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The annual survey of 2006/2007 wheat growing season revealed the presence of thrity two physiologic races of wheat leaf rust fungus (Puccinia triticina Eriks.). The more frequent race was PTTS (23.07%) followed by race PTTT (12.30%), race TTTS (9.23%), race TTTT (6.15%), race PTTP (4.61%) and the two races PSTN and PTKS which were represented by (3.07%) each. The rest of races were represented by (1.53%) each. However, the more effective leaf rust resistance genes were i.e. Lr2a (73.84%), Lr2b (61.53%) and Lr36 (50.76%). On the other hand , the highest virulence were observed with Lr's i.e., 10; 11, 14b, 17; 16, 21, 30; and 2c, 3, 24 which were represented by 100% susceptibility; 98.46%; 96.92% and 95.38%, respectively. Leaf rust resistance gene(s) probably present in four Egyptian commercial wheat cultivars in comparison with nineteen leaf rust near-isogenic lines against 65 isolates, the cultivars Gemmiza 10, Giza 168 and Sakha 94 probably have Lr's i.e. 9, 16, 24, 11, 17, 30 and 14b. On the other hand, the tested Egyptian wheat cultivars were postulated to the lack of Lr2a, Lr2b and Lr36 which were proved to be the more effective genes in the present study. These results will remain an integral part of resistance breeding program and studies relevant to the epidemology and evaluation of virulence to leaf rust pathogen populations.

Wheat stem rust caused by Puccinia graminis f. sp. tritici is one of the most destructive wheat diseases worldwide. Identifying stem rust races in general, Ug99 lineage particularly, and determining resistance genes are critical goals for disease assessment. Thirty wheat varieties and monogenic lines with major stem rust resistance genes (Sr) were examined here over the course of three succeeding seasons from 2020 to 2022. Fourteen stem rust races have been identified in ten African countries, as well as Central and West Asia and North Africa (CWANA) and ten European countries. The Ug99 group (Clade I) included four races (TTKSK, TTKST, TTKTK, and TTKTT) and was reported in five African countries (Egypt, Kenya, Rwanda, Tanzania, and Uganda) and Iran, but none of the European countries. On the other hand, none of the races in Clade III-B (TTRTF) and Clade IV-B (TKTTF and TTTTF) were found in Egypt. Furthermore, Egyptian races were clustered separately from races identified from other countries, and six races were found only in Egypt, including PKSTC, RKTTH, TKTTC, TTTSK, TCKTC, and TKTTH. Races from Kenya, Tanzania, Uganda, Rwanda, and Iran were all closely associated with one another, according to correlation analysis. However, most races identified from other investigated regions, including Eritrea, Spain, Ethiopia, Morocco, Italy, Poland, Kenya, Tanzania, and Uganda, were adversely linked with Egyptian races. The diagnostic 350 bp long PCR fragment linked with virulence to Sr31, Clement (Sr31), and Brigardier (Sr31) was used to identify the TTKSK (Ug99) race. The identification of the regional associations and genetic diversity of newly emerged races within the Ug99 lineage of P. graminis tritici in Africa, Asia, and Europe is one of the key goals of this study. It will help plant breeders to develop new resistant lines against the virulent races, especially TTKSK (Ug99) and TTTSK. This helps in ensuring global food security in the context of climate change.

Stem rust of wheat caused by Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn., is the most destructive disease of wheat worldwide as well as in Egypt. It can causes high sever losses of wheat crops over wide areas during epidemic years. Hence, this study was carried out to detect the virulence dynamic and diversity of P. graminis f. sp. tritici in different locations and studying the efficacy of stem rust resistant genes in Egypt seedling stage. Stem rust collections were obtained from infected wheat stems throughout the survey of wheat fields and nurseries in three locations (Sids, El Sharkia and El Nubaria) during 2011/2012 growin g season. Whereas during 2012/2013 growing season the samples collected from six locations (Giza, Sids, Tag El Aiz, Sakha, El Sharkia and El Nubaria). Based on race analysis of stem rust populations, and race determination by inoculating stem rust differential hosts, the phenotypic characterization of P. graminis f. sp. tritici during 2011/2012 growing season resulted in identification of 86 races from 22 successful samples, all of them showed 1.16% frequency. Race BBBBC was a virulent on all the tested Sr genes, except Sr MCN, whereas race TTTTK was virulent on all the tested Sr except Sr 24. On the other hand, analysis during the next growing season revealed that, 123 races with a frequency ranged from 0.81% to 2.43% were identified. Race groups BB-, LG-, BJ-and TT-were common at the tested locations during the two growing seasons. Regarding stem rust resistant gene efficacy during the study Sr24, Sr38 and Sr31 exhibit the highest efficacy% (95.34, 91.86 and 87.21 respectively) during the two seasons. Thus, deployment of effective Sr genes such as Sr24, Sr38 and Sr31 in single cultivar through gene pyramiding has paramount importance as the additive effects of several genes gives the cultivar a wider base stem rust resistance along with periodic race survey.

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The inheritance of seedling and adult plant resistance against race no 49 of P. triticina and more virulent race mixture, was studied under greenhouse and field conditions sequentially. The monogenic line Lr34 was crossed with each of Lr,s : B, 11, 12, 13, 17, 24, 31 and 35.The line Lr10 was crossed with either of Lr9, 23 and 24. Finally the line Lr35 was crossed with each of Lr31 and 38. At seedling stage, the cross Lr34 + Lr24 was segregated in F2 as ratio 9(R): 7(S), while at adult stage no segregation was observed and the resistance was dominant. Lr35 + Lr38 at seedling and adult stage F2 segregated to 9 (R): 7(S). On the other hand Lr9 + Lr10 at seedling stage F2 segregated to 7(R): 9(S), but at adult stage appeared no segregated and dominance of resistance. Likewise Lr10 + Lr23 at seedling stage F2 segregated to 1(R): 15(S), while adult stage segregated to 13(R): 3(S). The cross Lr34 + Lr35 at seedling stage F2 showed no segregation, the dominance was in the side of susceptibility, while adult stage segregated to 13(R) : 3(S). The rest crosses of adult stage appeared segregated and dominance tend to the side of susceptibility, but at seedling stage all crosses showed no segregation and dominance tend to the side of susceptibility. This investigation confirmed on studying the genetics of resistance at adult stage that have expression rather than seedling stage.

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