Items from the United States - Minnesota.

ITEMS FROM THE UNITED STATES

 

MINNESOTA


CEREAL DISEASE LABORATORY
(formerly CEREAL RUST LABORATORY)

USDA-ARS, University of Minnesota, 1551 Lindig, St. Paul, MN 55108, USA.


D.L. Long, K.J. Leonard, D.V. McVey, M.E. Hughes, D.H. Casper, and L. Wanschura.

 

Special note: virulence to Sr31 in wheat stem rust in Uganda-an update.

Z.A. Pretorius et al. (Plant Dis 84:203) reported virulence to Sr31 (T1BL·1RS) in a new pathotype of wheat stem rust from Uganda. Tests performed at the Cereal Disease Laboratory during the winter 1999-2000 were in agreement with those reported by Pretorius et al. Additional sources of resistance to the Sr31-virulent pathotype identified at the Cereal Disease Laboratory were the cultivars Waldron (CI 13958), Triumph 64 (CI 13679), and Kota (CI 5878). Seedling tests of 183 entries in the 2000 winter wheat Regional Performance Nurseries (Eastern and Southern Soft Red; and Northern, Southern, and Western Plains Hard Red Nurseries) for resistance to stem rust, yielded three entries susceptible to the Sr31 virulent isolate alone. All other entries susceptible to the Uganda isolate were susceptible to various other of the five selected highly virulent isolates of wheat stem rust. With the limited use of Sr31 in the U.S., this isolate does not appear to provide a threat to U.S. wheat production. For more information, contact Don McVey (phone: 612-625-5291, E-mail: donm@cdl.umn.edu).


The rusts of wheat in the United States in 1999.


Stem rust (Puccinia graminis f. sp. tritici). In 1999, wheat stem rust severities were generally light in varietal plots and fields throughout the southern U.S. During mid-May, a few late-maturing wheat varieties were rusted heavily in southern Louisiana nursery plots. In late May, severe stem rust was observed during harvest on late maturing susceptible wheat in central Texas plots. Wheat stem rust development was much lighter than normal throughout the southern U.S in 1999.

During the first week in June, stem rust foci were found on the cultivar Mit, and traces of rust were found scattered on other cultivars such as Onaga and 2174 in southcentral Kansas nurseries. In mid-June, wheat stem rust was light on susceptible cultivars, e.g., Onaga, throughout central and northcentral Kansas plots. In late June, trace-10 % severities of stem rust were observed at the hard-dough stage in northcentral Kansas and southcentral Nebraska fields, but losses were negligible. Wheat stem rust developed late in the Central Plains. Most of the cultivars were early maturing and, therefore, escaped the rust. The stem rust-infected areas in the Central Plains provided spores for susceptible wheats farther north.

In late June, foci of wheat stem rust, 1 m in diameter at 10 % severity, were found in plots of the susceptible spring wheat Baart in southcentral and westcentral Minnesota and in plots of winter wheat cultivars, e.g., 2137, in central and eastcentral South Dakota. In much of the central and northern Great Plains, the temperatures were near normal, and moisture was ideal for the spore infection process to occur. During the second week of July, stem rust severities of 5-80 % were reported in a winter wheat field of 2137 in central South Dakota. A significant yield loss to stem rust occurred in this field. In other fields in central South Dakota, trace-20 % severities were observed, but incidence was low. In mid-July, trace-20 % severities were observed in winter wheat plots in eastcentral South Dakota and southeastern North Dakota. By mid-July, check plots of highly susceptible spring wheat cultivars such as Baart had 20 % stem rust severities in southcentral Minnesota and eastcentral South Dakota, and traces of stem rust were found in southeastern North Dakota. In late July, 30 % severities were reported on Baart in northcentral North Dakota plots.

Stem rust was unusually prevalent in the Northern Plains this year. The number of stem rust samples received at the Cereal Disease Lab this year was twice as great as in recent years. The increased severity of stem rust in the Northern Plains can be attributed to the large amount of inoculum produced on winter wheat cultivars, e.g., 2137, farther south in the Central Plains, and to the warm temperature and good moisture, which were ideal for stem rust infection in the Northern Plains this year. If current spring wheat cultivars were susceptible to stem rust, a serious epidemic with substantial yield losses would have occurred.

