Barley Genetics Newsletter (2005) 35:23 - 26

Races of Puccinia striiformis f. sp. hordei, the pathogen of barley stripe rust in the United States in 2004

 

Xianming Chen1,2 and Laura Penman2

1 USDA-ARS Wheat Genetics, Quality, Physiology, and Disease Research Unit and

2 Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430.

 

 

Abstract

Stripe rust of barley, caused by Puccinia striiformis f. sp. hordei (PSH), occurred mainly in California, Idaho, Oregon, and Washington and caused localized damage to barley crops.  Growing cultivars with high-temperature, adult-plant resistance and the cropping system contributed to the low level of stripe rust.  Stripe rust samples were collected from the four states and tested under controlled greenhouse conditions on seedlings of a set of 12 barley genotypes used to differentiate races of the fungal pathogen.  A total of 15 races were detected, of which three were new.  PSH-72, a new race, was virulent on all 12 differential genotypes.  The most predominant race was PSH-71 that was virulent on differential genotypes Topper, Emir, Hiproly, Varunda, Abed Binder 12, Trumpf, Mazurk, Bigo, and Bancroft.

 

Introduction

Puccinia striiformis Westend. f. sp. hordei Eriks., the causal agent of barley stripe rust, has established in the United States since it was first reported in southern Texas in 1991 (Marshall and Sutton, 1995; Roelfs et al., 1992).  In the early 1990s, the disease occurred in the south central states and later spread to the states west of the Rocky Mountains (Chen et al., 1995).  The disease has caused major damage to barley crops in the U.S., mainly in California and the Pacific Northwest (Brown et al., 2001; Chen, 2004).

            Chen et al. (1995) selected 11 barley genotypes for differentiating races of P. striiformis f. sp. hordei.  Later, the barley cultivar ‘Bancroft’ was added to the differential set (Chen and Line, 2001).  Using the differential genotypes, 69 races were identified from the early 1990s to 2003 (Chen et al., 1995; Chen and Line, 2001; Chen, 2004).  The objectives of this study were to 1) monitor the occurrence and distribution of barley stripe rust and 2) identify races and determine their frequencies and distributions in the United States in 2004.

 

Materials and Methods

Monitoring barley stripe rust.  Stripe rust was monitored by surveying commercial fields during the growing season.  Trap plots consisting of the set of differential genotypes (Table 1) and other cultivars either susceptible or resistant to P. striiformis f. sp. hordei were planted at various locations.  For commercial field survey, infection type, severity (percentage of leaf areas infected), prevalence (percentage of plants infected), and information on cultivar, location, and growth stage were recorded.    For the trap plots, infection type and severity were recorded one to three times during the growing season.  Stripe rust infected leaf samples were collected for race identification.

 

Race identification.   Races of stripe rust samples were determined using a set of differential genotypes following the methods described by Chen et al. (1995).  In this study, 12 barley genotypes (Table 1) were used to differentiate races of P. striiformis f. sp. hordei. Samples of infected leaves that were usually shipped in glassine envelops were used to inoculate seedlings of ‘Steptoe’ or ‘Topper’, which are susceptible to all races of P. striiformis f. sp. hordei, for increasing urediniospores.  For samples of poor quality (received more than 7 days after collection or with limited uredia), leaf pieces were placed on moist filter paper in a Petri dish that was kept at temperatures of 4-12oC overnight.  Fresh spores produced on the leaves were used in inoculation for spore increase. 

            Inoculated plants were kept in a dew chamber at 10oC for 18 to 24 hours for infection and then grown in a greenhouse growth chamber at a diurnal temperature cycle gradually changing from 4oC at 2:00 am to 20oC at 2:00 pm.  The light period consisted of day light supplemented with metal halide lights to extend the photoperiod to 16 hours.  Urediniospores that were collected 16 to 30 days after inoculation were used to inoculate seedlings of the set of differential genotypes.  Inoculated plants were kept in the dew chamber for infection and then grown in a growth chamber for symptom development under the same conditions as described for the spore increase.  Infection type (IT) data were recorded 18-22 days after inoculation according to the 0-9 scale described by Line and Qayoum (1991).  Isolates that produced ITs 0 - 5 were considered avirulent and 6 - 9 were considered virulent on individual barley differential genotypes.  New races that had virulence patterns different from previously identified races were confirmed at least in one more test with the differential genotypes.  Frequency of each race was determined as percentage of the isolates that were identified as that race from the total of isolates in the study. 

