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2000 STEEP III Final 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 FINAL REPORT: PROJECT OBJECTIVES:
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 current 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 can often reduce 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. ZONE OF INTEREST: low and intermediate rainfall ABSTRACT OF RESEARCH FINDINGS: A STEEP III-funded
project 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 was carried out over three winter wheat seasons. Trials were conducted
in three counties (Gilliam, Sherman, and Wasco) of northcentral Oregon
under conditions of stubble mulch and early seeding (September 8-17).
Sixteen entries were established and replicated four times at each site
in 10 x 100 ft. plots in each season, and 13 of these entries were included
in all three seasons. The entries incorporated commonly-grown, common
soft white winter and club wheat cultivars; five advanced breeding lines,
four of which were released as cultivars during the course of this project;
and several cultivar mixtures. Substantial Cephalosporium stripe developed
at two of the three locations. The club wheats were more resistant to
Cephalosporium stripe than were the common wheats. Among the common wheat
entries, Madsen, Rod, and Weatherford showed more resistance than the
other varieties tested. Averaged over years, Coda and the Madsen/Rod mixture
were top yielders at all locations. The Coda/Rohde mixture was the highest
yielding entry at the two locations with the most severe Cephalosporium
stripe. Mixing varieties often increased both yield and yield stability
as compared to growing single cultivars. In the 1999-00 season, we included
two replicated sets of smaller plots at each site, with eight treatments
in each set. The first set tested lines as resistance sources against
Cephalosporium stripe. The second set was used to confirm that club wheats
are consistently more resistant than common wheats in Oregon and that
winter durum genotypes appear intermediate in level of susceptibility. RESULTS AND INTERPRETATION: Study sites - A commercial field with a known history of Cephalosporium stripe was chosen in each of Gilliam, Sherman, and Wasco Counties, in consultation with Extension personnel and local growers, for each of the three winter wheat seasons. Each trial was planted in a stubble-mulched field during the period of 8-10 September 1997, 14-16 September 1998, and 15-17 September 1999. Elevations of the sites range between 2,000-3,000 ft. Entries and plot design - Sixteen entries were evaluated at each site and included soft white winter wheat cultivars that are commonly grown in the region, newly released cultivars, advanced lines that were likely to soon be released as cultivars, and mixtures among these entries. Each plot was 10 x 100 ft. and replicated four times in a randomized complete block design at each of the three locations. For purposes of this final report, we will generally present data only for the 13 treatments that were common over all three seasons and the cultivar Hiller, which was included in the last two seasons of the project (Tables 1-7). Data from Sherman County in 1999 are not presented, as soil crusting interfered greatly with the results. Cephalosporium stripe - Cephalosporium stripe severity was measured by estimating the number of prematurely-ripening heads (whiteheads) in each plot at the late milk/early dough stage (Tables 1-3). Our previous experience indicated that, under the conditions of these trials, whiteheads are due primarily to Cephalosporium stripe. The whitehead ratings were consistent with our observations of leaf yellowing, striping, and stunting that were made during the spring and early summer (data not shown). There was also eyespot (strawbreaker foot rot) present in some of the trials, especially in the wet spring of 1998 (see below). However, if eyespot had been a primary cause of whiteheads, we should have found a large number of whiteheads in both of the highly eyespot-susceptible cultivars Rod and Rohde, which was never the case. Field observations did suggest, however, that Fusarium may have contributed to the whitehead ratings in Sherman County in 2000. In all three counties, Cephalosporium stripe severity was greatest in 1998 and least in 2000. The disease was consistently more severe in Wasco than in Gilliam County. Though final whitehead estimates were similar in Gilliam and Sherman Counties, it was quite obvious that symptoms of the disease developed much later in the growing season in Sherman County than in Gilliam or Wasco Counties, and thus had less impact on yield (see below). Of the varieties tested in all three seasons, Stephens was almost always the most susceptible one (Tables 1-3). Gene was sometimes equally susceptible to Stephens, while in other trials it was less susceptible. We have previously observed that Gene's degree of susceptibility to Cephalosporium stripe can vary substantially. MacVicar was also tested at all three sites in 1998, but was even more susceptible than Stephens (data not shown) and thus was not evaluated in the subsequent two years. Madsen and Rod showed similar degrees of resistance to Cephalosporium stripe, and had substantially fewer whiteheads than did the other common wheats. Previous to this project, there was no information available regarding the susceptibility of Weatherford to Cephalosporium stripe. Weatherford expressed substantially fewer whiteheads than the susceptible entries at all three sites, though its level of resistance was often slightly lower than that of Rod and Madsen. The advanced breeding line OR939515 has shown a very positive yield record in previous years and was being considered for release as a cultivar. Unfortunately, OR 939515 does not seem to have much resistance to Cephalosporium stripe and thus will not be adapted to situations where this disease is a significant problem. This project provided
an opportunity to compare club and common wheats side-by-side under substantial
Cephalosporium pressure. From mid-spring on, it was obvious that the club
wheats were performing very well against Cephalosporium stripe. In all
trials, there were substantially fewer whiteheads on all club wheats than
on even the best common wheats, with two exceptions: natural maturity
and drought stress interfered with whitehead estimates in Sherman County
1998 and Wasco County 1999, respectively. In both of these cases, it was
