Magnaporthe Oryzae Triticum Research Articles

Biological control potential of worrisome wheat blast disease by the seed endophytic bacilli.

Crop production often faces challenges from plant diseases, and biological control emerges as an effective, environmentally friendly, cost-effective, and sustainable alternative to chemical control. Wheat blast disease caused by fungal pathogen Magnaporthe oryzae Triticum (MoT), is a potential catastrophic threat to global food security. This study aimed to identify potential bacterial isolates from rice and wheat seeds with inhibitory effects against MoT. In dual culture and seedling assays, three bacterial isolates (BTS-3, BTS-4, and BTLK6A) demonstrated effective suppression of MoT growth and reduced wheat blast severity when artificially inoculated at the seedling stage. Genome phylogeny identified these isolates as Bacillus subtilis (BTS-3) and B. velezensis (BTS-4 and BTLK6A). Whole-genome analysis revealed the presence of genes responsible for controlling MoT through antimicrobial defense, antioxidant defense, cell wall degradation, and induced systemic resistance (ISR). Taken together, our results suggest that the suppression of wheat blast disease by seed endophytic B. subtilis (BTS-3) and B. velezensis (BTS-4 and BTLK6A) is liked with antibiosis and induced systemic resistance to wheat plants. A further field validation is needed before recommending these endophytic bacteria for biological control of wheat blast.

Rapid mini-chromosome divergence among fungal isolates causing wheat blast outbreaks in Bangladesh and Zambia.

The fungal pathogen, Magnaporthe oryzae Triticum pathotype, causing wheat blast disease was first identified in South America and recently spread across continents to South Asia and Africa. Here, we studied the genetic relationship among isolates found on the three continents. Magnaporthe oryzae strains closely related to a South American field isolate B71 were found to have caused the wheat blast outbreaks in South Asia and Africa. Genomic variation among isolates from the three continents was examined using an improved B71 reference genome and whole-genome sequences. We found strong evidence to support that the outbreaks in Bangladesh and Zambia were caused by the introductions of genetically separated isolates, although they were all close to B71 and, therefore, collectively referred to as the B71 branch. In addition, B71 branch strains carried at least one supernumerary mini-chromosome. Genome assembly of a Zambian strain revealed that its mini-chromosome was similar to the B71 mini-chromosome but with a high level of structural variation. Our findings show that while core genomes of the multiple introductions are highly similar, the mini-chromosomes have undergone marked diversification. The maintenance of the mini-chromosome and rapid genomic changes suggest the mini-chromosomes may serve important virulence or niche adaptation roles under diverse environmental conditions.

Suppressive Effects of Volatile Compounds from Bacillus spp. on Magnaporthe oryzae Triticum (MoT) Pathotype, Causal Agent of Wheat Blast.

The Magnaporthe oryzae Triticum (MoT) pathotype is the causal agent of wheat blast, which has caused significant economic losses and threatens wheat production in South America, Asia, and Africa. Three bacterial strains from rice and wheat seeds (B. subtilis BTS-3, B. velezensis BTS-4, and B. velezensis BTLK6A) were used to explore the antifungal effects of volatile organic compounds (VOCs) of Bacillus spp. as a potential biocontrol mechanism against MoT. All bacterial treatments significantly inhibited both the mycelial growth and sporulation of MoT in vitro. We found that this inhibition was caused by Bacillus VOCs in a dose-dependent manner. In addition, biocontrol assays using detached wheat leaves infected with MoT showed reduced leaf lesions and sporulation compared to the untreated control. VOCs from B. velezensis BTS-4 alone or a consortium (mixture of B. subtilis BTS-3, B. velezensis BTS-4, and B. velezensis BTLK6A) of treatments consistently suppressed MoT in vitro and in vivo. Compared to the untreated control, VOCs from BTS-4 and the Bacillus consortium reduced MoT lesions in vivo by 85% and 81.25%, respectively. A total of thirty-nine VOCs (from nine different VOC groups) from four Bacillus treatments were identified by gas chromatography-mass spectrometry (GC-MS), of which 11 were produced in all Bacillus treatments. Alcohols, fatty acids, ketones, aldehydes, and S-containing compounds were detected in all four bacterial treatments. In vitro assays using pure VOCs revealed that hexanoic acid, 2-methylbutanoic acid, and phenylethyl alcohol are potential VOCs emitted by Bacillus spp. that are suppressive for MoT. The minimum inhibitory concentrations for MoT sporulation were 250 mM for phenylethyl alcohol and 500 mM for 2-methylbutanoic acid and hexanoic acid. Therefore, our results indicate that VOCs from Bacillus spp. are effective compounds to suppress the growth and sporulation of MoT. Understanding the MoT sporulation reduction mechanisms exerted by Bacillus VOCs may provide novel options to manage the further spread of wheat blast by spores.