In mid-June, light stem rust was found in wheat plots in southwestern Virginia.

Stem rust races. In 1999, eight Pgt races were identified from 73 collections made in the U.S. (Table 1) as compared to six Pgt races identified from 47 collections in 1998. Pgt-RCRS was the most commonly identified race both in 1999 and 1998. From 1993 to 1997, race Pgt-TPMK had been the most common wheat stem rust found in the U.S.. and in 1999 it was number three. Pgt-QCCJ, the race that attacks barley and the second most commonly identified race, was not identified in 1998, but from 1991-95 the QCCJ race comprised 10-27 % of the identified isolates. Race RCRS was the most frequently identified race in the Southern and Central Plains states, but in the Northern Plains, Pgt-QCCJ was predominant.

Table 1. Races of Puccinia graminis f. sp. tritici identified from wheat in 1999.

   State    Source  *Number of  **Percentage of isolates of Pgt- race 2    
 Coll Isol  QCCJ  QCCS  QCMJ  QCMS  QFCJ QFCS  RCRS  TPMK  Other***
 KS  Field  1  2              100    
 Nursery  7  13              61    38
 LA  Nursery  1  3 100                 
 MN  Nursery  9  25 72        12   4    
 ND  Nursery  24  61 39     28  3  
 NE  Field  2  6              100    
 Nursery  1  3              100    
 SD  Field  1  3 67  33               
 Nursery  18  54  11  2        2  85    
 TX  Field  1  1              100    
 Nursery  6  15  47          13  40    
 VA  Nursery  2  6         100         
   USA  Field  5  12 17           75    
 Nursery  68  180 32   45  4
 Total  73  192 31   47  4
* Number of collections (Coll) and isolates (Isol).
** Pgt race code, after Roelfs and Martens, Phytopathology 78:526-533; set four consists of Sr9a, 9d, 10 and Tmp.
*** Under evaluation.

Wheat leaf rust (Puccinia triticina). During mid-March, wheat leaf rust severities ranged from traces on flag leaves to 60 % on the lower leaves of cultivars in nursery plots throughout southern Texas (Fig. 1). For example, plots of Custer had traces of leaf rust, but Karl 92 had 60 % severities. Commercial wheat fields in southern Texas had rust severities ranging from trace-20 % on the lowest leaves. In southern Texas, rust increased on the lower leaves when moisture was abundant, but rust increase farther up the plant was limited because of dry weather. In southern Texas in early April, leaf rust was severe on spring wheats like Norm (30 %).

In central Texas during early April, leaf rust was much more severe and widely distributed than normal in wheat fields and plots. The mild winter and moist conditions in February and March contributed to the rust development in much of this area. In mid-April, leaf rust severities of 80 % were observed in central Texas plots of TAM 107. During the last week in April, wheat leaf rust severities in northcentral Texas and southern Oklahoma ranged from trace-80 % in plots, and in fields where rust overwintered, severities were as high as 70 % on flag leaves. Leaf rust was more severe than last year in this area.

During November in Oklahoma, leaf rust was severe on some of the commonly grown cultivars. However, a hard freeze in mid- to late December, followed by dry conditions through January and early February, eliminated this leaf rust in many of these fields. Most of the rusted leaves died without the rust spreading to the younger leaves because of the dry weather in February, so leaf rust was less severe by early March. Moist conditions in late March allowed rust to increase again and provided inoculum for the wheat-growing areas farther north.

During the last week in April, wheat leaf rust severities in southern Oklahoma ranged from trace-80 % in plots and were as high as 70 % on flag leaves in fields where rust overwintered. Leaf rust was more severe than in 1998 in this area and provided rust inoculum for wheat grown in Kansas and Nebraska.

By the third week in May, leaf rust was severe in plots and light in most fields in north central Oklahoma. In plots in north central Oklahoma, 60 % severities were reported on flag leaves of susceptible cultivars such as Chisholm, Karl 92, and Jagger. However, severities of less than 2 % were observed on cultivars like 2163, Custer, and Tomahawk. Rust was severe in some fields in central Oklahoma where wheat was planted early, which allowed an autumn infection and overwintering of leaf rust.

