Identification and characterization of resistance gene analog [RGA] and the leaf rust resistance gene Lr21 from the wheat cultivar Giza 168

Leaf [brown] rust caused by Puccinia triticina is a fungal disease of wheat [Triticum aestivum L.] that causes significant yield losses annually in many wheat-growing regions of the world. Host-plant resistance is the most economically viable and environmentally responsible method for controlling Puccinia triticina, the causal agent of leaf rust in wheat. The identification and utilization of new resistance sources is critical to continue the development of improved cultivars. The objective of this work was to identify defense-related genes against rust in the Egyptian rust resistant cultivar Giza168. Specific primers were designed on the basis of converse motifs of cloned resistance genes of the resistance gene analog [RGA] and leaf rust resistance gene [Lr21] in wheat [Triticum aestivum L.]. The designed PCR primers were subsequently used for RT-PCR using RNA isolated from a resistant variety to amplify fragments of 445 bp and 235 bp for RGA and Lr21 genes, respectively. The amplified products were cloned, sequenced and submitted to the GenBank. The nucleotide sequences of the amplified fragments were aligned with their corresponding genes using the BLAST. The expressions of the two genes in the infected and healthy plants were studied using RT-PCR. The RGA expression was induced and detected by RT-PCR, which is up-regulated by fungal infection. The Lr21 expression was detected on both healthy and infected plants, although the expression was higher in infected plants