Susceptible Wheat Varieties Research Articles

Hessian Fly (Diptera: Cecidomyiidae) Management Using Seed Treatments in Winter Wheat1

Abstract The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), is a potentially severe pest of wheat, Triticum aestivum L. em Thell, in the southeastern United States. Plant resistance is an effective method to control Hessian fly, but when adapted high-yielding varieties with effective resistance are not available, neonicotinoid insecticide seed treatments may provide an alternative method of control of Hessian fly on susceptible varieties of winter wheat. A series of experiments were conducted to examine the efficacy of neonicotinoid seed treatments for control of Hessian fly in winter wheat. Infestations and immature numbers per tiller were assessed during the vegetative stages in autumn and winter and the wheat reproductive stage during the spring. Both imidacloprid 480FS at 0.31 g active ingredient (a.i.)/kg of seed and clothianidin at 0.39 g a.i./kg or higher rates provided consistent reductions in Hessian fly infestations during autumn and early winter. Lower rates were less effective, and they did not provide consistent reductions in autumn infestations. Thiamethoxam was evaluated at one rate in two experiments and was similar in efficacy to imidacloprid and clothianidin at the same rate. None of the seed treatments provided effective control of spring infestations during the wheat reproductive stage. Imidacloprid and clothianidin at rates of 0.31 g a.i./kg of seed or higher rates had a positive yield response in eight of nine comparisons, with an average increase of 285.9 ± 92.7 kg/ha. Neonicotinoid insecticide seed treatments at higher rates provide a useful method for managing Hessian fly on susceptible varieties of winter wheat.

Impact of managing yellow rust (Puccinia striiformis f.sp. tritici) by the use of fungicide sprays and resistant varieties on the physiochemical qualities of bread wheat

AbstractYellow rust disease caused by Puccinia striiformis f. sp. tritici is one of the major threats to wheat production in Ethiopia. In this paper, the impact of yellow rust on the physical qualities of bread wheat was studied. For this purpose, combinations of four bread wheat varieties (Digalu, Hidase, Danda'a, and Honkolo) and two fungicides (Nativo SC 300 and Tilt® 250E.C.) were tested at two different hotspot areas (Albazar and Alicho) in the Silte Zone, Southern Ethiopia, under natural epidemics of the disease during the 2018 growing season. A randomized complete block design in factorial arrangement with three replications was used to set up the experiment. A significant (p < .01) increase in hectoliters weight and wet gluten content were observed due to the application of Nativo SC 300; however, grain protein content did not respond significantly (p > .01) at both locations. Wheat varieties with high yellow rust severity exhibited maximum values of area under the disease progress curve and physical quality loss percentage (%). The highly susceptible wheat variety Digalu exhibited the highest values of hectoliter weight losses (%), and the actual losses ranged from 5.5% to 29.5%. Except for grain protein content, there was a significant negative correlation between the values of terminal rust severity, average coefficient infection, and area under the disease progress curve and that of hectoliters weight and wet gluten content, with correlation coefficients ranging from −0.85** to −0.33**. It is possible to improve the physiochemical properties of bread wheat through the application of foliar fungicides by selecting the appropriate genotypes that have an acceptable level of resistance to yellow rust.

Diversity of halotolerant endophytes from wheat (Triticum aestivum) and their response to mitigate salt stress in plants

Soil salinity is one of the major limiting factors that decline crop production. About 20% of irrigated land soil is presently affected by high salinity worldwide reducing the crop yield by 20–50%. Endophytes play an important role in coping with the salinity stress in plants. In present study, 224 bacterial endophytes exhibiting discrete salt tolerance ranging from 0.5 M to 4.0 M were isolated from the shoot and root of wheat. Endophytic isolates showed varying salt tolerance potential and only a few (7.14%) possess the capability to tolerate high salt concentration (≥3.0 M NaCl). The 16S rRNA gene sequence exhibited 65 discrete OTUs recovered from the root (53.85%) and shoot tissue (46.15%) of the wheat plant. The 16S rRNA gene sequencing revealed the majority of phylum were Firmicutes (81.54%), Proteobacteria (13.85%), and Actinobacteria (4.62%) and dominated by Bacillus (63.08%), Priestia (13.85%), Pseudomonas (10.77%), Exiguobacterium and Curtobacterium (3.08% each). Moreover, this study is the first report for the abundance of certain bacterial species as endophytes from wheat cultivated under saline-affected regions like Bacillus australimaris, B. vallismortis, B. haynesii, Rossellomorea marisflavi, Exiguobacterium undae, Curtobacterium pusillum. The selected endophytes significantly reduced the detrimental influence of salt stress and enhanced various growth parameters like root length, shoot length, fresh weight, and dry weight of salt susceptible wheat variety ‘HD 2733’ as compared to the control. The present study might be beneficial to restore soil fertility and reduce the loss of crop productivity under saline stress conditions.

