1a. Objectives (from AD-416)
Evaluate the reaction of advanced barley breeding lines from various public and private breeding programs to established races of barley stripe rust (Puccinia striiformis f.sp. hordei) endemic in the Central Valley of California.
1b. Approach (from AD-416)
Barley breeders will submit their advanced lines to UC Davis researchers, who will plant the accessions in the Davis, California area or other Central Valley locations where a natural epidemic of barley stripe rust can be expected. Data collected will be returned to the participating breeders and ARS distribution to interested parties.
3. Progress Report
This report serves to document research conducted under a specific cooperative agreement between ARS and the University of California, Davis. Additional details of research can be found in the report for the parent project, 5366-21000-027-00D, “Management of National Small Grains Collection Resources”. The agreement was established in support of Objective 2.c of the in-house project, the goal being to identify additional sources of resistance to barley stripe rust. The 2011 Barley stripe rust nursery consisted of 500 accessions from NSGC. The nursery was planted on January 10, 2011 on the University of California Davis Agronomy Farm. The susceptible cultivar, Max, used as a susceptible check and disease spreader, was planted after every sixth row of the nursery. The 2011 growing season was very conducive for stripe rust but very little disease had appeared in the nursery by April 15, 2011, even though stripe rust had begun to appear in other barley experiments on the UC Davis Agronomy Farm by that date. To help the infection process, plants of Max were artificially inoculated in the greenhouse with two isolates collected from California in 2010 (isolates 10-78 from Kern County and 10-216 from Yolo County, identified as PSH-33 and PSH-54 respectively). Artificially inoculated plants showing small amounts of stripe rust infection were transplanted into the nursery on April 25, 2011. However, it is unlikely that the inoculated plants were important in subsequent disease development since by April 28 (when most accessions were at the heading stage), several accessions already had very high levels of disease, including 4 accessions (from Morocco) with 100% severity and IT 8, and 7 other accessions with severities of 10-60%, and IT 6-8. Several collections of stripe rust infected tissue were made from the nursery and sent for race identification to determine whether stripe rust in the nursery was due predominantly to natural infection or to artificial inoculation. The nursery was evaluated for stripe rust severity on May 9-10 (heading to early grain fill, depending on the accession) and again on May 23 (late dough stage). Stripe rust reactions of each accession consisted of percent severity (0 to 100%) and Infection type (IT) (0 to 9). IT ratings of 0-4 indicate various levels of resistance under significant disease pressure. Spreader rows of the susceptible cultivar Max ranged from 30-100% severity and IT 6-8 at the final rating. Of the 500 accessions, 419 (83.8 %) were not infected. Of the remainder, 24 accessions had severity of 5-10% and IT 2-5, 21 accessions had severity with 10-30%, and IT 5-6, 15 accessions had severity of 20-30% and IT 6, and 21 accessions had severity of 30-100% and IT above 6 (Table 2). This last group is considered highly susceptible. Many of the accessions that were not infected originated from Ethiopia, while the most susceptible accessions originated from Turkey, Iran, Afghanistan, and Morocco. Monitoring of activities in this agreement were accomplished by telephone and e-mail.