Location: Cereal Crops Research2010 Annual Report
1a. Objectives (from AD-416)
The objectives of this cooperative research project are: 1) Characterize the genes/QTLs controlling resistance to three fungal diseases, including Fusarium head blight (FHB), tan spot, and Stagonospora nodorum blotch (SNB), in domesticated emmer wheat, and 2) to exploit the novel resistance genes for developing durum wheat germplasm adapted to the Northern Great Plains.
1b. Approach (from AD-416)
We previously identified a number of Persian wheat (Triticum turgidum L. subsp. carthlicum) and cultivated emmer wheat (T. dicoccum) accessions with resistance to FHB, tan spot, and SNB. We are currently transferring the resistance from some of these accessions into ND durum cultivars using the backcross method coupled with doubled haploid (DH) and single-seed descent (SSD). We have developed approximately 500 DH and 591 BC1-derived lines from crosses of five T. carthlicum and four T. dicoccum accessions with four durum cultivars (Lebsock, Ben, Mountrail, and Maier). In this project, we will evaluate the DH and BC1F1-derived (BC1F4 and BC1F5) lines for resistance to the three diseases in greenhouse and field nurseries. The 10 DH and BC1F5-derived lines with the highest level of resistance will be used as donors for the second cycle of introgression. In addition, we will initiate the introgression of the resistance from additional 10 T. carthlicum and T. dicoccum accessions with potential novel genes for a high level of resistance to the three diseases at the tetraploid level. The selected DH and BC1-derived lines and the T. carthlicum and T. dicoccum accessions first will be crossed with the durum cultivars Maier and Divide. The F1 hybrids will be backcrossed with their durum parents to produce BC1 seeds. All the BC1F1 plants will be evaluated for Type II FHB resistance in the greenhouse. The BC1F2 plants derived from the BC1F1 plants with low infection will be advanced to the BC1F5 through evaluation and selection. The resistance in the BC1F5-derived lines will be validated by evaluating the lines using a randomized complete block design (RCBD) with three replications in greenhouse and field nurseries in two locations. The BC1F5-derived lines with a high level of FHB resistance will be further evaluated for resistance to tan spot and SNB. The elite lines with multiple resistances will be used for further introgression and durum wheat breeding. To characterize the genes/QTLs controlling the resistance to FHB and SNB in tetraploid wheat, we have developed a population (LP749) consisting of 146 DH lines from a cross between the durum cultivar Lebsock and T. carthlicum accession PI 94749, which is resistant to FHB and SNB. The population will be used for developing linkage maps of all 14 chromosomes consisting of about 300 SSR markers, and then it will be evaluated for reaction to FHB and SNB. SNB evaluation will be conducted in three replicated experiments under controlled conditions. FHB evaluation will be performed for at least three seasons in greenhouse. The FHB and SNB phenotypic values will then be regressed on the marker data using single-factor regression, simple interval mapping, and composite interval mapping to identify QTLs associated with FHB and SNB resistance. In addition, we will initiate the development of a tetraploid recombinant inbred (RI) population derived from a cross between the emmer wheat accession PI41025 (with resistance to the three diseases) and the susceptible durum variety Ben. Approximately 150 RI lines will be developed from this cross using the SSD method and advanced to the F6:7 generation.
3. Progress Report
Introgression of the FHB resistance from T. carthlicum and T. dicoccum into ND durum cultivars was continued. In transferring FHB resistance from T. dicoccum and T. carthlicum to the durum cultivars, seven DH lines and 11 BC1F9 derived lines from the crosses of one T. dicoccum and four T. carthlicum accessions with the three durum cultivars were evaluated in field nurseries in Fargo and Langdon during the summer of 2010 to further confirm their enhanced FHB resistance. We previously selected four DH lines, six BC1F4-derived lines, and 19 T. dicoccum accessions as the FHB resistance sources. In 2008, the selected DH and BC1F4-derived lines and 19 T. dicoccum accessions were crossed and backcrossed with the durum cultivars. A total of 6,300 BC1F1 plants derived from 106 crosses were advanced to BC1F2 generations. From the greenhouse and field testing of FHB resistance in BC1F2-3 plants during the spring and summer of 2009, about 2,000 BC1F3-4 plants with putative resistance were selected and were further evaluated in the greenhouse, and from which, 56 BC1F3 and 99 BC1F4 plants were selected. In the summer of 2010, the BC1F4-5 progenies derived from the selected BC1F3-4 were evaluated in a field nursery in Langdon. Also, another set of BC1F4 and BC1F5 progenies derived from 128 BC1F3 and 139 BC1F4 plants were both evaluated in field nurseries in Fargo and Prosper. In addition, based on plant height, maturity, and general morphology, about 3,500 heads have been selected among 30,000 BC1F2 plants grown in two F2 nurseries in Casselton and Fargo, and 1396 of the BC1F3 head selections were initially evaluated in the field nursery in Langdon and Fargo in the summer of 2010. The lines with a combination of improved FHB resistance and good agronomic performance will be selected for further evaluation in greenhouse and field in the coming seasons. Regarding characterization of the genes/QTLs controlling FHB resistance: Evaluation of FHB resistance in LP749 in the greenhouse and field trials (Fujian, China) in 2009 showed that the population had inconsistent resistance, indicating the population was not suitable for identifying major resistance genes. Therefore, we developed a tetraploid population (BP025) of 200 recombinant inbred (F2:7) lines from a cross between the emmer wheat accession PI 41025 (with resistance to FHB, SNB and tan spot) and the susceptible durum variety Ben. Population BP025 will be evaluated for Type II resistance to FHB in the greenhouse and to identify QTLs conferring FHB resistance. However, it should be noted that our previous use of the LP749 allowed identification of major QTLs conferring tan spot and SNB resistance, and the newly identified genes along with the closely linked markers will facilitate the improvement of foliar disease resistance in tetraploid wheat. ADODR monitoring activities to evaluate research progress included regular discussions between ARS and NDSU collaborators.