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1998 STEEP III Progress ReportRESEARCH PROJECT TITLE: On-farm Evaluation of Cephalosporium Stripe Severity and Yield for Wheat Cultivars and Cultivar Mixtures Grown in Conservation Tillage Systems INVESTIGATORS: Leaders: Chris Mundt, Molly Hoffer, and Dan Coyle, Botany and Plant Pathology, OSU; Cooperators: Russell Karow and Warren Kronstad, Crop and Soil Science, OSU PROJECT OBJECTIVE:
KEY WORDS: Cephalosporium stripe, conservation tillage, host resistance, cultivar mixtures STATEMENT OF PROBLEM: Cephalosporium stripe has become a limiting factor for dryland winter wheat production in many areas of Pacific Northwest, especially when early planting and/or trashy fallow are practiced. Cultural methods are used to manage the disease, but these often conflict with attempts to control soil erosion. Though no soft white winter wheat cultivars are highly resistant to Cephalosporium stripe, there is considerable variation in the amount of disease observed on different cultivars when tested in the field. Such intermediate levels of resistance are often adequate to avoid significant economic impacts of the disease. Standard variety trials are not often conducted under conditions conducive to Cephalosporium stripe, and several years often elapse from release of a new cultivar until its reaction to Cephalosporium is known sufficiently. Thus, there is a need to evaluate simultaneously the yield and disease reaction of current and future cultivars in the presence of Cephalosporium stripe in conservation tillage systems. ZONE OF INTEREST: low and intermediate rainfall ABSTRACT OF RESEARCH FINDINGS: A STEEP III-funded project was begun in fall 1997 to evaluate current wheat cultivars, advanced breeding lines, and cultivar mixtures for disease severity and yield under conservation tillage systems in commercial fields with a history of Cephalosporium stripe. Trials were conducted in three counties (Gilliam, Sherman, and Wasco) of northcentral Oregon under conditions of stubble mulch and early (September 8-10) seeding during the 1997-98 season. Sixteen treatments were established and replicated four times at each site in 10 x 100 ft. plots. The sixteen entries incorporate the seven most popular soft white winter wheat cultivars currently being grown in the region, four promising, advanced lines from Pacific Northwest wheat breeding programs (three of which have since been officially released), and six mixtures among these entries. We confirmed that there is substantial and useful variation in resistance to Cephalosporium stripe among currently grown cultivars. The new common soft white winter cultivar "Weatherford", which had not been previously tested, demonstrated a level of resistance similar to that of the moderately resistant cultivars Rod and Madsen. Weatherford also possesses the VPM gene for resistance to eyespot (strawbreaker foot rot) and a solid yield record. Thus, this new cultivar may provide an attractive alternative for growers. In contrast, the advanced line OR 939515 appears susceptible to Cephalosporium stripe. The club wheat cultivars Coda, Rohde, and Temple demonstrated greater resistance than the common wheat entries. Reactions to eyespot (strawbreaker foot rot) were confirmed in one location where there was sufficient disease for evaluation. The highest-yielding entries, averaged over the three locations, were Coda, Coda/Rohde, Rohde, Rod/Weatherford, and Madsen/Rod. Cultivar mixtures demonstrated the potential to increase yields and buffer against yearly variations in yield experienced by single cultivars. A similar set of 16 entries was seeded into stubble mulch in the same three counties in mid-September 1998. RESULTS AND INTERPRETATION: Study sites - A field with a known history of Cephalosporium stripe was chosen in each of Gilliam, Sherman, and Wasco Counties, OR, in consultation with Extension personnel and local growers. Identical trials were planted near Condon (Randy Anderson), Dufur (Dick Neal), and Wasco (Tom McCoy). Each experiment was planted in a stubble-mulched field during the period of September 8-10. Elevation at the sites ranges between 2,000-3,000 ft. Entries and plot design - Sixteen entries were evaluated at each site: the seven most popular soft white winter wheat cultivars currently being grown in the region, four promising, advanced lines from Pacific Northwest wheat breeding programs (three of which have since been officially released), and six mixtures among these entries (Tables 1 and 2). Each plot was 10 X 100 ft. and replicated four times in a randomized complete block design at each of the three locations. Good soil moisture allowed for near-perfect stands in Condon and Dufur. We experienced some stand gaps at the Wasco site due to stubble build-up on the drill. In addition, Round-up drift from an aerial application eliminated about one-fourth of the plots in Wasco. Cheatgrass was heavy at Condon and Wasco and light at the Dufur site. Cephalosporium stripe - Whitehead ratings were conducted in late-June. A high percentage of whiteheads developed at all three sites, with the highest ratings at Dufur. Cephalosporium symptoms developed later in the season at Wasco as compared to the other two sites, which may explain why there were less yield differences among cultivars in Wasco (Table 3). The whitehead ratings are consistent with our observations of leaf yellowing, striping, and stunting that were made during the spring and early summer. As expected, Gene, Stephens, and MacVicar had the highest number of whiteheads. Madsen and Rod had substantially fewer whiteheads and were similar to each other. This was the first season where we had the opportunity to evaluate Weatherford for resistance to Cephalosporium stripe in the field. Weatherford expressed substantially fewer whiteheads than the susceptible cultivars at all three sites, though its level of resistance was not quite as high as Rod and Madsen. The advanced breeding line OR 939515 has shown a very positive yield record in previous years and is being considered for release as a cultivar. Unfortunately, OR 939515 does not have much resistance to Cephalosporium stripe and will not be adapted to situations where this disease is a significant problem. Our previous experience indicates that, under the conditions of these trials, whiteheads are due primarily to Cephalosporium stripe. There was also eyespot (strawbreaker foot rot) present at all three sites (see below). However, if eyespot was a primary cause of whiteheads, we should have seen a large number of whiteheads in the highly eyespot-susceptible cultivars Rod and Rohde, which was not the case. This is the first time we have had the opportunity to compare club and common wheats side-by-side under Cephalosporium pressure. From mid-spring on, it was obvious that the club wheats were performing very well against Cephalosporium stripe. We know from past experience that Rohde has a good level of resistance against Cephalosporium stripe. However, we were pleasantly surprised to find that the same may be true of both Coda and Temple. We should note that this is not a general characteristic of club wheats, as cultivars such as Tyee and Hyak can experience severe Cephalosporium stripe. Obviously, we will be making additional comparisons of these club wheat cultivars with common wheats in future trials. The distinction between the club wheat and common wheat entries was not as clear for the whitehead data collected in Wasco. This may be due to a timing problem. We made our first attempt at the whitehead ratings in Wasco on June 22, but abandoned that attempt as it seemed a little early for optimum readings. When we returned six days later to record whiteheads, it was slightly later than optimum, especially for the club wheat cultivars. In contrast, the timing of whitehead assessments at the other two sites was probably about optimum. Eyespot (strawbreaker foot rot) - Though Cephalosporium stripe was the main goal of the trials, wet weather this past spring also favored eyespot (strawbreaker foot rot), a disease that also is favored by early planting (but not stubble mulching). There was eyespot present at all three locations, but this disease seemed most severe at Dufur. Though we already know much about eyespot ratings of wheat cultivars, we took notes on lodging at Dufur as a confirmation (Table 1). We have found from previous work that lodging data tend to correlate more closely to yield effects of eyespot than do estimates of stem discoloration and integrity. Cultivars that have the "VPM" gene for resistance (Coda, Madsen, OR 939515, Temple, Weatherford) looked quite good. Gene has a different source of resistance to eyespot which, though not quite as strong, gave very good performance. The other cultivars showed significant lodging. Rod and Rohde showed the most severe lodging, which is consistent with previous observations of their susceptibility to eyespot. In some cases, there was significantly less lodging in the mixtures than we would expect based on the individual cultivars grown alone. This was simply because the more resistant cultivar in the mixture physically supported the susceptible one. Our past work has suggested that cultivar mixtures do not substantially reduce the amount of stem rotting per se, but sometimes can reduce lodging through this physical mechanism. Yield - Yield was determined by harvesting a 5-foot swath down the center of each 10-foot wide plot with a plot combine. We purposely used very early seeding dates to ensure that we would see sufficient Cephalosporium stripe severity. In retrospect, this probably was not necessary and the very early planting dates likely reduced yields of all cultivars. For the 1998 seeding (see below), we used mid-September dates so as to provide yield data that are more representative of current commercial production for conservation tillage. Among the individual common wheat cultivars, Madsen yielded the highest in Condon and Dufur. The cultivars that are susceptible to Cephalosporium stripe (Gene, MacVicar, Stephens and OR 939515) generally yielded less than the other cultivars. Disease did not seem to affect yield as severely in Wasco, as evidenced by smaller differences for yield among cultivars, and the fact that Stephens was the highest yielding entry. Rod did not perform as well as in previous Cephalosporium trials. This may be due, in part, because Rod is very susceptible to eyespot. Weatherford has resistance to both Cephalosporium stripe and eyespot, and yielded well relative to the other entries at all three locations. The common wheat mixtures yielded well relative