Blast Severity Research Articles

Identification of propranolol and derivatives that are chemical inhibitors of phosphatidate phosphatase as potential broad-spectrum fungicides

Plant diseases cause enormous economic losses in agriculture and threaten global food security, and application of agrochemicals is an important method of crop disease control. Exploration of disease-resistance mechanisms and synthesis of highly bioactive agrochemicals are thus important research objectives. Here, we show that propranolol, a phosphatidate phosphatase (Pah) inhibitor, effectively suppresses fungal growth, sporulation, sexual reproduction, and infection of diverse plants. The MoPah1 enzyme activity of the rice blast fungus Magnaporthe oryzae is inhibited by propranolol. Alterations in lipid metabolism are associated with inhibited hyphal growth and appressorium formation caused by propranolol in M. oryzae. Propranolol inhibits a broad spectrum of 12 plant pathogens, effectively inhibiting infection of barley, wheat, maize, tomato, and pear. To improve antifungal capacity, we synthesized a series of propranolol derivatives, one of which shows a 16-fold increase in antifungal ability and binds directly to MoPah1. Propranolol and its derivatives can also reduce the severity of rice blast and Fusarium head blight of wheat in the field. Taken together, our results demonstrate that propranolol suppresses fungal development and infection through mechanisms involved in lipid metabolism. Propranolol and its derivatives may therefore be promising candidates for fungicide development.

NITROGEN, POTASSIUM, AND SILICON FERTILIZATION TO ACHIEVE LOWER PANICLE BLAST SEVERITY AND IMPROVE YIELD COMPONENTS OF RICE USING RESPONSE SURFACE METHODOLOGY

Rice blast is one of the most critical limiting factors for rice plant growth performance, and it occurs in 85 countries, causing 10-35% grain yield losses. Several findings have indicated the positive benefits of nitrogen (N), potassium (K), and Silicon (Si) fertilization on plant development, yield, and biotic stress relief. However, due to rice blast attacks, its growth, development, and yield may be restricted or limited by insufficient or unbalanced N, K, and Si fertilizers. This study was conducted to optimize the fertilization strategies for rice panicle blast control and improve rice grain yield. The methods used were Central Composite Design and Response Surface Methodology. The application of N, K and Si did not influence the number of spikelets per meter square, filled grain (%) and 1000- grain weight (g). An increase in K and Si significantly reduced the rice blast severity in the off-season 2021 and the main-season 2021/2022. On the other hand, only Si had influenced rice grain yield production. An increase in Si showed a positive linear trend in rice grain yield. Based on these results, panicle blast disease is expected to be controlled with the recommended rate of 104 N kg/ha, 42 P2O5, 80 kg K2O, and an additional 200 Si kg/ha, which minimizes the rice blast severity (%) but at the same time maximizes the rice grain yield. The findings of this study provide a scientific base and technical advice for high-yield rice grain-growing under panicle blast disease hot spot areas.

Evaluation of Triazole and Strobilurin Fungicides against Leaf and Panicle Blast of Rice in Farmer's Field

Blast disease of rice caused by the ascomycetes fungus Magnaporthe grisea poses a major threat to rice production from terai to hilly region of Nepal. Field trials were conducted in two successive years, 2021 and 2022 at Bharatpur-5, Chitwan in a farmer's field producing seed of Hardinath-1 variety with the main objective of finding the effective single and/or pre-mix formulation of triazole and strobilurin fungicides against rice blast that could be an alternative to tricyclazole. The trials were conducted in randomized complete block design with three replications and eight treatments viz. azoxystrobin 18.2% + difenoconazole 11.4% SC, propiconazole 13.9% + difenoconazole 13.9% EC, azoxystrobin 11% + tebuconazole 18.3% SC, azoxystrobin 23% SC, propiconazole 25% EC, difenoconazole 25% EC, tebuconazole 25%WDG and a control. The fungicides were applied during tillering and heading stage at the rate of 0.1%. All fungicides significantly reduced the leaf and panicle blast severity resulting in a higher yield. Among the tested fungicides, pre-mix formulation fungicide azoxystrobin 18.2% + difenoconazole 11.4% SC, propiconazole 13.9% + difenoconazole 13.9% EC and azoxystrobin 11% + tebuconazole 18.3% SC gave excellent performance with the lowest leaf and panicle blast severity and higher yield. Hence, these three fungicides could be used for the management of leaf and panicle blast disease for higher yield. However, controlling rice blast disease has become increasingly challenging due to the pathogens' capacity to adapt and evolve into new, more potent strains, making the management and control of this disease more difficult.

