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United States Department of Agriculture

Agricultural Research Service

Research Project: Wheat Stem Rust Cooperative Research - Texas A&m University - College Station

Location: Hard Winter Wheat Genetics Research Unit

2013 Annual Report


1a.Objectives (from AD-416):
Develop elite hard winter wheat genotypes that incorporate multiple resistance genes that are effective against new African races of wheat stem rust.


1b.Approach (from AD-416):
Bread wheat germplasm lines with effective major gene and/or minor gene resistance against new African races of stem rust are being developed by USDA-ARS as well as many other institutions. These resistance donors will be crossed with multiple local elite breeding lines with high yield potential, grain quality, and tolerance to biotic and abiotic stresses. Good stewardship of valuable new resistance genes requires that they not be exposed singly in commercial cultivars. Endemic stem rust resistance genes, such as Sr24, Sr36, or Sr1A.1R, while very useful against most races, are not effective against all African races, and are not sufficient protection for new resistance genes. Therefore, the goal is to combine two or more new major genes into elite backgrounds. Minor gene or adult plant resistance genes are recommended as a supplement to major gene resistance. Minor genes are expected to be much more durable and do not require special stewardship protocols.

In order to produce commercially competitive varieties of the future, new stem rust resistance genes must be incorporated into a forward breeding program. In addition, a backcross breeding program is required both for parent-building and as a hedge if commercially acceptable resistant varieties are needed in the short term. Rapid breeding methods, such as doubled haploids, will be needed to achieve results as quickly as possible.

Phenotypic selection for resistance using common North American races will be difficult in most backgrounds due to the high frequency of endemic stem rust resistance genes. Therefore, marker-assisted selection for new resistance genes will be necessary. Molecular markers are available or under development for virtually all new sources of stem rust resistance. Marker genotypes will be generated locally or in a high throughput facility at the USDA-ARS Regional Small Grains Genotyping Laboratory in Manhattan, KS. Resistance of advanced lines against African races of stem rust will be confirmed by field testing at cooperative research facilities in Kenya or at the USDA-ARS Cereal Disease Laboratory. Testing for agronomic traits, yield, and quality will be performed as usual by the breeding program.


3.Progress Report:

Specific objectives for Years 1, 2, and 3: 1) Make Single, one-way crosses designed to combine Ug99 resistance genes into adapted Texas wheat backgrounds 2) Make two-way crosses in the second year greenhouse and work with the USDA-ARS to test marker genotypes for resistance genes 3) Use doubled-haploid technology to speed up generation advance and start deriving adapted lines for South, Central, and Northeast Texas that combine pyramided genes for Ug99 resistance with high yield potential, superior quality and resistance to other biotic and abiotic stresses prevalent in Texas

The most significant accomplishments: 1) The most significant accomplishment of the past two years: i. A number of 225 cross combinations to incorporate resistance to Ug99 based on Sr2, Sr24, 1A.1R, Sr25, Sr22, Sr36, Sr32, Sr35, Sr39, and Sr40 was made in 2011. ii. A number of 201 four-way crosses were made in spring 2012 to combine as many favorable genes as possible. iii. More promising cross combinations were made again in 2013 iv. The F2 generation arising from the 2012 F1’s were increased in 2013. Leaf tissue has been harvested and we getting ready to screen these for the presence of markers associated with the above listed genes 2) The major accomplishments over the life of the project, including their predicted/actual impacts: See above. 3) The expected accomplishments during the next year: Work with the USDA-ARS to test marker genotypes for resistance genes. The 201 F1 crosses were increased in a greenhouse at College Station from November 2012 to March 2013. Plant tissue from these lines was harvested in January 2013 and will be screened for markers at our genomics lab at the main campus in College Station. Best combinations will be advanced in the breeding pipeline using doubled-haploid and conventional breeding methods. 4) Any technologies that have been transferred and to whom: This is an expected future outcome. 5) When any technologies are likely to become available to end users: Doubled-haploid technology will be used to speed the release of lines that contain pyramided resistance to Ug99 within the next seven years 6) A listing of publications produced during the period of 1 October- 30 September of the current year: None.


Last Modified: 12/26/2014
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