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Development of a Recombinant Inbred Line (RIL) Population in Soft White Winter Wheat Arron Carter 1 , Jenny Hansen 1 , Thomas Koehler 1 , Xianming M. Chen 2 , and Robert Zemetra 1 1 University of Idaho, PSES Department, Moscow, ID 83844-2339 2 USDA-ARS, Pullman, WA 99164 Abstract Recombinant inbred line (RIL) populations are very useful to develop molecular markers in wheat. One market class that has been under-represented in RIL populations has been soft white winter wheat. A RIL population of 314 individuals was developed using a cross between Brundage and Coda. Brundage is an awnless, common, soft white winter wheat. Coda is an awned, club, soft white winter wheat. These two parents differ for many agronomic and quality traits including dwarfing genes, stripe rust resistance, and yield potential. In the 2003-2004 growing season, F 6 derived F 7 lines were planted in headrows for seed increase. During the 2004-2005 growing season the 314 individual lines plus parental controls were planted in a completely randomized block design with four replicates at two locations. Data was collected on agronomic traits through the growing season. The experiments were treated with a fungicide to minimize confounding yield data with stripe rust resistance. Response to stripe rust was evaluated in separated untreated trials. Differences were observed for both qualitative and quantitative traits in the RIL population. Heritabilities for traits were calculated by dividing the additive genetic variance by the total phenotypic variance. Data collected will be used to find associations between the traits of interest in soft white winter wheat and molecular markers to facilitate MAS in this market class in the future. Introduction Recombinant inbred line (RIL) populations are very useful tools to develop molecular markers in wheat (Roder et al., 1998) and to map quantitative trait loci (QTL) or specific genes (Adhikari et al., 2003, Zhou et al., 2004). One market class that has been under-represented in RIL populations has been soft white winter wheat. In addition, many of the currently available RIL populations have been in wheat that is not adapted to the growing region of the Pacific Northwest (PNW). Hence, a RIL population was created from a cross between Brundage and Coda, two cultivars adapted to the PNW. While many RIL populations are developed to look at one or two specific traits, this population was developed to maximize the amount of genetic segregation in as many traits as possible. The two parents differed for traits such as head type, awn type, dwarfing genes, heading date, yield potential, end-use quality, tiller number, straw strength, winter hardiness, stripe rust (Puccinia striiformis ) resistance, and foot rot ( Pseudocercosporella herpotrichoides) resistance. Besides being useful for developing molecular markers associated with specific traits, RIL populations can be used to calculate heritability values for specific traits. Materials and Methods Development of RIL Population: A RIL population of 314 individuals was created from a Brundage X Coda cross. Brundage (‘Stephens’/‘Geneva’) is an awnless, common, soft white winter wheat developed at the University of Idaho (Zemetra et al., 1998). Brundage is an early heading wheat with high yield potential, excellent end-use quality, and low high-temperature adult plant (HTAP) resistance to stripe rust. Coda (‘Tres’//‘Madsen’/‘Tres’) is an anwed, club, soft white winter wheat developed by USDA-ARS in Pullman, WA (Allan et al., 2000). Coda is a late heading wheat with high yield potential, good end-use quality, and moderate HTAP resistance to stripe-rust. Single seed decent was used to arrive at the F 6:7 population which was planted in the field. Field Testing: In the fall of 2003, the RIL population was planted in the field for seed increase. The harvested seed was planted in the fall of 2004 in a randomized complete block design at two locations, Moscow, ID and Genesee, ID, with four replicates at each location. Seventeen plots of each parent were added to