Differences in Rhizosphere Microbial Community Structure and Composition in Resistance and Susceptible Wheat to Fusarium Head Blight

Fusarium head blight (FHB) is a serious disease of wheat that threatens wheat production worldwide. In this study, high-throughput sequencing technology was used to analyze the rhizosphere soil microbial metagenomes of 4 wheat cultivars with different levels of resistance to FHB. The results showed that there were differences in the diversity, structure, and composition of rhizosphere microorganisms between resistant and sensitive varieties. The rhizosphere soil bacterial diversity of the resistant wheat varieties Su Mai 3 and Yang Mai 16 was higher than that of the susceptible wheat varieties Zheng Mai 9023 and Zhou Mai 20. The diversity of rhizosphere fungi in resistant varieties was lower than that in susceptible varieties, but the abundance was higher than that in susceptible varieties. Variety was found to alter the community structure of wheat rhizosphere microorganisms. Resistant varieties SM3 and YM16 and moderately susceptible variety ZM9023 had similar microbial community structure, while highly susceptible variety ZM20 was significantly different from other varieties. The study is aimed at analyzing the effects of wheat varieties of different resistance to FHB on the composition and abundance of rhizosphere soil microbial community to screen out bacteria or fungi that can be used to control FHB, providing the theoretical basis for FHB biological control.

Defence-related metabolic changes in wheat (Triticum aestivum L.) seedlings in response to infection by Puccinia graminis f. sp. tritici.

Stem rust caused by the pathogen Puccinia graminis f. sp. tritici is a destructive fungal disease-causing major grain yield losses in wheat. Therefore, understanding the plant defence regulation and function in response to the pathogen attack is required. As such, an untargeted LC-MS-based metabolomics approach was employed as a tool to dissect and understand the biochemical responses of Koonap (resistant) and Morocco (susceptible) wheat varieties infected with two different races of P. graminis (2SA88 [TTKSF] and 2SA107 [PTKST]). Data was generated from the infected and non-infected control plants harvested at 14- and 21- days post-inoculation (dpi), with 3 biological replicates per sample under a controlled environment. Chemo-metric tools such as principal component analysis (PCA), orthogonal projection to latent structures-discriminant analysis (OPLS-DA) were used to highlight the metabolic changes using LC-MS data of the methanolic extracts generated from the two wheat varieties. Molecular networking in Global Natural Product Social (GNPS) was further used to analyse biological networks between the perturbed metabolites. PCA and OPLS-DA analysis showed cluster separations between the varieties, infection races and the time-points. Distinct biochemical changes were also observed between the races and time-points. Metabolites were identified and classified using base peak intensities (BPI) and single ion extracted chromatograms from samples, and the most affected metabolites included flavonoids, carboxylic acids and alkaloids. Network analysis also showed high expression of metabolites from thiamine and glyoxylate, such as flavonoid glycosides, suggesting multi-faceted defence response strategy by understudied wheat varieties towards P. graminis pathogen infection. Overall, the study provided the insights of the biochemical changes in the expression of wheat metabolites in response to stem rust infection.

