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Finger millet is a food crop that provides nutritional security and is climatically resilient for farming and agricultural diversification. However, its quality and yield remain low due to biotic and abiotic factors, the greatest of which is blast disease caused by Magnaporthe oryzae. We surveyed the occurrence, distribution and severity of finger millet blast in five counties, namely, Busia, Bungoma, Kisii, Machakos and Makueni, in Kenya. Blast disease occurrence was determined by observing disease symptoms of different plant parts on each farm, and symptoms were recorded as either present or absent. Severity was evaluated based on the disease symptoms on plant fingers, leaves and necks and generally at the whole farm scale. Distribution was assessed based on the number of farms sampled for blast per county, and global positioning systems coordinates were recorded. Blast occurrence was 100%, with a uniform distribution pattern on all the farms surveyed across all the counties. Busia County had the highest disease severity at 82.3%, while Makueni had the lowest severity at 61%. Pearson’s correlation test revealed no statistically significant correlation between blast severity and plant parts infected (p< 0.05), with Busia (74.2%) having the highest number of plants showing symptoms of blast on fingers, followed by Bungoma (57.1%), Makueni (57%), Machakos (56%) and Kisii, 53.3%. This study reveals that finger millet blast is rampant in all the counties surveyed and is widely distributed in Kenya. This information is helpful in understanding the geographical distribution, occurrence and severity of M. oryzae. Key words: Finger millet blast, occurrence, severity, distribution, Magnaporthe oryzae.

Rice blast caused by Magnaporthe grisea is the major damaging disease in nearly all rice growing nations. Economically relevance with 60 percent of total population of world depending on rice as the main source of calories, may have destructive effects of the disease, however, this pathogen has developed into a pioneering model system for researching host-pathogen interactions. The disease outbreak depends on the weather and climatic conditions of the various regions. The disease's occurrence and symptoms vary from country to country. Susceptible cultivars cause huge rice production loss in yield. The principal cause of resistance breakdown in rice against rice blast disease is pathogenic variability. During sexual hybridization, pathogenic changes may provide evidence of pathogenic variation found at the asexual stage of the fungus. The virulent pathotypes cause severe disease incidence. Only through pathogenicity research the pathotypes can be determined using a collection of different rice varieties that are usually different carrying various resistance genes. Rice breeders now have a number of resistant genes however, most of the breeding programs emphasized upon monogenic resistance. Genetic heterogeneity of M. grisea should be taken into account when screening blast resistant rice genotypes through morphological analysis, pathogenicity and molecular characterization. Knowledge on the virulence of the rice blast and host resistant is essential for managing the disease. Cultivation of resistant varieties with chemical control is highly effective against blast pathogens.

MicroRNAs (miRNAs) are known to fine-tune growth, development, and stress-induced responses. Osa-miR1873 is a rice-specific miRNA targeting LOC_Os05g01790. Here, we show that Osa-miR1873 fine-tunes rice immunity against Magnaporthe oryzae and yield traits via LOC_Os05g01790. Osa-miR1873 was significantly upregulated in a susceptible accession but downregulated in a resistance accession at 24 h post-inoculation (hpi) of M. oryzae. Overexpressing Osa-miR1873 enhanced susceptibility to M. oryzae and compromised induction of defense responses. In contrast, blocking Osa-miR1873 through target mimicry compromised susceptibility to M. oryzae and enhanced induction of defense responses. Altered expression of Osa-miR1873 also resulted in some defects in yield traits, including grain numbers and seed setting rate. Moreover, overexpression of the target gene LOC_Os05g01790 increased rice blast disease resistance but severely penalized growth and yield. Taken together, we demonstrate that Osa-miR1873 fine-tunes the rice immunity-growth trade-off via LOC_Os05g01790, and blocking Osa-miR1873 could improve blast disease resistance without significant yield penalty. Thus, the Osa-miR1873-LOC_Os05g01790 regulatory module is valuable in balancing yield traits and blast resistance.

Rice (Oryza sativa L.) is the staple food of the majority of Indians, and India is both the major producer and consumer of rice. Rice cultivation in India is confronted with diverse agro-climatic conditions, varying soil types, and several biotic and abiotic constraints. Among major fungal diseases of Rice in India, the blast caused by Magnaporthe oryzae is the most devastating disease, with the neck blast being the most destructive form. Most of the blast epidemic areas in India have been identified with a mixture of races blast fungus resulting in the resistance breakdown in a short period. At present, a more significant number of the rice varieties cultivated in India were bred by conventional breeding methods with blast resistance conferred by a single resistance gene. Therefore, the blast disease in India is predominantly addressed by the use of ecologically toxic fungicides. In line with the rest of the world, the Indian scientific community has proven its role by identifying several blast resistance genes and successfully pyramiding multiple blast resistance genes. Despite the wealth of information on resistance genes and the availability of biotechnology tools, not a great number of rice varieties in India harbor multiple resistance genes. In the recent past, a shift in the management of blast disease in India has been witnessed with a greater focus on basic research and modern breeding tools such as marker-assisted selection, marker-assisted backcross breeding, and gene pyramiding.

