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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC CHARACTERIZATION AND UTILIZATION OF DISEASE RESISTANCE GENES IN TETRAPLOID WHEAT

Location: Cereal Crops Research

2009 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

We continued our effort to transfer the FHB resistance from T. carthlicum and T. dicoccum into ND durum cultivars using the backcross method coupled with double haploid (DH) and single-seed descent (SSD). We tested 98 DH and 66 BC1F5 derived lines from the crosses of five T. carthlicum and four T. dicoccum accessions with the four durum cultivars (Lebsock, Ben, Mountrail, and Maier) in field nurseries in Prosper and Langdon in 2008. Based on field testing, we selected 55 DH and BC1F6 lines with FHB resistance and further tested these lines in a FHB field nursery in Jianyang, China. Forty-five DH and BC1F6 lines were also tested in the greenhouse. In the spring of 2009, 72 lines (28 DH and 44 BC1F7 lines) were planted in field nurseries in Prosper and Fargo and 15 lines (8 DH and 7 BC1F7 lines) have been included in the Uniform Regional Scab Nursery in Langdon. The DH lines and BC1F4-derived lines with FHB resistance were used for the second cycle of introgression. In addition, the introgression of the FHB resistance from an additional 19 T. dicoccum accessions with a high level of FHB resistance was initiated. The selected DH and BC1F4-derived lines and 19 T. dicoccum accessions were crossed and backcrossed with the durum cultivars. About 6,300 BC1F1 plants derived from 106 crosses were advanced to BC1F2 generations. About 2,000 BC1F2 plants were evaluated in the greenhouse in the spring of 2009.

For characterizing the genes/QTLs controlling the resistance to FHB, tan spot, and SNB in tetraploid wheat, a population (LP749) consisting of 146 DH lines from a cross between the durum cultivar Lebsock and T. carthlicum accession PI 94749 was developed, and a whole genome linkage map based on this population that spanned over 2,000 cM was constructed using 280 SSR markers. The DH population and the whole genome maps were then used to identify QTLs associated with FHB, tan spot, and SNB resistance. So far, five QTLs for tan spot resistance and five QTLs for SNB resistance have been identified. For QTL analysis on FHB resistance, the DH population has been evaluated for one season in the greenhouse and in an FHB field nursery in Jianyang, China. The preliminary QTL analysis indicated that a major QTL is located on chromosome arm 2AL, whereas the other two minor QTLs were located on chromosome arms 3AL and 6BS. In addition, we initiated the development of a tetraploid recombinant inbred (RI) population derived from a cross between T. dicoccum accession PI41025 and the susceptible durum variety Ben. Over 200 F2 individuals have been produced from this cross and they will be advanced to the F7 using the SSD method in coming seasons.

ADODR monitoring activities to evaluate research progress included face-to-face meetings and discussions between project participants throughout the fiscal year.


Last Modified: 4/18/2014
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