VIRGINIA
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY
Department of Crop and Soil Environmental Sciences 1 and Department of Plant Pathology, Physiology and Weed Science 2; Blacksburg, VA 240610404, USA.
W. L. Rohrer, C.A. Griffey, and D.E. Brann.
Growing conditions. The 1999-00 growing season was relatively dry with warm spells throughout. The most significant amount of winter precipitation fell east of the Blue Ridge with one storm dumping up to 24 inches of snow on some parts of eastern Virginia in late January. Temperatures fluctuated, particularly around 25 February, when temperatures soared to 77-83°F (25-28°C). Temperatures dropped late in the season and on 7-9 April they dove to around 32°F (0°C) in the Blue Ridge region. The most significant amount of rainfall came in June, just prior to harvest in Blacksburg. Harvest was actually interrupted for a period of about one week due to the heavy rainfall. Despite pounding rains late in the growing season, lodging was kept to a minimum (state average of 1.0 on a scale from 0.2-10, 10 being complete lodging). Disease pressure was comparable to that occurring in 1999.
Disease incidence and severity. Leaf rust and powdery mildew were the prevalent diseases in Virginia in 2000. Barley yellow dwarf virus was present but not significant. A new race of powdery mildew with virulence for resistance gene Pm4 was observed in the Warsaw area, and two very small, isolated pockets of stripe rust were observed in the Blacksburg area. This is the first known occurrence of stripe rust in Virginia.
Production. According to Virginia Agricultural Statistics Service, 230,000 acres (93,150 ha) of winter wheat were planted in the Commonwealth in the autumn of 2000. This figure is down from 240,000 acres (97,200 ha) planted in the autumn of 1999 and 280,000 acres (113,400 ha) in the autumn of 1998. This reflects a continuing trend that is occurring in the southeastern U.S. and across the nation. Among the southeastern states of Florida, Georgia, North Carolina, South Carolina, and Virginia, only one state (Georgia) saw an increase in seeded area. All other states listed above had a decrease in the total acreage of winter wheat. Virginia producers harvested 205,000 acres (83,025 ha) of SRWW for grain in 2000. Grain yields across the state averaged 60 bu/acre (4,031 kg/ha). This figure is 7 bu/acre (470 kg/ha) lower than the state yield-record set in 1997 but is 3 bu/acre (202 kg/ha) higher than in 1999. Total grain production for the Commonwealth in 2000 was 12.3 million bushels (334,694 metric tons).
Virginia Wheat Yield Contests. Nine producers representing seven Virginia counties participated in the 2000 Virginia Conventional Till Wheat Yield Contest. Yields ranged from 79.8 bu/acre (5,362 kg/ha) to 104.4 bu/acre (7,015 kg/ha) over a minimum area of three acres (1.2 ha). Among participants, Mack Mansfield of Suffolk County had the highest yield with 104.4 bu/acre (7,015 kg/ha). In second place was Robert Taylor, III also of Suffolk County with a yield of 101.3 bu/acre (6,806 kg/ha). In third place was George Black of Charles City County with a yield of 98.9 bu/acre (6,645 kg/ha). Twelve producers representing six counties participated in the No-till Wheat Yield Contest. Yields ranged from 77.5 bu/acre (5,207 kg/ha) to 133.0 bu/acre (8,936 kg/ha) over a minimum area of three acres (1.2 ha). David Hula of Charles City County had the highest yield with 133.0 bu/acre (8,936 kg/ha). In second place was the team of Louis and Randolph Aigner of Henrico County with a yield of 119.6 bu/acre (8,036 kg/ha). In third place was Ted Haberland of Orange County with a yield of 111.0 bu/acre (7,458 kg/ha).
State Cultivar Tests. A total of 71 entries were evaluated at seven locations across Virginia in 2000. Included in the tests were 41 experimental lines (including one white-seeded line), 28 released cultivars, and two triticale cultivars. Average grain yields ranged from 63 to 85 bu/acre (4,233-5,711 kg/ha) with an overall test average of 75 bu/acre (5,039 kg/ha). Wheat genotypes with yields significantly above the test average included Baytan-treated Pioneer 26R24, Pioneer 26R61, and Pioneer 26R38; Dividend-treated Century II; Raxil-treated FFR 518, Trical 498, USG 3209, AGS 2000, Pioneer XW681, Sisson and 15 experimental Virginia lines. Yields among members of this group ranged from 78 to 85 bu/acre (5,241-5711 kg/ha). Tests conducted in the Coastal Plain Region yielded an average of 74 bu/acre (4,972 kg/ha), whereas tests conducted in the Piedmont and Blue Ridge Region yielded an average of 76 bu/acre (5,106 kg/ha).
