deA
Yuma Sus. 3.0 0.0aA 3.0 0.2aA 2.8 0.2aA 2.9 0.1aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA
Custer Sus. 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA
Barley
STARS 9301B Rdn1/Rdn2/Rdn3 1.0 0.0eA 1.1 0.1eA 1.1 0.0deA 1.0 0.0eA 1.0 0.0dA 1.0 0.0dA 1.0 0.0dA 1.0 0.2eA
STARS 9577B Rdn1/Rdn2 1.1 0.1edB 1.6 0.6deA 1.1 0.1deB 1.0 0.0eB 1.0 0.0dB 1.0 0.0dB 1.0 0.0dB 1.0 0.2eB
Schyler Sus. 3.0 0.0aA 2.7 0.2abA 2.7 0.3aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA 3.0 0.0aA
Leaf roll was rated as 1 ßat leaf, 2 folded leaf, and 3 fully rolled leaf.
a
Sus., Russian wheat aphid susceptible control; new, new RWA2 resistant germplasm.
b
Means within a column followed by the same lower-case letter, or within a row followed by the same upper-case letter, are not signiÞcantly different (P0.05, Kruskal Wallis test).
June 2014 PUTERKA ET AL.: EIGHT RUSSIAN WHEAT APHID BIOTYPES CHARACTERIZATION 1279
Table 5. Comparisons of mean plant heights of cereal genotypes taken 20 –24d after being infested with Russian wheat aphid biotypes in comparison to an uninfested control
Cereal
genotype Resistance gene
a
Biotype
b
RWA1 RWA2 RWA3 RWA4 RWA5 RWA6 RWA7 RWA8 Uninfested
Wheat
CO03797 Dn1 14.9 1.3B 15.1 0.9B 14.5 0.9B 13.7 0.9B 13.8 1.1B 14.4 0.7B 13.4 0.3B 14.8 1.0B 44.0 0.5A
CO03804 Dn2 17.3 1.7B 15.9 1.6B 17.0 2.0B 19.5 0.4B 20.6 1.2B 18.1 2.3B 16.6 2.0B 19.8 1.7B 43.6 7.6A
CO03811 Dn3 14.6 1.5C 13.7 1.3CD 14.5 0.9C 16.0 1.7BC 15.6 1.1BC 11.2 0.6DE 9.4 0.7E 18.0 1.6B 43.0 1.5A
Yumar Dn4 19.6 1.2B 18.5 1.3B 19.8 1.5B 20.7 1.2B 20.6 0.7B 18.3 1.6B 17.3 1.9B 19.1 2.8B 40.8 1.8A
CO9500043 Dn5 16.6 1.2B 12.9 0.7C 13.6 1.0BC 16.1 1.2BC 16.9 2.2B 14.9 0.6BC 14.4 1.3BC 16.0 0.6BC 40.6 1.6A
CO960223 Dn6 21.0 0.9CDE 16.8 1.1DE 15.7 1.2E 24.5 2.7BC 27.1 2.7B 19.0 1.5DE 16.5 1.4E 22.1 2.3BCD 59.3 1.9A
94M370 Dn7 29.7 2.5B 26.2 2.4B 29.5 2.3B 30.4 3.1B 28.4 4.7B 27.4 0.7bB 25.3 1.6B 27.6 1.7B 43.8 1.8A
Karee-Dn8 Dn8 12.4 1.4BC 12.9 1.5BC 14.3 0.5B 14.3 0.4B 12.8 0.2BC 11.8 0.7B 12.2 1.2BC 13.7 0.5BC 55.6 0.4A
Betta-Dn9 Dn9 12.5 1.3B 13.8 1.2B 14.1 0.6B 13.7 0.5B 13.5 1.2B 12.1 1.6B 11.7 1.2B 11.6 1.0B 52.6 1.7A
CI2401 New 19.3 1.5BC 17.7 1.5C 19.6 1.2BC 23.5 3.0B 22.0 0.7BC 19.1 1.9BC 17.1 1.6C 23.1 1.7B 46.6 2.9A
STARS 2414-11 New 29.5 2.1BC 27.9 1.0bBC 30.4 2.4BC 32.1 0.7B 33.0 2.8B 30.2 1.7BC 25.3 0.4C 27.3 0.4BC 38.8 1.4A
Yuma Sus. 15.2 1.3BC 14.6 0.8C 17.0 2.2BC 18.2 1.7B 17.5 1.8BC 15.9 1.7BC 15.5 2.4BC 17.5 1.4BC 42.8 0.2B
Custer Sus. 14.9 0.4B 15.0 0.4B 16.6 3.9B 14.2 1.1B 15.1 1.3B 15.6 6.1B 13.1 0.9B 14.5 0.8B 43.8 4.4A
Barley
STARS 9301B Rdn1/Rdn2/Rdn3 24.3 0.6C 26.7 1.5CD 36.1 1.9BC 38.8 1.8B 39.2 5.4B 34.4 2.4BCD 26.5 4.5CD 26.1 4.8CD 48.8 3.2A
STARS 9577B Rdn1/Rdn2 35.1 3.0BC 30.6 1.5BC 35.7 0.9BC 37.1 6.2B 34.3 1.7BC 32.1 1.8BC 27.6 2.7C 26.9 2.9C 51.8 2.8A
Schyler Sus. 14.7 1.1B 12.7 1.6B 14.9 0.5B 15.4 1.8B 14.3 1.2B 13.1 1.7B 14.0 0.2B 12.5 0.8B 44.0 1.2A
a
Sus., Russian wheat aphid susceptible control; new, new RWA2 resistant germplasm.
b
Means within a row followed by the same upper-case letter are not signiÞcantly different (P0.05, LSD test).