Economic versus technical efficiency in using ASM combined with fungicides to elicit wheat varieties with different disease susceptibilities

Despite the positive results of using elicitors to induce resistance against plant diseases, some factors have inhibited the popularization of their use in agriculture. There is an energetic cost related to the elicitors' induced response which can cause undesired effects on growth under low-pressure disease conditions. Elicitors can create phytotoxicity and show high variation in their efficiency between different genotypes within the same crop; in addition, the positive results related to the induced resistance may not repeat in field treatments, adding to the possibility that they are not economically viable. Thus, we carried out two experiments to investigate the technical and economic efficiency of acibenzolar-S-methyl (ASM) and its association with fungicides in the control of leaf diseases of susceptible and resistant wheat varieties, and as how it reflects on the photosynthetic and production performance of wheat. This study showed the limitations of incorporating ASM into foliar fungal disease control in economic terms. However, it was evident that ASM effectively induced plant resistance against Leaf Rust and Powdery Mildew in the field and can be considered a sustainable option for wheat cultivation. Even though its association with chemical control was not the best economic strategy the use of ASM is a tool that can be incorporated into wheat cultivation to minimize the emergence of fungicide-resistant pathogens due to the diversification of modes of action employed and reduce the toxic residue deposition to the environment and human health.

Comparative transcriptomics identifies the key in planta-expressed genes of Fusarium graminearum during infection of wheat varieties.

Fusarium head blight (FHB), caused mainly by the fungus Fusarium graminearum, is one of the most devastating diseases in wheat, which reduces the yield and quality of grain. Fusarium graminearum infection of wheat cells triggers dynamic changes of gene expression in both F. graminearum and wheat, leading to molecular interactions between pathogen and host. The wheat plant in turn activates immune signaling or host defense pathways against FHB. However, the mechanisms by which F. graminearum infects wheat varieties with different levels of host resistance are largely limited. In this study, we conducted a comparative analysis of the F. graminearum transcriptome in planta during the infection of susceptible and resistant wheat varieties at three timepoints. A total of 6,106F. graminearum genes including those functioning in cell wall degradation, synthesis of secondary metabolites, virulence, and pathogenicity were identified during the infection of different hosts, which were regulated by hosts with different genetic backgrounds. Genes enriched with metabolism of host cell wall components and defense response processes were specifically dynamic during the infection with different hosts. Our study also identified F. graminearum genes that were specifically suppressed by signals derived from the resistant plant host. These genes may represent direct targets of the plant defense against infection by this fungus. Briefly, we generated databases of in planta-expressed genes of F. graminearum during infection of two different FHB resistance level wheat varieties, highlighted their dynamic expression patterns and functions of virulence, invasion, defense response, metabolism, and effector signaling, providing valuable insight into the interactions between F. graminearum and susceptible/resistant wheat varieties.

Mapping and characterization of a novel adult-plant leaf rust resistance gene LrYang16G216 via bulked segregant analysis and conventional linkage method.

A novel adult-plant leaf rust resistance gene LrYang16G216 on wheat chromosome 6BL was identified and mapped to a 0.59cM genetic interval by BSA and conventional linkage method. Leaf rust (Puccinia triticina) is one of the most devastating fungal diseases of wheat (Triticum aestivum L.). Discovery and identification of new resistance genes is essential to develop disease-resistant cultivars. An advanced breeding line Yang16G216 was previously identified to confer adult-plant resistance (APR) to leaf rust. In this research, a recombinant inbred line (RIL) population was constructed from the cross between Yang16G216 and a highly susceptible line Yang16M6393, and genotyped with exome capture sequencing and 55K SNP array. Through bulked segregant analysis (BSA) and genetic linkage mapping, a stable APR gene, designated as LrYang16G216, was detected and mapped to the distal region of chromosome arm 6BL with a genetic interval of 2.8cM. For further verification, another RIL population derived from the cross between Yang16G216 and a susceptible wheat variety Yangmai 29 was analyzed using the enriched markers in the target interval, and LrYang16G216 was further narrowed to a 0.59cM genetic interval flanked by the KASP markers Ax109403980 and Ax95083494, corresponding to the physical position 712.34-713.94Mb in the Chinese Spring reference genome, in which twenty-six disease resistance-related genes were annotated. Based on leaf rust resistance spectrum, mapping data and physical location, LrYang16G216 was identified to be a novel and effective APR gene. The LrYang16G216 with linked markers will be useful for marker-assisted selection in wheat resistance breeding.

