Slow Rusting Resistance Research Articles

Characterization of Quantitative Trait Loci for Leaf Rust Resistance from CI 13227 in Three Winter Wheat Populations.

Leaf rust is a widespread foliar wheat disease causing substantial yield losses worldwide. Slow rusting is "adult plant" resistance that significantly slows epidemic development and thereby reduces yield loss. Wheat accession CI 13227 was previously characterized as having slow-rusting resistance. To validate the quantitative trait loci (QTLs) and develop diagnostic markers for slow rusting resistance in CI 13227, a new population of recombinant inbred lines of CI 13227 × Everest was evaluated for latent period, final severity, area under the disease progress curve, and infection type in greenhouses and genotyped using genotyping-by-sequencing. Four QTLs were identified on chromosome arms 2BL, 2DS, 3BS, and 7BL, explaining 6.82 to 28.45% of the phenotypic variance for these traits. Seven kompetitive allele-specific polymorphism markers previously reported to be linked to the QTLs in two other CI 13227 populations were validated. In addition, the previously reported QLr.hwwg-7AL was remapped to 2BL (renamed QLr.hwwg-2BL) after adding new markers in this study. Phenotypic data showed that the recombinant inbred lines harboring two or three of the QTLs had a significantly longer latent period. QLr.hwwg-2DS on 2DS showed a major effect on all rust resistance traits and was finely mapped to a 2.7-Mb interval by two newly developed flanking markers from exome capture. Three disease-resistance genes and two transporter genes were identified as the putative candidates for QLr.hwwg-2DS. The validated QTLs can be used as slow-rusting resistance resources, and the markers developed in this study will be useful for marker-assisted selection.

Identification of genes for leaf rust resistance in seedlings of wheat cultivars from the Yellow-Huai Basin in China and slow rusting observations in field trials

Wheat leaf rust is a devastating disease worldwide. Identification of leaf rust resistance genes in seedlings and of genes for slow rusting are important in resistance breeding and for gene deployment to control the disease. A total of 108 wheat cultivars from the Beijing and Shandong province and a set of 36 differentials, mostly near-isogenic lines in the background of Thatcher with known leaf rust resistance genes, were tested with 20 Puccinia triticina pathotypes (FHJS1, FGBQ,PGJQ, SHJT, FHGQ, PHTT1, FHGQ, FHGQ, PHJS, THSM, FHSQ, PHST, PRSQ, FNTQ, PHGM, KHGQ, PHTT2, TGTT, FHJS2, NHHT) at the seedling stage in the greenhouse. The cultivars and differentials were also planted in the field to test their slow rusting resistance using a mixture of races at Baoding, Hebei province and Zhoukou, Henan province, for two consecutive years. Ten leaf rust resistance genes, Lr1, 9, 10, 19, 20, 24, 26, 34, 37 and 46 were identified in the 57 commercial wheat cultivars, either singly or in combination, using molecular markers. Combined, the results from gene postulation and marker detection showed that one or more of the genes Lr1, 3, 10, 14a, 14b, 26, 36, 39, 34 and 46, were present in 57 cultivars, and that no known resistance gene was present in the remaining 51 cultivars. The resistance gene Lr26 was present in 42 cultivars, and nine cultivars contained Lr1. Lr46 was present in 10 cultivars, as indicated by the presence of the closely linked marker csLV46G22. Seven genotypes were identified as possibly carrying the gene Lr39. Lr3 and 10 were found in six and four genotypes, respectively. The ggenes Lr14b and 34 were each present in three cultivars, while evidence for the presence of Lr14a and 36 was obtained in single genotypes. Finally, 12 cultivars showed slow rusting resistance at two locations in two crop seasons. The identification of leaf rust resistance genes in Chinese wheat cultivars will be helpful for gene deployment to control leaf rust.

Evaluation of the Potential Risk of the Emerging Yr5-Virulent Races of Puccinia striiformis f. sp. tritici to 165 Chinese Wheat Cultivars.