During the last week in April, traces of leaf rust were found on Ae. cylindrica plants growing along the roadside in northcentral Texas. The pathotype (race) SBD generally identified from these collections normally does not infect the commonly grown wheat cultivars. By the third week in May, leaf rust severities ranging from 10-40 % were observed on Ae. cylindrica plants growing alongside the road in northcentral Oklahoma.

Central Plains. In Kansas, the autumn of 1998 was long and warm with frequent rains, which allowed for the buildup of leaf rust on susceptible varieties. The winter was relatively mild, but a cold snap in late December killed many of the leaves. By early March, overwintered leaf rust was found in northwestern and northeastern Kansas, but overwintering was generally light and localized. Cool weather in late April and early May slowed rust development. In early May, traces of leaf rust were found on the flag leaves of susceptible wheat cultivars in fields in the southern half of Kansas. During the third week in May, in a southcentral Kansas nursery plot, 40 % leaf rust severities were reported on the flag leaves of susceptible cultivars (e.g., TAM 107). Severities of 10 % were found on flag-1 leaves in fields of the cultivar Jagger in southeastern Kansas in mid-May. In some central Kansas fields, the flag leaves were clean, but the flag-1 leaves had leaf rust severities of trace-5 %. The northward development of leaf rust into the Great Plains states was slow because of the cooler than normal weather and moist conditions, which kept the spores within the crop canopy. However, with the advent of weather conditions more favorable for spore increase, trace-80 % severities were reported in southcentral Kansas nurseries during late May. In fields in the same area, 20 % severities were observed on flag leaves of susceptible cultivars like Jagger, but severities were much lower on most of the other cultivars. In northcentral Kansas, 20 % severities were observed on the lower leaves.

In early June, only traces of leaf rust were found in eastern Colorado. The leaf rust was less than in prior years, partly because less acreage of the common susceptible cultivar TAM 107 was grown. By mid-June in the central plains, 80 % leaf rust severities were common on susceptible cultivars such as TAM 107 from southeastern Colorado to northcentral Kansas. Leaf rust developed late, but still managed to kill the flag leaves of susceptible cultivars during the soft dough stage throughout much of this area.

The overall estimated loss from leaf rust in Kansas in 1999 was 3.4 %, (Table 4), which is below the 10-year average of 5 %, but above last year's estimate of 2.5 %. Yield losses were estimated from fungicide plot data, cultivar surveys, cultivar disease ratings, and disease surveys. Several varieties such as Big Dawg, Custer, Dominator, Heyne, and Jagger showed significant losses of resistance compared to last year in most Kansas plots.

During the first week in June, traces of leaf rust were found in a southeastern Nebraska winter wheat nursery. By mid-June, leaf rust was light in many fields in southern Nebraska and severe in some fields of susceptible cultivars, where rust had infected early in the spring or had overwintered.

Northern Plains. In late May, traces of leaf rust were found in winter wheat plots in Brookings, South Dakota. Growth stages ranged from emergence of the flag leaf to late boot. On 27 May, traces of leaf rust were observed on the lower leaves of the winter wheat cultivar Norstar in a southeastern North Dakota plot. On 3 June, trace-1 % severities were found in a plot of the winter wheat Roughrider in eastcentral Minnesota. Traces of rust also were observed on other winter wheat cultivars. The rust development in the northern Great Plains states probably originated from rust spores hat were deposited with rain in mid-May. This rust development was earlier than normal. During the first week in June, 5-30 % severities were reported in a winter wheat nursery and traces in spring wheat fields in southeastern South Dakota. By mid-June, 20 % severities were observed on the flag leaves of susceptible winter wheats and 30 % on lower leaves of susceptible spring wheats in east central South Dakota. Leaf rust developed faster in this area than in 1998.

During the final week in June, leaf rust severities ranged from trace-60 % on flag leaves of susceptible winter wheat cultivars in central and eastern South Dakota plots and fields. Winter wheat flag leaves dried up quickly because of heavy leaf rust infection throughout South Dakota and southern Minnesota. These rust infections probably originated from inoculum sources in Oklahoma and Nebraska. During the final week in June, leaf rust severities were 10% on the flag leaves and 60% on lower leaves of susceptible spring wheat cultivars, e.g., 2375, in plots in southwestern and westcentral Minnesota. In fields, severities ranged from trace-10 % on the lower leaves of spring wheats in western Minnesota and northeastern South Dakota. Leaf rust was more severe and concentrated in the upper Midwest in 1999 than it has been in the last 20 years. Abundant inoculum from the south was deposited with the frequent rains, and weather conditions favored infection. The spring wheat cultivars currently grown are more susceptible than those in previous years.