Prouzrokovač sušice klasa i lista strnih žita (Magnaporthe oryzae) - pojava i rizici za proizvodnju u Srbiji

Magnaporthe oryzae (anamorph Pyricularia oryzae) is the causal agent of wheat blast. Apart from being a pathogen of commercially significant plant species, it also infects weeds. Within the species M. oryzae, several pathotypes exist, with the pathotype Magnaporthe oryzae Triticum (MoT) infecting wheat and several other grass species. M. oryzae was first discovered in Brazil in 1985 and has since posed a threat to wheat production in various parts of the world, including Bangladesh and European Union countries. The MoT pathogen can infect all above-ground parts of the plant, but the most common symptoms appear on the ears and closely resemble symptoms of fusarium head blight. During the 2022/2023 growing season, precipitation levels in April and May at the Rimski šančevi exceeded seventeen-year averages, while the temperature in May was within the multi-year average range. These conditions created a favorable environment for the emergence of M. oryzae. Microscopic examination of infected ears revealed the presence of conidia from the asexual generation of Pyricularia oryzae. Considering that MoT is not classified as a quarantine pathogen in many EU countries, this study highlights the risk of the presence of M. oryzae in Serbia, as well as the importance of monitoring the occurrence of M. oryzae in weeds, grasses, and cereal grains to take timely action in protecting crops from this pathogen.

Efficacy of Ethanol Extract of Botanicals in Controlling Wheat Blast Fungus Magnaporthe oryzae triticum in vitro

The present research work was conducted to evaluate the efficacy of eight fresh botanicals namely Azadirachta indica (Neem leaf), Allium cepa (Onion bulb), Allium sativum (Garlic), Curcuma longa (Turmeric), Zingiber officinale (Ginger), Allamanda cathartica (Allamanda leaf), Nigella sativa (Black cumin) and Aloe vera (Aloe vera) against Magnaporthe oryzae triticum (MoT) and solvent, ethanol (95%) was used for the phytochemical extraction of various plant parts. Three concentrations namely 1:1 (w/v), 1:0.50 (w/v) and 1:0.25 (w/v) of plant parts and ethanol were used for botanical extraction. The antifungal activity of botanicals against a virulent MoT isolate CHMoT07 was evaluated in-vitro using poison food technique. The lowest mycelia growth was recorded with Aloe vera (Aloe vera leaf) extracts and Nigella sativa (Black cumin seeds) extracts @ 1:1 w/v and @ 1:0.25 w/v with growth rate of 3.00 mm and 3.33 mm respectively at 7 days after inoculation, whereas the highest mycelia growth rate of MoT isolates was recorded in control plates both at 7 DAI and 14 DAI under in-vitro condition.

MONITORING AND DETECTION OF WHEAT BLAST DISEASE CAUSED BY MAGNAPORTHE ORYZAE TRITICUM PATHOTYPE IN PUNJAB, PAKISTAN

The wheat blast caused by the Magnaporthe oryzae Triticum pathotype has become a serious threat to wheat production in Pakistan and India after its severe outbreak in Bangladesh in 2016 and intermittent occurrence since then. Thus, planned systemic surveillance of wheat crops in two phases in 2018–2019 and 2019–2020 began to determine the status of wheat blasts in Punjab, Pakistan. In the first phase, a survey of 160 wheat fields in districts in Punjab ensued for typical blast symptoms. The surveillance‟s second phase occurred after the threshing of the wheat crop, with composite grain samples collected from all over Punjab, then analyzed in the lab. The surveillance results indicated that all the wheat fields were free from the typical blast symptoms. Similarly, none of the analyzed samples showed the presence of wheat blast pathogens. Therefore, the study validates that this dreadful disease (blast) does not exist in Punjab, Pakistan. Hence, the reason to remain calm needs dissemination among the farming community and the training of technical agriculture extension staff for vigilance in the future for monitoring this disease in different agro-ecological zones of Punjab.