1280 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 107, no. 3
Discussion
The strong bimodal frequency distribution of leaf
chlorosis ratings for the 16 cereal genotypes reßected
a resistantÐsusceptible chlorosis rating relationship to
Russian wheat aphid virulence. Clustering of the chlo-
rosis ratings toward the lower and higher ends of the
1 to 9 rating scale and a small frequency of overlap
between the resistant and susceptible distributions
approaching the intermediate rating of 5 supported a
two-category plant damage response (Fig. 1). Non-
parametric analyses of the two-category data con-
Þrmed that the differential responses of cereal geno-
types to Russian wheat aphid biotypes were highly
signiÞcant (P
2
0.0001; Table 2). Those cereal
genotypes that responded differently to aphid feeding
(e.g., Dn1 to Dn6) had resistant or susceptible cate-
gories separated by a difference of 2 damage ratings
(30% chlorosis or necrosis) and supported signiÞcant
differences between the biotypes abilities to damage
cereal genotypes (Table 3). Those plant genotypes
with uniform responses to the Russian wheat aphid
biotypes showed clear-cut high levels of either resis-
tance or susceptibility. Inclusion of an intermediate
category of 4Ð5.9 would have clearly resulted in chlo-
rosis ratings being assigned different plant response
categories even though they did not differ signiÞ-
cantly (e.g., Table 3; intermediate for RWA4 on Dn1
5.8B; susceptible for RWA6 on Dn1 6.3AB). These
conßicts were also evident in other studies that used
an intermediate category to make comparisons among
Russian wheat aphid biotypes (Weiland et al. 2008,
Randolph et al. 2009).
Previous studies used either leaf chlorosis (Burd et
al. 2006) or leaf chlorosis plus leaf roll ratings
(Weiland et al. 2008, Randolph et al. 2009) to classify
aphid virulence to cereal genotypes. Leaf roll (Table
4) was moderately correlated (P0.0001; r
2
0.72)
with chlorosis ratings in both wheat and barley, thus,
was not a useful measure for Russian wheat aphid
virulence. This result is supported by other studies
that found no signiÞcant correlation between leaf roll-
ing and chlorosis ratings (Smith et al. 2004, Burd et al.
2006). Plant height (Table 5) was weakly correlated
(r
2
0.48; P0.0001) with chlorosis ratings. In con-
trast, plant stunting was reported to best describe the
quantitative damage response to RWA1 infestations in
cereals, although growth reductions occurred in both
resistant and susceptible germplasm. In general, plant
height was reduced by 50% for resistant and 75%
for susceptible responses for the cereal genotypes in
our study. These reductions support Þndings in similar
studies on barley (Puterka et al. 2006) and wheat
(Puterka et al. 2013) under greenhouse conditions.
However, the lack of a strong correlation between
plant height and leaf chlorosis made plant height an
unreliable factor for discriminating Russian wheat
aphid biotypes. Therefore, we used only leaf chlorosis
ratings to determine the virulence of Russian wheat
aphid biotypes to the cereal genotypes.
Table 6. Summary of resistant(R) and susceptible (S) responses of the plant genotypes based on chlorosis damage ratings produced
by Russian wheat aphid biotypes 20 –24d after infestation
Cereal
genotype
Biotype
Resistance gene
a
RWA1 RWA2 RWA3 RWA4 RWA5 RWA6 RWA7 RWA8
Wheat
CO03797 Dn1 RSSSSSSR
CO03804 Dn2 RSSSSSSR
CO03811 Dn3 RSSSSSSR
Yumar Dn4 RSSSSRSR
CO9500043 Dn5 RSSSSSSR
CO960223 Dn6 RS RRRRRR
94M370 Dn7 RRRRRRRR
Karee-Dn8 Dn8 SSSSSSSS
Betta-Dn9 Dn9 SSSSSSSR
CI2401 New RRRRRRRR
STARS 2414-11 New RRRRRRRR
Yuma Sus. SSSSSSSS
Custer Sus. SSSSSSSS
Barley
STARS 9301B Rdn1/Rdn2/Rdn3 RRRRRRRR
STARS 9577B Rdn1/Rdn2 RRRRRRRR
Schyler Sus. SSSSSSSS
Chlorosis ratings (Table 3) ranging 1 to 5resistant (R); 5Ð9 susceptible (S).
a
Sus., susceptible to all Russian wheat aphid biotypes; new, RWA2 new resistant germplasm.
Table 7. Primary wheat differential needed to identify biotypes
RWA1 to RWA8
RWA
biotype
a
Wheat genotype
b
CO03797
(Dn3)
Yumar
(Dn4)
CO960223
(Dn6)
Betta-Dn9
(Dn9)
RWA1 R R R S
RWA2 S S S S
RWA3/7 S S R S
RWA6 S R R S
RWA8 R R R R
Biotypes that are grouped (RWA3/7) produced similar responses
on the cereal genotypes.
a
RWA3/7 represents a consolidation of RWA3, RWA4, RWA5, and
RWA7.
b
Chlorosis ratings of 1 to 5resistant (R); 5Ð9 susceptible
(S).
June 2014 PUTERKA ET AL.: EIGHT RUSSIAN WHEAT APHID BIOTYPES CHARACTERIZATION 1281
Our study and previous Russian wheat aphid bio-
typing studies used similar 1Ð9 leaf chlorosis ratings,
which enabled a basis for comparing results. The chlo-
rosis ratings in our study (Table 3) were generally near
the ratings previously reported for speciÞc biotypeÐ
plant genotype interactions (Haley et al. 2004, Burd et
al. 2006, Weiland et al. 2008, Randolph et al. 2009).
Although it is not possible to discuss every discrepancy
between Russian wheat aphid biotyping studies, two
types of discrepancies for Russian wheat aphid viru-
lence to cereal genotypes will be highlighted. One
type of inconsistency is when an intermediate re-
sponse was used, e.g., Yumar rating 5.3 and 5.8 to
RWA4 and RWA5, respectively (Randolph et al.
2009). Our study found Yumar was susceptible to all
three biotypes (rating 7.6Ð6.7), which would be
aligned with Randolph et al. (2009) results as being
susceptible if a two-category response were used.
Variations in plant response between studies can only
be partially resolved by reducing the plant categories
to resistant or susceptible. A second example is where
opposite results on the resistance status of a cereal
genotype occurred among studies whether an inter-
mediate resistance category was used or not. For ex-
ample, RWA5 feeding on Yuma was originally re-
ported as resistant (chlorosis rating 3.9; Burd et al.
2006) but our results (rating 8.6; Table 3) and another
study (rating 7.4; Randolph et al. 2009) found Yuma to
be susceptible. Another example is 94M370 (Dn7),
when fed upon by RWA3 and RWA4, was originally
reported to be susceptible (6.5Ð6.9, Burd et al. 2006)
but was highly resistant in our study (chlorosis rating
2.2Ð2.4; Table 3) and Randolph et al. (2009) (both
rating 1.0). The large differences between these stud-
ies damage ratings for Yuma and 94M370 appeared to
be anomaly, which is difÞcult to explain. Yet, these
original ratings were unusual and, in cases like these,
are best veriÞed through independent laboratory test-
ing. The two-category plant response classiÞcation
should be less prone to misclassiÞcations by account-
ing for inherent variation in plant responses to similar
aphid clones owing to biotic or abiotic factors that
inßuence plant responses, or simply variation owing to
sampler error.