By mid-July, 40 % severities were common on flag leaves of spring wheat cultivars, e.g., Oxen, growing in plots in west central Minnesota. In spring wheat fields, 20 % severities at the early berry stage were common throughout west central Minnesota and east central South Dakota. By late July, severities were 40 % in spring wheat cultivars in a northeastern Montana nursery and 10% in spring wheat fields in north central North Dakota. This year, total yield losses from leaf rust of 2-4 % per state (Table 4 and Table 5) were common in both winter and spring wheats in the Northern Plains.

Southeast. In February, heavy rainfall in Louisiana did not allow the rust spores to move up the plants, so rust development was limited. By mid-March, wheat leaf rust was increasing in plots of southern SRWW cultivars in southern Louisiana.

In much of the southeastern U.S., dry weather through March and some of April was a limiting factor in rust development. In mid-April, leaf rust was severe in plots of susceptible southern SRWW cultivars within approximately 75 miles of the Gulf Coast, and some cultivars that previously were resistant showed significant rust development this year. During the last week in April in the southeastern U.S., severities of 60 % were observed in plots of susceptible soft red winter cultivars, although in fields, 1 % severities were common on the flag leaves. The drier and cooler than normal conditions during the last part of April slowed the rust development. Because of low relative humidities during the last half of April, there was little dew formation, which is needed for rust infection to occur. Therefore, the numbers of spores released as inoculum for areas farther north were lessened. Losses to leaf rust in the southeastern SRWW area were less than normal this year (Table 4).

During mid-April, traces of leaf rust were found in southern Arkansas. By the third week in May, leaf rust was heavier than normal, but wheat in the southern part of the state was too mature for rust to cause much loss. In northern Arkansas (north of I-40), losses occurred in fields that were later than normal in maturity. This area provided a source of inoculum for areas to the north. In some fields in this area, leaf rust development was stopped by severe Septoria infection of leaves.

In mid-April, 40 % severities of leaf rust were found on wheat in eastcentral South Carolina plots.

Midwest. By the first week in June, 20-30 % leaf rust severities were observed on susceptible wheat cultivars at the late milk growth stage in southwestern Indiana and western Kentucky plots. Leaf rust severities of 40 % were observed in wheat fields at full berry stage in northeast Missouri on 7 June, and severities in plots ranged from trace-40 %.

By the second week in June, 40 % leaf rust severities were reported in plots of susceptible wheat cultivars from northeastern Missouri to northeastern Indiana. In fields of the susceptible cultivar Clark in southern Illinois, 80 % rust severities were common during the second week in June. In plots and fields in places like east central Indiana, 20 % severities were noted on only 10 % of the wheat plants, because there was not enough dew or rainfall in late May to allow the infection process to occur and, therefore, rust did not spread from wheat plants infected earlier.

During the third week in May, traces of leaf rust were reported in southcentral Michigan. Leaf rust (low to moderate incidences and low severities) was found in southwest Michigan fields by 8 June. The infections were predominantly on the lower leaves.

East. During the last week in May, 80 % leaf rust severities were observed on susceptible winter wheat cultivars in eastern Virginia plots, and traces of rust were found on wheat in west central New York fields. Leaf rust was not a problem in the eastern U.S. this year, because conditions were so dry limited rust infection could occur.

California. In early May, 20 % leaf rust severities were reported on wheat lines growing in a nursery in the northern Sacramento Valley. By mid-May, late infections of wheat leaf rust occurred throughout the Central Valley, but because the infections were so late, losses were minimal. Disease levels were much lower in 1999 than in previous years because of the cool spring and a cold spell in late December, which killed some of the early rust-infected wheat.

Pacific Northwest. By the third week in May, leaf rust was just starting to show in nurseries in western Oregon, but none was found in commercial fields. In eastern Oregon, wheat leaf rust was light because of the cool dry May.

