Resistant Wheat Cultivars Research Articles

Molecular cytogenetic characterization of wheat\u2013Elymus repens chromosomal translocation lines with resistance to Fusarium head blight and stripe rust

BackgroundFusarium head blight (FHB) caused by the fungus Fusarium graminearum Schwabe and stripe rust caused by Puccinia striiformis f. sp. tritici are devastating diseases that affect wheat production worldwide. The use of disease-resistant genes and cultivars is the most effective means of reducing fungicide applications to combat these diseases. Elymus repens (2n = 6x = 42, StStStStHH) is a potentially useful germplasm of FHB and stripe rust resistance for wheat improvement.ResultsHere, we report the development and characterization of two wheat–E. repens lines derived from the progeny of common wheat–E. repens hybrids. Cytological studies indicated that the mean chromosome configuration of K15–1192-2 and K15–1194-2 at meiosis were 2n = 42 = 0.86 I + 17.46 II (ring) + 3.11 II (rod) and 2n = 42 = 2.45 I + 14.17 II (ring) + 5.50 II (rod) + 0.07 III, respectively. Genomic and fluorescence in situ hybridization karyotyping and simple sequence repeats markers revealed that K15–1192-2 was a wheat–E. repens 3D/?St double terminal chromosomal translocation line. Line K15–1194-2 was identified as harboring a pair of 7DS/?StL Robertsonian translocations and one 3D/?St double terminal translocational chromosome. Further analyses using specific expressed sequence tag-SSR markers confirmed that the wheat–E. repens translocations involved the 3St chromatin in both lines. Furthermore, compared with the wheat parent Chuannong16, K15–1192-2 and K15–1194-2 expressed high levels of resistance to FHB and stripe rust pathogens prevalent in China.ConclusionsThus, this study has determined that the chromosome 3St of E. repens harbors gene(s) highly resistant to FHB and stripe rust, and chromatin of 3St introgressed into wheat chromosomes completely presented the resistance, indicating the feasibility of using these translocation lines as novel material for breeding resistant wheat cultivars and alien gene mining.

Population dynamics of wheat aphid on different landraces of wheat under field conditions

Wheat (Triticum aestivum L.) is the leading food grain and staple diet in Pakistan. Cereal aphids are a severe problem in wheat growing areas. Among environmentally safe and economical methods for the control of aphids, the use of resistant wheat cultivars is one of the promising approach in pest management programs which can overcome the economic damage caused by aphid infestation. In the present study, the population dynamics of wheat aphid was observed on 114 landraces of wheat. The results showed that during March, nine landraces showed the highest population of Rhopalosiphum padi while the lowest R. padi population was recorded on fourteen different landraces with aphid populations ranging from 3.25 to 4.08. In the month of April, the highest population of R. padi was recorded on 81 landraces while the lowest population was recorded on 33 landraces with mean aphid numbers ranging from 2.91 to 6.9. The peak population was recorded during the month of May on 78 landraces of wheat and proved to be the susceptible while the remaining thirty eight landraces of wheat proved to be resistant with low aphid densities. The mean aphid population varied from 4.25 to 6.95. The results obtained from the month of March were non-significant while those obtained during the months of April and May were significant

Characterization of Ethiopian Wheat Germplasm for Resistance to Four Puccinia graminis f. sp. tritici Races Facilitated by Single-Race Nurseries.

In Ethiopia, breeding rust resistant wheat cultivars is a priority for wheat production. A stem rust epidemic during 2013 to 2014 on previously resistant cultivar Digalu highlighted the need to determine the effectiveness of wheat lines to multiple races of Puccinia graminis f. sp. tritici in Ethiopia. During 2014 and 2015, we evaluated a total of 97 bread wheat and 14 durum wheat genotypes against four P. graminis f. sp. tritici races at the seedling stage and in single-race field nurseries. Resistance genes were postulated using molecular marker assays. Bread wheat lines were resistant to race JRCQC, the race most virulent to durum wheat. Lines with stem rust resistance gene Sr24 possessed the most effective resistance to the four races. Only three lines with adult plant resistance possessed resistance effective to the four races comparable with cultivars with Sr24. Although responses of the wheat lines across races were positively correlated, wheat lines were identified that possessed adult plant resistance to race TTKSK but were relatively susceptible to race TKTTF. This study demonstrated the importance of testing wheat lines for response to multiple races of the stem rust pathogen to determine if lines possessed non-race-specific resistance.