Duration of fungicide activity against wheat powdery mildew

Abstract The most commonly used method to control wheat powdery mildew is by fungicides. The aim of the present study is to determine the duration of the fungicide activity of three fungicides: azoxystrobin; triadimenol; tebuconazole+spiroxamine+triadimenol. They were applied in three concentrations in phenophase 3-4 leaf of susceptible wheat variety. After treatment, each day one pot of the tested fungicide concentrations was inoculated with Blumeria graminis f. sp. tritici. When using azoxystrobin at concentrations of 0.2%, 0.4%, 0.8%, symptoms of powdery mildew appeared on plants inoculated with Blumeria graminis f.sp. tritici in the next day after treatment. When using triadimenol, first symptoms appeared in plants inoculated with the pathogen on the next day after applying a concentration 0.12%, on the second day after applying a concentration 0.25% and on the third day after treatment with a concentration 0.5%. With tebuconazole+spiroxamine+triadimenol, first postules appeared on plants inoculated with Blumeria graminis f. sp. tritici on the third day after treatment with a concentration 0.15%, on the 13th day after treatment with a concentration 0.3% and on the 14th day after treatment with a concentration 0.6%. This fungicide at a concentration of 0.6% (13 days) and 0.3% (12 days) has the longest duration of fungicide activity.

Plant Volatiles Mediate Host Selection of Sitodiplosis mosellana (Diptera: Cecidomyiidae) among Wheat Varieties.

Sitodiplosis mosellana is a major wheat pest that oviposits on spikes, and resistant wheat varieties have been released. However, wheat spike volatiles mediating S. mosellana host selection or resistance are largely unknown. In this study, we found that the highly susceptible wheat varieties Xinong 822, Xinong 88, and Xiaoyan 22 were preferred for S. mosellana oviposition, and their spike volatiles were more attractive to females compared to the resistant varieties Kenong 1006, Shanmai 139, and Jinmai 47. Importantly, we found five odor components evoking obvious concentration-dependent electroantennogram (EAG) and behavioral response. Notably, 3-hexanol, cis-3-hexenylacetate, and hexyl acetate strongly attracted females, whereas ocimene, a dominant component of three resistant varieties, and α-farnesene, absent in Xinong 88, repelled females. Significant attraction was also observed in a synthetic blend mimicking Xinong 822 volatiles. These results suggest that these wheat volatiles are involved in host selection of S. mosellana and provide a basis for development of semichemical-based pest management.

Identification of Differentially Expressed Genes in Resistant Tetraploid Wheat (Triticum turgidum) under Sitobion avenae (F.) Infestation.

The grain aphid Sitobion avenae (Fabricius) is one of the most destructive pests of wheat (Triticum aestivum). Deployment of resistant wheat germplasm appears as an excellent solution for this problem. Elite bread wheat cultivars only have limited resistance to this pest. The present study was carried out to investigate the potential of the tetraploid wheat (Triticum turgidum) variety Lanmai, which showed high resistance to S. avenae at both seedling and adult plant stages, as a source of resistance genes. Based on apterous adult aphids’ fecundity tests and choice bioassays, Lanmai has been shown to display antixenosis and antibiosis. Suppression subtractive hybridization (SSH) was employed to identify and isolate the putative candidate defense genes in Lanmai against S. avenae infestation. A total of 134 expressed sequence tags (ESTs) were identified and categorized based on their putative functions. RT-qPCR analysis of 30 selected genes confirmed their differential expression over time between the resistant wheat variety Lanmai and susceptible wheat variety Polan305 during S. avenae infestation. There were 11 genes related to the photosynthesis process, and only 3 genes showed higher expression in Lanmai than in Polan305 after S. avenae infestation. Gene expression analysis also revealed that Lanmai played a critical role in salicylic acid and jasmonic acid pathways after S. avenae infestation. This study provided further insights into the role of defense signaling networks in wheat resistance to S. avenae and indicates that the resistant tetraploid wheat variety Lanmai may provide a valuable resource for aphid tolerance improvement in wheat.

The Quantitative Analyses for the Effects of Two Wheat Varieties With Different Resistance Levels on the Fungicide Control Efficacies to Powdery Mildew.