Test weights obtained across the seven test sites ranged from 48.0 lb/bu (618 kg/m3) to 59.1 lb/bu (761 kg/m3) with a test average of 56.9 lb/bu (732 kg/m3). Of the 31 entries with test weights significantly higher than the test average, 14 were experimental lines (13 from Virginia) and 17 were released cultivars. Virginia experimental lines and released cultivars made up 55 % of this group. Entries exhibiting significantly higher than average yield and test weight included Baytan-treated Pioneer 26R61 and Pioneer 26R24; Dividend-treated Century II; Raxil-treated AGS 2000 and Sisson; and seven experimental Virginia lines.
Cultivar release. Sisson, formerly designated VA96W-250, was released by the Virginia Agricultural Experiment Station in March 2000. The name Sisson was selected in honor of William L. Sisson and in recognition of his 45 years of dedication and service to the Small Grain Breeding and Genetics Program of Virginia Polytechnic Institute and State University.
Sisson is a broadly adapted, moderately early heading, high-yielding, short-stature, awnleted SRWW. Sisson was derived from the cross 'Coker 9803/Freedom'. The cross was made in the spring of 1990, and the population was advanced to the F4 generation using a modified bulk breeding method. Sisson was derived as an F5 headrow selected in 1995.
Head emergence of Sisson is 1 day later than that of Pioneer 2580 and one day earlier than Coker 9835. Plant height of Sisson (35 inches, 90 cm) is approximately 1 inch (2 cm) taller than Coker 9835 and approximately 2 inches (4 cm) shorter than Pioneer 2580. Straw strength of Sisson is similar to that of Coker 9835 and better than that of Jackson. Based on limited data, winter survival (99.5 % in Ontario, Canada) of Sisson is moderately good and most similar to its parent Freedom. Grain yields of Sisson have been similar to or exceeded those of the best check cultivars averaging 87 bu/ac. Average test weight of Sisson (58.1 lb/bu) has been consistently higher than that of Pioneer 2580 (57.1 lb/bu) and Coker 9835 (56.4 lb/bu). Milling and baking qualities of Sisson are most similar to those of Jackson.
Sisson is resistant to moderately resistant to prevalent field populations of powdery mildew and moderately resistant to moderately susceptible to leaf rust depending on the prevalence of specific races. Sisson is resistant to the predominant race, TPMK, of stem rust and is moderately resistant to BYDV and glume blotch. Sisson has moderate resistance to WSSMV. Sisson is susceptible to Hessian fly biotypes GP, B, C, D, E, and L.
In tests conducted from 1997-99 at seven locations in Virginia,
Sisson consistently produced grain yields (87 bu/acre average)
above those of the commercial cultivars Pioneer 2580 and Jackson
(79 bu/acre average). Sisson was evaluated in replicated yield
trials in Ontario, Canada in 1998 (one location) and 1999 (six
locations) and produced grain yields (98 bu/acre) that were equal
to or higher than those of commercial check cultivars. Sisson
is best adapted for production in the mid-Atlantic and northeastern
regions of the U.S., but also has performed well in the southern
corn-belt and in Ontario, Canada.
Authorized seed classes of Sisson are Breeder, Foundation, and
Certified. Sisson is protected under the amended U.S. Plant Variety
Protection Act of 1994 (Application pending). The Department
of Crop and Soil Environmental Sciences and the Virginia Agricultural
Experiment Station, Blacksburg, Virginia, will maintain Breeder
seed. Requests for participation in production of Sisson and
availability of Foundation seed should be directed to Bruce Beahm
(804-472-3500), Manager, Foundation Seed Farm, Mt. Holly, VA.
C.A. Griffey, J. Chen, M. Chappell, T. Pridgen, W. Zhao, D. Nabati, W. Rohrer, and E.L.Stromberg.