Development and Validation of a Perfect KASP Marker for Fusarium Head Blight Resistance Gene Fhb1 in Wheat.

Fusarium head blight (FHB) is a devastating wheat disease with a significant economic impact. Fhb1 is the most important large effect and stable QTL for FHB resistance. A pore-forming toxin-like (PFT) gene was recently identified as an underlying gene for Fhb1 resistance. In this study, we developed and validated a PFT-based Kompetitive allele specific PCR (KASP) marker for Fhb1. The KASP marker, PFT_KASP, was used to screen 298 diverse wheat breeding lines and cultivars. The KASP clustering results were compared with gel-based gene specific markers and the widely used linked STS marker, UMN10. Eight disagreements were found between PFT_KASP and UMN10 assays among the tested lines. Based on the genotyping and sequencing of genes in the Fhb1 region, these genotypes were found to be common with a previously characterized susceptible haplotype. Therefore, our results indicate that PFT_KASP is a perfect diagnostic marker for Fhb1 and would be a valuable tool for introgression and pyramiding of FHB resistance in wheat cultivars.

Susceptibility of North Dakota Hessian Fly (Diptera: Cecidomyiidae) to 31 H Genes Mediating Wheat Resistance.

The agricultural landscape of North Dakota is changing. Corn and soybean are now commonplace, but once were rare. Spring sown wheat Triticum aestivum L. and durum wheat Triticum turgidum spp. durum continue to be dominant, but more winter-sown wheat is expected in the future. The presence of wheat in the landscape throughout much of the year will benefit populations of the Hessian fly, Mayetiola destructor (Say), which occurs throughout the state, sometimes in large numbers. Hessian fly is unusual among crop pests for which resources for plant resistance are well developed. On wheat genotypes expressing a single effective H resistance gene, 100% of larvae die before exhibiting any growth. Over 35 H genes in the public domain are available for crossing into elite cultivars. We explored the effectiveness of 31 Hessian fly resistance genes for a North Dakota Hessian fly population. Six genes-H4, H15, H21, H23, H26, and H29-caused 100% larval mortality. Seven others caused at least 80% mortality. Experimental data were used to address three additional questions. Do adult females avoid laying eggs on plants that will kill their offspring: Are neonate larvae able to detect resistance that will end up killing them? Do all 31 genes confer equal protection against larval-induced growth deficits? North Dakota wheat breeders have the necessary tools to create highly resistant wheat cultivars. So far, H genes have been deployed singly in cultivars. Advances in plant breeding will enable gene stacking, a more durable strategy over time.

Phylogeography and Population Structure Analysis Reveal Diversity by Gene Flow and Mutation in Ustilago segetum (Pers.) Roussel tritici Causing Loose Smut of Wheat.

Ustilago segetum (Pers.) Roussel tritici (UST) causes loose smut of wheat account for considerable grain yield losses globally. For effective management, knowledge of its genetic variability and population structure is a prerequisite. In this study, UST isolates sampled from four different wheat growing zones of India were analyzed using the second largest subunit of the RNA polymerase II (RPB2) and a set of sixteen neutral simple sequence repeats (SSRs) markers. Among the 112 UST isolates genotyped, 98 haplotypes were identified. All the isolates were categorized into two groups (K = 2), each consisting of isolates from different sampling sites, on the basis of unweighted paired-grouping method with arithmetic averages (UPGMA) and the Bayesian analysis of population structure. The positive and significant index of association (IA = 1.169) and standardized index of association (rBarD = 0.075) indicate population is of non-random mating type. Analysis of molecular variance showed that the highest variance component is among isolates (91%), with significantly low genetic differentiation variation among regions (8%) (Fst = 0.012). Recombination (Rm = 0) was not detected. The results showed that UST isolates have a clonal genetic structure with limited genetic differentiation and human arbitrated gene flow and mutations are the prime evolutionary processes determining its genetic structure. These findings will be helpful in devising management strategy especially for selection and breeding of resistant wheat cultivars.

