GENETIC STUDIES ON BREAD WHEAT RESISTANCE TO STEM RUST

Abstract

Screening experiment was performed on twelve varieties and lines of bread wheat (Ttriticum aestivum L.) to select the most contrasting genotypes in stem rust susceptibility. The results of the experiment revealed that the resistant variety is (Misr1) and the two most stem rust susceptible lines are (Line37 and Line92) according to stem rust reaction. Crosses were carried out between the resistant parent (Misr1) with each of the two susceptible parents as well as between the two susceptible parents (Line37 and Line92) to obtain the F1 kernels. Some of the F1 kernels were sown in the field and self-pollinated to obtain the F2 plants for each cross. These three selected parents, their F1 and the most resistant and susceptible F2 plant groups for the three crosses were evaluated for their response to stem rust resistance by recording some stem rust–related traits. However, the infection reduced the values of all yield related traits except spike length and number of spikelet’s/spike traits. The three parents, their F1 plants and some individual plants of the two contrasting F2 plant groups as the offspring of the crosses between the most resistant and the two most susceptible. The three crosses were used to develop some molecular genetic markers associated with stem rust resistance using SSR and STS protocols. The results indicated that the presence of two positive markers out of the three SSR and three STS primers which used in this study. Sr2 (SSR) and Sr25 (STS) primers produced positive markers at fragment sizes of 120 and 130 bp, respectively, for stem rust resistance that could be considered as reliable markers for stem rust resistance in bread wheat (Ttriticum aestivum). Key words: Wheat, Stem rust, Stem rust and yield related traits, Molecular markers for stem rust, SSR & STS markers.