In 2017, a new race (TSA-6) of the wheat stripe rust pathogen, Puccinia striiformis f. sp. tritici, virulent to resistance gene Yr5, was detected in China. However, whether Chinese wheat cultivars are resistant to the new race was unknown. In this study, two isolates (TSA-6 and TSA-9) with virulence to Yr5 were tested on other wheat Yr gene lines for their avirulence and virulence patterns and used, together with prevalent races CYR32 and CYR34 without the Yr5 virulence, to evaluate 165 major Chinese wheat cultivars for their reactions. Isolates TSA-6 and TSA-9 had similar but different virulence spectra and therefore should be considered two different races. Their avirulence and virulence patterns were remarkably different from that of CYR34 but quite similar to that of CYR32. Of the 165 wheat cultivars, 21 had all-stage resistance to TSA-6, 34 to TSA-9, and 20 to both races. Adult plant resistance (APR) was detected in 35 cultivars to TSA-6 and 27 to TSA-9, but only three cultivars showed APR to both new races. Slow rusting resistance was observed in 24 cultivars to TSA-6 and 33 to TSA-9. Analysis of variance of disease index indicated a significant difference between cultivars but not between the four races. Based on the molecular marker data, a low percentage of wheat cultivars carried Yr5, Yr7, Yr10, Yr15, Yr26, or YrSP. Because TSA-6 and TSA-9 can be a serious threat to wheat production in China, continual monitoring of TSA-6, TSA-9, and other races is needed.

Yield losses in wheat genotypes caused by stripe rust (Puccinia striifarmis f. sp. tritici) in North Delta, Egypt

Stripe (yellow) rust disease caused by Puccinia striifarmis f. sp. tritici, is a catastrophic wheat disease in wheat-growing regions around the world. The objective of this study was to investigate potential sources of stripe rust resistance and the yield loss of forty local wheat varieties at four locations in Egypt (Sakha, Mutubas, Qillin and Biyala), under yellow rust disease pressure compared to ‘Morroco’ variety, as control. To determine slow rusting in the field, the following parameters were recorded: final rust severity (FRS%), average coefficient of infection (ACI), relative resistance index (RRI) and reduction % in the 1000 kernel weight. The severity was higher in the second season than in the first. Seven wheat genotypes (‘Shaka 62’, ‘Shaka 9, ‘Shaka 95’, ‘Gemmiza 7’, ‘Sids 14’ and ‘Misr 3’) showed the high level of resistance, and FRS% values ranged from 0 to 20 moderately resistant (MR) during first season and achieved the least value of loss in TKW (1.28%) with ‘Misr 3’. Meanwhile, four genotypes (‘Sakha 93’, ‘Sakha 95’, ‘Sids 14’ and ‘Gim. 7’) remained highly resistant during the second season and identified to have good level of slow rusting resistance, which these genotypes showed FRS% values ranged from 5R to 30 moderately resistant-moderately susceptible (MRMS), ACI values ≤12, RRI values ≥6 and the loss % in TKW not exceed 12.54%. On the other hand, the lines; ‘Shaka 69’, ‘Shaka 88’, ‘Shaka 92’, ‘Giza 160’, ‘Giza 163’, ‘Gem 11’, ‘Sids 2’ and ‘Sids 6’ exhibited complete susceptibility at the four tested sites, recorded FRS% values >50. Meanwhile, cv. ‘Gem 11’ in 2018/2019 recorded the highest level of ACI ≥55, the lowest level of RRI≤4.05 and the highest loss% in TKW reached 40.69%. These findings could be used in the national wheat breeding program for stripe rust resistance in Egypt.

Wheat Resistance to Stripe and Leaf Rusts Conferred by Introgression of Slow Rusting Resistance Genes.

Twenty-three wheat genotypes were evaluated for stripe and leaf rusts, caused by Puccinia striiformis f. sp. tritici and Puccinia triticina f. sp. tritici, respectively, at seedling and adult stages under greenhouses and field conditions during the 2019/2020 and 2020/2021 growing seasons. The race analysis revealed that 250E254 and TTTST races for stripe and leaf rusts, respectively were the most aggressive. Eight wheat genotypes (Misr-3, Misr-4, Giza-171, Gemmeiza-12, Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46) were resistant to stripe and leaf rusts at seedling and adult stages. This result was confirmed by identifying the resistance genes: Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46 in these genotypes showing their role in the resistance. Sids-14 and Shandweel-1 genotypes were susceptible to stripe and leaf rusts. Twelve crosses between the two new susceptible wheat genotypes and the three slow rusting genes (Lr34/Yr18, Lr37/Yr17, and Lr67/Yr46) were conducted. The frequency distribution of disease severity (%) in F2 plants of the twelve crosses was ranged from 0 to 80%. Resistant F2 plants were selected and the resistance genes were detected. This study is important for introducing new active resistance genes into the breeding programs and preserving diversity among recently released wheat genotypes.