Assessing the Effectiveness of Newly Developed Fungicides in Managing Rice Blast Disease

Rice blast, which is caused by the fungus Magnaporthe oryzae, is a highly destructive disease that poses a significant threat to rice cultivation. It results in considerable crop damage, affecting both the yield and quality of rice. This makes rice blast a major concern for farmers and a significant issue in terms of food production. These studies were carried out at Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh with the aim to manage rice blast disease by means of different fungicides under in in-vitro and field conditions. In-vitro bioassay of six chemical fungicide(s) viz. Amister top 325SC, Seltima, Nativo 75 WG, Filia 525 SE, Avalon 27SC and Trooper 75 WP was done against Magnaporthe oryzae following poison food technique in the Plant Pathology Lab of BINA. The maximum mycelial growth inhibition (73.43%) of Magnaporthe oryzae was obtained by Avalon 27SC (Picoxystrobin 6.70%+ Tricyclazole 20.33%), Nativo 75WG (Tebuconazol 50% + Trifloxistrobin25%) and Seltima (Pyrachlostrobin 10%) at 0.0125% concentrations and 100% growth inhibition was obtained by all the six fungicides at 0.1% and 0.5% concentrations. In vivo evaluation of five fungicides viz. Amister top 325SC, Seltima, Nativo 75 WG, Filia 525 SE and Avalon 27SC against rice blast was carried out in research plot of the Plant Pathology of BINA. From the result, it was concluded that all the fungicides were effective in controlling leaf blast but Avalon 27SC (Picoxystrobin 6.70%+ Tricyclazole 20.33%) @ 0.2% was more effective among other fungicides, showing least leaf blast severity mean at three time interval (1.00, 1.33 and 1.46), least incidence (11.90%, 15.08%, 16.67%), and the highest grain yield (7.58 t ha-1).

Antifungal Efficacy of Chitosan against Blast Pathogenic Fungi (Magnaporthe oryzae) on Rice (Oryzasativa) Field

Blast disease (caused by Magnaporthe oryzae) is the most damaging disease to rice, and synthetic fungicides has been the primary means of control, however, concerns have been raised about the health risks posed, hence, the need for alternative biological crop protection strategies. This study evaluate the antifungal efficacy of chitosan against blast pathogenic fungi on rice field. Three chitosan (High, Medium and Low Molecular Weight) were purchased while the fourth Chitosan was synthesized from crab shell (CSCS). Faro 52 rice variety was collected from National Cereal Research Institute, Badeggi and Planted on Hydromorphic field. The degree of deacetylation of the synthesized chitosan was 98%. The rice field was inoculated with M. oryzae and treated with chitosan at two weeks after transplanting. The blast severity and incidence and other agronomic data were taken and data were analyzed using Analysis of Variance (ANAOVA) and means separated using Duncan multiple range test (DMRT). Results reveals that blast severity of 6,(highly susceptible) 5, (moderately susceptible) 4(susceptible) and incidence of 28.3%, 20%, 20% and 24.3% in rice plant tag with MMWC1.5%, 1HMWC 2.0%, LMWC2.0% and CSCS 2.0% before treatment with chitosan was observed. However, the severity reduce to 1(resistance) in all and incidence of 9.3%, 2.3%, 1.0% and 2.0% respectively at the end of the treatment. There was no significant difference (P≤0.05) in all other agronomic parameters except for panicle count with highest value (8.53) in HMWC 2.0% and lowest value (5.80) in HMWC 0.5%. Similarly, significant difference was observed in grain yield per plot with highest yield of 717 gram in HMWC 2.0% treated plot while the lowest yield of 190 gram was observed in MMWC 0.5% which was significantly different. It may therefore be concluded that chitosan treatment reduce the severity and incidence of blast pathogen as well as increase grain yield.

Spectral characterization and severity assessment of rice blast disease using univariate and multivariate models.

