Submitted to: Oat International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 6, 2008
Publication Date: June 28, 2008
Citation: Rines, H.W., Porter, H.L., Carson, M.L. 2008. Suppressors of oat crown rust resistance in interspecific oat crosses. In: Proceedings of the 8th International Oat Conference, June 28-July 2, 2008, Minneapolis, Minnesota. Available: http://wheat.pw.usda.gov/GG2/Avena/event/IOC2008/IOCposter/V-7Rines.pdf. Technical Abstract: Attempts to transfer disease resistance genes between related species may be hindered by suppression, or lack of expression, of the trait in the interspecific combination. In crosses of diploid oat Avena strigosa (Schreb.) accession CI6954SP with resistance to oat crown rust Puccinia coronata f. sp. avenae (Eriks.) by susceptible hexaploid A. sativa (L.) cv. Black Mesdag produced a susceptible interspecific F1. The suppressor effect segregated in backcrosses allowing recovery of a derived hexaploid with crown rust resistance. The recovered crown rust resistance showed the same rust isolate resistance specificity as Pc94 recovered earlier by Chong and co-workers from a different A. strigosa accession. Crossing the A. strigosa/Black Mesdag F1 colchicine-doubled C1 by lines with known Pc genes revealed similarities to the pattern of suppression that has been described in an oat line with resistance gene Pc38. Both lines suppress specifically Pc94 and Pc62 but not Pc58; however, the A. strigosa-derived suppressor differs in also suppressing Pc63. In more recent crosses of a different resistant A. strigosa accession, PI258731, by susceptible A. sativa cvs. Black Mesdag, Otana, and Ogle, no suppression was observed and the interspecific F1 plants showed full resistance. Suppression of resistance expression also was found in crosses of highly resistant accessions of tetraploid A. murphyi P10, P11, P12, P13, and P17 by A. sativa cv. Ogle with all F1 plants being susceptible. Suppression of the crown rust resistance has not been overcome or avoided either by extensive backcrossing of the derived materials or by making the initial crosses with five other susceptible A. sativa genotypes, including cvs. Otana, Marvellous, Sun II, Gopher, and Black Mesdag. Crosses of resistant accessions recently identified in tetraploid A. barbata to A. sativa cultivars will be tested to determine if suppression will be a problem in transfer of the A. barbata crown rust resistance.