Molecular Phylogenetic Relationships, Trichothecene Chemotype Diversity and Aggressiveness of Strains in a Global Collection of Fusarium graminearum Species.

Fusarium head blight (FHB), caused principally by the species belonging to the Fusarium graminearum species complex (FGSC), is an important disease in wheat, barley, and other small grain crops worldwide. Grain infected with species in the FGSC may be contaminated with trichothecene mycotoxins such as deoxynivalenol (DON) and nivalenol (NIV). In this study, we characterized the phylogenetic relationships, chemotype diversity, phenotypic characters, and aggressiveness of 150 strains in FGSC collected from eight different countries. Phylogenetic analysis based on portions of translation elongation factor 1-α (EF-1α) gene from 150 strains revealed six species in the FGSC, F. graminearum s.s, F. asiaticum, F. meridionale, F. cortaderiae, F. boothii, and F. austroamericanum. In this collection, 50% of the strains were 15-acetyldeoxynivalenol (15-ADON), 35% were 3-acetyldeoxynivalenol (3-ADON) and 15% were NIV. Evaluation of strains on moderately resistant (MR) wheat cultivar Carberry indicated that there is no significant difference among the species for FHB disease severity (DS), fusarium damaged kernel percentage (FDK%) and DON production. However, significant differences were observed among the chemotypes. Results showed significantly higher FHB DS, FDK%, DON production, growth rates, and macroconidia production for the 3-ADON strains than the 15-ADON and NIV strains. In addition, significant differences for FHB response variables were observed among the strains from different countries. Our results demonstrate that type and amount of trichothecene produced by a strain play a key role in determining the level of aggressiveness of that particular strain, regardless of the species.

Effects of Triazole and Strobilurin-Based Fungicides on Fusarium culmorum on Wheat

Fusarium culmorum is an important pathogen, that causes pre and post-emergence death in seedlings from both seed and soil-borne sources, in addition to causing root, crown root and wheat head infections on wheat. Treatment of seeds with fungicides is especially important to inhibit seed originated seedling infections when cultural methods are ineffective against the infection of the pathogen in root and crown root and the lack of completely resistant wheat cultivars against this pathogen. The efficiency of fungicides with prothioconazole + tebuconazole and triticonazole + pyraclostrobin active ingredients, licensed on Fusarium spp. in seeds, on seed originated seedling infections of F. culmorum is determined in vitro and in vivo conditions. Seeds of Flamura-85 bread wheat cultivar, naturally infected with F. culmorum S-14, were used in this study. The effect of treating seeds naturally infected with F. culmorum S-14 with fungicides on seed germination, root length, coleoptile length and disease severity was determined in the experiment in vitro. Germination rate of the seed was determined as 68% for triticonazole + pyraclostrobin and 43% for prothioconazole + tebuconazole, while disease severity was 42.70% and 61.30%, respectively. While both fungicides were determined to be effective on the disease severity, the effect of triticonazole + pyraclostrobin on disease severity was found to be higher than prothioconazole + tebuconazole. Because of the higher rate of effectiveness of triticonazole + pyraclostrobin to prevent seed-borne infections in vitro conditions, it was determined that the fungicide causes an increase in germination rate with wet and dry weight of the seed, while significantly decreasing the disease severity, in the tests to determine the effectiveness of the fungicide in vivo conditions.