The response of 16 cereal genotypes to feeding by
eight Russian wheat aphid biotypes showed no signif-
icant differences among Russian wheat aphid biotypes
RWA3, 4, 5, and 7 (Tables 3 and 6) when using resis-
tant or susceptible plant responses. Accordingly, these
biotypes have been consolidated to what is hereafter
referred to as RWA3/7 (Table 7). Our results support
a previous study that screened progeny from a sexually
reproducing Russian wheat aphid population and
found RWA3, 4, and 7 had similar virulence proÞles
(Puterka et al. 2012) and concluded they could be a
single biotype that consisted of different genotypes
that vary slightly in virulence. In summary, results
indicated that there are mainly Þve biotypes RWA1,
RWA2, RWA3/7, RWA6, and RWA8 that can be iden-
tiÞed using four wheat genotypes containing Dn3,
Dn4, Dn6, and Dn9. These results are comparatively
consistent with most of the previously reported results
and represent a consensus between our results and
other studies (Burd et al. 2006, Weiland et al. 2008,
Randolph et al. 2009). The potential for new biotypes
to occur via sexual reproduction (Puterka et al. 2012),
and the possibility for new biotype introductions into
the United States (Liu et al. 2010) poses signiÞcant
challenges to the development of durable resistance to
a range of Russian wheat aphid biotypes. Screening
RWA populations for biotypic diversity can be facil-
itate by use of four Russian wheat aphid resistance
sources (Table 7) that would identify the current
Russian wheat aphid biotypes, and by adding other
important sources of resistance (e.g., 94M370 (Dn7)
and STARS 2414-11) to identify new biotypes. Mon-
itoring Russian wheat aphid populations for shifts in
biotype composition and detecting new Russian
wheat aphid biotypes will be a crucial aspect in the
development and deployment of durable sources of
Russian wheat aphid resistance in cereals.
References Cited
Burd, J. D., R. L. Burton, and J. A. Webster. 1993. Evaluation
of Russian wheat aphid (Homoptera: Aphididae) damage
on resistant and susceptible hosts with comparisons of
damage ratings to quantitative plant measurements. J.
Econ. Entomol. 86: 974Ð980.
Burd, J. D., R. A. Butts, N. C. Elliott, and K. A. Shufran. 1998.
Seasonal development, overwintering biology, and host
plant interactions of Russian wheat aphid (Homoptera:
Aphididae) in North America, pp. 65Ð99. In: S. S. Quisen-
berry and F. B. Peairs (eds.), Response model for an
introduced pestÐÐthe Russian wheat aphid. Thomas Say
Publication, Entomology Society of America, Lanham,
MD.
Burd, J. D., D. R. Porter, G. J. Puterka, S. D. Haley, and F. B.
Peairs. 2006. Biotypic variation among North American
Russian wheat aphid populations. J. Econ. Entomol. 99:
1862Ð1866.
Butts, R. A. 1992. Cold hardiness and its relationship to
overwintering of the Russian wheat aphid (Homoptera:
Aphididae) in Southern Alberta. J. Econ. Entomol. 85:
1140Ð1145.
Collins, M. B., S. D. Haley, T. L. Randolph, F. B. Peairs, and
J. B. Rudolph. 2005. Comparison of Dn4- and Dn7-car-
rying spring wheat genotypes artiÞcially infested with
Russian wheat aphid (Homoptera: Aphididae) biotype 1.
J. Econ. Entomol. 98: 1698Ð1703.
Haley, S. D., F. B. Peairs, C. B. Walker, J. B. Rudolph, and
T. L. Randolph. 2004. Occurrence of a new Russian
wheat aphid biotype in Colorado. Crop Sci. 44: 1589Ð
1592.
Hammon, R. W., and F. B. Peairs. 1998. Natural history of
Diuraphis (Homoptera: Aphididae) species occurring in
western Colorado, pp. 280Ð287. In S. S. Quisenberry and
F. B. Peairs (eds.), A response model for an introduced
pestÐthe Russian wheat aphid (Homoptera: Aphididae).
Thomas Say Publications in Entomology, Entomology
Society of America, Lanham, MD.
Liu, X., J. Marshall, P. Stary, O. Edwards, G. Puterka, L.
Dolatti, M. El Bouhssini, J. Manglia, J. Lage, and C. M.
Smith. 2010. Global phylogenetics of Diuraphis noxia
(Hemiptera: Aphididae), an invasive aphid species: Ev-
idence for multiple invasions into the North America. J.
Econ. Entomol. 103: 958Ð965.
1282 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 107, no. 3
Mittal, S., L. S. Dahleem, and D. W. Mornhinweg. 2008.
Locations of quantitative trait loci conferring Russian
wheat aphid resistance in barley germplasm, STARS
9301B. Crop Sci. 48: 1452Ð1458.
Mittal, S., L. S. Dahleem, and D. W. Mornhinweg. 2009.
Barley germplasm, STARS 9577B lacks a Russian wheat
aphid resistance allele at a QT locus in STARS 9301B.
Crop Sci. 49: 1999Ð2004.
Mornhinweg, D. W., D. R. Porter, and J. A. Webster. 1999.
Registration of STARS-9577B Russian wheat aphid resis-
tant barley germplasm. Crop Sci. 39: 882Ð883.
Mornhinweg, D. W. 2012. Biotic stresses in Barley: Insect
problems and solutions, pp. 282Ð306. In S. E. Ullrich (ed.),
Barley production, improvement, and uses. Blackwell
Publications, LTD., J. Wiley, LTD. West Sussex, United
Kingdom.
Puterka, G. P., J. D. Burd, and R. L. Burton. 1992. Biotypic
variation in a worldwide collection of Russian wheat
aphid (Homoptera: Aphididae). J. Econ. Entomol. 85:
1497Ð1506.
Puterka, G. J., W. C. Black, IV, W. M. Steiner, and R. L.
Burton. 1993. Genetic variation and phylogenetic rela-
tionships among worldwide collections of Russian wheat
aphid, Diuraphis noxia (Mordvilko), inferred from allo-
zyme and RAPD-PCR markers. Heredity 70: 604Ð618.