Identification of known leaf rust resistance genes in bread wheat cultivars from China

Leaf rust caused by Puccinia triticina Eriks. (Pt) is one of the most devastating fungal pathogens affecting wheat (Triticum aestivum L.) production worldwide. Deployment of resistant cultivars is the most environmentally friendly approach to control the disease. In this study, thirty-seven wheat lines from the Hubei and Shaanxi provinces in China were evaluated for seedling resistance in the greenhouse using eighteen Pt races. These lines were also tested for slow rusting resistance in the field in the 2014 to 2018 growing seasons. Eleven molecular markers closely associated with known Lr genes were used as part of the postulation process. Seven known Lr genes, 1, 13, 18, 14a, 26, 34 and 46 either singly or in combination were postulated in twenty-five cultivars. Lr1 and Lr26 were the most commonly identified genes detected in thirteen and ten cultivars, respectively. Lr13 and Lr46 were each found in four and five cultivars. Lr34 was present in three cultivars. Lr18 and Lr14a were identified in cultivar Xi’nong 538. Six cultivars displayed slow rusting resistance in the field tests. The resistant cultivars identified in the present study can be used as resistance parents in crosses aimed at pyramiding and the deployment of leaf rust resistance genes in China.

Identification of leaf rust resistance genes in common wheat varieties from China and foreign countries

Wheat leaf rust, triggered by Puccinia triticina Eriks (Pt), is among the most important diseases of wheat worldwide. Deploying resistant varieties against leaf rust is the most effective, environmentally-friendly and economic way to control the disease. In the present study, 66 wheat varieties form China and foreign countries were tested with 17 Pt races for gene postulation during the seedling stage in the greenhouse. All the varieties were also planted to identify slow rusting responses to leaf rust at the adult plant stage in Baoding and Zhoukou field trials during the 2016/2017 to 2017/2018 cropping seasons. Moreover, 12 closely linked molecular markers to known leaf rust resistance (Lr) genes were used for assessing all the varieties. The results of both gene postulation and molecular marker identification showed that a total of eight Lr genes, Lr1, Lr10, Lr17, Lr20, Lr26, Lr34, Lr37 and Lr46, either singly or in combination were detected in 32 varieties. Known Lr genes were not identified in the remaining 34 varieties. Seventeen varieties were found to have slow rusting resistance. The resistance sources identified in this study can be used as resources for resistance against leaf rust in wheat breeding programs in China and the respective foreign countries.

Evaluation of Ethiopian Bread Wheat Cultivars for Slow Rusting Resistance to Yellow Rust (<i>Puccinia striiformis</i> f.s Tritici)

Wheat stripe rust (<i>Puccinia striiformis</i> f.s. <i>tritici</i>) is the greatest vicious rust disease in wheat-growing areas of Ethiopia. The cultivating of cultivars with polygenic gene resistance is the most efficient way of monitoring the disease. Field experiments were carried out at Kulumsa Agricultural Research Center main station and, Meraro and Bekoji substations of Ethiopia during 2019 to 2020 main cropping seasons to disclose variability for field based adult plant resistance to yellow rust among 25 newly developed bread wheat cultivars advanced in Ethiopia. Features used as criteria to identify adult plant resistance comprised response of wheat cultivars to yellow rust, Coefficient of infection (CI), relative final rust severity (FRS) and area under disease progress curve (rAUDPC) were found to be reliable to evaluate slow rusting in the cultivars. The outcomes shown that wheat cultivar only Balcha had low disease severity (< 30%) with MRMS reaction, lower rAUDPC values (>30%) and CI (< 20) and were recognized to have good level of adult plant resistance while eighty eight percent of the tested cultivars exhibited susceptible and grouped under low slow rusting resistance with high disease pressure over all three locations. Cultivars Dashen, Daka, Wane and Sanate had moderate values for slow rusting parameters and were recognized as having moderate level of slow rusting. The slow rusting cultivars identified from the present work can be used for extra management in wheat development programs.

Analysis of miRNA expression associated with the Lr46 gene responsible for APR resistance in wheat (Triticum aestivum L.)