Comparative metabolomics of temperature sensitive resistance to wheat streak mosaic virus (WSMV) in resistant and susceptible wheat cultivars

In order to evaluate wheat resistance to wheat streak mosaic virus (WSMV) at low temperature and resistance breakdown at high temperature, metabolic profile of WSMV-resistant (R) and susceptible (S) wheat cultivars were analyzed. Metabolites were detected by UPLC-QTOF/MS in leaves of R and S plants challenged with WSMV at 20 °C and 32 °C, 24, 48 and 72 h post inoculation (hpi). WSMV and mock inoculated plants were used for discriminating the most significant metabolites and metabolic pathways affected at those temperatures. At 24 hpi/20 °C and 48 hpi/20 °C, the most important metabolites in R plants were coumarins, a limited number of lipids, and unknown compounds, while at 72 hpi/20 °C, in addition to coumarins, alkaloids and several amino acids were increased. Compared to 24 and 48 hpi, at 72hpi, in R plants most metabolic pathways were up-regulated at 20 °C. These resistance-related specific pathways included amino acid metabolism, lipid metabolism and alkaloids pathways. Also, several pathways were up-regulated at 32 °C.These combined heat stress and pathogen related pathways, included lipid metabolism and amino acid metabolism. Some carbohydrate metabolism pathways were considered as heat stress related pathways and could be associated with resistance breakdown. On the other hand, the increased expression of lipid compounds, especially 24 hpi at 32 °C in R plant, can be attributed to plant adaptation to combined stressors such as pathogen and high temperature. Increased susceptibility of R plants at 32 °C coincided with a down-regulated expression of components of signal transduction pathways or in a decreased level of metabolites related to this pathway, especially at a later time after infection, leading to decreased metabolite signaling. Decrease of signaling compounds under combined stress is a possible outcome of deactivating WSMV specific signaling networks leading to compatible response in R plants. The significance of these findings considering the recent increase of global temperature and the challenge of breakdown of temperature sensitive resistance to some plant viruses is discussed.

Phenotypical and genotypical characterization of Pyrenophora tritici-repentis races in Brazil

Tan spot, caused by Pyrenophora tritici-repentis, is one of the major wheat diseases in southern Brazil as well as in the wheat production areas of several other countries. The fungal isolates have been classified into eight races according to the production of three fungal necrotrophic effectors. The knowledge about the pathogen population structure is essential for disease control strategies, but such information is lacking in Brazil. The aim of this study was to determine the P. tritici-repentis race structure of Brazilian isolates using, for the first time, biological and molecular techniques. P. tritici-repentis isolates were characterized for their virulence on a set of wheat genotypes, and for the presence of ToxA and ToxB gene. The results from the PCR amplification with the gene specific primers showed that all Brazilian P. tritici-repentis isolates carried ToxA, but no ToxB is present. Race typing on the set of wheat genotypes indicate 65% of the isolates were race 2 while 35% were race 1. This is the first study on the P. tritici-repentis race structure in Brazil and the information will be useful to the local wheat breeders who aim to improve tan spot resistance in wheat cultivars.

Comparative Proteomic Analysis of Wheat Carrying Pm40 Response to Blumeria graminis f. sp. tritici Using Two-Dimensional Electrophoresis.

Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is considered a major wheat leaf disease in the main wheat producing regions of the world. Although many resistant wheat cultivars to this disease have been developed, little is known about their resistance mechanisms. Pm40 is a broad, effective resistance gene against powdery mildew in wheat line L699. The aim of this study was to investigate the resistance proteins after Bgt inoculation in wheat lines L699, Neimai836, and Chuannong26. Neimai836 with Pm21 was used as the resistant control, and Chuannong26 without any effective Pm genes was the susceptible control. Proteins were extracted from wheat leaves sampled 2, 4, 8, 12, and 24 h after Bgt inoculation, separated by two-dimensional electrophoresis, and stained with Coomassie brilliant blue G-250. The results showed that different proteins were upregulated and downregulated in three wheat cultivars at different time points. For the wheat cultivar L699, a total of 62 proteins were upregulated and 71 proteins were downregulated after Bgt inoculation. Among these, 46 upregulated proteins were identified by mass spectrometry analysis using the NCBI nr database of Triticum. The identified proteins were predicted to be associated with the defense response, photosynthesis, signal transduction, carbohydrate metabolism, energy pathway, protein turnover, and cell structure functions. It is inferred that the proteins are not only involved in defense response, but also other physiological and cellular processes to confer wheat resistance against Bgt. Therefore, the resistance products potentially mediate the immune response and coordinate other physiological and cellular processes during the resistance response to Bgt. The lipoxygenase, glucan exohydrolase, glucose adenylyltransferasesmall, phosphoribulokinase, and phosphoglucomutase are first reported to be involved in the interactions of wheat-Bgt at early stage. The further study of these proteins will deepen our understanding of their detailed functions and potentially develop more efficient disease control strategies.