Puterka, G. J., J. D. Burd, D. W. Mornhinweg, S. D. Haley,
and F. B. Peairs. 2006. Response of resistant and suscep-
tible barley to infestations of Þve Diuraphis noxia bio-
types. J. Econ. Entomol. 99: 2151Ð2155.
Puterka, G. J., J. D. Burd, D. Porter, K. Shufran, C. Baker, B.
Bowling, and C. Patrick. 2007. Distribution and diver-
sity of Russian wheat aphid (Hemiptera: Aphididae) in
North America. J. Econ. Entomol. 100: 1679Ð1684.
Puterka, G. J., R. W. Hammon, J. D. Burd, F. B. Peairs,
T. L. Randolph, Cooper. 2012. Cyclical parthenogenetic
reproduction in the Russian wheat aphid (Hemiptera:
Aphididae) in the United States: sexual reproduction and
its outcome on biotypic diversity. J. Econ. Entomol. 105:
1057Ð1068.
Puterka, G. J., J. N. Scott, M. J. Brown, and R. W. Hammon.
2013. Response of Russian wheat aphid resistance in
wheat and barley to four Diuraphis (Hemiptera: Aphidi-
dae) species. J. Econ. Entomol. 106: 1029Ð1035.
Randolph, T. L., F. Peairs, A. Weiland, J. B. Rudolph, and G. J.
Puterka. 2009. Plant responses to seven Russian wheat
aphid biotypes (Hemiptera: Aphididae) biotypes found
in the United States. J. Econ. Entomol. 102: 1954Ð1959.
SAS Institute. 2010. SAS userÕs guide, version 9.3. SAS In-
stitute, Cary, NC.
Shufran, K. A., J. D. Burd, and J. A. Webster. 1997. Biotypic
status of Russian wheat aphid (Homoptera: Aphididae)
populations in the United States. J. Econ. Entomol. 90:
1684Ð1689.
Shufran, K. A., L. R. Kirkman, and G. J. Puterka. 2007. Ab-
sence of mitochondrial DNA sequence variation in Rus-
sian wheat aphid (Hemiptera: Aphididae) populations
consistent with a single introduction into the United
States. J. Kan. Entomol. Soc. 80: 319Ð326.
Shufran, K. A., and T. L. Payton. 2009. Limited genetic
variation within and between Russian Wheat aphid
(Hemiptera: Aphididae) biotypes in the United States.
J. Econ. Entomol. 102: 440Ð445.
Smith, C. M., T. Belay, C. Stauffer, P. Stary, I. Kubeckova, and
S. Starey. 2004. IdentiÞcation of Russian wheat aphid
(Homoptera: Aphididae) populations virulent to Dn4 re-
sistance gene. J. Econ. Entomol. 97: 1112Ð1117.
Webster, J. A., C. A. Baker, and D. R. Porter. 1991. Detec-
tion and mechanisms of Russian wheat aphid (Ho-
moptera: Aphididae) resistance in barley. J. Econ. Ento-
mol. 84: 669Ð673.
Weiland, A. A., F. B. Peairs, T. L. Randolph, J. B. Rudolph,
S. D. Haley, and G. J. Puterka. 2008. Biotypic diversity in
Colorado Russian wheat aphid (Hemiptera: Aphididae)
populations. J. Econ. Entomol. 101: 569Ð574.
Received 18 September 2013; accepted 21 March 2014.
June 2014 PUTERKA ET AL.: EIGHT RUSSIAN WHEAT APHID BIOTYPES CHARACTERIZATION 1283
... Currently, there are five recognized RWA biotypes (RWA1, RWA2, RWA 3/7, RWA6, and RWA 8) that can be determined by differences in resistant or susceptible responses using plant genotypes with resistance genes dn3, Dn4, Dn6, and Dn9. This study also determined that only Dn7, Dn2414, and Dn2401 remained resistant to all known RWA biotypes (Puterka et al., 2014). Unfortunately, the Dn7 gene was discovered to produce wheat with commercially inferior bread-making qualities (Graybosch et al., 1993). ...
... Overall, the remaining resistant germplasm, including Dn10, resisted plant damage from both RWA biotypes and expressed strong antixenosis, which could be a beneficial trait for breeding programs. Chlorosis and leaf roll ratings for Yuma, Yumar, Dn2401, Dn2414, and Dn7 (Table 1) were closely aligned with other reports on RWA1 and RWA2 damage assessments (Collins, Haley, Randolph, Peairs, & Rudolph, 2005;Puterka et al., 2014Puterka et al., , 2015Randolph, Peairs, Weiland, Rudolph, & Puterka, 2009;Weiland et al., 2008). Our data indicate that chlorosis and leaf roll damage ratings for the Dn10 gene were comparable with the other genotypes carrying resistance genes Dn2401, Dn2414, Dn7, and Dn626580 when infested by either RWA biotype. ...
... Our data indicate that chlorosis and leaf roll damage ratings for the Dn10 gene were comparable with the other genotypes carrying resistance genes Dn2401, Dn2414, Dn7, and Dn626580 when infested by either RWA biotype. Plant height reductions resulting from both RWA biotypes were greatest (>50%) for Yuma and Dn625580 (Table 2) and support other studies where plant heights were reduced by as much as 50% in resistant genotypes and by 75% in susceptible wheat genotypes (Puterka et al., 2013(Puterka et al., , 2014. Plant height reductions cause by the RWA infestations indicated that the Dn10 genotype was among the least affected in comparison with the other susceptible and resistant genotypes (Table 2, Figure 2). ...