Rice is the staple food of more than half of the population of the world and India as well. One of the major constraints in rice production is frequent occurrence of pests and diseases and one of them is rice blast which often causes yield loss varying from 10 to 30%. Conventional approaches for disease assessment are time-consuming, expensive, and not real-time; alternately, sensor-based approach is rapid,non-invasive and can be scaled up in large areas with minimum time and effort. In the present study, hyperspectral remote sensing for the characterization and severity assessment of rice blast disease was exploited. Field experiments were conducted with 20 genotypes of rice having sensitive and resistant cultivars grown under upland and lowland conditions at Almora, Uttarakhand, India. The severity of the rice blast was graded from 0 to 9 in accordance to International Rice Research Institute (IRRI). Spectral observations in field were taken using a hand-held portable spectroradiometer in range of 350-2500 nm followed by spectral discrimination of different disease severity levels using Jeffires-Matusita (J-M) distance. Then, evaluation of 26 existing spectral indices (r≥0.8) was done corresponding to blast severity levels and linear regression prediction models were also developed. Further, the proposed ratio blast index (RBI) and normalized difference blast index (NDBI) were developed using all possible combinations of their correlations with severity level followed by their quantification to identify the best indices. Thereafter, multivariate models like support vector machine regression (SVM), partial least squares (PLS), random forest (RF), and multivariate adaptive regression spline (MARS) were also used to estimate blast severity. Jeffires-Matusita distance was separating almost all severity levels having values >1.92 except levels 4 and 5. The 26 prediction models were effective at predicting blast severity with R2 values from 0.48 to 0.85. The best developed spectral indices for rice blast were RBI (R1148, R1301) and NDBI (R1148, R1301) with R2 of 0.85 and 0.86, respectively. Among multivariate models, SVM was the best model with calibration R2=0.99; validation R2=0.94, RMSE=0.7, and RPD=4.10. The methodology developed paves way for early detection and large-scale monitoring and mapping using satellite remote sensors at farmers' fields for developing better disease management options.

Characterization of Blast Resistance in a Diverse Rice Panel from Sub-Saharan Africa.

There is a recent unparalleled increase in demand for rice in sub-Saharan Africa, yet its production is affected by blast disease. Characterization of blast resistance in adapted African rice cultivars can provide important information to guide growers and rice breeders. We used molecular markers for known blast resistance genes (Pi genes; n = 21) to group African rice genotypes (n = 240) into similarity clusters. We then used greenhouse-based assays to challenge representative rice genotypes (n = 56) with African isolates (n = 8) of Magnaporthe oryzae which varied in virulence and genetic lineage. The markers grouped rice cultivars into five blast resistance clusters (BRC) which differed in foliar disease severity. Using stepwise regression, we found that the Pi genes associated with reduced blast severity were Pi50 and Pi65, whereas Pik-p, Piz-t, and Pik were associated with increased susceptibility. All rice genotypes in the most resistant cluster, BRC 4, possessed Pi50 and Pi65, the only genes that were significantly associated with reduced foliar blast severity. Cultivar IRAT109, which contains Piz-t, was resistant against seven African M. oryzae isolates, whereas ARICA 17 was susceptible to eight isolates. The popular Basmati 217 and Basmati 370 were among the most susceptible genotypes. These findings indicate that most tested genes were not effective against African blast pathogen collections. Pyramiding genes in the Pi2/9 multifamily blast resistance cluster on chromosome 6 and Pi65 on chromosome 11 could confer broad-spectrum resistance capabilities. To gain further insights into genomic regions associated with blast resistance, gene mapping could be conducted with resident blast pathogen collections. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Assessment of various fungitoxicants against major diseases of rice

Diseases damage to rice can seriously break productivity and with in short time destroys the crop. Screening of various groups of fungitoxicants in solo and in combination against major diseases of rice was carried out during summer and Kharif 2019. The pooled data revealed Fenoxanil 20% SC + Isoprothiolane 40% EC @ 2ml L-1 was effective in reducing the disease severity of leaf blast and neck blast by recording least percent disease index (PDI) of 13.33 and 12.22 with yield of 5099 kg ha-1as against 40.74 and 48.89 and yield 4034 kg ha-1 in control respectively. The combi fungitoxicants Azoxystrobin 25% SC + Hexaconazole 5% 16.25% SC @ 900 ml ha-1 and Kresoxim methyl 40% + Hexaconazole 8% WG @ 500 g ha-1 were effective against leaf blast, neck blast, sheath blight and sheath rot with PDI 9.25,10.40 13.33 and 17.77 respectively . The tank mix of Hexaconaxole 75% WG and Isoprothiolane 40% EC @ 66.7 g + 750 ml ha-1 was effective against leaf blast, neck blast, sheath blight and sheath rot with least PDI of 2.59, 6.33, 4.81 and 6.85 respectively. Kresoxim methyl 40% + Hexaconazole 8% in combination with Isoprothiolane 40% EC @ 500 g + 750 ml ha-1 recorded the reduced PDI of 4.81, 4.29, 11.85 and 11.11 for leaf blast, neck blast, sheath blight and sheath rot respectively .The fungitoxicants evaluated did not cause any phytotoxicity.