Lr46/Yr29/Pm39 (Lr46) is a gene for slow rusting resistance in wheat. The aim of the study was to analyze the miRNA expression in selected common wheat cultivars carrying resistance genes, Lr46 among others (HN Rod, Pavon‘S’, Myna‘S’, Frontana‘S’, and Sparrow’S’) in response to leaf rust infection caused by Puccinia triticina Erikss. In the Pavon ‘S’, Myna ‘S’, Frontana‘S’, and Sparow‘S’ varieties a product with a length of 242 bp has been identified, which is specific to the Xwmc44 marker linked to the brown rust resistance gene Lr46. In the next step, the differences in the expression of microRNA (miR5085 and miR164) associated with the Lr46 gene, which is responsible for different resistance of selected wheat cultivars to leaf rust, were examined using emulsion PCR (ddPCR). In the experiment, biotic stress was induced in mature plants by infecting them with fungal spores under controlled conditions in a growth chamber. For analysis the plant material was collected before inoculation and 6, 12, 24, and 48 h after inoculation. The experiments also showed that plant infection with Puccinia triticina resulted in an increase in miR164 expression in cultivars carrying the Lr46 gene. The expression of miR164 remained stable in a control cultivar (HN ROD) lacking this gene. This has proved that miR164 can be involved in leaf rust resistance mechanisms.

Identification of Leaf Rust Resistance Genes in Bread Wheat Cultivars from Ethiopia.

Wheat leaf rust, caused by Puccinia triticina (Pt), is a widespread disease of bread wheat worldwide. In the present study, 50 wheat cultivars from Ethiopia and 34 differential lines, mostly near-isogenic lines (NILs) in the background of Thatcher with known resistance genes to leaf rust (Lr), were tested with 14 Pt races in the greenhouse to postulate Lr genes at the seedling stage. Field experiments were also conducted to identify adult plant responses to leaf rust in Baoding in the 2017-2018 and 2018-2019 growing seasons and in Zhoukou in the 2018-2019 growing season. Thirteen Lr genes (Lr1, Lr18, Lr3ka, Lr15, Lr26, Lr20, Lr14a, Lr30, Lr2a, Lr11, Lr34, Lr46, and Lr68) either singly or in combination were found in 39 cultivars. Known Lr genes were not present in the remaining 11 cultivars. Lr1 and Lr46, each in 13 cultivars, and Lr34 in 12 cultivars were the most commonly identified resistance genes. Less frequently identified genes included Lr26 (five cultivars); Lr30 and Lr18 (each present in four cultivars); Lr15, Lr3ka, and Lr2a (each identified in three cultivars); and Lr68 (two cultivars). Evidence for the existence of Lr11, Lr20, and Lr14a (each in one cultivar) was also obtained. Twenty-one cultivars were found to have slow rusting resistance to leaf rust in the field tests. The results should be valuable for cultivar selection with combinations of effective Lr genes and used in breeding new cultivars with improved resistance to leaf rust in Ethiopia and China.

Adult Plant Slow Rusting Genes Confer High Levels of Resistance to Rusts in Bread Wheat Cultivars From Mexico.

Rust diseases continuously threaten global wheat production: stem rust, leaf rust, and yellow rust caused by Puccinia graminis f. sp. tritici, Puccinia triticina, and Puccinia striiformis f. sp. tritici, respectively. Recent studies indicated that the average losses from all these three rusts reached up to 15.04 million tons per year, which is equivalent to an annual average loss of around US $2.9 billion per year. The major focus of Mexican and worldwide breeding programs is the release of rust resistant cultivars, as this is considered the best option for controlling rust diseases. In Mexico, the emphasis has been placed on genes that confer partial resistance in the adult plant stage and against a broad spectrum of rust races since the 1970s. In this study, a set of the first-generation tall varieties developed and released in the 1940s and 1950s, the first semi-dwarfs, and other releases in Mexico, all of which showed different levels of rust resistance have been phenotyped for the three rust diseases and genotyped. Results of the molecular marker detection indicated that Lr34, Lr46, Lr67, and Lr68 alone or in different gene combinations were present among the wheat cultivars. Flag leaf tip necrosis was present in all cultivars and most were positive for brown necrosis or Pseudo Black Chaff associated with the Sr2 stem rust resistance complex. The phenotypic responses to the different rust infections indicate the presence of additional slow rusting and race-specific resistance genes. The study reveals the association of the slow rusting genes with durable resistance to the three rusts including Ug99 in cultivars bred before the green revolution such as Frontera, Supremo 211, Chapingo 48, Yaqui 50, Kentana 52, Bajio 52, Bajio 53, Yaqui 53, Chapingo 53, Yaktana Tardio 54, and Mayo 54 and their descendants after intercrossing and recombination. These slow rusting genes are the backbone of the resistance in the current Mexican germplasm.