Effective strategies to reduce the occurrence of wheat powdery mildew include the use of resistant varieties and application of fungicides. However, most studies rarely focus on the quantitative value of fungicide reduction using resistant varieties. To explore how the fungicides performed on different resistant wheat varieties to powdery mildew, field experiments were conducted during wheat growing seasons in 2018/19 and 2019/20 to investigate the control efficacies of enostroburin⋅epoxiconazole 18% SC and triadimefon 20% EC to wheat powdery mildew on a highly resistant wheat variety (“Baofeng104”) and a highly susceptible wheat variety (“Jingshuang16”). The analyses of variance on control efficacies showed that the control efficacies of enostroburin⋅epoxiconazole 18% SC to wheat powdery mildew were mostly significantly higher than triadimefon 20% EC under the same conditions (i.e., varieties, dosages). However, both fungicide and variety resistance made variabilities in the mildew disease index and played a significant role in mildew management. Particularly, the variety resistance made the greatest contribution in mildew-reducing, and the disease index could significantly be reduced on the highly resistant variety even in the absence of fungicide treatment. The control efficacies to mildew on the highly susceptible variety mainly depended on the high efficiency of fungicides whereas the highly resistant variety were mainly by virtue of variety resistance through the comparative analyses of linear regression models. Furthermore, the random-coefficient regression models and quantile models quantificationally expounded that the relationships between active ingredient dosage and disease index or control efficacy varied from the effects of variety, fungicide, and year, particular from variety. Thus, a dosage reference table of enostroburin⋅epoxiconazole 18% SC or triadimefon 20% EC for different resistant wheat varieties were provided; it would be helpful for users to formulate an appropriate dosage of fungicide on mildew management in the field and avoid overusing or superfluous application. Further study needs to consider the effects of fungicide reduction on wheat yields, only then the maximum-economic benefits on mildew management can be determined.

Rate of stripe rust (Puccinia striiformis) on wheat in the highland and lowland area

Stripe (Yellow) rust caused by Puccinia striiformis f.sp. tritici (Pst) is a crucial wheat disease causing severe damage to cultivated susceptible wheat varieties. The wheat yellow rust assessment was conducted during the primary rainy season of 2018/19 at Ada’a, Lume, and Gimbichu using the zigzag disease assessment method. Disease data, agro-ecological data, and other essential parameters were recorded. The disease was prevalent in all districts by diverse incidence and severity ranges. This implies that yellow rust is distributed wheat disease at all surveyed potential districts. The highest yellow rust prevalence, 62.5% was recorded at Gimbichu district; conversely, the lowest prevalence 31.25% was recorded at Ada’a district. The highest severity and incidence of yellow rust 60% and 100%, respectively, was recorded at Ada’a district with susceptible reaction. In comparison, the lowest severity and incidence (30% and 5%) respectively were recorded at Lume districts with moderately sensitive responses. Many distributions and occurrences govern yellow rust. The highest incidence of yellow rust, namely 100% on land cultivated with kakaba and kubsa wheat bread varieties, occurred at the milk growth stage to the ripe stage. The local cultivar has shown the lowest incidence and severity percentage with moderately susceptible responses than improved varieties.

Interaction effect of Root Lesion Nematodes and Fusarium culmorum Sacc. on disease complex in some wheat cultivars

The study was conducted to assess a possible interaction between fungal pathogen of Fusarium culmorum Sacc. and Root lesion nematodes at sequentially and simultaneously inoculation. Fusarium culmorum spore suspension effect evaluated on plant disease severity and nematode density on moderate resistant wheat line to F. culmorum (2-49) and susceptible wheat variety (İkizce) under controlled condition. The disease severity was higher on İkizce cv. than 2-49. This indicates that there is a considerable important pathogen resistance. Simultaneous and sequential inoculation of Pratylenchus thornei and F. culmorum reduced the final nematode density and reproduction rate more than inoculation with only nematode on İkizce cv. The simultaneously P. penetrans and F.culmorum inoculation (N+F) affected the positively of final density on İkizce cv. The N+ F treatment affected the positively of P. neglectus density on İkizce cv., whereas negative effect was found in pre or post inoculation of F. culmorum treatments. No synergistic interactions were detected on 2-49 when plants were co-infected by the root lesion nematode and fungus. It was determined that P. thornei had a positive effect on disease severity when it entered the plant simultaneously and before the F. culmorum on İkizce cv.. The disease severity decreased in F. culmorum was applied four weeks after the P. neglectus treatment on 2-49 wheat line and İkizce cv. In the interaction with F. culmorum on İkizce cv., differences were determined between the species of root lesion nematodes.

