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1999 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:
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 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. 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 continued into the second season. Trials were conducted in three counties (Gilliam, Sherman, and Wasco) of northcentral Oregon under conditions of stubble mulch and early (September 14-16) seeding during the 1998-99 season. Sixteen treatments were established and replicated four times at each site in 10 x 100 ft. plots. The sixteen entries incorporated five commonly-grown, soft white winter wheat cultivars; four recently released cultivars; one advanced breeding line that is likely to soon be released; and six mixtures among these entries. Substantial Cephalosporium stripe developed at two of the three locations. The club wheats were more resistant to Cephalosporium stripe than were the common wheats, as was the case last season. Among the common wheat varieties, Madsen, Rod, and Weatherford showed more resistance than the other varieties tested. Coda/Rohde, Coda, and Madsen/Rod were the top three yielding entries when averaged over the two sites. Last year, Coda and Rohde/Coda were the top two yielding club wheat entries and Madsen/Rod was the top common wheat entry. Given the extreme weather differences between the past two seasons, this provides confidence that these three entries have potential to perform well in areas with severe Cephalosporium stripe. A similar set of 14 entries was seeded into stubble mulch in the same three counties in mid-September 1999. In addition, we have included two replicated sets of smaller plots, with eight treatments each. The first set will test lines that appear to have greater resistance than currently available in Pacific Northwest wheat cultivars. The second set will be used to better determine differences in resistance among common soft white winter, club, and durum varieties. 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 in Gilliam (Jeff Nelson), Sherman (Gary Macnab), and Wasco (Dick Neal) Counties. Each experiment was planted in a stubble-mulched field during the period of September 14-16. Elevation at the sites ranges between 2,000-3,000 ft. Entries and plot design - Sixteen entries were evaluated at each site: five soft white winter wheat cultivars that are commonly grown in the region, four newly released cultivars, one advanced line that is likely to soon be released as a cultivar, and six mixtures among these entries (Tables 1-3). Each plot was 10 x 100 ft. and replicated four times in a randomized complete block design at each of the three locations. In Gilliam and Wasco Counties, good stand establishment was attained, weed densities were low, and substantial Cephalosporium stripe developed. In Sherman County, soil crusting resulted from high winds and a rain shower directly after seeding. The reduced emergence in turn caused a major problem with cheatgrass and goatgrass. Further, Cephalosporium stripe was not very severe at this site. Thus, the results from Sherman County in 1998-99 are not highly relevant to the objective of the trials, but are included in this report for the sake of completeness. Cephalosporium stripe - We assessed Cephalosporium stripe severity by two methods in Gilliam and Wasco Counties. The first method was a foliage rating of Cephalosporium symptoms at mid-grainfill. We assigned a score from 1-10 based on a combination of leaf yellowing, plant stunting, and stand density as influenced by Cephalosporium stripe. A "1" would indicate a perfectly healthy stand, while a "10" would indicate a stand where all plants were very severely affected by Cephalosporium stripe. The second method was to score the percentage of tillers showing whiteheads at late milk/early dough. We had some difficulty making whitehead estimates in Wasco County due to interaction with drought stress; the club wheats were especially difficult to assess. However, whitehead expression due to Cephalosporium stripe was clearer in Gilliam County. For both methods, the four plots of each entry were assessed separately, and the numbers shown below in Table 1 for each site are averages over the four plots. We were unable to take the same type of foliage rating at the Sherman County site due to low Cephalosporium stripe severity. However, we did assign each plot a crude score from 1-3 based on relative stand health at mid-grainfill, though none of the plots were severely affected by Cephalosporium stripe. A "1" indicates a healthier stand than a "2" or "3". Drought stress prevented collection of useful whitehead counts at this site. The club wheats were more resistant to Cephalosporium stripe than were the common wheats (Tables 1 and 3), as was the case last season. Among the common wheat varieties, Madsen, Rod, and Weatherford showed more resistance than the other varieties tested. As expected, Stephens was the most susceptible variety. OR 939515, which may be released as a cultivar, was susceptible, but not as susceptible as Stephens, as was the case last year. Unlike last year, Gene did not become as severely infected as did Stephens. We have previously observed that Gene's degree of susceptibility to Cephalosporium stripe can vary among years. Yield - Yield was determined by harvesting a 5-foot swath down the center of each 10-foot wide plot with a plot combine. The yield data from Gilliam and Wasco Counties (Table 2) indicate that locations and seeding dates were appropriate to the objectives of this project. Yields for the best entry at each site, around 45 bu/ac, are reasonable for these locations and the growing conditions of this season. In addition, we also had a substantial range from the highest to the lowest yielding entries, which helps to distinguish differences in performance among entries. Coda/Rohde, Coda,
