Characterization of the genetic structure and the physiological races of Puccinia triticina is a growing necessity to apply host genetic resistance against wheat leaf rust as a successful control strategy. Herein, we collected and identified about 130 isolates of P. triticina from 16 Egyptian commercial wheat cultivars grown at different locations, over two seasons (2019/2020 and 2020/2021). The 130 isolates of P. triticina were segregated into 17 different physiological races. TTTST and TTTKS were the most common virulent races, whereas TTTST and MTTGT were the most frequent races. The races were classified into three groups, based on their distinct DNA band sizes (150 bp, 200 bp, and 300 bp) after RAPD analysis. The new wheat cultivars (Sakha-94, Sakha-95, and Shandweel-1) infected with the most virulent race (TTTST), Gemmeiza-12, and Misr-3 were resistant to all physiological races. The resistance of these cultivars was mostly due to the presence of Lr19- and Lr28-resistant genes. Our results serve as a warning about emerging aggressive races capable of supplanting resistance to leaf rust, and help in the understanding of the pathotype–cultivar–location association and its role in the susceptibility/resistance of new wheat cultivars to P. triticina.

The purpose of the present study is to determine the effect of wheat yellow rust caused by Puccinia striiformis f. sp. tritici on quantitative and qualitative grain yield losses, in addition to predict them through regression model for each tested wheat variety, i.e.

eaf rust (Puccinia triticina Eriks.) and stem rust (Puccinia graminis f. sp. tritici) have been considered to be the most common rust diseases of wheat. Twelve Egyptian wheat cultivars were evaluated for resistance at seedling stage using four slow rusting components i.e. incubation period, latent period, pustule density /cm 2 and pustule size/mm 2. Additionally three parameters of slow rusting resistance at adult plant stage, rust reaction, infection response and rust severity (%). Rate of leaf and stem rust increase (r-value) and area under disease progress curves (AUDPC) were determined under artificial infection with the single race of the two fungi at the adult plant stage in greenhouse experiments. The five cultivars; Misr 3, Sids 12, Shandweel 1, Sakha 94 and Gemmeiza 12 showed low values of incubation period, pustule density/cm 2 , pustules size/mm 2 , infection response, r-value and AUDPC to wheat leaf and stem rust due to characterized as slow rusting resistance cultivars. Also, the cultivar Giza 168 showed complete resistance to leaf and stem rust, while, the two cultivars Misr 1 and Beni Sweif 5 showed slow rusting to leaf rust but characterized as highly susceptible and fast rusting cultivars to stem rust. Correlation between latent period and area AUDPC was negative and strong (r = 0.70) in leaf rust but in stem rust was (r = 0.46). Thus the slow rusting resistant wheat cultivars can be used for developing high-yielding with more durable resistance to leaf and stem rust diseases in bread wheat.

W HEAT leaf rust, caused by the fungus Puccinia triticina Eriks., is a destructive disease found throughout common wheat production areas worldwide. Fifty wheat leaf rust monogenic lines were tested with five of Puccinia triticina pathotypes, i.e. BJPPQ, LQFDS, PHFPG, PTPDN, TRFDJ at four stable temperatures (30 0 C, 25 0 C, 20 0 C and 15 0 C). The wheat monogenic lines viz. Lr 16, Lr 17 and Lr 23 were more resistant at 25 0 C, while these genes were found susceptible at 15 0 C, 20 0 C and 30 0 C to all tested races. Eight monogenic lines, i.e. Lr11,

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.

This research has been carried out to study the disease incidence and genetic analysis of adult plant resistance to leaf rust in eight Egyptian wheat varieties, Misr1, Misr2, Misr3, Gemmeiza11, Gemmeiza12, Sids1, Shandweel-1 and Sakha94 crossed with Triticum spelta saharensis (T.s.s.) as a highly susceptible tester wheat variety at Bahtem Agricultural Research Station, Agr. Res. Center during 2018-2021 growing seasons. The nine wheat genotypes and F2 plants of eight crosses with T.s.s. were estimated to disease incidence measurements and quantitative genetic analysis to leaf rust adult plant resistance. The nine wheat genotypes tested were divided into two resistance groups according to disease incidence measurements (FRS, r-value and AUDPC), the first group having the high and moderate levels of partial resistance i.e., Misr1, Misr2, Misr3, Gemmeiza12, Shandweel-1 and Sakha94, this group is of major importance for efficacious breeding for leaf rust durable resistance, while cultivars Gemmeiza11, Sids1 and T.s.s. were included in the second group with high values of FRS, r-value and AUDPC. The F2 populations, F1 and parents for each of the eight crosses were tested for adult plant disease severity. The quantitative analysis of the F1and F2 mean value of leaf rust severity in the eight crosses was mostly lower than the mean value estimated for their respective mid parents and indicated that rust resistance was partial dominance expecting crosses (T.s.s. × Sids1) in F1 and (T.s.s. × Gemmeiza11) in F2, the positive values were higher than the respective mid-parents, which indicates existence an over-dominance towards susceptibility of these crosses. The heritability in its broadsense estimated from the variance parents F1and F2 for partial leaf rust resistance, is considered to be high in magnitude, since the values ranged from 63.99 to 96.51%. The number of genes of each analyzed parent is controlled by three, two and a pair of genes. Generality, this outcome in the adult plant stage suggests which selection for this trait may be possible in the first segregating generations. Although the delay would be more efficacious, according to the important role that dominance impacts play in trait expression the selection of resistant adult plants in the subsequent generation of segregation would be useful for the development of a high-yielding wheat genotype under Egyptian condition.

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