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Dispersal Simulation of Rice Blast Disease Using Spatial Multi Criteria Evalution Model: Case Study In District of Karawang and PurwakartaRice blast is caused by Pyricularia oryzae. The potential epidemic of this disease can be spatially simulated using the MCA (Multi Criteria Analysis) method based on geographical characteristics, cultivation practices, and eviromental condition. A software that can be used for MCA is SMCE (Spatial Multi Criteria Evaluation). This study was aimed to predict the spatial dispersal of blast disease using SMCE model, and identify the factors that supports the epidemic. The study was conducted in February - August 2018 in Karawang and Purwakarta District. The research methods include observing the severity of blast disease, cultivation practices and environmental conditions, and analyzing SMCE. The SMCE analysis uses rice crop maps from the Sistem Monitoring Pertanaman Padi (Simotandi), which consists of grouping factors, standardizing factors, and weighting factors. The SMCE results are a simulation map of blast disease dispersal which is then compiled with predictions of its severity. Accuracy of prediction results was evaluated by MAPE (Mean Absolute Percentage Error) based on observational data on actual disease severity. The prediction results for Karawang and Purwakarta showed means of accuration 78.16% and 73.95% respectively. In general, factors that have a strong influence on the development of blast disease include altitude, distance from source of the epidemic, history of disease in the fields, number of spores (inoculum) trapped, irrigation quality, application of herbicides, soil nutrient (N, P, K) contents and the level of soil acidity.

Rice blast caused by the fungus Magnaporthe oryzae (syn. Magnaporthe grisea) is one of the most lethal diseases for sustainable rice production worldwide. Blast resistance mediated by major resistance genes is often broken down after a short period of deployment, while minor blast resistance genes, each providing a small effect on disease reactions, are more durable. In the present study, we first evaluated disease reactions of two rice breeding parents ‘Minghui 63’ and ‘M-202’ with 11 blast races, IA45, IB1, IB45, IB49, IB54, IC1, IC17, ID1, IE1, IG1, and IH1, commonly present in the United States, under greenhouse conditions using a category disease rating resembling infection types under field conditions. ‘Minghui 63’ exhibited differential resistance responses in comparison with those of ‘M-202’ to the tested blast races. A recombinant inbred line (RIL) population of 275 lines from a cross between ‘Minghui 63’ and ‘M-202’ was also evaluated with the above-mentioned blast races. The population was genotyped with 156 simple sequence repeat (SSR) and insertion and deletion (Indel) markers. A linkage map with a genetic distance of 1,022.84 cM was constructed using inclusive composite interval mapping (ICIM) software. A total of 10 resistance QTLs, eight from ‘Minghui 63’ and two from ‘M-202’, were identified. One major QTL, qBLAST2 on chromosome 2, was identified by seven races/isolates. The remaining nine minor resistance QTLs were mapped on chromosomes 1, 3, 6, 9, 10, 11, and 12. These findings provide useful genetic markers and resources to tag minor blast resistance genes for marker-assisted selection in rice breeding program and for further studies of underlying genes.

There are important biological process involved in rice blast disease that are now well-studied during the early events in plant infection which include: the cell biology of appressorium formation, the biology of invasive growth and effector secretion, the two distinct mechanisms of effector secretion, the nature of the plant-pathogen interface, PAMP-triggered immunity modulation by secreted effectors and effector-triggered immunity and blast resistance. The devastating losses caused by the blast fungus have been documented in most grasses, but this chapter discusses the use of major resistance genes to rice blast and wheat blast disease as an emerging threat to global food security. This chapter also highlights an emerging approach to breed for durable resistance to plant pathogens using gene editing technologies with an example: CRISPR-Cas9 mutagenesis of dominant S-genes for disease control.

Phyllosphere—the harsh foliar plant part exposed to vagaries of environmental and climatic variables is a unique habitat for microbial communities. In the present work, we profiled the phyllosphere microbiome of the rice plants using 16S rRNA gene amplicon sequencing (hereafter termed metabarcoding) and the conventional microbiological methods (culturomics) to decipher the microbiome assemblage, composition, and their functions such as antibiosis and defense induction against rice blast disease. The blast susceptible rice genotype (PRR78) harbored far more diverse bacterial species (294 species) than the resistant genotype (Pusa1602) that showed 193 species. Our metabarcoding of bacterial communities in phyllomicrobiome revealed the predominance of the phylum, Proteobacteria, and its members Pantoea, Enterobacter, Pseudomonas, and Erwinia on the phyllosphere of both rice genotypes. The microbiological culturomic validation of metabarcoding-taxonomic annotation further confirmed the prevalence of 31 bacterial isolates representing 11 genera and 16 species with the maximum abundance of Pantoea. The phyllomicrobiome-associated bacterial members displayed antifungal activity on rice blast fungus, Magnaporthe oryzae, by volatile and non-volatile metabolites. Upon phyllobacterization of rice cultivar PB1, the bacterial species such as Enterobacter sacchari, Microbacterium testaceum, Pantoea ananatis, Pantoea dispersa, Pantoea vagans, Pseudomonas oryzihabitans, Rhizobium sp., and Sphingomonas sp. elicited a defense response and contributed to the suppression of blast disease. qRT-PCR-based gene expression analysis indicated over expression of defense-associated genes such as OsCEBiP, OsCERK1, and phytohormone-associated genes such as OsPAD4, OsEDS1, OsPR1.1, OsNPR1, OsPDF2.2, and OsFMO in phyllobacterized rice seedlings. The phyllosphere bacterial species showing blast suppressive activity on rice were found non-plant pathogenic in tobacco infiltration assay. Our comparative microbiome interrogation of the rice phyllosphere culminated in the isolation and identification of agriculturally significant bacterial communities for blast disease management in rice farming through phyllomicrobiome engineering in the future.