Differential response to DMI, QoI and SDHI fungicides in wheat and signal grass blast populations from Minas Gerais, Brazil

AbstractFungicides play an important role in wheat blast management in Brazil. To determine whether the reported patterns of fungicide resistance are present in Pyricularia oryzae populations from wheat and signal grass grown in Minas Gerais state, Brazil, we characterized the sensitivity of a contemporary collection (2018 and 2019) of 64 fungal isolates to seven fungicides belonging to DMI (tebuconazole and epoxiconazole), QoI (azoxystrobin and pyraclostrobin) and SDHI (bixafen, fluxapyroxad and benzovindiflupyr) groups. We further assessed if the differential sensitivity of selected isolates affected disease control using commercial doses of the fungicides applied protectively (prior to inoculation) on the heads of potted plants. Despite finding relatively low levels of in vitro sensitivity to some of the fungicides (e.g., azoxystrobin, fluxapyroxad and bixafen), control efficacies (percentage reductions in head blast severity) were significantly higher than the untreated plants and not affected by the sensitivity of the strain to all fungicides but azoxystrobin. The levels of head blast control for some of the fungicides (>70%) in the greenhouse were similar to or higher than previously reported in the field. The molecular data for a set of isolates representing different fungicide sensitivity levels were generally not predictive of the phenotype. The wheat‐infecting isolates were less sensitive than signal grass‐infecting isolates to all fungicides including azoxystrobin. Our study not only confirms previous reports of low sensitivity to some fungicides, but it also suggests options among site‐specific fungicides, most notably tebuconazole and benzovindiflupyr, that can still be used under an antiresistance strategy such as coformulation with multisite fungicides.

Hyperspectral imaging-based classification of rice leaf blast severity over multiple growth stages

BackgroundRice blast, which is prevalent worldwide, represents a serious threat to harvested crop yield and quality. Hyperspectral imaging, an emerging technology used in plant disease research, is a stable, repeatable method for disease grading. Current methods for assessing disease severity have mostly focused on individual growth stages rather than multiple ones. In this study, the spectral reflectance ratio (SRR) of whole leaves were calculated, the sensitive wave bands were selected using the successive projections algorithm (SPA) and the support vector machine (SVM) models were constructed to assess rice leaf blast severity over multiple growth stages.ResultsThe average accuracy, micro F1 values, and macro F1 values of the full-spectrum-based SVM model were respectively 94.75%, 0.869, and 0.883 in 2019; 92.92%, 0.823, and 0.808 in 2021; and 88.09%, 0.702, and 0.757 under the 2019–2021 combined model. The SRR–SVM model could be used to evaluate rice leaf blast disease during multiple growth stages and had good generalizability.ConclusionsThe proposed SRR data analysis method is able to eliminate differences among individuals to some extent, thus allowing for its application to assess rice leaf blast severity over multiple growth stages. Our approach, which can supplement single-stage disease-degree classification, provides a possible direction for future research on the assessment of plant disease severity during multiple growth stages.

Classification of rice leaf blast severity using hyperspectral imaging

Rice leaf blast is prevalent worldwide and a serious threat to rice yield and quality. Hyperspectral imaging is an emerging technology used in plant disease research. In this study, we calculated the standard deviation (STD) of the spectral reflectance of whole rice leaves and constructed support vector machine (SVM) and probabilistic neural network (PNN) models to classify the degree of rice leaf blast at different growth stages. Average accuracies at jointing, booting and heading stages under the full-spectrum-based SVM model were 88.89%, 85.26%, and 87.32%, respectively, versus 80%, 83.16%, and 83.41% under the PNN model. Average accuracies at jointing, booting and heading stages under the STD-based SVM model were 97.78%, 92.63%, and 92.20%, respectively, versus 88.89%, 91.58%, and 92.20% under the PNN model. The STD of the spectral reflectance of the whole leaf differed not only within samples with different disease grades, but also among those at the same disease level. Compared with raw spectral reflectance data, STDs performed better in assessing rice leaf blast severity.

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.