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The Russian wheat aphid (RWA, Diuraphis noxia Kurdjumov) is a global pest of wheat (Triticum aestivum L.) that became a significant problem to wheat and barley (Hordeum vulgare L.) in the United States soon after it was detected in 1986. Russian wheat aphid‐resistant wheat varieties expressing the Dn4 gene were effective in managing the first biotype, RWA1, from 1995–2003 until a new biotype, RWA2, overcame this resistance in 2003. Currently, only three genes are useful in developing RWA2 resistance in wheat. A new gene, Dn10, was recently discovered that is resistant to RWA2. This study characterized the effects that RWA1 and RWA2 had on the damage (leaf chlorosis and leaf roll) and growth components (plant height and leaf number) of plants expressing RWA resistance genes Dn4, Dn7, Dn10, Dn2401, Dn626580, and Dn2414 and the susceptible ‘Yuma’ 22 d after infestation. All plant genotypes that were RWA resistant expressed strong resistance to leaf chlorosis and leaf roll after RWA1 feeding. Results were similar for RWA2 except for the Dn4 genotype, which was equally susceptible as Yuma. Plant height was reduced by 50% for susceptible Yuma and Dn626580 by RWA1 and RWA2 feeding. Plant height and leaf reduction from RWA2 feeding on the susceptible Dn4 genotype were also reduced by 50%, whereas Dn7, Dn10, and Dn2414 reductions were <23%. Dn10 exhibited strong resistance to RWA1 and RWA2 feeding damage comparable with Dn7 and Dn2414 and showed less reduction in plant height than Dn2401 and Dn626580, which makes it a potentially valuable gene for wheat breeding programs.
... In the United States, eight RWA biotypes (RWA1-RWA8) have been identified (Burd et al., 2006;Weiland et al., 2008). Based on their responses to a set of differential lines, Puterka et al. (2014) combined biotypes RWA3, RWA4, RWA5, and RWA7 into one biotype and renamed it as RWA3/7, which reduced the US RWA biotypes to five. RWA1, RWA2, RWA3/7, RWA6, and RWA8 are virulent to two, eight, seven, six, and one of the 11 abovementioned genes, respectively, with RWA2 the most virulent US biotype (Botha, 2021). ...
... Therefore, continuous identification of new RWA resistance sources and development of RWA-resistant wheat cultivars are essential for global food safety. Currently, five RWA biotypes have been identified in the United States (Puterka et al., 2014), and only a few wheat accessions exhibiting resistance or high resistance to all US RWA biotypes have been identified . Characterization of RWA resistance genes in these resistant accessions will pave the way for their utilization in wheat breeding. ...
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Russian wheat aphid (RWA, Diuraphis noxia Kurdjumov) is a highly invasive and destructive wheat pest evolving rapidly to overcome host resistance. Novel genes conferring resistance to multiple RWA biotypes are needed to sustain wheat production. The Iranian landrace PI 625139 is resistant to all five US RWA biotypes. To map the RWA resistance gene in PI 625139, both F2 and F2:3 populations were developed from cross PI 625139 × Smith's Gold, and the F2:3 population was evaluated for responses to five RWA biotypes, RWA1, RWA2, RWA3/7, RWA6, and RWA8. RWA assays identified a single gene in PI 625139, designated Dn625139, conditioning resistance to all five US RWA biotypes. Selective genotyping of a subset of F2 plants using genotyping‐by‐sequencing (GBS) revealed a set of single‐nucleotide polymorphism (SNP) markers on the short arm of chromosome 7D that are closely associated with RWA resistance. Kompetitive allele‐specific PCR (KASP) markers were developed from selected GBS‐SNPs in 7DS. Genetic analysis using the new KASP and simple sequence repeat (SSR) markers placed Dn625139 to a 2.6 cM interval. Dn625139 was 1.2 cM proximal to the KASP marker Stars‐KASP1007 (169.57 Mb) and 1.4 cM distal to the SSR marker Stars1039 (195.27 Mb) in the International Wheat Genome Sequencing Consortium (IWGSC) RefSeq v2.1 reference sequence, and co‐segregated with the SSR marker Stars1029 (180.82 Mb). Dn625139 is a valuable gene conferring resistance to multiple RWA biotypes, and the molecular markers developed in this study can facilitate its rapid introgression into locally adapted cultivars to enhance wheat RWA resistance.
... The pool of known genes that are still suitable for deployment in R cultivars is, however, limited and needs to be expanded. The Dn7, Dn2401, and Dn2414 are three RWA resistance genes R to most known RWA biotypes globally Crop Science (Jankielsohn, 2014;Puterka et al., 2014). However, both Dn7 and Dn2414 have been introgressed from rye (Secale L.) via the 1RS translocation and 1RS is associated with bad breadmaking quality traits (Graybosch et al., 1990), thus making them unsuitable for use in SA and global breeding programs. ...
... Breeders in the United States use different rating scales to assess the plant damage from RWA including 0-100% equivalent to 1-10 rating scale where 1/10% = healthy plant, 5/50% = MR and >50 = S (Puterka et al., 2014). Others use 1-9 damage rating scale (Collins et al., 2005). ...
Article
Russian wheat aphid (RWA)Diuraphis noxiais a global pest of small grains, suchas wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena L.), andrye (Secale L.). Though laborious and time-consuming in terms of efforts requiredto eliminate the unwanted traits, wheat landraces have been widely used in breeding programs to deliver resistance sources and genes responsive to RWA amongother stresses. Continuous exploitation of resistance traits/alleles in the landracesshould be prioritized as a RWA intervention strategy to minimize its devastatingimpacts on wheat. Eighty donor lines were evaluated for their resistance to four SouthAfrican RWA biotypes, namely RWASA1, RWASA2, RWASA3, and RWASA4. Thecollection was composed of 74 donor lines and six breeding lines collected fromAfghanistan (38), Iran (22), Pakistan (11), United States (4), South Africa (2), Turkey(1), Georgia (1), and Egypt (1). Majority of the accessions were susceptible toRWASA3. Of the 80 accessions evaluated, 14 were uniformly resistant to moder-ately resistant to RWASA1, 9 to RWASA2, 7 to RWASA3, and 9 to RWASA4. Aheterogeneous resistance (resistant–moderately resistant:≥50%) was recorded in 18accessions for RWASA1, 28 for RWASA2, 13 for RWASA3, and 17 for RWASA4. Inaddition, 25 genotypes performed comparably to the check genotype CItr 2401, withresistance to all four RWA biotypes. Selection of resistant lines for genetic improve-ment of RWA resistance is of paramount importance. The use of genotypes conferringboth high levels and moderate resistance could offer scope for effective resistance toRWA in wheat. The merits of their exclusive resistance should be emphasized in pre-breeding programs.
... The pool of known genes that are still suitable for deployment in R cultivars is, however, limited and needs to be expanded. The Dn7, Dn2401, and Dn2414 are three RWA resistance genes R to most known RWA biotypes globally Crop Science (Jankielsohn, 2014;Puterka et al., 2014). However, both Dn7 and Dn2414 have been introgressed from rye (Secale L.) via the 1RS translocation and 1RS is associated with bad breadmaking quality traits (Graybosch et al., 1990), thus making them unsuitable for use in SA and global breeding programs. ...
