Corn rusts - Plant Management Network€¦ · Corn Rusts Presentation Outline Basic biology &...
Transcript of Corn rusts - Plant Management Network€¦ · Corn Rusts Presentation Outline Basic biology &...
Corn rusts: Common rust,
Southern rust
& Tropical rust
Wm. E. Dolezal Maize Product Development
Pioneer Hi-Bred
Johnston, IA
APS 2011 Field Crops Rust Symposium
San Antonio, TX
Dec. 14, 2011
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Corn Rusts Presentation Outline
Basic biology & identification tips of the three common rusts found on Corn
• Tropical Rust (Physopella zeae)
• Common Rust (Puccinia sorghi)
• To be discussed in more detail by Snook Pataky in an upcoming presentation
• Southern Rust (Puccinia polysora)
Southern Rust – lack of host differential set & issues to rebuild a set
• Discussion around Robert’s 1962 differential set
• Other P. polysora host differentials in the literature
• Background on a new race detected (Rpp9 virulent race)
• Update on cooperative effort to rebuild host differentials
• Opportunities to leverage with new identification methodology.
Questions & Answers
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The three rusts of maize
With a little practice in observing
symptoms, and the use of a
microscope, it is relatively easy
to tell the corn rust from one
another, but …….identifying the
race is occurring on the plant is a
whole different story.
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Identifying rusts of corn
There are three rusts that infect corn
Two belong to the genus Puccinia
Puccinia sorghi: Common Rust
Puccinia polysora: Southern Rust
The third is in the genus Physopella
Physopella zeae: Tropical Rust
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Tropical Rust – White rust of corn
Physopella zeae • Microcyclic
• Believed to autoecious
• Zea mays
• Teosinte
• Tripsacum spp.
Distribution: Americas
• Brazil – mainly in Goias but also in other areas of the high plateaus
• Mexico – mainly in Chiapas & Campeche
• USA – outbreak in 1969/1970 in FL, eradicated and not found since
Urediniospore germination:
• Free leaf moisture for 1-2 hrs. @ 22’ C
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Tropical Rust
White pustules – small but many on a leaf
In many ways, to me, it resembles Southern Corn Rust
Often found in tropical / subtropical areas with P. polysora
Dual infection on a plant can be devastating to yield and standability
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Tropical Rust – Pustules & urediniospores
Note: Teliospores have no
pedicel in contrast to the
two Puccinia rusts.
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Tropical Rust – Races – How many?
Very little research being done in this area.
Most recent work from Brazil.
Historical data:
• Roberts (1962) Report • Identified PI 185054 (Turkey)
• She established two races
• PZ1 & PZ2
• M. Lima, et al. (1996) [Brazil]
• Inst. Agrononomio de Campinas
• Evaluated 440 inbreds derived from
• 8 different origins
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Tropical Rust – Races
M. Lima et al. (1996) [Brazil]
Classes Pop.
103
Pop.
101
Taiuba Suwan-2 Diversas Pop.
102
Pop.
104
Thai.
Composite
R 9.6 7.6 13.1 3.6 10.3 3.4 11.8 0
I 24.8 44.3 21.3 46.4 41.4 27.6 29.4 8.3
S 58.6 46.8 65.6 41.1 41.4 58.6 58.8 83.3
AS 7.0 1.3 0 8.9 6.9 10.3 0 8.3
n 157 79 61 56 29 29 17 12
Scale 1 2 3 4 5 6 7 8 9
% infection 0 1 2.5 5 10 25 50 75 >75
Classes; R = Resistant; I = Intermediate; S = Susceptible; AS = Very Susceptible Disease Rating
Adapted from: Bragantia, Campinas, 55(2)269-273
None of the inbreds were found
to be immune to infection
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Common Rust
Puccinia sorghi • Macrocyclic
• Heteroecious
• 30+ Oxalis species
• Zea mays
Distribution: Worldwide
Urediniospore germination:
• Range: 4 – 31’ C
• Optimal: @ 15 – 25’C
Infection: @ 6 – 12 hrs.