Screening of Finger Millet (<em>Eleusine coracana</em>) Germplasm for the Blast Disease-Resistance in Sri Lanka

Finger millet is the third important cereal crop in Sri Lanka, mostly cultivated in rainfed uplands in dry and intermediate zones. Blast disease (leaf, finger, and neck blast) caused by Magnaporthe grisea is economically devastating to rice and finger millet worldwide. Host resistance is the most viable option for managing the disease as it is mainly grown in low-input systems. One hundred thirty-nine finger millet accessions collected from the Plant Genetic Resources Center in Sri Lanka were field screened for leaf blast disease in three seasons under artificial inoculation at the Field Crops Research and Development Institute at Mahailluppallama, Sri Lanka. The results revealed that almost all the tested accessions were susceptible to leaf blast at the early seedling stage. However, 5–6 weeks after sowing, the severity of leaf blast disease decreased drastically, and all the germplasm were resistant or moderately resistant. The finger blast and neck blast severity, scored under natural infection, was low under both high and low-density planting. Seven and 87 finger millet accessions consistently showed immune reactions for finger blast and neck blast, respectively. A negative correlation was observed between the days to flowering and blast disease. The early flowering accessions, namely, Ac12968 and Ac2384 from Jaffna, TVFM, 13-1, TVFM-04, and TVFM-02 from Killinochchi, showed a higher severity score for leaf, finger, and neck blast compared to other accessions. A significant positive correlation (P<0.05) was found between finger blast and neck blast, however, these two diseases did not show a significant correlation (P>0.05) with leaf blast.

A Lightweight Real-Time Rice Blast Disease Segmentation Method Based on DFFANet

The evaluation of rice disease severity is a quantitative indicator for precise disease control, which is of great significance for ensuring rice yield. In the past, it was usually done manually, and the judgment of rice blast severity can be subjective and time-consuming. To address the above problems, this paper proposes a real-time rice blast disease segmentation method based on a feature fusion and attention mechanism: Deep Feature Fusion and Attention Network (abbreviated to DFFANet). To realize the extraction of the shallow and deep features of rice blast disease as complete as possible, a feature extraction (DCABlock) module and a feature fusion (FFM) module are designed; then, a lightweight attention module is further designed to guide the features learning, effectively fusing the extracted features at different scales, and use the above modules to build a DFFANet lightweight network model. This model is applied to rice blast spot segmentation and compared with other existing methods in this field. The experimental results show that the method proposed in this study has better anti-interference ability, achieving 96.15% MioU, a speed of 188 FPS, and the number of parameters is only 1.4 M, which can achieve a high detection speed with a small number of model parameters, and achieves an effective balance between segmentation accuracy and speed, thereby reducing the requirements for hardware equipment and realizing low-cost embedded development. It provides technical support for real-time rapid detection of rice diseases.

Combining ability and selection of wheat populations for a tropical environment

The selection of segregating populations with the potential for derived lines is essential for breeding programs. The present work analyzes the potential of tropical F2 wheat (Triticum aestivum L.) populations originated from complete diallel cross combinations. For this purpose, eight tropical wheat cultivars were combined in a complete diallel design in 2019 after F1 seeds were multiplied in a greenhouse and the seeds of 56 F2 populations, plus the eight parents, were evaluated in the field in Viçosa, MG, Brazil in the winter harvest of 2020 using a simple lattice design (8×8). The trait scores of (1) severity of tan spot (Pyrenophora tritici-repentis), (2) severity of wheat head blast (WHB) (Magnaporthe oryzae pathotype Triticum), (3) days to heading, (4) spike height, (5) and total grain weight of the plot were evaluated. We performed a diallel analysis using mixed models to obtain the effects of general combining ability (GCA), specific combining ability (SCA), and estimation of population genotypic values. The additive effect predominated for the control of all traits, except for spike height. There were greater GCA effects for the set of parental maternal plants. Heritability, in the narrow sense, ranged from 0.20 (blast) to 0.66 (heading). There was an effect of maternal GCA for all variables, while for paternal GCA the effect was only for days passed for head and total grain weight. Populations derived from the cultivars TBIO Aton, TBIO Ponteiro, and TBIO Sossego had lower disease severity, while the combinations from BRS 254, BRS 264, and BRS 394 had earlier maturation time. The most promising combinations to derive lines for the set of traits were BRS 254 × CD 1303, BRS 394 × TBIO Aton, TBIO Aton × BRS 254, CD 1303 × BRS 254, and CD 1303 × BRS 264.

