Stem rust (Puccini graminis). In Late April, traces of stem rust were found in a barley plot in north central Texas. Limited amounts of barley are grown commercially in the southern and central plains states and generally only traces of stem rust are found in this area. In early July, traces of barley stem rust were found in a southern North Dakota field. This was the first report in the northern barley growing area in 1995. Traces of barley stem rust also were found on wild barley (Hordeum jubatum) growing alongside a road in southeastern North Dakota. In early August, trace-10% severities were common in fields and plots in northeastern North Dakota and northwestern Minnesota. This is the most barley stem rust that has been reported in the last five years in this area. Overall, losses to barley stem rust were light in 1995, but there were some losses in late planted fields in northeastern North Dakota and northeastern Minnesota (Table 1).

Race Pgt-QCCJ comprised 89% of the isolates identified, which compared to 65, 90, 94, 87, 56 and 81% in 1989 through 1994, respectively. Pgt-QCCJ and pgt-QFCS each comprised 46% of the isolates identified from hordeum jubatum (Table2).

Leaf Rust (Puccini hordei). Based on the early reports of infection on barley, leaf rust likely overwintered in south Texas, the central San Joaquin Valley of California, and near Guelph, Canada. The first report of leaf rust was in late March from south Texas where rust severities ranged from 10-20% in plots. From the last week of April to mid-May, leaf rust increased on susceptible barley genotypes in the central San Joaquin Valley California (maximum severity of 60%), northern Texas (20%), North Carolina (80%), and Tennessee (10%). The maximum leaf rust severity observed on barley in Virginia and the lower Sacramento Valley of California was 10% and 60%, respectively, during the first part of June. A summer-sown barley nursery in Salinas, California sustained leaf rust severities of 30% in early October. The first report of leaf rust in the upper Midwest region was on July 17, near Lisbon, North Dakota (5-20% severity). Leaf rust was widespread throughout the eastern half of North Dakota by August with severities reaching as high as 50% in some fields. This is the highest severity of leaf rust that has been observed in this area over the last five years. Losses to this disease, however, were minimal as was the case for most of the U.S. (Table 1).

Twelve differential barley genotypes were used to identify races of P. hordei (Table 3). These races were designated according to the system of Roelfs and Martens (Phytopathology 78:526-533) as shown in Table 4. Twenty-one different races of P. Horde were identified from thirty-three viable isolates collected in 1995 (Table 5). This is the largest number of races reported over the past seven years of the survey. As in 1994, the California population of P. hordei exhibited a high degree of diversity as ten different races were identified from 12 isolates. MCJ was the most common race identified in the survey (19% of collections) and was found only in North Dakota. MCJ (formerly designated as race 8) has been one of the most common races of P. hordei in the upper Midwest region over the past ten years. RHS, which was the most common race identified in 1993 and 1994, comprised only 4.7% of the isolates and was found only in California. Isolates with virulence for the resistance gene Rph7 were not detected in 1995.

Stripe rust (Puccini striiformis). In late March, traces of stripe rust on barley were reported in nursery plots in Uvalde and Beeville, Texas and in a field 30 miles southwest of San Antonio, Texas. During the second week in May, strip rust was found on green flag leaves in barley plots in the San Joaquin Valley of California. Stripe rust was much more widespread in barley nurseries in the Sacramento Valley in California in 1995 than in 1994, because the weather was cooler than normal. In late May, barley stripe rust was found in western Oregon and western Washington plots. The rust was scattered throughout the plots and in one instance, there was a hot spot where the rust severities reached 80%. Greenhouse tests confirmed this was the barley form of strip rust rather than the wheat form, which also can cause some infection on barley, In early June, in the Skagit Valley of Washington, 10% severities were found in some barley plots. In early July, severe barley stripe rust was reported in fields in the Klamath Valley of south central Oregon and light severities in south central Idaho fields. In mid-July, light barley stripe rust was found scattered throughout the nurseries at the Pullman, Washington experiment station. This was the most barley stripe rust ever seen at this location.