serve as controls. Plots were 1.5 feet wide by 15 feet long. Data was collected on head type, heading date, plant height, lodging, and grain yield. This trial was sprayed with a fungicide (Folicur 3.6) to control for stripe rust. A separate unsprayed trial, at Moscow, ID, was used to evaluate stripe rust resistance. Headhills of each line, along with the two parents, were planted in a 5 by 5 block, with 14 blocks total. Stripe rust infection was allowed to occur naturally and data was collected weekly over a six-week period. Data included infection type (IT) on a scale of 0-9 and infection percent (0-100%), which was a percentage of the plant infected. Analysis: Range and mean numbers were generated for the population as well as the parents at each location. Heritabilities were calculated using SAS 9.1 (SAS Institute Inc. 1989) using a SAS code presented by Holland et al. (Holland et al ., 2003). The traits heading date, plant height, grain yield and stripe rust resistance were selected for analysis to demonstrate the variation found in this population. Results and Discussion Data for heading date, plant height, and grain yield were recorded and analyzed with means and ranges reported in Table 1 for each location. Transgressive segregation was observed, with individual lines being lower than the low parent and higher than the high parent. Heading Date: Means for heading data (Julian) were on average 4 days later in Genesee than in Moscow, with the mean of the population falling in the middle of the mean for the two parents. The range for the RIL population was similar in both locations, while there was a large difference in the parents. Brundage was 152-157 in Moscow, while in Genesee it was 157-164. Coda, on the other hand, had a 4 day range in Moscow, 164-168, while in Genesee it was increased to 10 days, 161-171. Plant Height: For the RIL population, Moscow had a 10 cm height increase over Genesee. The ranges were again similar, with the range in Genesee dropping 8 cm from 46-142 cm in Moscow to 38-135 cm in Genesee. Brundage had a consistent height in both locations, having only a 2.5 cm mean difference. Coda had a significant height reduction in Genesee, with a mean 13 cm shorter than Moscow. The range followed a similar pattern. Grain Yield: Yield, as expected, was the most variable of the three traits. The RIL population had a mean yield of 9,146 kg/ha in Moscow and 5,918 kg/ha in Genesee. The low end of the range was similar at each location, while the high end of the range was 14,122 and 9,213 kg/ha in Moscow and Genesee, respectively. This shows there was a yield limiting factor in Genesee during the 2004-2005 growing season. The parental lines showed similar results. Brundage had a mean yield similar to the RIL population in Moscow at 9,213 kg/ha. This dropped 2,959 kg/ha when grown at Genesee, with a mean of only 6,254 kg/ha. Coda had a 874 kg/ha increase over the RIL population in Moscow, but also dropped to a mean of 6,254 kg/ha when grown at Genesee, a 3,766 kg/ha decrease. On average, both parents yield more than the population at both locations. Stripe Rust Resistance: Stripe rust was first seen in the field on May 12th, and the first week of data was collected on May 18th. As the weeks progressed, differing responses to the disease were observed in both the population and the parents. Table 2 presents some specific lines along with the controls which show the four differing responses. Line R-335 shows a resistant response to stripe rust. Line R-394 shows a highly susceptible response to the disease. Figure 1 shows these two lines. The other five lines in Table 2 show varying responses to the disease. Most lines showed an increasing or steady infection type rating over the six week period. Once infected, most lines showed an increase in area infected as the season progressed. Brundage is a cultivar that is moderately susceptible to stripe rust. Coda showed an initial resistance response, but showed susceptibility to a late infection. Heritabilities: Heritabilities were determined using combined data from both locations. The heritability