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AustralianCerealRustControlProgram
Robert Park & Colin WellingsPlant Breeding Institute
International Wheat Stripe Rust SymposiumICARDA, Aleppo, Syria18-20 April 2011
Continental sweeps and aggressiveness in wheat rust pathogens
CIMMYT
Wheat rusts in Australasia
-isolated from other cereal growing regions
-wheat rust pathogens are clonal
-long-term (90+ years) surveys have provided rare insight into rust pathogen population dynamics
- surveys since 1919 suggest that pathogenic variability arises from:
• periodic incursions of exotic rust isolates• mutation• somatic hybridisation
- mutation is believed to be most common; frequencies of somatic hybridisation and exotic incursions are thought to be low
Pathogenic variability in wheat rusts in Australia
Pathogen Pathotype Year Likely origin
1. Stem rust 126-5,6,7,11 1925 ?
2. Stem rust 21-0 1954 Central Africa?
3. Stem rust 326-1,2,3,5,6 1969 Central Africa
4. Stem rust 194-1,2,3,5,6 1969 Central Africa
5. Stripe rust 104 E137 A- 1979 France
6. Leaf rust 53-1,(6),(7),10,11 1981 ?
7. Leaf rust 104-2,3,(6),(7),11 1984 ?
8. Leaf rust 76-1,3,5,10,12 1996 ?
9. Stripe rust 134 E16 A+ 2002 North America?
10. Leaf rust
11. Leaf rust
10-1,3,9,10,12
76-3,5,9,10 +Lr37
2004
2004
?
?
Pathogenic variability in wheat rusts in Australia- 11 exotic incursions of wheat rust since 1919
Pathogen Pathotype Year Likely origin
1. Stem rust 126-5,6,7,11 1925 ?
2. Stem rust 21-0 1954 Central Africa?
3. Stem rust 326-1,2,3,5,6 1969 Central Africa
4. Stem rust 194-1,2,3,5,6 1969 Central Africa
5. Stripe rust 104 E137 A- 1979 France
6. Leaf rust 53-1,(6),(7),10,11 1981 ?
7. Leaf rust 104-2,3,(6),(7),11 1984 ?
8. Leaf rust 76-1,3,5,10,12 1996 ?
9. Stripe rust 134 E16 A+ 2002 North America?
10. Leaf rust
11. Leaf rust
10-1,3,9,10,12
76-3,5,9,10 +Lr37
2004
2004
?
?
Pathogenic variability in wheat rusts in Australia- 11 exotic incursions of wheat rust since 1919
On 4 occasions, exotic isolate has displaced existing rust races in less than 10 years, presumably due to greater aggressiveness
- Stem rust race surveys began in 1919, 6 races (=“old” races) were detected- Exotic stem rust race 126 was first detected in WA in 1925- By 1929 (5 years), it had all but replaced the “old” races
1. Wheat stem rust race 126-frequency of isolation, 1922 through 1945
- Stem rust race surveys began in 1919, 6 races (=“old” races) were detected- Exotic stem rust race 126 was first detected in WA in 1925- By 1929 (5 years), it had all but replaced the “old” races
1. Wheat stem rust race 126-frequency of isolation, 1922 through 1945
- Stem rust race surveys began in 1919, 6 races (=“old” races) were detected- Exotic stem rust race 126 was first detected in WA in 1925
1. Wheat stem rust race 126-frequency of isolation, 1922 through 1945
By 1929 (5 years), race 126 had all but replaced the “old” races:
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60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1922
1924
1926
1928
1930
1932
1934
1936
1938
1940
1942
1944
Year
Fre
quen
cy (
%)
“Old” races
Race 126 group
- Stem rust race surveys began in 1919, 6 races (=“old” races) were detected- Exotic stem rust race 126 was first detected in WA in 1925
1. Wheat stem rust race 126-frequency of isolation, 1922 through 1945
By 1929 (5 years), race 126 had all but replaced the “old” races:
2. Wheat stem rust race 21-frequency of isolation, 1951 through 1970
- Exotic stem rust race 21 was first detected in 1954- “Hybrid” group arose from spomatic hybridisation between 126 and 21
By 1962 (8 years), the race 21 group had all but replaced race 126:
2. Wheat stem rust race 21-frequency of isolation, 1951 through 1970
- Exotic stem rust race 21 was first detected in 1954- “Hybrid” group arose from spomatic hybridisation between 126 and 21
By 1962 (8 years), race 21 group had all but replaced race 126:
2. Wheat stem rust race 21-frequency of isolation, 1951 through 1970
- Exotic stem rust race 21 was first detected in 1954- “Hybrid” group arose from spomatic hybridisation between 126 and 21
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Fre
quen
cy (
%)
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
Year
Race 126 group
Race 21 group
By 1962 (8 years), race 21 group had all but replaced race 126:
2. Wheat stem rust race 21-frequency of isolation, 1951 through 1970
- Exotic stem rust race 21 was first detected in 1954- “Hybrid” group arose from somatic hybridisation between 126 and 21
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Fre
quen
cy (
%)
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
Year
Race 126 group
Race 21 group
“Hybrid” group
By 1962 (8 years), race 21 group had all but replaced race 126:
3. Wheat leaf rust race 104-frequency of isolation, 1980 through 2000
- Exotic leaf rust race 104 was first detected in 1984 in Victoria- Race 76 is another exotic isolate, first detected in 1993
By 1991 (7 years), race 104 group had all but replaced existing races:
3. Wheat leaf rust race 104-frequency of isolation, 1980 through 2000
- Exotic leaf rust race 104 was first detected in 1984 in Victoria- Race 76 is another exotic isolate, first detected in 1993
By 1991 (7 years), race 104 group had all but replaced existing races:
3. Wheat leaf rust race 104-frequency of isolation, 1980 through 2000
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Fre
quen
cy (
%)
“Old” races
Race 104 group
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Year