 

Table 1.  Barley genotypes used to differentiate races of Puccinia striiformis f. sp. hordei

Differential genotype

Resistance

Number

Name

ID number

genea

1

Topper

-

-

2

Heils Franken

PI 290183

Rps4, rpsHF

3

Emir

CIho 13541

rpsEm1, rpsEm2

4

Astrix

CIho 13862

Rps4, rpsAst

5

Hiproly

CIho 03947

rpsHi1, rpsHi2

6

Varunda

PI 410865

rpsVa1, rpsVa2

7

Abed Binder 12

PI 327961

rps2

8

Trumpf

PI 548762

rpsTr1, rpsTr2

9

Mazurka

PI 399501

Rps1.c

10

Bigo

CIho 11795

Rps1.b

11

I 5

PI 288187

Rps3, rpsI5

12

Bancroft

PI 605474

Not determined

a  Chen and Line (2003).

  

Results and Discussion

        In 2004, stripe rust occurred in California, Oregon, Washington, and Idaho.  Of a total of 39 viable isolates of P. striiformis f. sp. hordei, 18 were obtained from California, 3 from Oregon, 13 from Washington, and 5 from Idaho.  All isolates were from barley (Hordeum vulgare) cultivars, except for one isolate that was collected from wild barley (H. spontaneum) in California.  The isolate from wild barley was identified as race PSH-33 that was virulent only on two (Topper and Abed Binder 12) of the differential genotypes.  As shown in Table 2, a total of 15 PSH races were identified, of which three were new and designated as PSH-70, PSH-71, and PSH-72 (Table 3).  PSH-70 was virulent on four (Topper, Abed Binder 12, Bigo, and Bancroft) of the 12 differential genotypes.  PSH-71 was virulent on nine (Topper, Emir, Hiproly, Varunda, Abed Binder 12, Trumpf, Mazurk, Bigo, and Bancroft).  PST-72 was virulent on all 12 differential genotypes.  Of the 15 races, nine were presented by only one isolate, one by two isolates, three by four isolates, one by five isolates, and one by 14 isolates.  Although PSH-71 was new, it was the most predominant race.  Nearly 85% of the isolates were collected from disease monitoring and germplasm screening nurseries.  Only 15% of the isolates were obtained from commercial fields, indicating that the severity levels of stripe rust in commercial field were generally low. 

       The barley stripe rust incidence was relatively low compared to wheat stripe rust in 2004.  The barley yield losses due to stripe rust were estimated as 63,000 bushels in the four states (http://www.cdl.umn.edu/loss/loss.html).  In contrast, wheat stripe rust had a much wider spread and severer epidemic, which caused yield losses of about 6.6 million bushels (http://www.cdl.umn.edu/loss/loss.html), plus millions of dollars spent on fungicide application in the four states.  The relatively light stripe rust epidemic on barley compared to wheat stripe rust epidemic in the Pacific Northwest were attributed to 1) the smaller barley acreage, 2) the lack of winter barley, which reduces rust inoculum from previous crops, and 3) the use of high-temperature, adult-plant resistant cultivars such as Baronesse (Chen, 2004).  In California, the reduced barley acreage compared to that in early 1990s and growing resistant cultivars have contributed the low level of stripe rust in the recent years.      

        Even though stripe rust was generally light in commercial fields, susceptible cultivars in various nurseries had up to 100% of severity in California and western Washington.  The disease monitoring data suggest that stripe rust is still a threat to barley production in the western United States.  For this region, stripe rust resistance should remain as one of the top priorities for barley breeding programs. 