Rapid Parallel Evolution of Azole Fungicide Resistance in Australian Populations of the Wheat Pathogen Zymoseptoria tritici.

Zymoseptoria tritici is a globally distributed fungal pathogen which causes Septoria tritici blotch on wheat. Management of the disease is attempted through the deployment of resistant wheat cultivars and the application of fungicides. However, fungicide resistance is commonly observed in Z. tritici populations, and continuous monitoring is required to detect breakdowns in fungicide efficacy. We recently reported azole-resistant isolates in Australia; however, it remained unknown whether resistance was brought into the continent through gene flow or whether resistance emerged independently. To address this question, we screened 43 isolates across five Australian locations for azole sensitivity and performed whole-genome sequencing on 58 isolates from seven locations to determine the genetic basis of resistance. Population genomic analyses showed extremely strong differentiation between the Australian population recovered after azoles began to be used and both Australian populations recovered before azoles began to be used and populations on different continents. The apparent absence of recent gene flow between Australia and other continents suggests that azole fungicide resistance has evolved de novo and subsequently spread within Tasmania. Despite the isolates being distinct at the whole-genome level, we observed combinations of nonsynonymous substitutions at the CYP51 locus identical to those observed elsewhere in the world. We observed nine previously reported nonsynonymous mutations as well as isolates that carried a combination of the previously reported L50S, S188N, A379G, I381V, Y459DEL, G460DEL, and N513K substitutions. Assays for the 50% effective concentration against a subset of isolates exposed to the tebuconazole and epoxiconazole fungicides showed high levels of azole resistance. The rapid, parallel evolution of a complex CYP51 haplotype that matches a dominant European haplotype demonstrates the enormous potential for de novo resistance emergence in pathogenic fungi.IMPORTANCE Fungicides are essential to control diseases in agriculture because many crops are highly susceptible to pathogens. However, many pathogens rapidly evolve resistance to fungicides. A large body of studies have described specific mutations conferring resistance and have often made inferences about the origins of resistance based on sequencing data from the target gene alone. Here, we show the de novo acquisition of resistance to the ubiquitously used azole fungicides in genetically isolated populations of the wheat pathogen Zymoseptoria tritici in Tasmania, Australia. We confirm evidence for parallel evolution through genome-scale analyses of representative worldwide populations. The emergence of complex resistance haplotypes following a well-documented recent introduction of azoles into Australian farming practices demonstrates how rapidly chemical resistance evolves in agricultural ecosystems.

Breeding Progress in Seedling Resistance against Various Races of Stripe and Leaf Rust in European Bread Wheat

Background: Stripe and leaf rust are major constraints of wheat production with substantial impacts on grain yield. Population dynamics of both pathogens and the emergence of new virulent races have resulted in relentless efforts related to wheat breeding to improve resistance during the last decades. Methods: To evaluate the breeding progress achieved with respect to race-specific resistance, a set of nine isolates of the two rust pathogens have been tested in seedling assays on a panel of 191 elite winter wheat cultivars representing wheat breeding in Europe between 1966 and 2013. Results: Significant differences in the resistance of wheat cultivars concerning both pathogens have been detected by means of two-way ANOVA. Isolates as well as genotype × isolate interaction had a significant effect for both pathogens. Breeding progress, resulting in an increased seedling resistance, has been achieved against all nine isolates over the past five decades. The slope of progress was steeper for leaf rust than for stripe rust isolates. Progress against the highly common leaf rust isolate “4171” and” the stripe rust isolate “Warrior(-)” was strongest. Conclusions: The study reveals that a steady increase in seedling resistance was achieved during the past five decades. An additive contribution of these isolate specific R genes after breakdown has been hypothesised.