During mid-April, leaf rust was light in wheat plots in the Skagit valley of western Washington. Because of the cool dry May, leaf rust increased at a slow rate in the state of Washington. By the second week in June in western Washington plots, 50 % severities were reported on winter wheats and traces on the spring wheats. In mid-June, traces of leaf rust were found on spring wheats in eastern Washington plots. By late June, wheat leaf rust was increasing on spring wheats in the Mount Vernon area of western Washington. In early July, traces of leaf rust were found in eastern Washington and northern Idaho fields. In mid-July, leaf rust was increasing on spring wheats in western Washington. Leaf rust was very light east of the Cascades in Washington. The cool dry conditions in early spring were not conducive for leaf rust to develop, and losses were light this year in the Pacific Northwest (Table 4 and Table 5).

Leaf rust races. Virulence formulas for the leaf rust races collected in 1999 are shown in Table 2. The four most common leaf rust races found in the U.S. in 1999 were MBDL, MCDL, MCRQ, and THBL (Table 3). Races MBDL and MCDL comprised a significant part of the race population in the Great Plains states from Oklahoma northward to North Dakota. These two races (Lr17 virulence) overwintered in Oklahoma and increased on cultivars like Jagger that have Lr17 resistance. Jagger is grown on significant acreage in Oklahoma and Kansas. From the initial inoculum source, the rust spores then infected other wheats along the Great Plains Puccinia pathway. Another significant change this year was the increase in the number of T races (Lr1,2a,2c,3 virulence) that were identified. For example, the second most commonly identified race was THBL, which was found in the northern Great Plains area. Losses were much higher than normal in northern plains states (Table 5). Much of this loss was due to an increase in virulence of Lr2a, which is included in the Lr gene resistance of many of the spring wheats.


Table 2. Wheat leaf rust code and corresponding virulence formula for collections made in 1999.
 Race code [1]  Virulence formula [2]  Race code [1]  Virulence formula [2]
 FBMQ  2c,3,3ka,10,18,30  TBRL  1,2a,2c,3,3ka,10,11,30
 FBRQ  2c,3,3ka,10,11,18,30  TBRQ  1,2a,2c,3,3ka,10,11,18,30
 FCMQ  2c,3,3ka,10,18,26,30  TCBL  1,2a,2c,3,10,26
 LCGG  1,11,18,26  TCBQ  1,2a,2c,3,10,18,26
 MBBL  1,3,10  TCDL  1,2a,2c,3,10,24,26
 MBDL  1,3,10,17  TCML  1,2a,2c,3,3ka,10,26,30
 MBGB  1,3,11  TCMQ  1,2a,2c,3,3ka,10,18,26,30
 MBGL  1,3,10,11  TCRL  1,2a,2c,3,3ka,10,11,26,30
 MBGQ  1,3,10,11,18  TDBL  1,2a,2c,3,10,24
 MBKL  1,3,10,11,17,30  TDGL  1,2a,2c,3,10,11,24
 MBRL  1,3,3ka,10,11,30  TDRB  1,2a,2c,3,3ka,11,24,30
 MBRQ  1,3,3ka,10,11,18,30  TDRL  1,2a,2c,3,3ka,10,11,24,30
 MCBL  1,3,10,26  TDRQ  1,2a,2c,3,3ka,10,11,18,24,30
 MCDL  1,3,10,17,26  TFBL  1,2a,2c,3,10,24,26
 MCGL  1,3,10,11,26  TFGL  1,2a,2c,3,10,11,24,26
 MCRL  1,3,3ka,10,11,26,30  TFML  1,2a,2c,3,3ka,10,24,26,30
 MCRQ  1,3,3ka,10,11,18,26,30  TFRL  1,2a,2c,3,3ka,10,11,24,26,30
 MCTL  1,3,3ka,10,11,17,26,30  TGBL  1,2a,2c,3,10,16
 MDBL  1,3,10,24  THBL  1,2a,2c,3,10,16,26
 MDRL  1,3,3ka,10,11,24,30  THDL  1,2a,2c,3,10,16,17,26
 MFBL  1,3,10,24,26  THML  1,2a,2c,3,3ka,10,16,26,30
 MGBL  1,3,10,16  TJBL  1,2a,2c,3,10,16,24
 MGDL  1,3,10,16,17  TKBL  1,2a,2c,3,10,16,24,26
 PBRQ  1,2c,3,3ka,10,11,18,30  TLGG  1,2a,2c,3,9,11,18
 PNMQ  1,2c,3,3ka,9,10,18,24,30  TLGQ  1,2a,2c,3,9,10,11,18
 TBBL  1,2a,2c,3,10  TLRL  1,2a,2c,3,3ka,9,10,11,30
 TBDL  1,2a,2c,3,10,17  TNRL  1,2a,2c,3,3ka,9,10,11,24,30
 TBML  1,2a,2c,3,3ka,10,30    
[1] Race code plus Lr10 and 18 near-isogenic supplementals, after Long and Kolmer, Phytopathology 79:525-529.
[2] Resistances evaluated for formula: Lr1, 2a, 2c, 3, 9, 16, 24, 26, 3ka, 11, 17, 30, 10, and 18.