Highly effective type-II scab resistance has not been identified in SRWW. Most of the type-II resistance sources currently being used are progeny of Sumai 3 and are spring habit, low yielding and susceptible to glume blotch, powdery mildew and leaf rust in Virginia and the mid-Atlantic region. A major objective of our program is to transfer type-II resistance from known sources into SRWW backgrounds. Assessment and selection methods have been developed to accomplish this objective, and parents, progeny and advanced lines have been evaluated and selected for scab resistance. Moderate levels of scab resistance have been identified and confirmed in SRWW lines and cultivars such as Roane and Ernie. Type-II resistance is being transferred into scab susceptible and tolerant SRWW backgrounds via top-cross and back-cross procedures. Scab-resistant progeny and advanced lines are being selected based on greenhouse and field assessments made in mist-irrigated tests inoculated with Fusarium. Progress in transferring type-II resistance into SRWW backgrounds has been facilitated by the use of the wheat by maize double haploid system.
Thirty scab-resistant sources (21 Chinese, two French, one Japanese, and six SRW wheat lines) have been used as parents in the breeding program and over five hundred populations from F1 to F5 have been evaluated in scab nurseries at Warsaw and Blacksburg, Virginia. Twenty-seven advanced wheat lines possessing scab resistance combined with higher yield potential and resistance to other diseases, such as powdery mildew, leaf rust, or both, were evaluated simultaneously for scab resistance in a scab nursery at Blacksburg and for agronomic traits in observation yield tests at Warsaw and Blacksburg. Three of these lines will be evaluated in preliminary variety yield trials and seven lines will be tested in the uniform winter wheat scab nurseries this coming year. Three hundred wheat lines were selected from 2,470 F5 head-rows, and 50 of these lines will be evaluated in observation yield tests at two locations in the coming year. In addition, 2,800 head rows derived from diverse resistance sources were selected from 11 F4 populations and 41 F3 populations. One hundred F2, 238 F1, and 50 BC2 F1 populations were advanced. Type-II resistance derived from nine different sources is currently being back-crossed into 11 different SRWW backgrounds to develop NILs. Approximately 240 DH lines, derived from 12 single crosses produced in the spring of 1999, were assessed for scab resistance in Blacksburg, VA, and evaluated for agronomic traits in head row tests at Warsaw in spring 2000. Thirteen of these lines will be evaluated in yield tests this year. An additional 150 double haploid plants derived from 10 multiparent crosses and 300 haploid plants from three single crosses were produced in 2000. Using half-strength MS medium and applying precold treatment to embryos were found to be an effective means to increase the efficacy of haploid green plant regeneration.
M. Chappell, C.A. Griffey, J. Chen, T. Pridgen, W. Zhao, D. Nabati, and E.L.Stromberg.
Twenty (1997-98) and thirty (1998-99; 1999-00) SRWW genotypes were grown in replicated 100-ft2 plots using a randomized complete block design with two treatments. In the third year of field tests, two locations (Blacksburg, VA and Warsaw, VA) were utilized in order to procure an additional test site, study possible environmental differences, and test two methods of inoculation (conidial suspension versus scabby corn kernels). Replications 1-3 comprised the inoculated block and replications 4-6 the noninoculated control throughout the 3 years.
Significant differences were found among tested SRWW genotypes with respect to yield loss, test weight loss, FHB severity, FHB index, percentage of scabby seed, and DON concentration. Analysis of variance and LSD indicate that there is a continuous distribution of genotypes rather than easily definable classes. For each parameter, a statistically distinct grouping has been established for genotypes that performed well over multiple environments. In addition, losses were determined for all genotypes. Those that performed well over multiple environments will be discussed.
Test weight and yield losses are the basis for type-IV and V resistance, as described by Mesterhazy (1999). None of the genotypes in our study performed in the top 20 % in regards to yield loss over more than two environments. Those genotypes in the top 20 percent included Freedom, Ernie, NY87048W-7388, Roane, AgriPro Foster, and IL94-1549. Of these, NY87048W-7388, Freedom, and INW9824 were in the top 30 % with regards to yield loss over three environments. With regards to test weight loss, NY87048W-7388 and Roane were in the top 20 % over three environments and Freedom was in the top 20 % over two environments. The above-mentioned genotypes may provide breeders with useful parents for type-IV and V resistance to combine with type-II resistance. The newly released cultivar Roane from our program will provide producers with a more tolerant genotype to offset future FHB losses.