ПРОЯВЛЕНИЕ УСТОЙЧИВОСТИ К МУЧНИСТОЙ РОСЕ У ОБРАЗЦОВ ЯРОВОЙ МЯГКОЙ ПШЕНИЦЫ ИЗ КОЛЛЕКЦИИ ГЕНЕТИЧЕСКИХ РЕСУРСОВ РАСТЕНИЙ ВИР

Background. Powdery mildew caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal. is a widespread foliar disease of common wheat in regions with cool and wet conditions. The disease infects the foliage, stem and spike of the wheat host. The most economical and environmentally safe method for controlling powdery mildew is the development of resistant bread wheat cultivars. The objective of this work was to analyze wheat (Triticum aestivum L.) cultivars for resistance to a powdery mildew population. Materials and methods . The VIR collection of plant genetic resources is a rich source of genetic materials. The study of resistance to the fungus employed 465 common wheat cultivars. The plants were inoculated at the seedlings, heading and flowering stages of plant development. The population of fungus was virulent to Pm1, Pm2, Pm3a-d, Pm4a-b, Pm5a, Pm6, Pm7, Pm8, Pm9, Pm16, Pm19 and avirulent to Pm12. For the estimation of plant damage, a scale from 0 (no damage) to 4 (abundant pustules) was used. Results and conclusions . The estimation of powdery mildew resistance was made in the field on adult plants. Out of 465 cultivars, resistant accessions amounted to 10,5%, intermediate ones to 16.8%, and susceptible ones to 72.7%. Generally, the resistant varieties originated from Europe and Russia. The group of the resistant cultivars (adult plants) was inoculated with fungus at the seedling stage and the plant damage was estimated. The cultivars 'Kandela', 'Arabeska', 'Batalj', 'Stillet' were resistant at all growth stages. The genetic control of powdery mildew resistance at different wheat growth stages was discussed.

Exploring and exploiting the genetic variation of Fusarium head blight resistance for genomic-assisted breeding in the elite durum wheat gene pool

Key messageGenomic selection had a higher selection response for FHB resistance than phenotypic selection, while association mapping identified major QTL on chromosome 3B unaffected by plant height and flowering date.Fusarium head blight (FHB) is one of the most destructive diseases of durum wheat. Hence, minimizing losses in yield, quality and avoiding contamination with mycotoxins are of pivotal importance, as durum wheat is mostly used for human consumption. While growing resistant varieties is the most promising approach for controlling this fungal disease, FHB resistance breeding in durum wheat is hampered by the limited variation in the elite gene pool and difficulties in efficiently combining the numerous small-effect resistance quantitative trait loci (QTL) in the same line. We evaluated an international collection of 228 genotyped durum wheat cultivars for FHB resistance over 3 years to investigate the genetic architecture and potential of genomic-assisted breeding for FHB resistance in durum wheat. Plant height was strongly positively correlated with FHB resistance and led to co-localization of plant height and resistance QTL. Nevertheless, a major QTL on chromosome 3B independent of plant height was identified in the same chromosomal interval as reported for the prominent hexaploid resistance QTL Fhb1, though haplotype analysis highlighted the distinctiveness of both QTL. Comparison between phenotypic and genomic selection for FHB resistance revealed a superior prediction ability of the former. However, simulated selection experiments resulted in higher selection responses when using genomic breeding values for early generation selection. An earlier identification of the most promising lines and crossing parents was feasible with a genomic selection index, which suggested a much faster short-term population improvement than previously possible in durum wheat, complementing long-term strategies with exotic resistance donors.

Development, Validation, and Re-selection of Wheat Lines with Pyramided Genes Yr64 and Yr15 Linked on the Short Arm of Chromosome 1B for Resistance to Stripe Rust.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat worldwide. The disease is most preferably managed by developing and growing cultivars with high-level, durable resistance. To achieve high-level and long-lasting resistance, we developed a wheat line, RIL-Yr64/Yr15, by pyramiding Yr64 and Yr15, both on the chromosome 1BS and providing high resistance to all tested Pst races. To validate RIL-Yr64/Yr15 possessing both genes, we crossed it to Avocet S (AvS). The F4 RILs from this cross were phenotyped with Pst races under controlled greenhouse conditions and also under natural Pst infection in the field. The population was genotyped with SSR markers previously reported to be linked to the resistance gene loci and with additional SSR and SNP-KASP markers along chromosome 1B. Both phenotype and genotype data confirmed the copresence of Yr64 and Yr15 in RIL-Yr64/Yr15, and the high-resolution linkage map dissected the chromosomal regions and traced their origins. New lines possessing these genes were selected from the F5 population of cross AvS × RIL-Yr64/Yr15 by marker-assisted selection. These lines with the two highly effective genes should be more useful than individual gene lines for developing high-level, durable resistant wheat cultivars.

