Wheat stripe rust (Puccinia striiformis Westend f. sp. tritici; Pst) is a severe disease that affects wheat-growing areas worldwide. In the last few years, Pst head infection (PstHI) was recorded to cause severe yield damage in Egypt. Little information is known about PstHI. In the current study, a set of 34 Egyptian cultivars were evaluated for their Pst foliar infection (PstFI) and PstHI in two growing seasons (2021 and 2022) in Egypt. High genotypic variations in PstFI and PstHI were found. A very weak correlation was found between the resistance to PstFI and PstHI in both growing seasons. Therefore, the resistance to each symptom might be controlled by different genetic systems. The effect of PstFI and PstHI on kernel traits was investigated. PstHI was found to significantly reduce kernel width and weight in heavily diseased years. Therefore, a significant reduction in wheat yield and quality is expected in case of severe PstHI. Three Egyptian genotypes were resistant to PstFI and PstHI in both growing seasons. These genotypes could help in improving the resistance to both symptoms. However, due to the low genetic distance among them, looking for additional sources of resistance is recommended. In 2021, higher head infection was found compared with 2022. Highly significant differences in maximum temperature, minimum temperature, maximum dew point, and average dew point were found between the two growing seasons. Out of these four factors, dew point and ambient temperature were found to be possible reasons for increasing PstHI. Furthermore, 51 isolines carrying different resistance genes were included in the evaluation. At least ten stripe rust resistance genes were found to be effective against PstFI and PstHI. These ten genes should be included in future breeding programs to improve Pst resistance and understand the effect of climate change on Pst.

Leaf rust caused by Puccinia triticina Eriks., is one of the most common diseases of wheat (Triticum aestivum L.) in Egypt and worldwide. To investigate the population genetic structure of the causal pathogen, 468 single isolates were obtained from 193 samples collected from 12 Egyptian governorates and analyzed during 2016/17 and 2017/18 growing seasons. A total of 125 and 101 leaf rust pathotypes were designated during 2016/17 and 2017/18 growing seasons. The most frequent pathotype was STTTK (9.81% frequency), followed by race PTTNS (2.80% frequency) during 2016/17. While, pathotype PTTTT was occurred at a high frequency (12.16% frequency), followed by the four pathotypes; TTTBT, PTTGS, TTTTT and PTTCT (5.88, 5.10, 5.10 and 4.31%, respectively), during 2017/18. Pathotype STTTK is the most geographically distributed as it was detected in nine governorates in 2016/17, but in 2017/18, PTTTT is the most geographically distributed pathotype, where it was found in seven governorates. High similarity was found between leaf rust populations in the five locations, i.e. Domiatta, Sohag, Alexandria, Kafr El-Sheikh and Bani Sweif, during 2016/17 growing season. Also, high similarity was found between leaf rust pathogen populations of Kafr-Elsheikh, Sohag, Beheira, Dakahlia, Sharqiya, Domiatta, Gharbiya, Fayoum and Minufiy, during 2017/18 growing season. The phenotypic diversity within different populations under study was characterized using the three indexes; Shannon, Gleason and Simpson. Shannon index proved to be more suitable to accurately measure the phenotypic diversity between the tested populations of the causal pathogen, as it was sensitive to sample size, number of isolates, number of races and standard deviation of race frequency than the others.

Wheat leaf rust caused by Puccinia triticina Eriks. is a common disease in Egypt and worldwide. Survey of wheat leaf rust samples and identification of physiological races using twenty single Lr genes are very important in describing virulence pattern variation, geographical distribution of leaf rust pathotypes and how its change in response to host selection. Variability in population of the causal organism is annually determined using samples collected from wheat growing areas in Egypt for three growing seasons that is, 2011/2012, 2012/2013 and 2013/2014. The results obtained showed a significant variability in pathotypes which are different from season to season. In the course of this study a total of 50, 65 and 33 leaf rust samples were collected in 2011/2012, 2012/2013 and 2013/2014, respectively from different wheat growing areas in eight governorates of Egypt that is, Beheira, Dakahlia, Gharbiya, Minufiya, Sharqiya, Domiatta, Qalyubia and BaniSweif. A total of 118, 166 and 61 physiologic races were identified in 2011/2012, 2012/2013 and 2013/2014, respectively. The most frequent races included STTST and TKTTT (each with 2.54%) in 2011/2012; PKTST (6.63%), TTTTT (7.83%) and TTTST (10.24%) in 2012/2013 as well as FKTTT (4.92%) and PTTTT (11.47%) in 2013/2014. Race groups PT--- and TK--- were common at eight locations during the three growing seasons. Cluster analysis based on percentage frequency of virulence of P. triticina race groups in different location showed that in 2011/2012 and 2012/2013 growing seasons two main clusters were formed. While, in 2013/2014 growing season the cluster analysis was divided into six main clusters. Lines with Lr 1, Lr 2c, Lr 3, Lr 16, Lr 24 and Lr 26 were susceptible against most race groups, while, the leaf rust monogenic lines Lr 2a and Lr 9 showed different reactions against the tested race groups. Key words: Wheat, Puccinia triticina, race analysis, geographical distribution, cluster analysis.

Wheat 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 0C, 25 0C, 20 0C and 15 0C). The wheat monogenic lines viz. Lr 16, Lr 17 and Lr 23 were more resistant at 25 0C, while these genes were found susceptible at 15 0C, 20 0C and 30 0C to all tested races. Eight monogenic lines i.e. Lr11, Lr12, Lr13, Lr14a, Lr18, Lr47, Lr50 and Lr68 displayed temperature sensitivity which were completely resistant at 15 0C and 20 0C. Lr11, Lr12, Lr13, Lr14a, Lr18, Lr47, Lr50 and Lr68 were completely susceptible at 25 0C and 30 0C to all races of Puccinia triticina. Lr 34 showed temperature sensitivity to three of the tested races (LQFDS, PHFPG and PTPDN) which was resistant at 15 0C and 20 0C to, but was susceptible at 25 0C and 30 0C. Genes like Lr1, Lr2a, Lr2b, Lr2c, Lr3ka, Lr3, Lr9, Lr10, Lr14b, Lr15, Lr10+27+31, Lr19, Lr24, Lr28, Lr33, Lr36, Lr39, Lr42, Lr51 and Lr67 were slightly resistant at all temperatures to some races and were susceptible to other races. The other tested monogenic lines were susceptible at all temperatures to all tested races. Further, this study will be helpful to develop resistant cultivars against leaf rust of wheat.