Sources of Resistance to Stripe Rust in Synthetic Hexaploid Wheat

 

Habte-Mariam Z., A.Badebo and W. Denbel

 

 

K. Nazari, O.Francis

 EIAR

Stripe/yellow rust

Caused by Puccinia striiformis

Major wheat disease in the temperate regions as well as in the highlands of the tropics and subtropics

Stripe rust in Ethiopia

Reported in 1947

Increased its importance since the late 1970s

Occurs regularly in the highlands >2400masl

Yield loss is severe (58%-96%) when spikes are infected

Importance

Stripe rust in Ethiopia…

In 1970s, on variety, “Laketch”- (Kalyansona ‘S’)

In 1988, on variety, “Dashen” (VEE’S’)

In 2010, on major varieties, including “ Kubsa” (Attila’S’) and “Galema” (4777(2)//FKN/GB/3/PVN’S’)

Major Epidemics

Stripe rust races

Monitored 1973-2003

1973-1992 in IPO, The Netherlands

1998-2003Goettingen/Kulumsa

(6E16) Yr 6, 7, 8

(38E16) Yr6, 7, 8, SD

(38E150) Yr6, 7, 8, SD,6+,7+, 2+

(166E150) Yr6, 7, 8, SD,6+, 7+, 2+ , 9+

(166E158) Yr6, 7, 8, SD, 6+, 7+, 2

+, 9+ , 3N

(230E158)Yr6, 7, 8, SD,

6+, 7+, 2+ , 9+, 3N, SU 

(70E16)Yr6,7, 8, SU

(70E150)Yr6,7,6+, 7+, 8, SU, 2+

(82E16)Yr7, 9,10, SU 8

(82E0)

Yr7, 9, 10, SU

(86E0)Yr 7, 9,10, SU, 6

(6E6)Yr6,7, 6+,7+

(70E30)Yr6,7, 8, SU,3N, 6+, 7+

(78E30)Yr6,7, 8, SU,3N, 6+, 7+, 3V 

(78E158)Yr6,7, 8, SU,3N, 6+, 7+ 3V, 2+

(206E158)Yr6,7, 8, SU,3N, 6+, 7+, 3V, 2+,

9+

(198E158)Yr6,7,6+, 7+, 8, SU, 2+,3N, 9+

 

Evolution of YR races in Ethiopia, 1973-2003 (Badebo et al., 2008)

Cultivar Race166E150 – V Dashen

230E150 -V Wabe

230E158 –V Kubsa

Dashen (Vee’s’) + + +

Wabe (MRL’S’/BUC’S’)

- + +

Kubsa (Attia’S’) - - +

Dominant races 1998-2003 in Ethiopia

All the commercial bread wheat succumbed to the ‘Kubsa’ race (230E158) at seedling tests in 1998 (Badebo et al., 2008)

Stripe rust races..

Most of the cultivated bread wheat varieties are susceptible to the prevailing races of stripe rust

Only a few Yr genes are effective: Yr 1 (Chinese 166), Yr4 (Hybrid 46), Yr5 (T.spelta album), Yr17 (Vpm), Yr15 (T. dicoccoides G-25), Yr SP and Yr32 (CV)

Stripe rust Resistance

Searching for new sources of resistance

Landraces

Primitive cultivars - center of diversity

Wild or semi-wild materials- Center of origin

Related mostly wild species

Where to look for?

The objective of this study was to identify new sources of stripe rust resistance in synthetic hexaploid wheat derived from Triticum durum and Aegilops tauschii

Objective

Materials and Method

Planting materials

A total of 764. synthetic hexaploid wheat derived from Aegilops tauschii and Triticum durum and developed in CIMMYT, Australia and ICARDA

Seedling test

Seedling test was carried out in the greenhouse at ICARDA using a local race of P. striiformis virulent on Yr2, Yr6, Yr7, Yr9, YrA, Yr25 and Yr27 genes, 2010

The field test was conducted at two locations in Ethiopia and at Tel-Hadya, Syria in 2010

In Syria, the nursery was planted at Tel-Hadya, ICARDA pathology plot, and evaluated under artificial inoculation

