The influence of environment on the expression of Russian wheat aphid; Diuraphis noxia (Kurdjumov) resistance

[摘要] English: The purpose of this study was to investigate the effect of variations in climatic factors such as vernalization periods, minimum- and maximum temperatures and rainfall on the expression of host plant resistance to RWASA1 (original biotype) and RWASA2 (newly identified biotype) in the eastern Free State of South Africa between 2003 and 2006. Climatic records indicate above-average temperatures and reduced rainfall occurred in the Eastern Free State in 2003 to 2005 probably contributing to widespread RWA damage on dryland wheat crops. Greenhouse experiments confirmed that vernalization did not alter RWA plant resistance ranking of wheat entries. However, infestation did produce significant damage by RWASA2 on Elands, Gariep and Limpopo but not on CItr 2401 (containing Dn-4 and another unidentified Dn-gene) and Halt (Dn-4). Resistance rating to RWASA1 of Halt, Komati and Matlabas in greenhouse tests at 18°C/12°C, 22°C/16°C and 26°C/22°C shifted to less resistant- or susceptible categories and changed the ranking of SST 966 as temperature increased. Also, RWASA2 ratings at increased temperature shifted Halt to a more resistant category and changed rankings of Komati and SST 399. Komati, Matlabas, SST 966 or SST 399 did not express any host plant resistance to RWASA2 through leaf area or leaf roll and chlorosis supporting the susceptible ratings that were given to the same varieties in the visual screening test. Seeddressing in AMMI results for 2003 to 2006 were able to increase yields under higheryielding conditions in seasons when moisture- and heat stress occured and the yield performance of cultivars was stabilized irrespective of whether they contained genetic resistance to RWA. Identifying new RWA resistance donors provide an excellent opportunity to exploit novel germplasm with potential new genetic variance for RWA resistance, as well as other beneficial traits such as drought-tolerance. Three germplasm pools were evaluated for this purpose. Twenty-one entries from the Stillwater, Oklahoma/SGI RWA resistance pool expressed resistance against RWASA2 in the seedling test and where generally well adapted to local conditions. Seedling evaluation of the CIMMYT pool revealed twenty entries with acceptable resistance to RWASA2 though field adaptability particularly to biotic stress was occasionally lacking. Twenty entries from the Iranian pool were resistant to RWASA2 though unadapted for resistance to stripe rust; Puccinia striiformis Westend f.sp tritici Eriks., occurring in the Eastern Free State.

[发布机构] University of the Free State