Comparative efficacy of fungicide and gamma radiation for controlling blast of wheat

This research is conducted for comparison of an eco-friendly gamma radiation method and chemical fungicidal spray in reducing wheat blast incidence and severity in BINA under both artificial and natural conditions during 2019-2022. Wheat blast infection occurred on the leaves, spikes and newly emerged heads contained typical eye shaped blast symptoms. Magnaporthe oryzae Triticum (MoT), a causal agent of wheat blast was isolated by tissue panting method, cultured on OAT medium at 30 ±10C, confirmed by PCR amplified with universal MoT3 primer pairs that resulted 361 bp. The MoT inoculated (@ 5x106 CFU/mL) wheat plants successfully developed blast symptoms after 16 days in four tested wheat varieties/germplasm. An in vitro evaluation of five chemical fungicides was done against MoT where Nativo and Filia completely inhibited (100%) its radial mycelial growth. A total three spray, combination of half doses of Nativo + Filia [(0.3g + 1mL)/L] at 10 days intervals starting from one week of pre-heading or critical stage significantly reduced wheat blast incidence and severity in both artificially inoculated and natural conditions. Gamma radiated M3 population of wheat vars. also showed better performance in reduction of blast severity. Among the four doses of gamma radiation, 300 Gy significantly showed the better performance in reducing blast disease incidence and severity on wheat var. BG 26. Although combined fungicidal spray treatment (TF) significantly reduced 93.1% DI and 94.3 % DS in var. BG26 over control, but the highest percent reduction of wheat blast incidence (97.7%) and severity (98.4%) was observed on gamma irradiated (300 Gy) M3 line (BG26M3L4) under natural condition indicating gamma radiation brought a change in the genetic level positive for developing source of resistance against wheat blast. Moreover, gamma irradiated M3 line BG26M3L4 increased higher vegetative traits / yield than the combined fungicidal spray indicating gamma radiation might be a good replacement of chemical fungicides for management of blast of wheat.

A CRISPR-based lateral flow assay for plant genotyping and pathogen diagnostics.

Efficient pathogen diagnostics and genotyping methods enable effective disease management and breeding, improve crop productivity and ensure food security. However, current germplasm selection and pathogen detection techniques are laborious, time-consuming, expensive and not easy to mass-scale application in the field. Here, we optimized a field-deployable lateral flow assay, Bio-SCAN, as a highly sensitive tool to precisely identify elite germplasm and detect mutations, transgenes and phytopathogens in <1 h, starting from sample isolation to result output using lateral flow strips. As a proof of concept, we genotyped various wheat germplasms for the Lr34 and Lr67 alleles conferring broad-spectrum resistance to stripe rust, confirmed the presence of synthetically produced herbicide-resistant alleles in the rice genome and screened for the presence of transgenic elements in the genome of transgenic tobacco and rice plants with 100% specificity. We also successfully applied this new assay to the detection of phytopathogens, including viruses and bacterial pathogens in Nicotiana benthamiana, and two destructive fungal pathogens (Puccinia striiformis f. sp. tritici and Magnaporthe oryzae Triticum) in wheat. Our results illustrate the power of Bio-SCAN in crop breeding, genetic engineering and pathogen diagnostics to enhance food security. The high sensitivity, simplicity, versatility and in-field deployability make the Bio-SCAN as an attractive molecular diagnostic tool for diverse applications in agriculture.

Wheat blast: A review from a genetic and genomic perspective.

The newly emerged wheat blast fungus Magnaporthe oryzae Triticum (MoT) is a severe threat to global wheat production. The fungus is a distinct, exceptionally diverse lineage of the M. oryzae, causing rice blast disease. Genome-based approaches employing MoT-specific markers are used to detect MoT field isolates. Sequencing the whole genome indicates the presence of core chromosome and mini-chromosome sequences that harbor effector genes and undergo divergent evolutionary routes. Significant genetic and pathotype diversity within the fungus population gives ample potential for evolutionary change. Identifying and refining genetic markers allows for tracking genomic regions with stable blast resistance. Introgression of quantitative and R gene resistance into popular cultivars is crucial to controlling disease in areas where the pathogen population is diverse and well established. Novel approaches such as CRISPR/Cas-9 genome editing could generate resistant varieties in wheat within a short time. This chapter provides an extensive summary of the genetic and genomic aspects of the wheat blast fungus MoT and offers an essential resource for wheat blast research in the affected areas.