Assessment of Rice Blast (Pyricularia Grisea) Disease Under Different Concentrations of Nitrogen on Different Rice Cultivars

Rice is a staple food contributing high calorie intake to humans. In Nepal, rice contributes 39% of GDP, among agricultural crops. Blast disease (Pyricularia grisea Sacc.) has been a continuous threat to rice production. This disease causes 10-20% yield reduction in susceptible varieties, whereas in severe case it causes upto 80%. Excessive nitrogen increases N-metabolism in plant, leading to enhanced tissue susceptibility to blast disease. Farmers’ household survey was carried out in Mangalpur V.D.C. ward no. 1, Chitwan during March, 2013, for determining the knowledge and perception of rice blast incidence and severity, their constraints in rice cultivation and their practices, knowledge on the disease management and amount of fertilization use. Similarly, a field experiment was carried out during June to September, 2013 to assess the impact of different concentrations of nitrogen on rice blast disease (caused by Pyricularia grisea Sacc.) incidence, severity and their effect on yield of Mansuli, Aekle and O.R. varieties of rice. Four treatments (0 kg/ha, 100 kg/ha, 200 kg/ha and 300 kg/ha) were used in RCBD with 3 replications in three different cultivars. In the field experiment, disease incidence and severity varied significantly (P≤0.05) among the treatments. The highest incidence was observed for higher concentration of nitrogen of Mansuli variety (42.22%) and lowest in no concentration of nitrogen of Aekle variety (25.56%) on 69 days after transplantation. Maximum disease severity was also recorded on Mansuli rice variety in highest concentration of nitrogen (53.43%) and minimum in Aekle variety in no concentration of nitrogen (24.32%) at September 9, 2013. Significantly highest yield (5.217 t/ha), number of grains per panicle (182.3) and 1000 grains weight (32.45 gm) were also obtained at no concentration of nitrogen. Among three varieties, Mansuli was the susceptible variety and Aekle was resistance variety.

Microscopic and molecular studies in the biological control of rice blast caused by Pyricularia oryzae with Bacillus sp. BMH under greenhouse conditions

Rice (Oryza sativa L.) feeds around half of humanity mainly in Asia, South America, and Africa. Pyricularia oryzae Cav. (syn. Magnaporthe oryzae Couch) is the causative agent of the most devastating disease of rice worldwide. The purpose of this study was to evaluate the efficiency of the selected Bacillus sp. strain BMH in relation to its antagonistic attributes against P. oryzae as well as rice cultivar BRS.MG Caçula growth promotion, productivity, and its ability to colonize tissues and induce resistance in plants using microscopy, genes expression, and pot assay under greenhouse conditions. The soil and seedlings were inoculated with Bacillus sp. BMH and the seedlings were sprayed with P. oryzae isolate A10965. The severity evaluation and microscopic analysis showed that BMH was able to reduce rice blast severity with 53.12%, 50%, and 37.5% for soil inoculation, preventive control, and the mixture of pathogen-BMH treatments respectively at 28 DAI. Rice plants were higher following the Bacillus sp. BMH inoculation in soil with 25.73 cm compared to the control treatment with 21.93 cm at 63 days after sowing (DAS). Likewise, the number of tillers was higher with 12.6 for BMH against 9.13 for control as well as grain weight with 10.17 g for BMH treatments against 7.14 g for untreated one. BMH enhanced plant growth promotion (PGP) and production, which illustrates its potential use as a biocontrol agent. The Confocal Laser Microscopy (CLM) and Scanning Electron microscopy (SEM) showed the colonization of rice root vascular tissues as well as foliage by Bacillus sp. BMH cells, which indicates its endophytic potential. In the molecular study, the expression of genes responsible for conferring resistance to the blast was studied upon colonization of the plants by beneficial and pathogenic microbe’s invasion, namely ALD1, OsPR1a, OsPR1b, OsGLN1, OsWRKY28. Soil inoculation with BMH or sprayed on the surface of leaves resulted in the stimulation of rice defense mechanisms against blast disease by upregulating the rice β-1,3-glucanases (OsGLN1) and OsPR1a, which are thought to be involved in plant normal growth and development, playing a direct role in defense against fungi, and other stressors. The results obtained in this research demonstrate the beneficial interaction between rice plants and BMH, as well as the blast management strategy, that could help to reduce dependence on fungicides and contribute to the sustainability of rice cropping.