 

Wheat stripe rust (Puccinia striiformis). The first report of stripe rust this year in the central part of the U.S. was in a southcentral Kansas nursery, during the last week in May. Wheat stripe rust foci were found in some plots (e.g. 2137), and traces of rust were scattered throughout the central and southern parts of the state. Where this rust originated from is anybody's guess. Last year, light amounts of wheat stripe rust were scattered from the lower Mississippi Valley north to eastcentral Minnesota. In Kansas, the cool spring weather allowed development of stripe rust, but the hot temperatures of early June disrupted further development, so losses were negligible (Table 4).

During the third week in June, traces of stripe rust were found in east central Colorado fields. Normally, stripe rust is found at higher elevations in Colorado, i.e., San Luis Valley (7,500 ft) or front range of the Rockies (~5,000 ft).

In early June, light amounts of stripe rust were observed in wheat plots in west central Indiana.

During mid-April, wheat stripe rust was severe in a field in the Sacramento Valley of California. In other fields in the same area, severe rust was expressed in small foci. By the first week in May, wheat stripe rust was increasing in the Sacramento Valley, where temperatures remained relatively cool. Disease foci readings ranged from 1-80 % severities in fields of the autumn-sown HRSW cultivars Express and RSI 5, the predominant cultivars grown there. During the third week in May, because of the cool weather, wheat stripe rust was continuing to increase in fields in the Sacramento and San Joaquin Valleys. A 7 % yield loss from stripe rust occurred in California.

In mid-April, wheat stripe rust severities of 30 % were reported on susceptible winter wheat lines in the Skagit valley nursery in western Washington. In late May in western Oregon nurseries, wheat stripe rust was starting to show, but none was found in commercial fields. During the last week in May, 80 % wheat stripe rust severities were reported on susceptible winter wheat lines in northwestern Washington plots at the boot stage. In mid-June, 60 % severities were observed on spring wheats in western Washington. Wheat cultivars with adult-plant resistance continued to provide durable resistance in farmers' fields. Stripe rust foci of 60 % severity were found in winter wheat plots in eastern Washington, but they were few in number. The dry autumn and cool dry May led to the low rust severities, but the rains in mid-June improved conditions for rust buildup.

By late June, wheat stripe rust was increasing on spring wheats in the Pacific Northwest, but rust losses were minimal, because most of the cultivars have high temperature, adult-plant resistance. During mid-July, 100 % stripe rust severities were reported on susceptible spring wheat cultivars in the Mount Vernon area of western Washington. In mid-July, wheat stripe rust was increasing in spring wheat fields in the Palouse region, but the adult-plant resistance of commercial cultivars minimized losses (Table 5).

In early July, significant amounts of wheat stripe rust were reported in nurseries in the Bozeman area of Montana.

Table 4. Estimated losses in winter wheat due to rust in 1999.

Table 5. Estimated losses in spring and durum wheat due to rust in 1999.


 

UNIVERSITY OF MINNESOTA AND USDAARS PLANT SCIENCE RESEARCH UNIT

Department of Agronomy and Plant Genetics, University of Minnesota and USDAARS, St. Paul, MN 55108, USA.