RH > 98% required for germination. Optimal @ 100%RH
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Common Rust – Puccinia sorghi
• Pustules mostly on BOTH leaf surface, but usually not on husk.
• Pustules usually a reddish to reddish brown color
• Disease develops in cooler temperatures
• Urediniospores (conidia) usually are ROUND
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Common vs. Southern Rust
15- 25’C + 25’C
Caution:
Some corn
germplasm
may show
pustules on
the upper
surface only!
Examine the
spores.
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Often occurs in banding pattern on the leaf
Foliar reaction dependent upon host resistance factor
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Southern Rust
Puccinia polysora • Microcyclic
• Believed to be autoecious hemiform
• Zea mays
• Teosinte
• Tripsacum spp.
Distribution: Worldwide tropical & subtropical regions.
Urediniospore germination:
• Optimal: @ 23 – 28’C
Optimal Infection: 16 hrs dew period @ 26’C.
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Southern Rust
USA:
• 1941 - First identified on corn
• 1949 – First detected in the Corn Belt
• Several well documented outbreaks in the past 60 years
• 2006 – new race (Rpp9 virulent) observed
1949 - 1950s:
• Well documented outbreaks in Africa & Asia (Philippines)
• Races first identified in Eastern Africa
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Identifying Southern Corn Rust
“Come back to the field in
one week…if it is dead,
then you definitely had
Southern Corn Rust!”
Method 1 - Temporal
Two quick ways to determine if it is SCR
Several accounts in the
literature about how
rapidly P. polysora
can kill a crop.
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Identifying Southern Corn Rust
1. Wear a clean white shirt and/or a
short sleeve shirt.
2. Walk a zigzag sampling pattern
through the corn field.
3. Now look at your shirt & your arms. If
they are now orange, then…you have
Southern Corn Rust!
Method 2 – Color Recognition
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Southern Rust – Economic Damage
• Yield loss reported can be big:
• USA up to 45 – 75%
• Africa – 1950s > 50%
• Philippines 1956 > 80%
• Often it is comes in a little later in
fields with HIGH yield potential,
major stalk lodging can occur.
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Southern Corn Rust – Identification Tips
• Pustules mostly on upper leaf surface
• Caution: occasionally you will find
some pustules develop along the
midrib on the bottom of the leaf.
• Pustules can also be on the husk.
• Pustules usually an orange to a
reddish-orange color
[Tennessee “Vol” orange]
• Disease develops in warm moist
conditions
• Urediniospores (conidia) usually
oblong, ellipsoid but most are NOT
ROUND.
• Caution:
Immature spores are round!
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Telial Differences
Common Rust:
Teliospores produced in the
same sorus as urediniospores.
Southern Rust:
In the USA, teliospores are usually not
commonly found in the field except late
in season as the tissue starts to die.
More common in tropical regions. Often
they display a semicircular (horseshoe)
type or completely circular type pattern.
Telial stage not often seen in fields.
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Easiest way to tell the rusts - Telial stage
P. polysora:
Short pedicels
@ ¼ length of spore
Long pedicels
@ 1-2x spore length
Contrast to P. sorghi teliospores
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What race of
P. polysora is it?
Early race identification done in Africa
• Storey & Howland (late 1950s)
• Rpp1 & Rpp2
• Used to differentiate EA1 & EA2
Alice Robert expanded this effort (1962)
• =Rpp3 – Rpp8
The issues surrounding
race identification today
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Race change in P. polysora 2006:
February - Goias, Brazil:
• A cooperative effort between USDA-ARS & Pioneer Hi-Bred
to screen a set of 225 maize accessions for P. polysora
resistance identified uredial formation on several Rpp9 lines. • A USDA Maize Crop Germplasm Committee Goal
August - York, NE:
• Widespread southern rust outbreak in the region. Several
Pioneer inbreds and hybrids that contained the Rpp9 gene
were observed to have some uredial formation.