In Ethiopia, the nursery was planted at two locations (Meraro- ca. 2920 masl and Kulumsa-2200 masl) and evaluated under natural epidemics

Field test

Disease assessment

In seedling test, a 0 to 4 scale was used (McIntosh et al., 1995), and IT, 0-2 was considered as resistant and 3-4 as susceptible

In adult plant test, a modified Cobb’s scale was used for severity (%), for infection types (R, MR, MS and S) according Roelfs et al. (1992)

The field severity data were converted to CI by multiplying with constant numbers (R=0.2, MR=0.4, M=0.6, MS=0.8 and S=1) (Stubbs et al., 1986).

The SHWs were categorized into different resistance classes based on the CI values of the check cultivars

Results and DiscussionThere was high pressure of stripe rust both in Syria and Ethiopia in 2010

In Ethiopia, the disease appeared unusually early in the season in Arsi zone

Stripe rust epidemics

The epidemics covered almost all wheat growing regions except in Tigray

Most of the commercial bread wheat cultivars were susceptible

Durum wheat varieties were resistant

Increased in aggressiveness of the existing race (s) reported elsewhere (Milus et al., 2009) ?

New race (s) ? Mono-cropping/buildup of spore load?

Climate change ?

What are the possible causes?

0.020.040.060.080.0

100.0120.0140.0160.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC0.0

50.0100.0150.0200.0250.0300.0

2001-09 (mean)2010

Bekoji, 2870

Kulumsa, 2200masl

Monthly rainfall (mm)distribution

Monthly Minimum Temperature (oC)

Kulumsa

0.0

2.0

4.0

6.0

8.0

10.0

12.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC0.0

2.0

4.0

6.0

8.0

10.0

12.02001-09 2010Bekoji

Challenges and opportunities?

Screening of synthetic hexaploid wheat to stripe rust

Variety Severity CI Value Resistant Group

Kubsa 100S 100 S

Galama 100S 100 S

ET13-A2 3OMS 24 MS

K6295-4A 20MS 16 MR

Kenya Kudu 1oMS 8 R

Meraro 0 0 R

The reaction of check varieties to stripe rust at Meraro, 2010

Field test

The highest disease scores were noted at Meraro followed by Tel-Hadya.

0

20

40

60

80 73.6

11.4 7.1 6.7 1.2

01020304050

21

7.6 11.918.6

40.9

Meraro, N=754

R MR MS MSS S0

10203040 34.3

5.6 7.1

18.6

34.4Tel-Hadya, N=749

Kulumsa , N= 764

Frequency (%) of SHWs under different stripe rust reaction classes at three locations in Ethiopia and Syria, 2010

R MR MS MSS S0

10

20

30

40

50

60

12.1

4.6

10

21.2

52

Frequency (%) of SHWs under different resistance groups at adult plant growth stage across locations

Ethiopia + Syria, N=651

Seedling test

Out of 644 SHWs evaluated, 36.8 % exhibited resistance whereas the rest 63.2% were susceptible at seedling stage

SS/AS SS/AMSS SS/AMS SS/ARMR

SR/ARMR

SR/AMS SR/AMSS SR/AS0

5

10

15

20

25

30

35

40

45

N= 644

SR+ARMR, 11.8%SS+ARMR, 3.3%

Frequency (%) of SHWs under different reaction classes after being tested both at seedling and adult plant growth stage at Tel-Hadya, 2010

Summary and Conclusion

A total of 173 SHWs were identified as Resistant (78), Moderately Resistant (30), and Moderately susceptible (65) Out of these, about 20 % exhibited stem rust resistance (R- MS) including to Ug99 race at Debre Zeit, Ethiopia (Data not included).

In addition, some of the resistant SHWs in this study has been reported to be resistant to the Ethiopian and European (Badebo and Fehrman, 2005)

Based on the results, the SHWs are potential sources of resistance to stripe rust which should be exploited in wheat breeding program.

EIAR in collaboration with ICARDA, have initiated crosses to introgress resistance into adapted cultivars.

Summary and Conclusion…