Barley Rusts in the United States in 2001

D.L. Long¹, B.J. Steffenson², M.E. Hughes¹, and L. A. Wanschura¹

¹Cereal Disease Laboratory, USDA-ARS
²Department of Plant Pathology, University of Minnesota

Stem rust (Puccinia graminis f. sp. tritici). The first report of barley stem rust in 2001 was in a south Texas nursery at Uvalde in mid-May. Moderate severities were reported on a few entries in the nursery.

In late June, trace to 5% severities were reported in nurseries in east central Nebraska and east central South Dakota.

In southern Minnesota disease detection plots, 5% stem rust severities were noted on the barleys Robust (six-rowed with the resistance gene Rpg1) and Hypana (two-rowed with no known resistance gene) in mid-July. During the same period, trace to 30% stem rust severities were observed on six-rowed barleys in northeast and east central South Dakota. Trace to 20% stem rust severities also were noted on Hordeum jubatum (wild barley) plants growing along the roadside in eastern South and North Dakota. In some cases, a single stem of H. jubatum was heavily infected with stem rust, but the disease did not progress further due to dry hot weather.

Seven races of P. graminis f. sp. tritici were identified from 34 rust collections from barley in 2001 (Table 1). The most common race, QCCJ, comprised 79% (59 isolates) of the total isolates. In 2000, QCCJ comprised only 2% of the total isolates. QCCJ is virulent on barley cultivars with the Rpg1 (T) gene resistance. Race QFCS was the next most common race comprising 8% of the total isolates. Five other races (QCCS, QCMJ, QCMS, RCCJ, and RCMJ) were identified from rust collections on barley in 2001 and comprised individually less than 6% of the total isolates.

Losses to stem rust were generally light in 2001 (Table 2).

Leaf rust (Puccinia hordei). During the third week in March, low severities of leaf rust were observed in barley plots at the Beeville and Uvalde experiment stations in southern Texas. By early April, barley leaf rust was severe in plots at Uvalde. During the last week in June, light leaf rust was found on barley in east central Nebraska plots.

Leaf rust was observed on susceptible barley cultivars in southwestern Ontario in late May and early June, but severities remained relatively low because of the cool weather conditions. However, by late July, barley leaf rust was severe on the upper leaves of susceptible cultivars. Powdery mildew and leaf rust reduced yields in the main barley growing regions of Ontario.

Fourteen collections of P. hordei were made from barley in 2001, but no viable cultures were obtained for race testing. Losses to leaf rust were generally light in 2001 (Table 2).

Stripe rust (Puccinia striiformis f. sp. hordei). During the third week of March, trace amounts of barley stripe rust were found on two experimental lines at the Uvalde, Texas nursery.

In east central Nebraska, stripe rust was reported on barley in early June.

Stripe rust was increasing in barley plots at Davis, California in mid-March, but spread from infection foci was slow. By mid-April, stripe rust was increasing throughout the nursery where 50-80% severities were observed on susceptible lines. The incidence of stripe rust was low and the severity moderate on barley lines planted in the Central Valley and south central coastal foothills of California in mid-April.

In the Mt. Vernon nursery in the Skagit Valley of northwestern Washington, 20% severities were reported on susceptible barley entries in mid-April. By late May, barley stripe rust was increasing on susceptible barley cultivars in western Washington and Oregon. Rust development was slower than normal because of the dry conditions in mid-May, but during the third week in May weather conditions were more conducive for stripe rust increase over most of the Pacific Northwest. In mid-June, stripe rust was severe on susceptible barley cultivars in western Washington and starting to increase on cultivars in eastern Washington. In early July, stripe rust was found in eastern Washington barley fields at low severity levels. Severities of 75-90% were observed in some susceptible spring barleys in eastern and western Washington nurseries. Further stripe rust development was limited by the hot dry weather in July.

Losses to stripe rust were generally light in 2001. The greatest losses occurred in California where a 2.5% yield reduction was reported (Table 2).

Barley crown rust (Puccinia coronata var. hordei).

No losses were reported due to crown rust in 2001.

Table 1. Races of Puccinia graminis f. sp. tritici identified from barley in 2001

Table 2.  Estimated losses in barley due to rust in 2001

*T = Trace
**NA = Not available, therefore, not included in loss totals.