Pathogenesis-related protein genes involved in race-specific all-stage resistance and non-race specific high-temperature adult-plant resistance to Puccinia striiformis f. sp. tritici in wheat

Interactions of the stripe rust pathogen (Puccinia striiformis f. sp. tritici) with wheat plants activate a wide range of host responses. Among various genes involved in the plant-pathogen interactions, the expressions of particular pathogenesis-related (PR) protein genes determine different defense responses. Different types of resistance have been recognized and utilized for developing wheat cultivars for resistance to stripe rust. All-stage resistance can be detected in seedling stage and remains at high levels throughout the plant growth stages. This type of resistance is race-specific and not durable. In contrast, plants with only high-temperature adult-plant (HTAP) resistance are susceptible in seedling stage, but become resistant when plants grow older and the weather becomes warmer. HTAP resistance controlled by a single gene is partial, but usually non-race specific and durable. The objective of this study was to analyze the expression of PR protein genes involved in different types of wheat resistance to stripe rust. The expression levels of 8 PR protein genes (PR1, PR1.2, PR2, PR3, PR4, PR5, PR9 and PR10) were quantitatively evaluated at 0, 1, 2, 7 and 14 days after inoculation in single resistance gene lines of wheat with all-stage resistance genes YrTr1, Yr76, YrSP and YrExp2 and lines carrying HTAP resistance genes Yr52, Yr59, Yr62 and Yr7B. Races PSTv-4 and PSTv-37 for compatible and incompatible interactions were used in evaluation of PR protein gene expression in wheat lines carrying all-stage resistance genes in the seedling-stage experiment while PSTv-37 was used in the HTAP experiment. Analysis of quantitative real-time polymerase chain reaction (qRT-PCR) revealed that all of the PR protein genes were involved in the different types of resistance controlled by different Yr genes. However, these genes were upregulated at different time points and at different levels during the infection process among the wheat lines with different Yr genes for either all-stage resistance or HTAP resistance. Some of the genes were also induced in compatible interactions, but the levels were almost always higher in the incompatible interaction than in the compatible interaction at the same time point for each Yr gene. These results indicate that both allsalicylic acid and jasmonate signaling pathways are involved in both race-specific all-stage resistance and non-race specific HTAP resistance. Although expressing at different stages of infection and at different levels, these PR protein genes work in concert for contribution to different types of resistance controlled by different Yr genes.

Different growing strategies of two winter wheat cultivars under rainfed conditions during dry years in North China Plain