and Madsen/Rod were the highest yielding entries when averaged over the
Gilliam and Wasco County sites. Last year, Coda and Rohde/Coda were the
top two yielding club wheat entries and Madsen/Rod was the top common
wheat entry. Given the extreme weather differences between the past two
seasons, this gives us confidence that these three entries may be useful
for growers who are trying to deal with Cephalosporium stripe. This is the first year that we have evaluated Hiller under Cephalosporium pressure. Hiller yielded very well in Gilliam County, but somewhat below the better entries in Wasco County. Obviously, we need to evaluate Hiller for another season before making any conclusions. Cultivar mixtures often yielded very well relative to individual cultivars. This was particularly noticeable in Wasco County, where the mixtures yielded an average of 15.7% higher than the component cultivars grown separately in pure stand (Table 2), even though the mixtures did not reduce the severity of Cephalosporium stripe (Table 1). We have sometimes seen such results previously under Cephalosporium pressure, but currently have no mechanism to explain such large yield responses due to mixing. There were a few clear trends in the yield data from Sherman County (Table 3). First, and not surprisingly, Cephalosporium susceptibility was not correlated with yield due to low disease pressure at this site. Second, the common wheats yielded substantially better than most of the clubs, for reasons that we cannot explain. Third, Gene yielded substantially more than any other entry. This may be due to Gene's ability to escape drought stress, or perhaps to compete better against the heavy weed pressure. Establishment of 1999-00 plots - Similar trials were again established in each of Gilliam (Bob Kamerrar), Sherman (Tom McCoy), and Wasco (Dick Neal) Counties. Plots were seeded during the period from 15-17 September 1999. Stands currently range from very good to acceptable, despite the very dry conditions this fall. Thirteen of the entries were the same as in the previous two seasons (Table 4), which will allow us to make comparisons across seasons. "Hiller" was included for a second season of evaluation. Entry 15 (Table 4) consists of eight lines that Jim Peterson (OSU wheat breeder) identified as good potential sources of resistance in his trials at the Moro Experiment Station last season. Entry 16 in Table 4 consists of eight varieties that we included to support our efforts to determine relative susceptibility of soft white, club, and durum wheats. A combination of field and laboratory work suggests that club wheats may consistently be more resistant than the soft whites and that durums may be more resistant than either the common soft whites or the clubs. As OSU is developing some winter durums, we now have the chance to compare all three types in the same trials. This comparison may help us to better understand the suitability of market classes for growers who have to deal with Cephalosporium stripe. In addition, it should be feasible to transfer resistance genes among these classes if we confirm large differences in resistance among them. 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. We have confirmed the reaction to Cephalosporium stripe for popular wheat cultivars and now have a fairly clear evaluation of newly released cultivars and advanced breeding lines. Coda, Hiller, Rohde, and Temple have shown substantial resistance to Cephalosporium and positive yields relative to the common soft white winter wheats. Thus, these 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. Coda has shown a particularly impressive combination of Cephalosporium resistance and yield potential. The new cultivar "Weatherford" had not previously been field-tested for resistance to Cephalosporium stripe, and demonstrated a level of resistance similar to that of Madsen and Rod. Unfortunately, OR 939515 appears to be susceptible to Cephalosporium stripe, but it is nonetheless useful to have this information available in the event that it is released. Cultivar mixtures seem useful in buffering against year-to-year yield variation of individual cultivars. Cultivar mixtures with consistently good performance in our trials include Madsen/Rod and Coda/Rohde. Entries added to
the 1999-2000 trials may help us to identify sources of increased resistance
to Cephalosporium stripe. Table 1. Foliage ratings and whitehead percentages in Gilliam and Wasco Counties. Entries are listed in ascending order from fewest to most whiteheads when averaged over the two sites.
Table 2. Yields
in Gilliam and Wasco Counties. Entries are listed in descending order
from highest to lowest when averaged over the two locations. Table 3. Foliage rating and yield of entries in Sherman County. Entries are listed in descending order from highest to lowest yield.
Table 4. 1999-00 Cephalosporium trial entries.
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:
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