... Breeders in the United States use different rating scales to assess the plant damage from RWA including 0-100% equivalent to 1-10 rating scale where 1/10% = healthy plant, 5/50% = MR and >50 = S (Puterka et al., 2014). Others use 1-9 damage rating scale (Collins et al., 2005). ...
Article
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Russian wheat aphid (RWA) Diuraphis noxia is a global pest of small grains, such as wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena L.), and rye (Secale L.). Though laborious and time‐consuming in terms of efforts required to eliminate the unwanted traits, wheat landraces have been widely used in breeding programs to deliver resistance sources and genes responsive to RWA among other stresses. Continuous exploitation of resistance traits/alleles in the landraces should be prioritized as a RWA intervention strategy to minimize its devastating impacts on wheat. Eighty donor lines were evaluated for their resistance to four South African RWA biotypes, namely RWASA1, RWASA2, RWASA3, and RWASA4. The collection was composed of 74 donor lines and six breeding lines collected from Afghanistan (38), Iran (22), Pakistan (11), United States (4), South Africa (2), Turkey (1), Georgia (1), and Egypt (1). Majority of the accessions were susceptible to RWASA3. Of the 80 accessions evaluated, 14 were uniformly resistant to moderately resistant to RWASA1, 9 to RWASA2, 7 to RWASA3, and 9 to RWASA4. A heterogeneous resistance (resistant–moderately resistant: ≥ 50%) was recorded in 18 accessions for RWASA1, 28 for RWASA2, 13 for RWASA3, and 17 for RWASA4. In addition, 25 genotypes performed comparably to the check genotype CItr 2401, with resistance to all four RWA biotypes. Selection of resistant lines for genetic improvement of RWA resistance is of paramount importance. The use of genotypes conferring both high levels and moderate resistance could offer scope for effective resistance to RWA in wheat. The merits of their exclusive resistance should be emphasized in prebreeding programs.
... Significant yield losses from both pests persist, despite the deployment of several of these genes in varieties of wheat resistant to each aphid [20,21]. Several S. graminum biotypes exist in wheat, sorghum and lawn and pasture grasses [22] and currently there are nine characterized biotypes of D. noxia in the U. S. and South Africa ( [23,24]. assembly containing both coding and non-coding genes has been deposited in USDA's Ag Data Commons at https://data.nal.usda.gov/dataset/denovo-transcriptome-assembly-schizaphisgramium-biotype-i-feeding-wheat ...
... For example, [67] identified five major proteins from secreted saliva of virulent and avirulent D. noxia biotypes, however their function as virulence factors remains unproven. Similarly, Nicholson and Puterka [23] identified quantitative variation in the salivary proteomes of four differentially virulent S. graminum biotypes for glucose dehydrogenase, carbonic anhydrase, and an abnormal oocyte protein, yet their function as virulence factors also remains unproven. It is also interesting to note that Ji et al. [68] identified salivary gland secretory proteins that are differentially expressed in biotypes of a related Hemipteran species, the brown planthopper, Nilaparvata lugens (Stal), but again, their function as virulence factors remains unproven. ...
Article
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The molecular bases of aphid virulence to aphid crop plant resistance genes are poorly understood. The Russian wheat aphid, Diuraphis noxia, (Kurdjumov), and the greenbug, Schizaphis graminum (Rondani), are global pest of cereal crops. Each species damages barley, oat, rye and wheat, but S. graminum includes fescue, maize, rice and sorghum in its host range. This study was conducted to compare and contrast the transcriptomes of S. graminum biotype I and D. noxia biotype 1 when each ingested phloem from leaves of varieties of bread wheat, Triticum aestivum L., containing no aphid resistance (Dn0), resistance to D. noxia biotype 1 (Dn4), or resistance to both D. noxia biotype 1 and S. graminum biotype I (Dn7, wheat genotype 94M370). Gene ontology enrichments, k-means analysis and KEGG pathway analysis indicated that 94M370 plants containing the Dn7 D. noxia resistance gene from rye had stronger effects on the global transcriptional profiles of S. graminum and D. noxia relative to those fed Dn4 plants. S. graminum responds to ingestion of phloem sap from 94M370 plants by expression of unigenes coding for proteins involved in DNA and RNA repair, and delayed tissue and structural development. In contrast, D. noxia displays a completely different transcriptome after ingesting phloem sap from Dn4 or 94M370 plants, consisting of unigenes involved primarily in detoxification, nutrient acquisition and structural development. These variations in transcriptional responses of D. noxia and S. graminum suggest that the underlying evolutionary mechanism(s) of virulence in these aphids are likely species specific, even in cases of cross resistance.
... These chemicals are expensive and could end up in grain produced from treated fields. There are currently eight biotypes of RWA identified in the United States (Puterka et al., 2014). Genetic diversity is necessary in deployed cultivars to stay ahead of biotype shifts. ...
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USDA Fortress’ (Reg. no. CV‐375, PI 696161), a multiple aphid‐resistant, high yielding, six‐rowed, mid‐season–maturing, winter feed barley (Hordeum vulgare L.) adapted to the Southern Plains, was developed and released by USDA‐ARS in Stillwater, OK. USDA Fortress is highly resistant to Russian wheat aphid [RWA; Diuraphis noxia (Kurdjumov)] and greenbug [Shizaphis graminum (Rondani)], with seedling resistance to the new invasive pest, hedgehog grain aphid [HGA; Sipha maydis (Passerini)]. USDA Fortress has the pedigree ‘Post 90’ *4/R012. Recurrent parent Post 90 has Rsg1 resistance to greenbug, and R012 is an unadapted RWA‐resistant germplasm line selected by USDA‐ARS Stillwater from PI 10706. Post 90 and USDA Fortress rate 2 on Starks’ greenbug resistance scale of 1–9, while USDA Fortress and R012 rate a 3 on Websters Russian wheat aphid resistance scale of 1–9, where 1 is immune and 9 is dead on both scales. Over 17 location‐years, in the absence of aphids, grain yield of USDA Fortress was 19 and 12% greater than ‘Thoroughbred’ and Post 90, respectively. USDA Fortress has average test weight of 60 kg hl–1 and has stable grain yield over state‐wide variability in climatic conditions. USDA Fortress is the first multiple‐aphid resistant barley cultivar in the United States.
