Evaluation of New Sources of Resistance to Wheat Stripe Rust (Puccinia striiformis f. sp. tritici), under Egyptian Field Conditions

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is the most destructive rust disease in Egypt and worldwide. The current study was performed during 2014/2015 and 2015/2016 growing seasons to evaluate 57 wheat genotypes, selected from a total of 554 wheat genotypes from CIMMYT for their field reaction to stripe rust infection, as the new sources of resistance. Four epidemiological parameters, i.e. FRS %, ACI, AUDPC and rAUDPC, as well as 1000 kernel weight were used as criteria to evaluate stripe rust resistance and yield potentiality. The analysis of variance data depicted extensive and high significant differences among different wheat genotypes under study for their response to stripe rust infection each year. Out of 57 wheat genotypes, only 12 wheat promising lines; no^'s 1, 2, 3, 12, 13, 14, 16, 21, 22, 25, 50 and 51 had high resistance potentiality to be used as new sources to enhance the level of stripe rust resistance in the local breeding cultivars, making it possible to minimize the reliance on fungicides without impairing disease control. Correlation analysis gave an evidence to the importance of all parameters under study, especially FRS (%) and ACI as good indicators for the evaluation of adult plant resistance (APR) in the tested wheat lines against stripe rust under field conditions. High heritability estimates (up to 99%) and moderate to high values of genetic advance, expected from selection, were obtained for all the studied traits, revealing that most of the phenotypic variations were due to genetic factors or genetic structure of the studied genotypes. Also, it is an indicative for the possibility to achieve high success in recovering the desired genes for stripe rust resistance in future generations. Moreover, it means that the genetic variations were less affected by the changes in environmental conditions from season to another season.  It could be concluded that FRS (%) and ACI are considered to be more appropriate indicators, rather than AUDPC and rAUDPC for screening large numbers of breeding materials, because they were more easily to be applied or handled for the breeders that facilitates the success of selection process, during a national breeding program without more time consumption.