In analyzing parameters for assessing resistance, only those genotypes that have statistically low values for disease parameters will be mentioned. We concluded that FHB severity and FHB index were the best in-field measurements, with FHB severity being the least time consuming of the two. Over four environments, Ernie was the only genotype with significantly low FHB severity. Roane, INW9824, Freedom, NY87048W-7388, and AgriPro Patton showed low FHB severity over three of four environments. Ernie was again the only genotype with low FHB index values over four environments, with INW9824 and AgriPro Patton having low values over three of four environments. Percentage of visibly scabby seed may provide a quick method for breeders and producers to separate genotypes with regard to yield and test weight loss. No genotype showed low scabby seed values over four environments; however, Roane and INW9824 showed low scabby seed over three of four environments. DON toxin data also was correlated with yield and test weight loss over four environments. More importantly, toxin level is employed in grading of wheat post-harvest and can lead to significant price deductions. Coker 9803, VA96W-326, and NY87048W-7388 exhibited low toxin values over two of four environments.
Reference.
J. Chen, C.A. Griffey, W. Zhao, M.A. Saghai Maroof1, R.M. Biyashev, and W. Xie (Coöperator, University of Minnesota, St. Paul, MN 55108).
Objectives of the current study are to 1) determine the inheritance of scab resistance in three identified resistance sources; 2) elucidate the genetic relationship between type-II, III and IV resistance based on segregation for scab severity, DON content, and scabby seeds in four F2 populations; and 3) identify SSR molecular markers associated with type-II, III and IV resistance in source W14 using F2 population 'Pioneer 2684/W14'.
Three resistance sources, W14, Shaan 85, and Ernie, identified in previous studies, were crossed with susceptible SRWW cultivar Madison and/or Pioneer 2684. The F2 populations were evaluated in greenhouse tests using single floret inoculation procedures. W14 and Shaan 85 are improved type-II resistance sources derived from Sumai 3 and may also possess other types of resistance. Ernie is a SRWW cultivar that lacks any of the known scab resistant sources in its ancestry (Chen et al. 2000a, b).
Two complementary genes with major effects were found to confer scab resistance in W14 and Shaan 85 based on similar segregation patterns of F2 populations for type-II, III, and IV resistance characterized by disease severity, DON content and percentage of infected kernels (scabby seeds), respectively. One to two genes were found to confer resistance in the SRW wheat Ernie.
Significant positive correlations were found between disease severity (type-II resistance), DON content (type-III resistance), and scabby seeds (type-IV resistance) based on analysis of segregation data from four F2 populations. Highly resistant individuals with type-II resistance were found to also possess type-III and type-IV resistance; however, about 25 % of individuals with type-III and IV resistance did not express type-II resistance. Individuals with type-IV resistance also expressed type-III resistance in most cases.
The F2 population 'Pioneer 2684/W14' (150 individuals) was used to initiate mapping studies. Sixty-two SSR markers previously located on chromosomes 3B, 5A, and 6B (Röder et al. 1998) were selected and evaluated for polymorphism between parental lines. Of the 62 SSR markers, 21 (34 %) were polymorphic between resistant parent W14 and susceptible parent Pioneer 2684. Three markers, GMS389, GMS410, and GMS533, likely are associated with scab resistance and cumulatively accounted for 23, 18, and 19 % of the phenotypic variance for type-II, III and IV resistance, respectively in the current study.
Correlation and regression analyses indicate that a specific association may exist between SSR markers and type of resistance. GMS410, previously located on chromosome 5A, explained more of the phenotypic variance for DON production than for disease severity and scabby seeds; whereas, GMS533 explained more of the variation for disease severity and scabby seeds than for DON. GMS389 explained more of the variation for disease severity and DON than for scabby seeds. GMS533 explained less of the phenotypic variance for resistance in the current study than in that of Anderson et al. (2001) and may be the result of multiple alleles being present at this resistance locus and/or variable linkage distances between the marker and QTL in different genetic backgrounds. This is supported by analyses of DNA polymorphism of the three markers evaluated in the current study among resistance sources Sumai 3, Funo (one of parents of Sumai 3), Shaan 85, W14, VR95B717, and SRW wheat cultivars Ernie, Madison, and Pioneer 2684.
Additional molecular markers, SSR and other types, will be evaluated in current and other mapping populations to identify putative QTLs associated with resistance, saturate chromosome regions associated with resistance, and develop a skeletal map. This research has the potential to identify new QTLs associated with scab resistance, provide additional markers linked to previously reported QTLs and to identify markers that are effective across a variety of genetic backgrounds, all of which are essential for successful exploitation of marker-assisted selection.
References.