J. Anderson, R. Busch, G. Linkert, L. Matthiesen, E. Wennerlind, A. Procopiuk, H. Mickelson, S. Liu, and K. McGowan.

 

Personnel changes.

Dr. Sixin Liu joined our project in January, 2000, as a postdoctoral associate. Kari-Lynn McGowan is a new M.S. student. Ana Maria Procopiuk finished her Ph.D. in December, 1999. Heidi Mickelson, a joint graduate student with S. Rajaram (CIMMYT) and R. Busch, died in September, 1999, after being ill for several years.

 

Wheat production, breeding, and scab screening.

Minnesota produced an estimated 79.2 million bushels (2.67 million metric tons) from 1.99 million acres (0.81 million hectares) in 1999. Losses from leaf rust were estimated at 4 %. During the 1998-99 crossing cycle, 317 crosses were made. Most of these crosses involved elite germ plasm from the University of Minnesota HRSW breeding program and sources of FHB resistance. A total of 1,980 lines were under small-scale increase (8 ft. rows) in the 1998-99 winter nursery in California. A total of 17,000 F3 seeds were planted in New Zealand in the autumn of 1998 for generation advance by SSD. During the 1999 growing season, 439 and 140 experimental lines were evaluated in replicated preliminary and advanced yield trials, respectively. The preliminary yield and advanced yield trials were grown at two and three locations, respectively. The Variety Trial, which contained 31 released varieties and two University of Minnesota experimental lines, was grown at seven locations. FHB-inoculated, misted, replicated nurseries were established at three locations. Approximately 2,500 lines were tested for FHB resistance in the greenhouse during the past year. Most of these materials were experimental lines, but also included potential new resistance sources from China and elsewhere and materials for genetic studies. McVey (MN93413) was released in 1999. Developed under the project leadership of Dr. Robert Busch, McVey has shown high yield levels, even in the presence of FHB.

 

Fusarium head blight-resistance gene mapping.

J.A. Anderson and E. Wennerlind.

We are using SSR markers to saturate genomic regions known to contain FHB-resistance genes. We are concentrating our efforts on chromosomes 3BS and 2AL, where we have previously located major QTLs for this disease using RFLP and AFLP markers. Previous research identified an AFLP fragment associated with FHB resistance on 3BS. We cloned and sequenced this fragment and designed PCR primers. Unfortunately, these primers did not reveal polymorphism in either of two populations. We have continued mapping SSR markers in three populations of wheat segregating for resistance to FHB: 'Sumai 3/Stoa', 'ND2603/Butte 86', and 'Wuhan/Norm'. Of the 142 microsatellite markers screened to date, 37 % were polymorphic between Sumai 3 and Stoa and 62 % between ND2603 and Butte 86 or between Wuhan and Norm. The marker Xgwm533 was mapped in the 'ND2603/Butte 86' population and explained 24.6 % of the phenotypic variation in scab resistance in this population. This marker explains the highest proportion of FHB resistance of those that we have identified to date for a gene inherited from Sumai 3. Unfortunately, this microsatellite was not polymorphic between Sumai 3 and Stoa. Based on a common marker (AFLP locus XEagcMcta.1) mapped on 3BS in the 'Sumai 3/Stoa' and 'ND2603/Butte 86' populations, we believe the same gene(s) on chromosome 3BS is contributing to scab resistance in both populations. Two additional SSRs were mapped on 3BS in 'ND2603/Butte 86', so that this region is now well covered with markers.

 

Screening for FHB resistance using a seedling test.