 

Table 2.  Races of Puccinia striiformis f. sp. hordei (PSH) and their frequencies and distributions in 2004

 

PSH

 

1st year

No. of

Frequency

Distribution

race

Virulencea

detected

isolates

(%)

state (No.)

19

1,3,5,6,7,8

1995

1

2.4

WA(1)

22

1,4,7,8,9,10

1995

1

2.4

WA(1)

33

1,7

1996

1

2.4

CA(1)

35

1,4,7

1996

2

4.8

CA(2)

45

1,3,4,6,7,8

1996

1

2.4

CA(1)

46

1,7,8

1996

1

2.4

WA(1)

52

1,5,7,8

1998

1

2.4

CA(1)

56

1,5,7,8,12

2001

4

9.5

CA(1), WA(3)

60

1,5,7,8,9,10,12

2001

4

9.5

CA(2), WA(2)

64

1,5,7,8,10,12

2002

5

11.9

CA(3), ID(1), WA(1)

65

1,2,3,4,7,8,12

2002

1

2.4

CA(1)

69

1,5,6,7,8,9,10,11,12

2003

1

2.4

ID(1)

70

1,7,10,12

2004

1

2.4

CA(1)

71

1,3,5,6,7,8,9,10,12

2004

14

33.3

CA(6), ID(2), WA(5)

72

1,2,3,4,5,6,7,8,9,10,11,12

2004

4

9.5

CA(1), ID(1), OR(2)

a  See Table 1 for the barley genotypes used to differentiate races of P. striiformis f. sp. hordei.


 

 

Table 3.  New races of Puccinia striiformis f. sp. hordei (PSH) detected in 2004, type isolates, and dates, locations, and cultivars collected

 

PSH

Type

Date

Collected from

race

Isolate

Collected

State

Location

Cultivar

70

04-304

7/14/2004

California

Tulelake

Steptoe

71

04-023

3/29/2004

California

Davis

APB b-12

72

04-51-12

4/9/2004

Oregon

Corvallis

88Ab536

 

 

Acknowledgement

We would like to thank Drs. Lee Jackson, Patrick Hayes, and Don Obert for sending samples of barley stripe rust.  We also like to thank David Long and Mark Hughes for compiling yield loss data from various states.  The financial support from USDA-ARS and Washington Barley Commission is highly appreciated.

 

References

Brown, W. M. Jr, Hill J. P., Velasco V. R. 2001. Barley yellow rust in North America.  Annual Review of Phytopathol. 39:367-384.

Chen, X. M. 2004.  Epidemiology of barley stripe rust and races of Puccinia striiformis f. sp. hordei: the first decade in the United States.  Cereal Rusts and Powdery Mildews Bulletin 32: [www.crpmb.org/]2004/1029chen.  

Chen, X. M., and Line, R. F. 2001.  Races of barley stripe rust in the United States.  Barley Newsletter 44. On-line at: http://grain.jouy.inra.fr/ggpages/BarleyNewsletter/44/WashReport2.html.

Chen, X. M., Line, R. F., 2003.  Identification of genes for resistance to Puccinia striiformis f. sp. hordei in 18 barley genotypes. Euphytica 129:127-145.

Chen, X. M., Line, R. F., Leung, H., 1995.  Virulence and polymorphic DNA relationships of Puccinia striiformis f. sp. hordei to other rusts. Phytopathology 85:1335-1342.

Dubin, H. J., and Stubbs, R. W., 1986. Epidemic spread of barley stripe rust in South America. Plant Dis. 70:141-144.

Line, R. F., and Qayoum, A., 1991. Virulence, aggressiveness, evolution, and distribution of races of Puccinia striiformis (the cause of stripe rust of wheat) in North America, 1968-87. USDA-ARS, Technical Bulletin 1788, 44 pp.

Marshall, D., Sutton, R. L., 1995.  Epidemiology of stripe rust, virulence of Puccinia striiformis f. sp. hordei, and yield loss in barley.  Plant Dis. 79:732-737.

Roelfs, A. P., Huerta-Espino, J., and Marshall, D., 1992.  Barley stripe rust in Texas.  Plant Dis. 76:538.