Molecular identification of slow rusting resistance Lr46/Yr29 gene locus in selected triticale (\xd7 Triticosecale Wittmack) cultivars

Recently, leaf rust and yellow rust caused by the fungi Puccinia triticina Erikss. and P. striiformis Westend f. sp. tritici Eriks and Henn are diseases of increasing threat in triticale (× Triticosecale Wittmack, AABBRR, 2n = 6x = 42) growing areas. The use of genetic resistance is considered the most economical, effective and environmentally friendly method to control the disease and minimize the use of fungicides. Currently, breeding programs mainly relied on race-specific Lr and Yr genes (R), but new races of the rust fungi frequently defeat resistance. There is a small group of genes that causes partial type of resistance (PR) that are characterized by a slow epidemic build up despite a high infection type. In wheat slow rusting resistance genes displayed longer latent periods, low infection frequencies, smaller pustule size and less spore production. Slow rusting Lr46/Yr29 gene, located on chromosome 1B, is being exploited in many wheat breeding programs. So far, there is no information about slow rusting genes in triticale. This paper showed significant differences between the results of identification of wheat molecular markers Xwmc44 and csLV46G22 associated with Lr46/Yr29 in twenty triticale cultivars, which were characterized by high levels of field resistance to leaf and yellow rust. The csLV46G22res marker has been identified in the following cultivars: Kasyno, Mamut and Puzon. Belcanto and Kasyno showed the highest resistance levels in three-year (2016–2018), leaf and yellow rust severity tests under post-registration variety testing program (PDO). Leaf tip necrosis, a phenotypic trait associated with Lr34/Yr18 and Lr46/Yr29 was observed, among others, to Belcanto and Kasyno, which showed the highest resistance for leaf rust and yellow rust. Kasyno could be considered to have Lr46/Yr29 and can be used as a source of slow rust resistance in breeding and importantly as a component of gene pyramiding in triticale.

Development of Triticale × Wheat Prebreeding Germplasm With Loci for Slow-Rusting Resistance.

There is a growing interest in breeding and production of hexaploid triticale (× Triticosecale Wittmack ex A. Camus) in European Union and in the world. It is reported that triticale can be an alternative to wheat (Triticum aestivum L.) for livestock feed production and has a potential to become preferred industrial energy crop. Fungal diseases, mainly leaf and stripe rusts, are the limiting factors of triticale growth and yield. Geneticists and breeders are now focusing on accumulation of the major genes for durability of rust resistance. Slow-rusting genes Lr34/Yr18 and Lr46/Yr19 are being exploited in many wheat breeding programs. This type of horizontal resistance is reported to be effective over space and time. Classical breeding techniques supported by marker-assisted selection (MAS) are the main tools in breeding programs. The aim of this study was to assess the possibility of transfer of slow-rusting genes from resistant genotypes of wheat into hexaploid triticale through cross-hybridizations. A total of 5,094 manual pollinations were conducted between two triticale cultivars Fredro and Twingo and 33 accessions of common wheat, which were reported as sources of slow-rusting resistance genes. The investigation of the slow-rusting gene transmission was performed using both molecular markers analyses and genomic in situ hybridization (GISH). In total, 34 F1 hybrid plants were obtained, and 29 of them carried both slow-rusting loci. Therefore, these hybrids may be used for triticale prebreeding program.

Field Evaluation of Bread Wheat (&amp;lt;i&amp;gt;Triticum aestivum&amp;lt;/i&amp;gt; L.) Genotypes for Stripe Rust (&amp;lt;i&amp;gt;Puccinia striiformis&amp;lt;/i&amp;gt; W.) Resistance in Arsi Highlands, South -Eastern-Ethiopia