Incidence-severity relationships in non-treated and fungicide-treated wheat head blast epidemics in Brazil

The relationship between wheat head blast incidence (I; proportion of diseased heads in a sample) and severity (S; the average diseased area in a sample of heads) was studied with the aim of determining whether severity could be reliably predicted from incidence. Data were collected from two main sources: a) the EPAMIG (non-treated) field experiments spanning seven years (2013–2019 with three cultivars) designed to evaluate the effect of planting dates on wheat blast (no fungicide use); and b) the UFTs (fungicide-treated) field experiments conducted by researchers of the network of uniform fungicide trials conducted during nine years (2012–2020) across 10 locations (totaling 14 cultivars). An ordinary linear regression model fitted to the complementary log-log transformation of the data provided a good fit to the data based on the square correlation of the predicted Ŝ, and the observed S (R2): The R2 was 0.95 for the pooled (all years) non-treated dataset and 0.88 for the pooled fungicide-treated dataset. A covariance analysis indicated that year, but not cultivar, significantly affected the parameters of the I-S relationship in the non-treated dataset. We conclude that wheat head blast S can be predicted from I but more reliably in non-treated epidemics given the larger influence of chemical treatments on the relationship than cultivar or year, a surrogate for varying weather.

Anti-Fungal Analysis of Bacillus subtilis DL76 on Conidiation, Appressorium Formation, Growth, Multiple Stress Response, and Pathogenicity in Magnaporthe oryzae.

In recent years, biological control has gained more attention as a promising method to combat plant disease. Such severe diseases cited include rice blasts caused by Magnaporthe oryzae. However, more effective microbial strains with strong adaptability still need to be identified. Therefore, we sought to assess the conidia germination, and formation of appressorium of DL76 in Magnaporthe oryzae. Besides, we also aimed at understanding the growth, multiple stress response and pathogenicity in Magnaporthe oryzae. We isolated Bacillus subtilis DL76 from a rice farm, which observed a strong antimicrobial effect on M. oryzae. The sterilized culture filtrate of DL76 inhibited the growth of M. oryzae, which motivated us to deduce the influence of DL76 on the pathogenicity of M. oryzae. We screened the effect of Bacillus subtilis DL76 on M. oryzae guy11. It demonstrated that sterilized culture filtrate (1 × 107 CFU/mL) of DL76 can delay and even suppress the germination of conidia and (1 × 107 and 1 × 106 CFU/mL) prevent the formation of appressorium in vitro and in vivo. DL76 became hypersensitive to osmotic, oxidative, and cell wall degrading agents. In addition, the relative transcript levels of stress-responsive genes oxidative and osmotic were down-regulated by DL76 except for sod1, cat1, and cat2. In vivo assessment of the antifungal activity of Bacillus subtilis using conidia suspension of DL76 reduced the incidence and severity of rice blast. Conclusively, our results show that DL76 is essential for controlling rice blast by inhibiting conidiation, growth, multiple stress tolerance, and pathogenicity in M. oryzae.

Assessment of Proso millet Genotypes against Blast Caused by Pyricularia grisea (Cooke) Sacc. under Field Condition at Mid Hill Region of Nepal

A total of 14 proso millet genotypes, including the farmers' variety, which was the most commonly cultivated landrace in the Karnali region and most susceptible to blast disease as a susceptible check, were evaluated for resistance to leaf blast at the Hill Crops Research Program, Kabre, Dolakha, Nepal during the summer seasons of 2020 and 2021. The experiment was conducted under natural epiphytotic conditions. The experiment revealed that none of the tested genotypes were found immune or highly resistant. Most of the genotypes showed moderately susceptible and susceptible reactions to the leaf blast disease for both experimental years. However, genotypes C04654, Humla-239, and C04651 were found to have lower blast severity and produce higher grain yields. Genotype C04654 was found as resistant with 34.6% disease severity and high yielding (2.6 t/ha), followed by Humla-239 and C04651 as moderately susceptible with 44.8 and 45.9% disease severity resulting grain yields of 2.5 and 2.4 t/ha, respectively. The higher disease severity (68.1%) with lower grain yield (1.4 t/ha) was recorded in the farmer's variety (susceptible check). The genotypes reported with lower blast severity and higher grain yield could be the source for the release of a leaf blast resistant and high-yielding proso millet variety in the mid-hill region of Nepal.