Further progress on wheat blast epidemiology: Identification of novel alternate hosts of Magnaporthe oryzae Triticum pathotype in Paraguay

Further progress on wheat blast epidemiology: Identification of novel alternate hosts of Magnaporthe oryzae Triticum pathotype in Paraguay

Bonactin and Feigrisolide C Inhibit Magnaporthe oryzae Triticum Fungus and Control Wheat Blast Disease.

Wheat blast caused by the Magnaporthe oryzae Triticum (MoT) pathotype is one of the most damaging fungal diseases of wheat. During the screening of novel bioactive secondary metabolites, we observed two marine secondary metabolites, bonactin and feigrisolide C, extracted from the marine bacteria Streptomyces spp. (Act 8970 and ACT 7619), remarkably inhibited the hyphal growth of an MoT isolate BTJP 4 (5) in vitro. In a further study, we found that bonactin and feigrisolide C reduced the mycelial growth of this highly pathogenic isolate in a dose-dependent manner. Bonactin inhibited the mycelial development of BTJP 4 (5) more effectively than feigrisolide C, with minimal concentrations for inhibition being 0.005 and 0.025 µg/disk, respectively. In a potato dextrose agar (PDA) medium, these marine natural products greatly reduced conidia production in the mycelia. Further bioassays demonstrated that these secondary metabolites could inhibit the MoT conidia germination, triggered lysis, or conidia germinated with abnormally long branched germ tubes that formed atypical appressoria (low melanization) of BTJP 4 (5). Application of these natural products in a field experiment significantly protected wheat from blast disease and increased grain yield compared to the untreated control. As far as we are aware, this is the first report of bonactin and feigrisolide C that inhibited mycelial development, conidia production, conidial germination, and morphological modifications in the germinated conidia of an MoT isolate and suppressed wheat blast disease in vivo. To recommend these compounds as lead compounds or biopesticides for managing wheat blast, more research is needed with additional MoT isolates to identify their exact mode of action and efficacy of disease control in diverse field conditions.

Natural Protein Kinase Inhibitors, Staurosporine, and Chelerythrine Suppress Wheat Blast Disease Caused by Magnaporthe oryzae Triticum.

Protein kinases (PKs), being key regulatory enzymes of a wide range of signaling pathways, are potential targets for antifungal agents. Wheat blast disease, caused by Magnaporthe oryzae Triticum (MoT), is an existential threat to world food security. During the screening process of natural metabolites against MoT fungus, we find that two protein kinase inhibitors, staurosporine and chelerythrine chloride, remarkably inhibit MoT hyphal growth. This study further investigates the effects of staurosporine and chelerythrine chloride on MoT hyphal growth, conidia production, and development as well as wheat blast inhibition in comparison to a commercial fungicide, Nativo®75WG. The growth of MoT mycelia is significantly inhibited by these compounds in a dose-dependent manner. These natural compounds greatly reduce conidia production in MoT mycelia along with suppression of conidial germination and triggered lysis, resulting in deformed germ tubes and appressoria. These metabolites greatly suppress blast development in artificially inoculated wheat plants in the field. This is the first report of the antagonistic effect of these two natural PKC inhibitory alkaloids on MoT fungal developmental processes in vitro and suppression of wheat blast disease on both leaves and spikes in vivo. Further research is needed to identify their precise mechanism of action to consider them as biopesticides or lead compounds for controlling wheat blast.

Marine Natural Product Antimycin A Suppresses Wheat Blast Disease Caused by Magnaporthe oryzae Triticum.