In 1995, barley stripe rust was reported from Texas to Washington. The first report of barley strip rust ever being found in the U.S. was I the spring of 1991 in southern Texas. Barley stripe rust now seems firmly established in the Pacific Northwest, where the climate is most favorable for its development. This is a perfect example of a disease finding its niche and increasing at a fast rate over a large area.

Crown rust (Puccini coronata). The aecial stage of barley crown rust on common buckthorn (Rhamnus cathartica) was first observed on May 26, 1995 in Casselton, ND. Crown rust aecia appeared about a week earlier in southern Minnesota. Aecial infections of the alternate host were severe in North Dakota, South Dakota, and Minnesota, as compared with the previous year. Crown rust infections on barley occurred at the tillering stage of growth in a nursery in Casselton, ND and a few commercial fields adjacent to buckthorn plants in the Red River Valley. The rust on barley progressed up to 20% in severity on the lower leaves at the Casselton location. Severe infections of barley crown rust on several alternative hosts were observed in the region; these include foxtail barley (Hordeum jubatum), downy brome (Bromus tectorum), slender wheatgrass (Elymus trachycaulus), western wheatgrass (Pascopyrum smithii), and quackgrass (Elytrigia repens). Light crown rust was found on barley at three southern Minnesota locations not in close proximity to buckthorn plants. As yet, crown rust has not become widespread enough to cause significant yield loss in barley in the U.S.

Table 1. Estimated losses in barley due to rust in 1995.

Table 2. Pgt- races of Puccini graminis f. sp. tritici identified from barley in 1995.

Table 3. Barley genotypes used to differentiate isolates of Puccini hordei.

Genotype	Resistance gene(s)
Sudan	Rph1
Peruvian	Rph2
Estate	Rph3
Gold	Rph4
Magnif	Rph5
Bolivia	Rph6+2
Cebada	Rph7
Egypt 4	Rph8
Hor 2596	Rph9
Clip BC8	Rph10
Clip BC67	Rph11
Triumph	Rph12

 
 
 

Table 4. A proposed North American system of pathotype nomenclature for Puccini hordei based on 12 differential barley hosts^a.

		Infection phenotype of pathogen and barley Rph genes
	Set 1	Rph1	Rph2	Rph3	Rph4
	Set 2	Rph5	Rph6+2	Rph7	Rph8
Ph-code	Set 3	Rph9	Rph10	Rph11	Rph12
B		Low	Low	Low	Low
C		Low	Low	Low	High
D		Low	Low	High	Low
F		Low	Low	High	High
G		Low	High	Low	Low
H		Low	High	Low	High
J		Low	High	High	Low
K		Low	High	High	High
L		High	Low	Low	Low
M		High	Low	Low	High
N		High	Low	High	Low
P		High	Low	High	High
Q		High	High	Low	Low
R		High	High	Low	High
S		High	High	High	Low
T		High	High	High	High

 
 
 

^a Pathotype designations are based on the infection phenotypes of the pathogen isolate on the 12 differential barley hosts. Low = incompatibility (infection phenotypes 0, 0; 1or 2) and High = compatibilty (infection phenotypes 3 or 4). The infection pheotypes from set 1 determine the first letter of the code, those from set 2 the second letter, etc.

Table 5. Races of Puccini hordei identified from the United States in 1995

	Number of
State	collections	Source	Races
AZ	2	Nursery	RGL(1)
CA	13	Nursery	MCB(1) MGB(1) MGK(1) RBB(1)
			RGL(1) RGN(1) RHD(1) RHL(1)
			RHN(3) RHS(1)
NC	5	Nursery	RHJ(1) RKN(1) RKS(2)
ND	6	Field	MBJ(1) MCG(1) MCJ(3) RHD(1)
	2	Nursery	MBJ(1) MCJ(1)
TN	1	Nursery
TX	6	Nursery	MBD(1) MGD(1) RCL(2) RGN(1)
VA	3	Nursery	RHB(2) RKD(1)
Total	38a

^a Five collections produced no infection.