especially difficult to estimate whiteheads on the club wheats, and we
are confident that the ratings underestimated the resistance of the club
wheats. In the 1999-00 season, we also evaluated, in smaller plots, two
older club wheat cultivars (Tyee and Hyak) that have a reputation for
susceptibility to Cephalosporium stripe. These "susceptible"
club wheat cultivars also were consistently less susceptible than the
best common wheats (for more detail, see the 2000 STEEP report entitled
"Improved Methods for Evaluation of Resistance to Cephalosporium
Stripe of Wheat"). In 2000, we also evaluated eight wheat lines identified by the OSU Wheat Breeding Program as potential sources of resistance to Cephalosporium stripe. We were able to determine which of these lines had consistent resistance based on whitehead ratings (data not shown). One line that has demonstrated outstanding yield potential in northcentral Oregon also showed a higher level of Cephalosporium stripe resistance than Madsen, and thus may be an excellent source of resistance for future cultivars. Eyespot (strawbreaker foot rot) - Though Cephalosporium stripe was the main focus of the project, wet weather in the spring of 1998 also favored eyespot (strawbreaker foot rot), a disease that is favored by early planting (but not stubble mulching). There was eyespot present at all three locations, but this disease seemed most severe at the Gilliam County site, where we took lodging notes as an indication of the severity of eyespot. Varieties that have the "VPM" gene for resistance (Coda, Madsen, OR939515, Temple, and Weatherford) held up very well against eyespot (Table 4). 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 high degree of 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 probably 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 caused by eyespot. Yield - Yields were determined by harvesting a 5-foot swath down the center of each 10-foot wide plot, using a plot combine. We chose very early seeding dates in the 1997-98 season to ensure that we would see sufficient Cephalosporium stripe severity. In retrospect, this probably was not necessary, and the resulting disease caused low yields (Tables 5-7) at all sites. We moved seeding dates forward about one week in the subsequent two seasons, and obtained yields that are more representative of current commercial production under conservation tillage at these locations. Averaged over years, the lowest yielding variety was 37, 21, and 14% less than the highest yielding variety in Wasco, Gilliam, and Sherman Counties, respectively. This corresponds with our perception of the degree of disease impact that the crop experienced in the three locations. Supporting this view is the fact that the susceptible cultivar Stephens yielded very well in Sherman County. Further, the club wheat cultivars, which are more resistant to Cephalosporium stripe than are the common wheats, showed the greatest yield advantage at the Wasco County site, where Cephalosporium stripe severity was highest (Tables 5-7). Ranking of varieties for yield was similar in Gilliam and Wasco Counties. Averaged over the three seasons, the Coda/Rohde mixture was the highest yielding club wheat entry, followed by Coda alone. The Madsen/Rod mixture was the top-ranked common wheat entry, followed by Rod alone. The varieties that are susceptible to Cephalosporium stripe (Gene, MacVicar, Stephens and OR 939515) generally yielded less than the other varieties. In Sherman County, the susceptible entries yielded higher than at the other two locations, most likely due to due to the lesser disease pressure. Averaged over the two seasons, the four highest-yielding entries (Stephens, Coda, Madsen/Rod, and Madsen/Stephens) had nearly identical yields. Hiller yielded well in the two years that it was included in the trials. However, Hiller does not seem to have any advantage over Coda, and has the disadvantage of being susceptible to eyespot. The new cultivars Weatherford and Temple have a good disease resistance profile, but did not yield as well as other entries evaluated in this project. The Madsen/Rod and Coda/Rohde mixtures contributed to yield stability, in addition to increased productivity. For example, despite Madsen's favorable disease resistance spectrum, its yield varied substantially among years, which is consistent with the experience of many wheat growers. Similarly, Rod performed less well in 1998 than in the subsequent two years, perhaps due to its eyespot susceptibility and the wet spring of that year. In contrast, the yield ranking of the Madsen/Rod mixture fluctuated less among years. Summary of Benefits
to Growers - The overall outcome of the project is improved knowledge
that wheat growers can use to determine optimum combinations of yield
potential, yield stability, and level of disease resistance for wheat
cultivars used in conservation tillage systems. Including the newest cultivars
and advanced breeding lines helped us to provide a more accurate evaluation
of new cultivars when they first became available for commercial use,
including four cultivars that were still numbered lines at the time this
project was initiated. Our results suggest that the Coda/Rohde mixture,
the Madsen/Stephens mixture, and Coda are all good choices for conservation
tillage systems when Cephalosporium stripe is severe. Coda and the Madsen/Rod
mixture yielded well at all locations. Some of the newly released club
wheat cultivars look particularly useful at sites where Cephalosporium
stripe is most severe, and would have the added advantage of being eligible
for club wheat premiums in some years. Further, we have helped to identify
genotypes that may be sources of increased levels of resistance in future
cultivars. INTERACTION (COOPERATION) 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: 1998
1999
2000
Table 1. Percent whiteheads, Wasco County.
Table 2. Percent whiteheads, Gilliam County.
Table 3. Percent whiteheads, Sherman County.
Table 4. Percent
lodging caused by eyespot (strawbreaker foot rot) in Gilliam County, 1998. Table 5. Grain yields (bu/ac), Wasco County. Rankings within the club and common groups are in parentheses for each year.
Table 6. Grain yields
(bu/ac), Gilliam County. Rankings within the club and common groups are
in parentheses for each year.
Table 7. Grain yields (bu/ac), Sherman County. Rankings within the club and common entries are in parentheses for each year.
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