The application of chemical pesticides to protect agricultural crops from pests and diseases is discouraged due to their harmful effects on humans and the environment. Therefore, alternative approaches for crop protection through microbial or microbe-originated pesticides have been gaining momentum. Wheat blast is a destructive fungal disease caused by the Magnaporthe oryzae Triticum (MoT) pathotype, which poses a serious threat to global food security. Screening of secondary metabolites against MoT revealed that antimycin A isolated from a marine Streptomyces sp. had a significant inhibitory effect on mycelial growth in vitro. This study aimed to investigate the inhibitory effects of antimycin A on some critical life stages of MoT and evaluate the efficacy of wheat blast disease control using this natural product. A bioassay indicated that antimycin A suppressed mycelial growth (62.90%), conidiogenesis (100%), germination of conidia (42%), and the formation of appressoria in the germinated conidia (100%) of MoT at a 10 µg/mL concentration. Antimycin A suppressed MoT in a dose-dependent manner with a minimum inhibitory concentration of 0.005 μg/disk. If germinated, antimycin A induced abnormal germ tubes (4.8%) and suppressed the formation of appressoria. Interestingly, the application of antimycin A significantly suppressed wheat blast disease in both the seedling (100%) and heading stages (76.33%) of wheat at a 10 µg/mL concentration, supporting the results from in vitro study. This is the first report on the inhibition of mycelial growth, conidiogenesis, conidia germination, and detrimental morphological alterations in germinated conidia, and the suppression of wheat blast disease caused by a Triticum pathotype of M. Oryzae by antimycin A. Further study is required to unravel the precise mode of action of this promising natural compound for considering it as a biopesticide to combat wheat blast.

Daylight-Driven Rechargeable TiO2 Nanocatalysts Suppress Wheat Blast Caused by Magnaporthe oryzae Triticum

Abstract Wheat blast, caused by the Magnaporthe oryzae Triticum (MoT) pathotype, threatens wheat production in many countries, including Bangladesh. Traditional fungicides are ineffective in combating this pathogen, and no resistant wheat variety is available. This study investigated the mechanism of wheat blast suppression by a nanostructured TiO2 nanocatalyst (NC) that generates reactive oxygen species through a photocatalytic process under daylight settings. In the presence of sunlight, the NCs displayed a high antifungal activity against MoT in vitro (minimum inhibitory concentration - MIC 0.025 mg/ml), as well as suppressed conidial formation and mycelial growth of MoT. Moreover, the fungal biomass was drastically reduced at NC concentrations ≥0.5 mg/ml. In vivo seedling assays showed inhibition of wheat blast when wheat seedlings were artificially inoculated with conidia. Under daylight conditions, NCs at a concentration from 0.1 to 0.5 mg/ml can protect wheat plants from MoT likely by inducing oxidative stress in the pathogen. Field trials of TiO2 NCs prevented more than 90% of disease incidence, with optimum yields, at NC concentrations ≥0.5 mg/ml. These results indicate that daylight-driven rechargeable NCs effectively suppress MoT in vitro and control wheat blast in the field.

Effector Genes in Magnaporthe oryzae Triticum as Potential Targets for Incorporating Blast Resistance in Wheat.

Wheat blast (WB), caused by Magnaporthe oryzae Triticum pathotype, recently emerged as a destructive disease that threatens global wheat production. Because few sources of genetic resistance have been identified in wheat, genetic transformation of wheat with rice blast resistance genes could expand resistance to WB. We evaluated the presence/absence of homologs of rice blast effector genes in Triticum isolates with the aim of identifying avirulence genes in field populations whose cognate rice resistance genes could potentially confer resistance to WB. We also assessed presence of the wheat pathogen AVR-Rmg8 gene and identified new alleles. A total of 102 isolates collected in Brazil, Bolivia, and Paraguay from 1986 to 2018 were evaluated by PCR using 21 pairs of gene-specific primers. Effector gene composition was highly variable, with homologs to AvrPiz-t, AVR-Pi9, AVR-Pi54, and ACE1 showing the highest amplification frequencies (>94%). We identified Triticum isolates with a functional AvrPiz-t homolog that triggers Piz-t-mediated resistance in the rice pathosystem and produced transgenic wheat plants expressing the rice Piz-t gene. Seedlings and heads of the transgenic lines were challenged with isolate T25 carrying functional AvrPiz-t. Although slight decreases in the percentage of diseased spikelets and leaf area infected were observed in two transgenic lines, our results indicated that Piz-t did not confer useful WB resistance. Monitoring of avirulence genes in populations is fundamental to identifying effective resistance genes for incorporation into wheat by conventional breeding or transgenesis. Based on avirulence gene distributions, rice resistance genes Pi9 and Pi54 might be candidates for future studies.

