D. Marshall et Rl. Sutton, EPIDEMIOLOGY OF STRIPE RUST, VIRULENCE OF PUCCINIA-STRIIFORMIS F-SP HORDEI, AND YIELD LOSS IN BARLEY, Plant disease, 79(7), 1995, pp. 732-737
Barley stripe rust (caused by Puccinia striiformis f. sp. hordei) was
found for the first time in the United States in 1991. This study was
conducted from 1991 to 1994 to determine the occurrence and spread of
the disease, the identity and relative frequency of races present, and
the amount of yield loss attributable to the disease on cultivars hav
ing different levels of resistance. Surveys and urediniospore collecti
ons were made in commercial barley fields, barley breeding nurseries,
and wild Hordeum spp. throughout Texas, southwest Oklahoma, and northe
ast New Mexico. Commercial fields of the cultivars Post and Tambar 500
in Winters and Era, Texas, were systematically assessed for stripe ru
st severity. Race determinations were made by inoculating the uredinio
spore collections onto a set of 18 differential cultivars. To determin
e yield loss, four fungicide treatments (triadimefon + mancozeb, propi
conazole, tebuconazole, and flusilazole) were compared with untreated
checks of seven barley cultivars. In 1991, P. s. f. sp. hordei was fou
nd only in the breeding nursery at Uvalde, and on H. jubatum and H. le
porinum in the Uvalde area. Stripe rust occurred in commercial barley
throughout the state in 1992 and 1993, yet was found only on highly su
sceptible cultivars in nurseries in 1994. The highest severity found i
n commercial barley was 8% at the soft dough development stage on cv.
Post at Winters in 1993. From a total of 273 isolates, 255 were race 2
4, 14 were race 23, and 4 were of a different race, labeled TXG. The m
ost grain yield loss was about 72% on cv. Perkins at Uvalde in 1992. W
e found that cv. Tambar 401 was resistant and cvs. Tambar 500 and Kold
were moderately resistant to P. s. f. sp. hordei, and none of these t
hree cultivars sustained significant yield loss to barley stripe rust.
Over cultivars, locations, and years, all of the fungicide-treated pl
ots had significantly less yield loss than untreated checks. Even thou
gh barley stripe rust has the potential to become a severe disease in
the U.S., host resistance in winter barley and fungicides can effectiv
ely minimize yield