to the individual cultivars, especially the Madsen/Rod and Rod/Weatherford mixtures. The Madsen/Rod mixture is now being grown widely in Washington and Oregon and may be a way to provide a good spectrum of disease resistance and to buffer against the year-to-year yield variation often seen with individual cultivars. Rod/Weatherford may be a good combination when seed of Weatherford becomes more widely available. Overall, the club wheat entries yielded better than the common soft white winter wheats, especially Coda and Rohde. Cephalosporium resistance was definitely one factor contributing to the yield performance of the clubs, but we do not know if this is a general phenomenon for the newer club wheat cultivars, or if this past season simply turned out to be a good year for club wheats in general. The subsequent two years of this project will help us to evaluate this in more detail. Establishment of 1998-99 plots - Similar trials were again established in each of Gilliam (Jeff Nelson), Sherman (Bo Macnab), and Wasco (Dick Neal) Counties. Plots were seeded into acceptable to very good moisture during the period from 14-16 September 1998. Thirteen of the entries were the same as in the 1997-98 season (Table 3), which will allow us to make comparisons across seasons. However, a few substitutions were made so as to provide the most relevant information to growers. MacVicar, the OR 515/Weatherford mixture, and the Rohde/Temple mixture were dropped from the 1998-99 trials. The club wheat cultivar "Hiller" was added because of its very favorable yield record, and because difficulties with grading this cultivar as a club wheat have now apparently been resolved. A Gene/Rod mixture was added because a significant number of growers were considering using this mixture in the 1998-99 season. Finally, we added a five-way mixture of Gene/Madsen/Rod/Stephens/Weatherford to test whether the increased level of genetic diversity in this mixture will provide any additional benefits over the two-way mixtures; some growers and seedsmen have been interested in how cultivar number affects performance of a mixture. Benefits to Growers - The overall outcome of the project will be improved knowledge that wheat growers can use to optimize yield and disease levels in conservation tillage systems. Including the newest cultivars and advanced breeding lines is helping to provide a more accurate evaluation of new cultivars when they first become available for commercial use. In the first year of the project, we have confirmed the reaction to Cephalosporium stripe for popular wheat cultivars and completed our first evaluation of newly released cultivars and advanced breeding lines. The new cultivar "Weatherford" had not previously been field-tested for resistance to Cephalosporium stripe, and demonstrated significant resistance in all three trials. As Weatherford also has the VPM gene for resistance to eyespot and a good yield record, this new cultivar may have significant impact on commercial production. Unfortunately, OR 939515 appears to be susceptible to Cephalosporium stripe, but it is nonetheless useful to have this information available before decisions are made regarding release of this line. Coda, Rohde, and Temple showed substantial resistance to Cephalosporium and positive yields relative to the common soft white winter wheats. If these results are confirmed in the next two seasons of this project, the newer club wheat cultivars may provide an attractive alternative to common soft white winter wheat for growers in areas where Cephalosporium stripe is a serious constraint. The performance of the club wheat cultivar "Hiller" is being evaluated in the 1998-99 season. Results demonstrated that cultivar mixtures can buffer against seasonal variation n the yield of wheat cultivars. For example, Rod has generally yielded well in the past, but often showed disappointing yields in northcentral Oregon in the 1997-98 season. However, the Rod/Madsen yielded well, as in past trials, as did the Rod/Weatherford mixture in its first year of evaluation. INTERACTION WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: Information regarding the biology and control of Cephalosporium stripe is exchanged with other pathologists in the Pacific Northwest, primarily Tim Murray (WSU) and Dick Smiley (OSU). In addition, contact is maintained with wheat breeding programs in Idaho, Oregon, and Washington to identify promising lines for evaluation, and to provide breeding programs with information regarding reactions of wheat cultivars and lines to Cephalosporium stripe. PUBLICATIONS AND PRESENTATIONS: - "Resistance of Wheat Varieties and Advanced Lines to Cephalosporium Stripe", Columbia Basin Agricultural Research Station, Pendleton Station Field Day, June 1998 - "Resistance of Wheat Varieties and Advanced Lines to Cephalosporium Stripe", Columbia Basin Agricultural Research Station, Sherman Station Field Day, June 1998 - Results of trials were published by Jordan Maley (Gilliam County Extension) in the Dryland Newsletter (Sept. 1998 edition), which reaches wheat growers, extension personnel, and researchers in Gilliam County and surrounding areas. - Informal tours of plots were conducted with small groups of growers on two occasions during the season.
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