Soil supplementation with Si, B and Zn and their synergetic effects in reducing severity of wheat blast (Magnaporthe oryzae Triticum)

Wheat blast (Magnaporthe oryzae Triticum) in Bangladesh and South America is recognized as one major limiting factor of wheat production. Its control using chemical pesticides raises concerns about food safety and pesticide resistance, which have dictated the need for alternative blast management approach, nutrient supplementation could be an ecofriendly alternative. Experiments were carried out under confined net house condition for two consecutive cropping seasons. Single doses of the nutrients (Si, B and Zn) were incorporated during soil preparation. Plants of the wheat blast susceptible variety BARI Gom-26 were inoculated with spores (1 x 107 spores ml-1) of Magnaporthe oryzae Triticum at blast vulnerable pre-heading stage of 52 days age. Typical wheat blast symptoms of spike bleaching from top to downward appeared on sight 14 days after inoculation i.e., 66 days age of the crop. Incidence and severity of blast bleaching of spike were scored for four times starting from 68 days age @ three day’s interval. None of the nutrients could stop the incidence of blast on wheat; however, some nutrients reduced the blast incidence significantly. Solo application of Si, B and Zn or combination of two caused significant reduction of spike bleaching. With the mixed application of Si, B and Zn, &gt; 47% reduction of wheat blast severity was obtained. The results revealed that the soil application of silicon, zinc and boron had a synergistic effect on the intensity of blast disease of wheat. Int. J. Agril. Res. Innov. Tech. 11(2): 76-84, Dec 2021

Brusone e produção de trigo no Brasil

Abstract This review paper presents the current context of wheat production in Brazil, the management strategies to reduce yield losses due to blast, and the biotechnological approaches to improve wheat resistance. Wheat blast or brusone is caused by the Magnaporthe oryzae Triticum (MoT) pathotype fungus that can infect all the aboveground parts of the plant. The main symptom of the blast disease is spike bleaching that impairs grain production, causing yield losses up to 100% in susceptible wheat cultivars. The first world report of blast in wheat spikes was in Brazil, in 1985, and, currently, the disease is the main constraint to wheat cultivation in tropical and subtropical areas of the Cerrado and Mata Atlântica biomes. For a long time, the use of fungicides has been found to be ineffective under high-pressure disease conditions. However, recent works have pointed out that fungicide efficiency depends on the integration of other control measures, particularly the choice of cultivars with moderate resistance. In this review paper, the high variability of wheat reaction to MoT is presented, as well as a panel of resistant or moderately resistant cultivars (including non-2NS carriers), promptly available for cultivation in regions where blast is endemic.

Effects of soil amendments using potassium in elevating resistance against wheat blast disease

Potassium (K) is unique among the essential nutrient elements for its diversified role in plant metabolic processes. Potassium improves crop output, protects the crop from diseases and insect-pest infestation, prevents lodging, and reduces the effects of terminal heat stress. Based on this information, it was hypothesized that K will enhance host plant resistance and blast control while increasing yields. A pot experiment was conducted by artificially inoculating Magnaporthe oryzae Triticum (MoT) on a susceptible wheat (Triticum aestivum L.) variety (BARI Gom-26) to determine the effect of soil application of K on blast disease management and the growth and yield. The experiment was carried out in separate plastic pots containing 18kg of virgin soil at the net house of the farm of the Bangladesh Institute of Nuclear Agriculture headquarters, Mymensingh, for two growing seasons of 2018-19 and 2019-20 following a completely randomized design with five treatments and three replications. The dose for soil application were 0, 50, 75, 100 and 125 K kg ha-1, respectively. Disease incidence (%) and severity (%) of wheat blast were evaluated at 11, 13 and 15 days after inoculation (DAI). At 15 DAI, the highest disease incidence (95.45%) was found in absolute control followed by K0 (0 kg K ha−1) (91.98%) and the lowest blast incidence (64.49%) was found in K4 (125kg K ha−1) which was statistically similar with K3 (100kg K ha−1) (70.87%). At 15 DAI, the highest blast severity matrix (90%) was found in absolute control followed by K0 (0 kg K ha−1) (76.02%) and the lowest blast incidence (46.18%) was found in K4 (125kg K ha−1) which was significantly different with others. Among the treatments, 125 kg K ha-1 produced the highest grain yield (26.97 g pot-1) and the lowest (5.79 g pot-1) was found from the absolute control. Flag leaf samples were randomly collected before head emergence from each pot and analyzed in the laboratory for plant nutrient content. The K concentration of flag leaves sample ranged from 1.71% to 5.51% with the average concentration of 3.02%, where the highest K content (%) was recorded in K4 (5.51%) and the lowest was found in absolute control (1.71%). Potassium fertilization appeared to reduce the severity and improve yield of wheat. Correlations suggested that improving dry matter production and K uptakes at the boot stage by K fertilization can reduce severity later in the growing season and increase wheat grain yield. It can be concluded that high K concentration on leaf tissue was important to decrease wheat blast symptom.