2007:
February - Goias, Brazil: Similar results on Rpp9 material as in 2006.
March - Puerto Vallarta, Mexico:
• A set of Pioneer inbreds & hybrids containing the Rpp9 gene
had significant uredial development
June - Victoria, TX – a few pustules were observed on Rpp9 hybrids.
July - Cairo, GA: the same material that contained the Rpp9 had NO
observation of uredial development (no sporulation observed)
2008 Southern Rust Outbreak- GA
Collected isolates non-virulent
on hybrids containing the
Rpp9 gene
Collected isolates virulent
on hybrids containing the
Rpp9 gene
Inbreds & hybrids containing
the Rpp9 gene observed
having uredial formation.
There appeared to be mixed race
infections on leaves with some
hypersensitive (resistant) and
moderately susceptible reactions
observed on the same plant. Map source: http://quickfacts.census.gov/qfd/maps/georgia_map.html
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Overcoming an old standard source of resistance
Rpp9 source of resistance has been stable for many years (20+)
The “new” race overcomes the Rpp9
The exact identity of the new race can not be positively determined, only
that it has virulence to the Rpp9 gene
The question was asked:
Why can we not determine the exact race of the fungus?
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Isolate Place
Collected
AF
RO
5329
7/35
0
AF
RO
474
NC
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Po
p 3
6
E30
9
Co
rnel
i 54
Flo
ury
Syn
thet
ic
CI3
8B x
Cu
zco
PI 1
6359
7
PI 1
9890
2
PI 1
8620
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Race
EA. 1 East Africa R0 S X S S S S S S R1,2 S EA.1
EA. 2 East Africa S S S S S S S X S R1 R1,2 EA.2
Ga-2 Georgia S S X X X S S X S R1,2 R1 EA.2
Ga-3 Georgia S S S - X S S S S R1,2 R1 EA.2
Ven-1 Venezuela S S X S X S S S S R1 R1,2 EA.2
Ga-1 Georgia S R2 R1 R2 S R2 R1,2 X S R1,2 S PP.3
Nic-1 Nicaragua S S X S X S S X S R1 S PP.4
Nic-3 Nicaragua S S S S R1,2 S S S S X R1,2 PP.5
Col-1 Colombia R0 S X S S S S S R1,2 R1 S PP.6
Mex-1 Mexico S S X S X S S R1,2 S R1 S PP.7
Fla-1 Florida S S S S S X S S S X X PP.8
Nic-2 Nicaragua S S X S X S S X S S S PP.8
PR-1 Puerto Rico S X X S X S S X S X S PP.8
Robert’s Host Differential Reactions – P. polysora
R0, R1, R2 = Resistant; S and X = Susceptible From: A. L. Roberts, Phytopathology 52:1010-1012
Lines
No
Longer
Exist
Lines
No
Longer
Exist
Rpp9
Races
No
Longer
Exist
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Host Resistance – Rpp Study
Lines evaluated for reactions to P. polysora isolates
Rpp9a Tropical Rppb Other Rpp Susceptible
PI186208 1416-1 Sure Gold B37
PI186215 1497-2 Calvary Oh43
B37 Rpp9 NC300 B1138T W64a
Oh43 Rpp9 DS61 Mo17 (poly resist)
W64a Rpp9 Va59 Mp78:62
Green Giant 1 Garrisonc
Green Giant 2 SS Jubilee Plusc
P33M52 P33M57
From: Pataky, Dolezal & Brewbaker, 2010
a = allelic with Rpp9 or resistance from PI186208 b= map to 10S c = Rp1-D but not Rpp resistant = Not Rpp9 (allelism or race specificity)
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LinesCal Rpp Source GA isolate IL isolate
Susceptible Checks none 4 4
PI186208 (Boesman) Rpp9 4 0
PI186215 (2-687) Rpp9 4 0
Green Giant 1 Rpp9 4 0
Green Giant 2 Rpp9 4 0