The North China Plain (NCP) is a severe water shortage region, especially during the wheat growing season. Understanding the response of grain yield and water availability in winter wheat cultivars (Triticum aestivum L.) is important to adjust planting structure under groundwater reducible exploitation in rainfed dry years of NCP. Field experiments were conducted at the Luancheng Agroecosystem Experiment Station of the Chinese Academy of Sciences, Hebei, China. Two different drought resistant winter wheat cultivars (Jinmai47 and Shiluan02-1) were grown under rainfed conditions during four years of 2010-2011, 2011-2012, 2012-2013 and 2013-2014. Grain yield and its components, aboveground biomass (AB), dry matter accumulation translocation efficiency, water consumption, water use efficiency at field scale, and photosynthetic characteristics were measured. The results showed that Jinmai47 rapidly accumulated AB by higher tiller and photosynthetic potential comparing with those of Shiluan02-1. Its grain yield was 16.49% higher than that of the drought-sensitive winter wheat variety Shiluan02-1 during the four rainfed years. However, the dry matter remobilization efficiency (DMRE) and contribution of dry matter remobilization from heading stage to maturity stage to grain (CDMRE) of Shiluan02-1 was higher than those of Jinmai47. The average water use efficiency at grain yield level (WUEy), WUE at aboveground biomass level (WUEab), and WUE at grain yield under rainy conditions (WUEr) of Jinmai47 were 11.08%, 16.41%, and 17.21% higher than those of Shiluan02-1. There was a significant difference in the WUEab and WUEr between the two wheat cultivars. The two wheat varieties under drought condition have different growing strategies. Jinmai47 has more tiller number, earlier vigor, and higher AB than Shiluan02-1, helping it to adapt to the fluctuations in the environment. Keywords: winter wheat cultivar, grain yield, rainy treatment, water use efficiency, dry year DOI: 10.25165/j.ijabe.20181105.4344 Citation: Dong B D, Yang H, Qiao Y Z, Zhang M M, Wang Y K, Jin L L, et al. Different growing strategies of two winter wheat cultivars under rainfed conditions during dry years in North China Plain. Int J Agric & Biol Eng, 2018; 11(5): 150–159.

Effect of Wheat Cultivar on the Concentration of Fusarium Mycotoxins in Wheat Stems

Effective control of Fusarium-mycotoxin accumulation in grain affected by Fusarium head blight (FHB) (caused by Fusarium graminearum) begins with selecting moderately resistant wheat cultivars; however, little is known about how this resistance affects mycotoxin levels in the stem. A study was conducted from 2011 to 2014 in a mist-irrigated FHB nursery in Urbana, IL to determine whether the FHB resistance class of a cultivar (very susceptible, susceptible, moderately susceptible, and moderately resistant) affects the concentration of Fusarium mycotoxins in the stem. FHB incidence, FHB severity, and Fusarium-damaged kernel ratings were collected and used to calculate FHB index; incidence, severity, and kernel damage (ISK) index; and deoxynivalenol (DON), incidence, severity, and kernel damage (DISK) index. Grain was assayed for levels of DON, and the bottom 25 cm of plant stems was collected from each plot and assayed for DON, 3-acetyl-deoxynivalenol (3ADON), and 15-acetyl-deoxynivalenol (15ADON). Significant differences in DON concentration in the grain were detected among cultivars (P = 0.0001) and for the concentration of all DON (P = 0.003), 3ADON (P = 0.03), and 15ADON (P < 0.0001) in the stem. Significant differences among resistance classes were observed for FHB index value (P < 0.0001), ISK index (P = 0.006), and DISK index (P = 0.004). In all years of this study, the concentration of DON in the grain and the concentrations of all mycotoxins in the stem were consistently lower in the moderately resistant cultivars. All three indices were poor indicators of mycotoxin concentrations in the stem. Overall, the selection of a moderately resistant cultivar provides effective control of DON accumulation in the grain and mycotoxin accumulation in the stem.

Agronomical, biochemical and histological response of resistant and susceptible wheat and barley under BYDV stress.

Barley yellow dwarf virus-PAV (BYDV-PAV) is one of the major viruses causing a widespread and serious viral disease affecting cereal crops. To gain a better understanding of plant defence mechanisms of BYDV resistance genes (Bdv2 and RYd2) against BYDV-PAV infection, the differences in agronomical, biochemical and histological changes between susceptible and resistant wheat and barley cultivars were investigated. We found that root growth and total dry matter of susceptible cultivars showed greater reduction than that of resistant ones after infection. BYDV infected leaves in susceptible wheat and barley cultivars showed a significant reduction in photosynthetic pigments, an increase in the concentration of reducing sugar. The protein levels were also low in infected leaves. There was a significant increase in total phenol contents in resistant cultivars, which might reflect a protective mechanism of plants against virus infection. In phloem tissue, sieve elements (SE) and companion cells (CC) were severely damaged in susceptible cultivars after infection. It is suggested that restriction of viral movement in the phloem tissue and increased production of phenolic compounds may play a role in the resistance and defensive mechanisms of both Bdv2 and RYd2 against virus infection.