Chitin Triggers Tissue-Specific Immunity in Wheat Associated With Fusarium Head Blight.

Fusarium graminearum is one of the primary causal agents of Fusarium head blight (FHB) on wheat and barley. FHB reduces grain yield and contaminates grain with various mycotoxins, including deoxynivalenol (DON). DON acts as a virulence factor to promote the fungus passing the rachis node and spreading throughout the head of wheat but not barley. Reactive oxygen species (ROS) are one of the earliest defense responses during plant and pathogen interactions. However, the complex roles of ROS during FHB development remain unclear. We investigated immune responses in wheat triggered by chitin, a major component of fungal cell walls. Although no ROS burst was detected in chitin-treated wheat leaves from eight tested varieties, a robust ROS peak was triggered by chitin in tested barley leaves. Interestingly, ROS were induced by chitin in wheat rachises and rachis nodes, which are critical barriers for FHB spread in wheat. We demonstrated that ROS were induced in wheat rachis nodes from both FHB susceptible and resistant wheat varieties. Further, we showed different defense gene expression patterns in rachis nodes and wheat heads treated with chitin, and wheat heads inoculated with F. graminearum. Our study showed the tissue-specific immune responses induced by chitin in wheat, which may play an important role during F. graminearum infection.

Pathotype Identification and Virulence Variation in Cochliobolus sativus in China

Spot blotch caused by Cochliobolus sativus has become an important disease in the wheat-growing regions in China that has resulted from changes in the regional climate, agricultural cultivation patterns, and the susceptible wheat varieties that are widely grown. Little information is available about virulence variability and pathogenic specialization of the C. sativus isolates from major wheat-growing regions in China. Here, 12 representative wheat varieties and foundation breeding stocks were selected to characterize the pathotypes of C. sativus isolates from infected wheat plants. Based on the infection phenotypes in the 12 differential genotypes at the seedling stage, 70 Chinese pathotypes were identified from 110 isolates and clustered into three virulence groups. The high virulence isolates were collected from wheat leaves, crowns, and roots, with most (10 of 14) from the Henan province in the Huang-Huai plain. No relationship was evident between virulence variability of C. sativus isolates and their geographic origins or types of diseased wheat tissues. C. sativus showed a significant pathogenic specialization in hosts of wheat and barley. Most of the wheat isolates (50 of 65) were avirulent to all the differential barley genotypes, and a few were virulent only to highly susceptible barley genotypes. These results indicated that C. sativus isolates from the wheat-growing regions in China varied considerably for their virulence in wheat varieties, and showed significant pathogenic specialization to the wheat and barley hosts.

Cultivar Mixture Enhances Crop Yield by Decreasing Aphids

The reduction in biodiversity owing to agricultural intensification has brought negative effects on sustainable crop production in the agro-environment. Plant diversity can help regulate insect pests; however, research that demonstrates that genotypic diversity of multiple varieties with prominent agroecological practices to suppress insect pests and benefit crop yield at agricultural landscapes is limited. To examine the effects of diversity of wheat varieties on aphids and crop productivity, we performed field experiments by designing plots of single (resistant/susceptible) and cultivar mixtures in 2018–2020. The effects of population abundance of cereal aphids (Sitobion miscanthi and Rhopalosiphum padi) and crop yield on resistant and susceptible wheat varieties and mixture of wheat cultivars were determined to reveal the most dominant mixed broadcasting mode in Kaifeng of China. The results showed that cultivar mixture significantly decreased aphid abundance compared with the single varieties (resistant/susceptible). Cultivar mixture had a higher yield compared with the single varieties (resistant/susceptible). Additionally, cultivar mixture had significantly higher thousand-grain weights than susceptible and resistant wheat varieties in 2019 and 2020. Cultivar mixture enhanced wheat yield by decreasing cereal aphids, indicating a bottom-up or top-down effect from genetic diversity to pest abundance. Our results indicated that appropriate cultivar mixtures could manage insect pests to some extent and stabilize crop yield.