... df = 11; P < 0.0001) and clone-by-plant entry interaction (F = 12.82; df = 33; P < 0.0001), suggesting that the plant entries responded differently to the different aphid clones. Biotypes are identified by the distinct feeding damage responses they produce on wheat carrying different RWA resistance genes from Dn1 to Dn9 [30]. Infestations of RWASA1 caused susceptible damage symptoms on the wheat entry containing the Dn2 and Dn3 gene ( [34]. ...
Chapter
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Russian wheat aphid (RWA) is an international pest on wheat and occurs in most countries where large scale wheat cultivation is practiced. Consequently, considerable efforts have been made to manage RWA globally. The two management options used currently are chemical control and breeding for deployment of resistant wheat cultivars. There are however drawbacks to both of these management practices. Chemical control has a negative impact on the environment, especially other insect groups such as predators, pollinators and decomposers. With widespread and continuous use of the same active ingredients, there is the possibility that RWA can build up resistance against these specific active ingredients. The drawback with resistance breeding is that certain RWA populations can overcome the resistance in the wheat, resulting in new biotypes virulent to the resistant wheat cultivars.
... A limited number of RWA2-resistant sources have been identified and include 94M370 (Dn7 gene), CI2401, and STARS 2414-11 (Collins et al. 2005a, Puterka 2014. While Dn4 and Dn7 were compared using RWA1 in spring wheat (Collins et al. 2005b), the genes have not been tested against susceptible lines for winter wheat yield response to RWA2 in the field. ...
Article
Plant damage and yield responses to three infestation levels (0, 1, and 10x) of biotype RWA2 Russian wheat aphid, Diuraphis noxia (Kurdjumov), were compared in winter wheat, Triticum aestivum L., during the 2010-11, 2011-12, and 2012-13 growing seasons at two sites in eastern Colorado. Wheat lines contained either no resistance gene (Yuma), Dn4 resistance (Yumar), or the Dn7 resistance gene (CO08RWA050). Fewer Russian wheat aphids and symptomatic tillers were on CO08RWA050 at any infestation. Yuma and Yumar tillers had an average of seven times more aphids present than CO08RWA050. Yields decreased as infestation increased in Yuma and Yumar, but yield was not less in CO08RWA050 at any infestation level. Kernel weights of Yuma and Yumar, but not CO08RWA050, were less with greater infestation. Data from the study suggested that resistance conferred by the Dn7 gene would be effective in reducing Russian wheat aphid abundance, and ultimately benefit wheat producers during outbreak years.
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This datasheet on Diuraphis noxia covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Natural Enemies, Impacts, Prevention/Control, Further Information.
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Diuraphis noxia, commonly known as the Russian wheat aphid, is an economically important cereal pest species, highly invasive and reproduces mostly asexually. Remarkably, many new virulent populations continue to develop, despite the lack of genetic diversity in the aphid. Russian wheat aphid is a phloem feeder and is therefore engaged in a continuous arms battle with its cereal host, with the acquisition of virulence central to the breakdown of host resistance. In the review, most attention is given to recent topics about mechanisms and strategies whereby the aphid acquires virulence against its host, with special reference given to the role of noncoding RNA elements, bacteria, and the epigenetic pathway in possibly directing virulence.
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Three Diuraphis species, Diuraphis frequens (Walker), Diuraphis mexicana (McVicar Baker), and Diuraphis tritici (Gillette), were known to exist in the United States before the 1986 appearance of the Russian wheat aphid, Diuraphis noxia Kurdjumov. The Russian wheat aphid soon became a significant pest of wheat although other endemic Diuraphis species were known to infest wheat. Wheat and barley entries resistant and susceptible to Russian wheat aphid biotype 2 were evaluated against all four Diuraphis species to determine their host interrelationships. Leaf chlorosis, leaf roll, leaf number, plant height, and infestation levels were assessed 21 d after the plants were infested by aphids in a no-choice caged environment. D. mexicana was unable to survive on wheat by 21 d after infestation and effects on the plant damage variables were negligible. D. frequens survived at low levels on resistant and susceptible plant entries and had a low impact on plant damage and growth. Russian wheat aphid biotype 2 and D. tritici were damaged most wheat and barley lines except the Russian wheat aphid biotype 2-resistant wheat lines containing genes from Dn7, STARS 2414-11, and CI2401; and resistant barley containing genes from STARS 9577B and 9301B. Russian wheat aphid biotype 2 and D. tritici reduced the growth of resistant plants by 25-50% and susceptible entries by 65-75%. Reductions at this level are typical under no-choice studies but resistant cultivars do not have these reductions under field conditions. The Russian wheat aphid biotype 2 resistant wheat lines would be effective in managing both wheat pest species.
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Eight isolates of Russian wheat aphid, Diuraphis noxia (Mordvilko), from a worldwide collection were evaluated on resistant and susceptible barley, triticale, and wheat entries. Aphid population levels and damage ratings for leaf chlorosis, plant stunting, and leaf rolling were used to determine ifbiotypic variation occurs within this species. Overall, percentage leaf chlorosis was the best criterion for detecting biotypic variation in D. noxia on cereals; however, the differing mechanisms of resistance expressed by these cereals makes it important to consider other plant and insect factors. Each plant entry responded differently to the D. noxia isolates. Seven of the eight aphid isolates had unique virulence profiles across entries indicating a high degree ofbiotypic diversity. Moreover, isolates differed biotypically in countries where more than one isolate was collected (France and former USSR). An isolate from the former USSR was the most virulent, whereas an isolate from Turkey was the least virulent across all plant entries. Discriminant analysis showed that the U.S. isolate was most similar to a French isolate. The entries that performed best against the D. !loxia collection were the resistant triticales PI 386148 and PI 386156 and the resistant barley PI 366450. However, resistant plant germplasm will have geographical limits because of biotypic variation in D. noxia.
Chapter
Three species of Diuraphis in addition to the Russian wheat aphid, Diuraphis noxia (Mordvilko), occur in western Colorado. Diuraphis (Holcaphis) tritici (Gillette), the western wheat aphid, and Diuraphis nodulus (Richards) were collected near Meeker (Rio Blanco County) in 1990. Both species were found feeding in seed production fields of mountain brome, Bromus marginatus, and have required chemical control at times to avert economic damage. Diuraphis (H.) frequens Walker was found in 2 localities in 1990. It was found in all but 1 growing season since that time in the West Elk Wilderness (Gunnison County), feeding on blue wild rye, Elymus glaucus. Males and oviparae of all 3 species were collected in 1991. Eggs of D. (H.) tritici and D. nodulus were collected in the spring and again in the fall of 1992. Two species of parasitic Hymenoptera, and 2 species of hyperparasites were collected from D. (H.) tritici and D. nodulus during the study. Several predatory beetles, flies, true bugs, and green lacewings were collected from all of the Diuraphis species.