Hydrogen peroxide detoxifying enzymes show different activity patterns in host and non-host plant interactions with Magnaporthe oryzae Triticum pathotype.

Wheat blast caused by the hemibiotroph fungal pathogen Magnaporthe oryzae Triticum (MoT) pathotype is a destructive disease of wheat in South America, Bangladesh and Zambia. This study aimed to determine and compare the activities of antioxidant enzymes in susceptible (wheat, maize, barley and swamp rice grass) and resistant (rice) plants when interacting with MoT. The activities of reactive oxygen species-detoxifying enzymes; catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione S-transferase (GST), peroxidase (POX) were increased in all plants in response to MoT inoculation with a few exceptions. Interestingly, an early and very high activity of CAT was observed within 24h after inoculation in wheat, barley, maize and swamp rice grass with lower H2O2 concentration. In contrast, an early and high accumulation of H2O2 was observed in rice at 48 hai with little CAT activity only at a later stage of MoT inoculation. The activities of APX, GST and POD were also high at an early stage of infection in rice. However, these enzymes activities were very high at a later stage in wheat, barley, maize and swamp rice grass. The activity ofGPX gradually decreased with the increase of time in rice. Taken together, our results suggest that late and early inductions of most of the antioxidant enzyme activities occurs in susceptible and resistant plants, respectively. This study demonstrates some insights into physiological responses of host and non-host plants when interacting with the devastating wheat blast fungus MoT, which could be useful for developing blast resistant wheat.

Genome‐wide association reveals limited benefits of pyramiding the 1B and 1D loci with the 2NvS translocation for wheat blast control

AbstractResistance to wheat spike blast (WSB), caused by the Magnaporthe oryzae triticum pathotype (MoT), has relied upon a single major source: the 2NvS translocation introgressed from the wild relative Aegilops ventricosa Tausch. However, this resistance is partial and recently partially overcome by newer MoT races. To characterize potential novel loci conferring resistance to WSB, we conducted a genome‐wide association study (GWAS) using a diverse panel of 384 wheat genotypes phenotyped under three controlled‐environment conditions using MoT isolates T‐25 (301 genotypes), B‐71 (87 genotypes), and 008 (49 genotypes). Genotyping‐by‐sequencing identified 13,175 single nucleotide polymorphisms (SNPs) after filtering. Principal components analysis (PCA) identified two clusters based on the presence or absence of the 2NvS translocation, and the first three PCAs explained 13% of the genetic variation. Three individual analyses were performed (full [all genotypes combined], 2NvS genotypes only, and non‐2NvS genotypes only) using a linear mixed model and a threshold of significance of false discovery rate at 5%. Association analysis detected 25 significant SNPs for the full GWAS with isolate T‐25, in which 21 were mapped on chromosome 2A in the same physical position as the 2NvS translocation. Highly significant linkage disequilibrium among these SNPs suggested they might tag the same quantitative trait locus (QTL). No significant associations were identified with isolates B‐71 and 008, likely due to the small sample size. A QTL pyramiding analysis showed that the combination of multiple QTL was not statistically different from the individual effect of the 2A QTL. Further validation of these genomic regions can aid breeding for broad spectrum and durable WSB resistance.