P33M52 Rpp9 4 0
B1138T Rpp9 4 0
NC300 Rpp9 4 0
B37 Rpp9 Rpp9? 1 0
Oh43 Rpp9 Rpp9? 1 / 2 0
W64a Rpp9 Rpp9 2 / 3 0
1416-1 Maps 10S 2 / 1 0 / 1
1497-2 Maps 10S 1 /0 0 / 1
DS 61 Not Rpp9 2 / 1 0
Va59 Not Rpp9 1 / 2 0
Sure Gold 10S 0 0
Calvary 10S 0 0
Scale = 0-4
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Differential Varieties Race designation
P. sorghi
P. polysora 1 2 3 4 5 6 7 8 9
1
0
1
1
1
2
1
3
1
4
1
5
1
6
S. L. P. 20 R R R R S R R R S S S R S S S S
Rp1g79-109 70-2/Q6198 R R R S R R S S R R S S R S S S
A632 11/Q6199 R R S R R S R S R S R S S R S S
67/Q6200 R S R R R S S R S R R S S S R S
Yeh’s proposed P. polysora race differentials
R = Resistant; S = Susceptible
S.L.P. 20 = San Luis Postosi 20
Q Lines are from Queensland Australia
Adapted from: C.C. Yeh. Studies on rusts of maize
Journal. of Agricultural Research Of China 35:81-93 1986.
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Sources of Resistance – P. polysora
6 experimental hybrids were used to characterize pathogen variability.
• Among 60 isolates collected at 6 sites over two years
– 17 virulence patterns were identified
• Most frequent virulence patterns were identified.
• They were observed in all locations where sampled suggesting
the absence of geographical differentiation among the prevalent
P. polysora populations.
• Recommended more intensive analysis using
• Larger number of isolates
• Single gene differentials &/or
• Molecular markers
• No hybrid was resistant to all isolates
2002: Variability in Isolates of Puccinia polysora in Brazil C. R. Casela & A. S. Ferreira Fitopatologia Brasileira 27: 414-416
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Sources of Resistance – P. polysora
QTLs associated with P. polysora resistance found on:
Chromosomes #s 3, 4, 9 & 10
Major gene Rpp9, found on Chromosome 10
Contrast with QTL’s associated with P. sorghi resistance found on:
Chromosomes #s: 1-10
2006: The Genetic Architecture of Disease Resistance In Maize:
A Synthesis of Published Studies R. J. Wisser, P. J. Balint-Kurti & R.J. Nelson
Phytopath. 2006 Vol. 96, No. 2, 120-129
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Do we reconstruct the
Host Differential set for P. polysora?
Supplement it with what germplasm?
• Start with remnant lines from Robert’s 1962 List
• 6 of 11 differentials are still available
• Many vary in their maturity
• PI186208 (Boesman Yellow Flint) is a segregating source
• Retest of NCRPIS lines tested earlier in Brazil?
• Brewbaker’s lines?
• Chávez-Medina, Leyva-López & Pataky’s lines?
• Select set of GEM released lines?
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IVP IVNO ITEM
Ames 27141 NC290A
Ames 27144 NC296
PI 639056 GEMS-0031 (XL380:S11 F2S4 2282-01 )
CUBA164:S2012-235-1-B
BR105:T33a
BR106:T33a
Ames 29394 1497-2
Ames 29448 1416-1
PI 506244 Tzi 3
PI 506245 Tzi 4
PI 540746 Tzi 14
PI 595560 CML 40
PI 186208 BOESMAN YELLOW FLINT
PI 234767 ENANO
PI 217413 Zapalote Chico
PI 445062 Narino 330
PI 506348 Suwan 2
PI 443845 Antioquia 423
PI 489361 Cuba 164
PI 483816 Cuba 117
PI 576247 Chiapas 645
PI 498498 Cuba 96
PI 593017 Hi39
Retest of
NCRPIS lines
shown
resistant
earlier testing
in Brazil?