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Russian wheat aphid (RWA; Diuraphis noxia Kurdjumov) infestations of barley (Hordeum vulgare L.) have reduced yield and quality in the United States since 1986. Resistant germplasm lines, including STARS-9577B, have been used for cultivar development. Our objective was to map quantitative trait loci (QTL) for RWA resistance in STARS-9577B and compare them to previously mapped loci. A set of 185 F2:3 families from ‘Morex’/STARS-9577B was tested in replicated trials in the greenhouse based on a 1 to 9 visual rating of chlorosis. Morex is a susceptible six-rowed malting barley. Polymerase chain reaction–based markers polymorphic between STARS-9577B and Morex were used to create a 146 marker linkage map. Quantitative trait loci analysis located two loci for resistance, one on the short arm of chromosome 1H and the other on the long arm of 3H. The 1H locus was associated with a B-hordein marker, showed additive gene action, and explained 19% of the variation. The 3H locus was associated with marker EBmac0541, showed partial dominance and explained 47% of the variation. Combined, the two loci explain 55% of the phenotypic variation for RWA reaction. Results showed that STARS-9577B lacks a resistance allele at one of the QTL found in STARS-9301B, which may explain the consistently higher RWA score (lower resistance) of 3 in STARS-9577B versus the lower score (higher resistance) of 2 in STARS-9301B, indicating that the QTL on chromosome 2H is an important factor in determining resistance.
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on wheat lines carrying the Dn1 (from PI 137739), Dn2 (from PI 262660), and Dn4 resistance genes. An isolate Russian wheat aphid (RWA, Diuraphis noxia (Mordvilko)) is a of RWA recently identified in Chile (Smith et al., 2004) serious pest of wheat (Triticum aestivum L.) in the western USA Great Plains region. While variation in virulence among different was shown to be highly virulent to Dn4-carrying wheat RWA isolates has been reported elsewhere, no such variation has lines while lines carrying the resistance genes Dn2, Dn5 been documented among North American RWA isolates. Our objec- (from PI 294994), Dn6 (from PI 243781 or CI 6501), tive was to confirm observations in spring 2003 suggesting that a new Dnx (from PI 220127), and Dny (from PI 220350) were biotype of RWA was present in southeastern Colorado. The new resistant to this isolate. In the USA, minor biotypic biotype induced greater injury (leaf rolling and overall plant damage) variation has been identified in RWA collections from than the original biotype in standard greenhouse seedling screening the Great Plains, but it has not been considered to be tests with a limited collection of resistant and susceptible cultivars. of practical significance as no differential host-plant re- A second experiment with a broader collection of known RWA resis-
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Baseline information on the biotypic status of Russian wheat aphid, Diuraphis noxia (Kurdjumov), populations in the United States prior to the commercial planting of Russian wheat aphid-resistant small grains is reported. Ten Russian wheat aphid clones, collected from 5 states, were evaluated for biotypic variation on 4 wheat, Triticum aestivwm L., and 2 barley, Hordeum vulgare L., gernplasm entries. Although minor statistical differences were detected in measurements of chlorosis, root weight, aphid numbers, and aphid weight among some clones, host responses to Russian wheat aphid infestation among the 10 clones were similar. No genotypic differences were detected among the aphid clones based on random amplified polymorphic DNA profiles. Ten years after its introduction to the United States and before the commercial release of resistant cultivars, the Russian wheat aphid has not exhibited biotypic variation like that found in another cereal aphid, Schizaphis graminum (Rondani). It has been previously shown that Russian wheat aphid populations from other parts of the world exhibit considerable biotypic variation. Thus, with the threat of future introductions into the United States, Russian wheat aphid should be periodically monitored for biotypic variation, before and after the deployment of resistant cultivars.
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Russian wheat aphid, Dim'uphis noxiu (Mordvilko), is a new pest of winter wheat, Triticum uestivum L., in western Canada. Studies were conducted to compare the cold hardiness of Russian wheat aphid, as expressed by the supercooling point, with overwintering mortality in the field, Mean supercooling points ranged from -26.8'C for first ins tars to -24.9'C for adults. These differences were not reflected in the winter survival of each stage in the field. Generally, aphid numbers declined steadily at surface temperatures between 0 and -10'C. In 1988-1989, temperatures at 1 cm above the soil surface dropped lower than _25°Cfor 4 d on one occasion, resulting in 100% mortality of Russian wheat aphid. In 1989-1990, when temperatures did not drop below -25°C, a low number of Russian wheat aphids were able to overwinter successfully. For the Russian wheat aphid, the supercooling point and the ability to survive cold temperatures are notclosely related. Although extremely cold temperatures result in extinction of exposed populations, most winter mortality occurs at temperatures above the supercooling point.
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A collection of 524 barley lines from areas of the world where the Russian wheat aphid, Diuraphts nona (Mordvilko),and barley, Hordeum vulgare L., have coexisted was evaluated for sympatric resistance to this pest. Mass screening tests were conducted in a growth chamber and greenhouse with seedlingsplanted in flats. Additional teststo determine the mechanisms of resistance were performed with nine of these lines. The lines and their sources are PI 366444, PI 366447, PI 366449, PI 366450 , PI 366453 (Afghanistan); CI 1412, PI 430140, PI 430142 (Iran); and PI 447219 (Spain). Various levels of antibiosis and tolerance were exhibited in most of the lines tested in comparison with 'Wintermalt' (CI 15767), the susceptible control. For example, in the antibiosis test, an average of 27.3 nymphs per adult were produced on PI 366449 compared with 50.0 on 'Wintermalt'. In the tolerance test, plant growth and leaf area of some of the resistant entries were not affected by the Russian wheat aphid, whereas growth and leaf area of infested 'Wintermalt' plants was only 61% of noninfested 'Wintermalt' plants. Plant survivors of these tests have been saved for developing Russian wheat aphid plant-resistant germplasm for the North American barley industry.