for heading date was h 2 =0.75. The heritability for plant height was h 2 =0.91. The heritability for yield potential was h 2 =0.48. Heritability was not calculated for stripe-rust resistance. Estimates for heritability are in accordance with the type of trait they are predicting. Plant height is a qualitative trait and should have a high heritability. Yield potential is a quantitative trait, and hence would have a low heritability. The variation in the two environments also slightly lowers the estimates for heritability. Conclusion Based on the results, we were successful in creating a RIL population that is segregating for both quantitative and qualitative traits. Based on the level of segregation observed, this population will be a useful candidate to do molecular mapping in soft white winter wheat. It will be of great interest to the PNW region since the parents used in deriving the population are adapted to this growing region, although this does not limit its usability in other growing regions. Future Work • Evaluate end-use quality of the RIL population and identify quality traits with the necessary level of segregation for the development of molecular markers. • Calculate heritabilities for end-use quality traits. • Begin molecular work of mapping specific genes and QTL’s. References Adhikari, T.B., Anderson, J.M., and Goodwin, S.B. 2003. Identification and molecular mapping of a gene in wheat conferring resistance to Mycosphaerella graminicola. Phytopathology 93:1158-1164. Allan, R.E., Morris, C.F., Line, R.F., Anderson, J.A., Walker-Simmons, M.K., and Donaldson, E. 2000. Cultivar registration of ‘Coda’ wheat. Crop Science 40:578-579. Holland, J.B., Nyquist, W.E., and Cervantes-Martinez, C.T. 2003. “Estimating and Interpreting Heritability for Plant Breeding: An Update” Plant Breeding Reviews, Vol. 22, pp. 9-112. Edited by Jules Janick. John Wiley & Sons, Inc. Roder, M.S., Korzun, V., Wendehake, K., Plashke, J., Tixier, M., Leroy, P., and Ganal, M.W. 1998. A microsatellite map of wheat. Genetics 149:2007-2023. SAS Institute Inc. 1989. SAS/STAT user’s guide, version 6, 4th edition. SAS Institute Inc., Cary, N.C. Zemetra, R.S., Souza, E.J., Lauver, M., Windes, J. Guy, S.O., Brown, B., Robertson, L., and Kruk, M. 1998. Cultivar registration of ‘Brundage’ wheat. Crop Science 38:1404. Zhou, W., Kolb, F.L., Yu, J., Bai, G., Boze, L.K., and Domier, L.L. 2004. Molecular characterization of Fusarium head blight resistance in Wangshuibai with simple sequence repeat and amplified fragment length polymorphism markers. Genome 47:1137-1143. Table 1 Means and ranges for Brundage, Coda, and the RIL population created from their cross, over two locations, Moscow, ID, and Genesee, ID. Traits reported are heading date (Julian), plant height (centimeters), and grain yield (kg/ha). Figure 1 On the left, RIL line R-394 showing a highly susceptible response to stripe rust. On the right, line R-335 showing a resistant response stripe rust. Table 2 Individual lines from the RIL population representing the types of disease reactions that were seen in the field at Moscow, ID. The two parental lines, Brundage and Coda, are also listed. Infection type (IT) is rated on a scale of 0-9, with 9 being the most severe. Also reported is the percentage of the plant covered (IT%) from 0-100%. 4371-8137 6254 8070-12912 10010 Coda 4775-8002 6254 6927-11836 9213 Brundage 3026-9213 5918 2892-14122 9146 RIL Population Yield (kg/ha) 79-107 90 91-114 102 Coda 76-91 84 81-91 86 Brundage 38-135 86 46-142 97 RIL Population Height (cm) 161-171 168 164-168 165 Coda 157-164 159 152-157 155 Brundage 154-173 164 152-171 160 RIL Population Range Mean Range Mean Heading Date (Julian) Genesee Moscow 80 5 40 5 10 5 5 3 0 0 0 0 Coda 70 3 70 5 50 5 50 5 15 5 5 5 Brundage 90 9 80 8 70 9 60 8 30 8 15 7 R-394 80 5 40 5 15 5 15 3 0 0 0 0 R-625 70 7 40 5 5 3 0 0 0 0 0 0 R-620 30 3 20 3 10 3 5 7 0 0 0 0 R-500 50 3 20 3 5 3 0 0 0 0 0 0 R-649 20 3 20 3 5 3 5 3 0 0 0 0 R-571 5 3 10 3 5 3 5 3 0 0 0 0 R-325 0 0 0 0 0 0 0 0 0 0 0 0 R-335 % IT % IT % IT % IT % IT % IT Line Week 6 Week 5 Week 4 Week 3 Week 2 Week 1