A. Procopiuk and R. Busch.

Fusarium spp. can cause an important wheat disease that has resulted in an estimated $1.3 billion in losses in the Midwest of the U.S. in the last 6 years. Present methods of screening wheat for improved resistance to FHB requires adult-plant testing in the field and in the greenhouse. Our objective was to increase screening efficiency by determining if seedling tests for FHB resistance would predict adult FHB reaction of spring wheat genotypes. Preliminary experiments to determine the best method of inoculating seed with F. graminearum macroconidia, using vacuum and suspension, indicated that the suspension method was superior. After preliminary testing using only Sumai 3 (resistant) and Wheaton (susceptible), we determined that scoring roots provided little useful information. Twenty-four genotypes with diverse reactions to FHB then were evaluated for seedling height and emergence in three separate greenhouse tests. The reaction of the 24 genotypes to FHB had been evaluated previously in a FHB-inoculated nursery and in a natural field epidemic. Genotypes did not differ from the control for seedling height, indicating that this trait was of little value in determining FHB reaction. Genotypes also did not differ for seedling emergence, adjusted for control, when combined over greenhouses because of a 'genotype x greenhouse' interaction. Results within each greenhouse trial and for combined greenhouse trials indicated that emergence percent was reduced more for Pioneer 2375 than for any other genotype. Pioneer 2375 provides some resistance to FHB and was the most widely grown cultivar in the upper Midwest during the FHB epidemic years 1994 through 1998. Sumai 3, the most resistant genotype in the study, also had severely reduced emergence in two of three greenhouse trials. The seedling leaf reaction to the toxin DON was tested using six genotypes. The reactions of the genotypes did not differ from each other but differed from those of the controls. We concluded that none of the seedling tests were sufficiently predictive of adult plant reaction to FHB to justify their use for discarding even the most susceptible genotypes.

 

Publications.

  • Anderson JA, Waldron BL, Stack RW, and Frohberg RC. 1999. Update on DNA markers for Fusarium head blight resistance QTL in two wheat populations. In: Proc 1999 Natl Fusarium Head Blight Forum (Wagester JA, Ward R, Hart LP, Hazen SP, Lewis J, and Borden H eds). University Printing, East Lansing, MI. pp. 19-21.
  • Anderson JA, Effertz RJ, Faris JD, Francl LJ, Meinhardt SW, and Gill BS. 1999. Genetic analysis of sensitivity to a Pyrenophora tritici-repentis necrosis-inducing toxin in durum and common wheat. Phytopathology 89:293-297.
  • Campbell KG, Bergman CJ, Gualberto DG, Anderson JA, Giroux MJ, Hareland G, Fulcher RG, Sorrells ME, and Finney PL. 1999. Quantitative trait loci associated with kernel traits in a soft x hard wheat cross. Crop Sci 39:1184-1195.
  • Carter BP, Morris CF, and Anderson JA. 1999. Optimizing the SDS sedimentation test for end-use quality selection in a soft white and club wheat breeding program. Cereal Chem 76:907-911.
  • Devos KM, Sorrells ME, Anderson JA, Miller TE, Reader SM, Lukaszewski AJ, Dubcovsky J, Sharp PJ, Faris JD, and Gale MD. 1999. Chromosome aberrations in wheat nullisomic-tetrasomic and ditelosomic lines. Cereal Res Comm 27:231-239.
  • Groth JV, Ozmon EA, and Busch RH. 1999. Repeatability and relationship of incidence and severity measures of scab of wheat caused by Fusarium graminearum in inoculated nurseries. Plant Dis 83:1033-1038.
  • Ma H, Busch RH, Riera-Lizarazu O, Rines HW, and Dill-Macky R. 1999. Agronomic performance of lines derived from anther culture, maize pollination and single-seed descent in a spring wheat cross. Theor Appl Genet 99:432-436.
  • Mesfin A, Frohberg RC, and Anderson JA. 1999. RFLP markers associated with high grain protein from Triticum turgidum L. var. dicoccoides introgressed into hard red spring wheat. Crop Sci 39:508-513.
  • McKeehen JD, Busch RH, and Fulcher RG. 1999. Evaluation of wheat (Triticum aestivum L.) phenolic acids during grain development and their contribution to Fusarium resistance. J Agric Food Chem 47:1476-1482.
  • Procopiuk, AM. 1999. Early generation bulk testing to evaluate the introgression of unadapted wheat (Triticum aestivum L.) germplasm into adapted spring wheat. PhD Dissertation, University of Minnesota. pp 89.
  • Udall JA, Souza E, Anderson JA, Sorrells ME, and Zemetra RS. 1999. Quantitative trait loci for flour viscosity in winter wheat. Crop Sci 39:238-242.
  • Waldron BL, Moreno-Sevilla B, Anderson JA, Stack RW, and Frohberg RC. 1999. RFLP mapping of QTL for Fusarium head blight resistance in wheat. Crop Sci 39:805-811.