SLP20
70-2/Q6198
71/Q6199
67-1/Q6200
Include
Yeh’s lines?
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Supplement with what germplasm?
• Retest of NCRPIS lines? • Brewbaker’s lines?
• Chávez-Medina, Leyva-López & Pataky’s lines?
• Select set of GEM released lines?
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Inbred Origin Avg.CIMMYTA-21 2.5
CML295 1
GT601 1
Hi34 Antigua 2.22
Hi43 SetG 1
Hi44 Suwon 1
Hi45 Suwon 1
Hi53 ICAL210 2
Hi54 ICAL221 2.3
Hi55 ICAL224 2.3
Hi56 KenyaF 2.25
Hi57 Ki9 1.38
Hi63 Pi23 1.5
Hi64 Pi31 1
Hi65 Tx601 2.83
Hi75 190 1.67
Hi76 217 1.73
ICAL219 2.25
ICAL220 1.75
ICAL223 2
ICAL36 2
INV138 2.5
Ki3 2.5
Ki18 2.5
Ki20 2.5
KP1 1
KP131 2.5
KP288 2.5
KP293 2.5
KP310 2.5
KP311 2.5
KS23-3 1
KS23-4 1
KS23-5 1
KS23-6 1
Narino 330 3
PH110-26 2.5
TZi8 1
TZi11 2.5
TZi14 2
TZmi1822 2.2
41 1.89
Inbred Origin Avg.
Brewbaker’s lines?
(Scale: 1=resistant; 9= susceptible)
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• Retest of NCRPIS lines?
• Brewbaker’s lines? • Chávez-Medina, Leyva-López & Pataky’s lines?
• Select set of GEM released lines?
Supplement with what germplasm?
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Rating: 0 = chlorotic-fleck reaction, no uredinia; 0.5 = very few,
very small uredinia or segregating for chlorotic fleck reactions,,,
Sources of Resistance – P. polysora
Data from
Chávez-Medina, Leyva-López & Pataky
Plant Disease: November 2007, Volume 91, Number 11
Accession rated 0:
Accession Accession Name
Ames 19016 Virginia VA59
NSL 75976 IA DS61
PI 186209 Yellow flint
PI 186215 Inbred 2-687
PI 198905 4F-374 GE3
PI 186191 Inbred 627
Accession rated 0.5:
Accession Accession Name
PI 484024 Puerto Rico 13
PI 515053 Loreto 9
PI 515055 Loreto 11
PI 515097 San Martin 126
PI 553058 OC5
PI 558524 Mo6
PI 596502 OC15
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• Retest of NCRPIS lines?
• Brewbaker’s lines?
• Chávez-Medina, Leyva-López & Pataky’s lines?
• Select set of GEM released lines?
Supplement with what germplasm?
A number of the Germplasm Enhancement of Maize Program
released Lines contain genetic backgrounds that would suggest
a good chance of having resistance.
• They are more adapted than some PI’s in the collection.
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Corn – Diseases: Lesion Mimics
Just to make
it a little more
interesting!
These are hypersensitive responses.
Many are believed to be mutations of
the Rp (common rust resistance)
genes and may be involved in
providing resistance to infection.
These are the examples
of the foliar expression
of specific genes…
LES genes
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My P. polysora identification wish list:
PCRs that identify the rust race without having to grow
out the host differential plant.
Recent development: July, 2011 Plant Disease:
Real-Time PCR Detection and Discrimination of the Southern and Common Corn
Rust Pathogens Puccinia polysora and Puccinia sorghi by Jo Anne Crouch and
Les J. Szabo
Using PCRs to sample spores deposited in rain water samples,
air samplers, on leaves, etc. to monitor pathogen populations