Economic Injury Levels and Dynamic Action Thresholds for Diuraphis noxia (Hemiptera: Aphididae) in Australian Cereal Crops.

The Russian wheat aphid (Diuraphis noxia [Kurdjumov, Hemiptera: Aphididae], RWA) was first detected in Australia in 2016 and is threatening an annual cereal industry valued at nearly 10 billion AUD per annum. Considerable uncertainty surrounds the economic risk of D. noxia to Australian cereals, which limits cost-effective farm management decisions. Through a series of inoculated and non-inoculated field trials in 2018 and 2019 in south-eastern Australia, we generated a range of D. noxia pressure metrics under different growing conditions for barley, wheat, and durum wheat. Relative yield loss was best explained by the 'percentage of tillers with D. noxia' (%TwRWA) with 0.28% yield loss per percent of tillers with D. noxia, which is significantly lower than 0.46-0.48% for susceptible winter wheat varieties in dryland conditions in the United States. Highest infestation levels were typically reached around GS40-50. To develop an action threshold, we calculated the rate of increase in the %TwRWA through time at 0.021% per day per %TwRWA (with little variation across sites). This allowed prediction of the expected maximum %TwRWA based on observations post tillering (GS30) and the expected duration before GS50 is reached. For earlier growth stages (<GS30), we were unable to determine yield impact and action thresholds since cereal plants produce many new tillers between GS20 and GS30, which may compensate for feeding damage as reported in other studies. This research should improve the cost-effectiveness of management decisions involving D. noxia in Australian cereal production systems.

Comparative Metabolite Profiling of Wheat Cultivars (Triticum aestivum) Reveals Signatory Markers for Resistance and Susceptibility to Stripe Rust and Aluminium (Al3+) Toxicity.

Plants continuously produce essential metabolites that regulate their growth and development. The enrichment of specific metabolites determines plant interactions with the immediate environment, and some metabolites become critical in defence responses against biotic and abiotic stresses. Here, an untargeted UHPLC-qTOF-MS approach was employed to profile metabolites of wheat cultivars resistant or susceptible to the pathogen Puccinia striiformis f. sp. tritici (Pst) and Aluminium (Al3+) toxicity. Multivariate statistical analysis (MVDA) tools, viz. principal component analysis (PCA) and hierarchical cluster analysis (HiCA) were used to qualify the correlation between the identified metabolites and the designated traits. A total of 100 metabolites were identified from primary and secondary metabolisms, including phenolic compounds, such as flavonoid glycosides and hydroxycinnamic acid (HCA) derivatives, fatty acids, amino acids, and organic acids. All metabolites were significantly variable among the five wheat cultivars. The Pst susceptible cultivars demonstrated elevated concentrations of HCAs compared to their resistant counterparts. In contrast, ‘Koonap’ displayed higher levels of flavonoid glycosides, which could point to its resistant phenotype to Pst and Al3+ toxicity. The data provides an insight into the metabolomic profiles and thus the genetic background of Pst- and Al3+-resistant and susceptible wheat varieties. This study demonstrates the prospects of applied metabolomics for chemotaxonomic classification, phenotyping, and potential use in plant breeding and crop improvement.

Efficacy of different fungicides for leaf blight (Alternaria triticina) management in wheat

A. triticina, a seedborne pathogen, can cause major damage to susceptible wheat varieties under wet or humid conditions. Considering the importance of leaf blight of wheat caused by Alternaria triticina,the field study was conducted using different fungicides. The different fungicides like, Mancozeb 75% WP, Propineb 70% WP, Hexaconazole 5% SC, Propiconazole 25 % EC, Azoxystrobin 11% + Tebuconazole 18.30% SC and Hexaconazole 4% + Zineb 68% WP tested as foliar spray under field conditions the lower disease intensity (15.79 %) was recorded in foliar application of Propiconazole 25 % EC (500 ppm) followed by Hexaconazole 4 % + Zineb 68 % WP (18.44 %) at 1000 ppm. The maximum grain yield (3831 kg/ha) was also recorded in foliar spray of Propiconazole 25 % EC which was at par with Hexaconazole 4 % + Zineb 68 % WP and Hexaconazole 5 % SC.