- Exotic leaf rust race 104 was first detected in 1984 in Victoria- Race 76 is another exotic isolate, first detected in 1993
By 1991 (7 years), race 104 group had all but replaced existing races:
3. Wheat leaf rust race 104-frequency of isolation, 1980 through 2000
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Fre
quen
cy (
%)
“Old” races
Race 104 group
Race 76 group
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Year
- Exotic leaf rust race 104 was first detected in 1984 in Victoria- Race 76 is another exotic isolate, first detected in 1993
By 1991 (7 years), race 104 group had all but replaced existing races:
4. Wheat stripe rust race 136-frequency of isolation, 2000 through 2009
- Exotic stripe rust race 136 was first detected in 2002 in WA
4. Wheat stripe rust race 136-frequency of isolation, 2000 through 2009
- Exotic stripe rust race 136 was first detected in 2002 in WA
By 2004 (2 years), race 136 had all but replaced existing races:
4. Wheat stripe rust race 136-frequency of isolation, 2000 through 2009
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10
Fre
quen
cy (
%)
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
“Old” races
Race 134
Year
- Exotic stripe rust race 136 was first detected in 2002 in WA
By 2004 (2 years), race 136 had all but replaced existing races:
Aggressiveness in wheat rust isolates
- Four clear cases in which an introduced rust genotype has increased rapidly in frequency and displaced existing genotypes:
• Stem rust race 126 [1925]• Stem rust race 21 [1954]• Leaf rust race 104 [1984]• Stripe rust race 134 [2002]
- In each case, the “new” race did not have virulence attributes that conferred a fitness advantage (i.e. virulence for resistance genes)
- Evidence available strongly supports the hypothesis that each new genotype was more aggressive
- Stripe rust race 134 is considered to be the same as one studied by Milus et al. (2006) who showed it produced 2–3 times more urediniospores per day
Aggressiveness in wheat rust isolates
- Four clear cases in which an introduced rust genotype has increased rapidly in frequency and displaced existing genotypes:
• Stem rust race 126 [1925]• Stem rust race 21 [1954]• Leaf rust race 104 [1984]• Stripe rust race 134 [2002]
- In each case, the “new” race did not have virulence attributes that conferred a fitness advantage (i.e. virulence for resistance genes)
- Evidence available strongly supports the hypothesis that each new genotype was more aggressive
- Stripe rust race 134 is considered to be the same as one studied by Milus et al. (2006) who showed it produced 2–3 times more urediniospores per day
Aggressiveness in wheat rust isolates
- Four clear cases in which an introduced rust genotype has increased rapidly in frequency and displaced existing genotypes:
• Stem rust race 126 [1925]• Stem rust race 21 [1954]• Leaf rust race 104 [1984]• Stripe rust race 134 [2002]
- In each case, the “new” race did not have virulence attributes that conferred a fitness advantage (i.e. virulence for resistance genes)
- Evidence available strongly supports the hypothesis that each new genotype was more aggressive
- Stripe rust race 134 is considered to be the same as one studied by Milus et al. (2006) who showed it produced 2–3 times more urediniospores per day
Aggressiveness in wheat rust isolates
- Four clear cases in which an introduced rust genotype has increased rapidly in frequency and displaced existing genotypes:
• Stem rust race 126 [1925]• Stem rust race 21 [1954]• Leaf rust race 104 [1984]• Stripe rust race 134 [2002]
- In each case, the “new” race did not have virulence attributes that conferred a fitness advantage (i.e. virulence for resistance genes)
- Evidence available strongly supports the hypothesis that each new genotype was more aggressive
- Stripe rust race 134 is considered to be the same as that shown by Milus et al. (2009; Phytopathology 99, 89–94.) to produce 2–3 times more urediniospores per day
Economic impact of exotic wheat rust isolates
- Stem rust race 126:• epidemic in 1930 - losses of £380,000• epidemic in 1934 – losses of £470,000• epidemic in 1947 – losses of £7 million
- Stem rust race 21:• epidemic in 1973 – losses of $200 million• epidemics in triticale in 1983 and 1984
- Leaf rust race 104:• epidemic in WA in 1991, extensive fungicide
usage
- Stripe rust race 134:• from 2003 onwards, up to $90 million spent
on fungicides per year
WA 1991 courtesy of Dr R. Loughman
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1 2 3 4 5
Year
Num
ber
of in
curs
ions
1919-1935 1936-1955 1956-1975 1976-1995 1996-2010
The frequency of exotic incursions is increasing:
Pathogenic variability in wheat rusts in Australia- 11 exotic incursions of wheat rust since 1919
“Rustmapper”10 day prediction, made November 4th
Intercontinental tracking of rust pathogens
-modelling wind trajectories, Dr Dave Hodson FAO [UN]
Concluding remarks
“It is remarkable that a change in frequency of pathotypes can occur so rapidly in the absence of a pathogenic advantage (Luig 1985)”.
- long-term pathogen surveys in Australia have shown four instances of new exotic rust pathogen genotypes with greater aggressivness
- all four have had major impacts on cereal production (wheat and triticale)
- breeders were successful in responding to three of these; despite some setbacks, good progress has also been made in relation to the most recent stripe rust incursion
- exotic incursions seem to be occurring more frequently; intercontinental spread of rust pathogens will therefore likely continue to be a challenge in rust control
© University of Sydney