Wheat is one of the world's foremost crops where its production is growing yearly. However, the emerged virulent stripe rust races at one point of the world spread to the rest of wheat producing countries by wind as well as human travels and damaged popular resistant wheat cultivars thereby posed food insecurity. This study was carried out with the aim to identify possible sources of stripe rust resistance among Ethiopian bread wheat pipelines for durable resistance breeding. Twenty-eight advanced bread wheat pipelines, local susceptible and resistant check cultivars Kubsa and Wane respectively were field tested in randomized complete block design with three replications across two stripe rust hot-spot locations for their slow rusting characteristics. Slow rusting resistance at the adult-plant stage was assessed through the determination of final rust severity (FRS), average coefficient of infection (ACI), and relative area under disease progressive curve (rAUDPC). Among the twenty-eight, 24, 2 and 2 genotypes displayed high, moderate and low level of slow rusting over two locations respectively. The results revealed that wheat lines, ETBW- 8858, ETBW-8870, ETBW-8583, ETBW-8668, ETBW-8595, ETBW-8684, ETBW-9548, ETBW-9549, ETBW-9552, ETBW-9554, ETBW-9558, ETBW-9559, ETBW-9560, ETBW-875, ETBW-8802, ETBW-8862, ETBW-8804, ETBW-8896, ETBW-9556, ETBW-9557, ETBW-8991, ETBW-9486, ETBW-9556 and ETBW-9561 had low values of FRS, ACI and rAUDPC and were regarded as good slow rusting lines. Strong positive correlations were observed between different parameters of slow rusting. As compared with susceptible, resistant check variety and other test lines, three lines namely. ETBW-8684; ETBW-9558 and ETBW-8751 are high yielders and could be released for production. Twenty-four lines with high and moderate levels of slow rusting and expected to possess both major and minor resistance genes could be used for durable stripe rust resistance breeding in wheat. Nevertheless, the exact resistant genes contented in suggested lines shall be confirmed through seedling phenotyping and molecular approaches.

Field Evaluation of Bread Wheat (Triticum aestivum L.) Genotypes for Stripe Rust (Puccinia striiformis W.) Resistance in Arsi Highlands of Oromia Region, South -Eastern-Ethiopia

Wheat is one of the world's most important crops whose grain production is increasing year after year. However, the emerged virulent stripe rust races at one point of the world spread to the rest of wheat producing countries by wind as well as human travels and damaged popular resistant wheat cultivars thereby posed food insecurity. This study was carried out with the aim to identify possible sources of stripe rust resistance among Ethiopian bread wheat pipelines for durable resistance breeding. Twenty-eight advanced bread wheat pipelines, local susceptible and resistant check cultivars Kubsa and Wane respectively were field tested in randomized complete block design with three replications across two stripe rust hot-spot locations for their slow rusting characteristics. Slow rusting resistance at the adultplant stage was assessed through the determination of final rust severity (FRS), average coefficient of infection (ACI), and relative area under disease progressive curve (rAUDPC). Among the twenty-eight, 24, 2 and 2 genotypes displayed high, moderate and low level of slow rusting over two locations respectively. The results revealed that wheat lines, ETBW- 8858, ETBW-8870, ETBW-8583, ETBW-8668, ETBW-8595, ETBW-8684, ETBW-9548, ETBW-9549, ETBW-9552, ETBW-9554, ETBW-9558, ETBW-9559, ETBW-9560, ETBW-875, ETBW-8802, ETBW-8862, ETBW- 8804, ETBW-8896, ETBW-9556, ETBW-9557, ETBW-8991,ETBW-9486,ETBW-9556 and ETBW-9561 had low values of FRS, ACI and rAUDPC and were regarded as good slow rusting lines. Strong positive correlations were observed between different parameters of slow rusting. As compared with susceptible, resistant check variety and other test lines, three lines namely. ETBW-8684; ETBW-9558 and ETBW-8751 are high yielders and could be released for production. Twenty-four lines with high and moderate levels of slow rusting and expected to possess both major and minor resistance genes could be used for durable stripe rust resistance breeding in wheat. However, is advised to postulate inherent resistance genes in these lines and their seedling susceptibility for providing fruitful recommendations.

Evaluation of Wheat Cultivars for Slow Rusting Resistance to Leaf and Stem Rust Diseases in Egypt

Evaluation of Wheat Cultivars for Slow Rusting Resistance to Leaf and Stem Rust Diseases in Egypt

Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust, caused by Puccinia triticina (Pt), is an important foliar disease that has an important influence on wheat yield. The most economic, safe and effective way to control the disease is growing resistant cultivars. In the present study, a total of 46 wheat landraces and 34 wheat lines with known Lr (leaf rust resistance) genes were inoculated with 16 Pt pathotypes for postulating seedling resistance gene(s) in the greenhouse. These cultivars and five wheat differential lines with adult plant resistance (APR) genes (Lr12, Lr22b, Lr34, Lr35 and Lr37) were also evaluated for identification of slow rusting resistance in the field trials in Baoding, Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons. Furthermore, 10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes. Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage. Nonetheless, Lr1 was detected only in Hongtangliangmai. The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance. Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46. Lr genes namely, Lr9, Lr19, Lr24, Lr28, Lr29, Lr47, Lr51 and Lr53 were effective at the whole plant stage. Lr18, Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage. Lr34 as a slowing rusting gene showed good resistance in the field. Four race-specific APR genes Lr12, Lr13, Lr35 and Lr37 conferred good resistance in the field experiments. Seven race-specific genes, Lr2b, Lr2c, Lr11, Lr16, Lr26, Lr33 and LrB had lost resistance. The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.

Evaluation of Ethiopian Durum Wheat Varieties and Landrace Cultivars for the Adult Plant Resistance of Wheat Leaf Rust (Puccinia triticina)

Wheat Leaf rust caused by the pathogen Puccinia triticina is a serious threat of wheat production in Ethiopia, yield loss due tothis disease reached up to 70%. A study was carried out to identify leaf rust adult plant resistance in commercial durum wheatcultivars and landraces. 35 durum wheat Varieties and 200 durum wheat landraces with three susceptible checks arranged inAugment design and evaluated against leaf rust at Debere Zeit Agricultural Research Center, Ethiopia during the 2017/18 mainseason. Terminal Rust Severity (TRS), Coefficient of Infection (CI), Area under Disease Progress Curve (AUDPC) and Disease Progress Rate (DPR) were used to measure leaf rust adult plant resistance in the test materials. Analysis of all disease parameters was carried out using SPAD software. There were highly significant differences (Pl0.01) for all disease parameters among the test cultivars. Above half of evaluated Varieties and landraces (57.9 %) showed better Adult plant resistance under high disease pressure. From the total of 235 tested Varieties and landraces, 136 had slow rusting resistance of which 14 were released varieties and the rest 122 were landraces. Four commercial Varieties (Selam, Mossobo, Bekelcha, and Utuba) and a landrace cultivar (Mcd4-32) had high levels of field resistance with very low AUDPC, ACI, and TRS with MR infection type; hence, they may carry major resistance gene (s). However, the rest 99 Varieties and landraces exhibited high to moderate level of slow rusting resistance with MS responses and may have adult plant resistance controlled by minor resistance genes. The slow rusting cultivars identified from the current study can be used for further manipulation in wheat improvement programs.

Identification of known leaf rust resistance genes in common wheat cultivars from Sichuan province in China

Leaf rust, caused by Puccinia triticina (Pt), is one of the most important wheat diseases of common wheat (Triticum aestivum L.). Using resistant cultivars is the most economical and efficient way to control the disease. A total of 86 wheat cultivars from Sichuan province in China were inoculated with 14 Pt races for postulating seedling leaf rust resistance (Lr) gene(s) in the greenhouse. Meanwhile, these cultivars were also planted in Baoding and Zhoukou trial fields for identifying slow leaf rusting genes during the 2014–2015 and 2015–2016 cropping seasons. Twelve specific markers for ten known Lr genes (Lr1, Lr9, Lr10, Lr19, Lr20, Lr24, Lr26, Lr34, Lr37 and Lr46) were also used for molecular marker detection. Based on the results from the gene postulation and molecular marker detection, nine Lr genes (Lr1, Lr2a, Lr26, Lr3ka, Lr30, Lr36, Lr15, Lr37, and Lr46) were identified in 45 cultivars either singly or in combination. Most frequently identified Lr genes were Lr26 in 25 cultivars and Lr37 in 21 cultivars. Less frequently detected genes were Lr1 and Lr46 each in nine cultivars, Lr3ka in five cultivars, Lr30 in three cultivars and Lr36 in two cultivars. Lr2a and Lr15 were found in Chuannong 16 and Chuanmai 1, respectively. Twenty-nine cultivars were found to have slow rusting resistance during the two growing seasons. The results should be useful for selecting cultivars with combinations of genes for effective resistance to grow and in breeding new cultivars with improved resistance to leaf rust.

Characterization of Slow Rusting Resistance Against Stem Rust (Puccinia graminis f. sp. tritici) in Selected Bread Wheat Cultivars of Ethiopia

Characterization of Slow Rusting Resistance Against Stem Rust (Puccinia graminis f. sp. tritici) in Selected Bread Wheat Cultivars of Ethiopia