Rice Leaf Blast Disease and Brown Spot Disease are among the most significant diseases affecting rice cultivation. Monitoring and maintaining rice plants from many diseases are very important to regulate their production. In this study, the key objective was to develop an application that identifies whether a rice leaf has leaf blast or brown spot disease. The You Only Look Once (YOLO) Algorithm was implemented for the development of the system. The YOLO algorithm was trained with a custom dataset of 200 rice leaf images. It was found out that the device’s accuracy for leaf blast disease was 90.00% while the class 2 brown spot disease was at 70.00%. For the third class, which was the unknown disease, the device’s performance resulted in a 100.00% of accuracy. Therefore, it was concluded that the overall accuracy of the device was at 73.33% and the error of commission was only 26.67%.

A nursery comprising 25 elite bread wheat genotypes were evaluated to identify the sources of resistance to wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT), under artificial and natural infection experiments in three consecutive years from 2018 to 2020 in two different locations of Bangladesh. Seedling evaluation results revealed the absence of resistant and most genotypes displayed moderately susceptible to susceptible reaction. In the adult-plant field testing, six genotypes namely Borlaug 100, BARI Gom 33, BAW 1272, BAW 1280, BAW 1286, and BAW 1297 consistently showed resistant response to wheat head blast (WHB) infection with low levels of disease severity ranging from 0.2 to 8.1%. Among the remaining genotypes, some were moderately resistant, and the others exhibited various levels of susceptibility. The resistant genotypes that were most promising showed good agronomic performance under inoculated field trials. A significant positive correlation was observed between seedling and adult plant resistance. The above mentioned six genotypes also showed resistant reaction to WHB infection under controlled conditions when tested with three selected MoT isolates. The presence of 2NS/2AS translocation conferring WHB resistance was confirmed in four of the tested genotypes. Three (BAW 1272, BAW 1286, and BAW 1297) lines having non-2NS background exhibited good blast resistance under both the field and controlled conditions. These results will be useful for breeders and pathologists in exploiting the 2NS and non-2NS based resistant sources to pyramid and develop broad genetic based resistant germplasm.

Blast disease of rice is caused by Pyricularia oryzae (Cavara), has become a major concern not only in India, but also in almost all rice-growing areas of the world. The fungal pathogen attacks all areal parts of the plants at all stages of growth, although leaves and the neck of the panicle are more commonly affected. The neck of the panicle is infected when the ear emergence. When the grains are set, the panicle breaks at the neck due to weakening of the neck tissue. Such panicle hangs down and can be distinguished at a distance. In severe cases losses to the extent of 70–80%. Application of many nitrogenous fertilizers with intensive measure of rice cultivation results in the severe form of the disease. Now-a-day the disease is managed only by administering prophylactic foliar spray of selected chemical fungicides. Prediction of the disease for its better eco-friendly management needs attention proper management strategies with eco-friendly chemicals, host plant resistance, bio-agents, adoption of cultural practices such as summer plowing, application of moderate nitrogen level, etc., are given priority as important components for implementation of integrated disease management.

Rice (Oryza sativa L.), is one of the most widely cultivated and major food crops of the world. However the productivity of crop was affects by the attack of various fungal as well as bacterial diseases. Among the various diseases the most predominant one was blast disease caused by Pyricularia oryzae which is very severe in hot and humid climate of Konkan region. Eight essential oils along with one fungicide were tested under field condition. The results revealed that, the lowest incidence of blast was recorded in treatment T4 (Nirgundi oil) with disease incidence 52.59% as compare to the control (71.85%).The highest reduction of disease control was 26.80% and was statistically significant over other treatments. This was followed by treatments T2 (Eucalyptus oil), T5 (Lemon grass oil), and T1 (Citronella oil) with disease incidence of 52.9, 52.96 and 57.03 percent respectively as compare to the control and percent disease reduction was in the tune of 26.29%, 26.29% and 20.63% over control. Data also revealed that treatment of Eucalyptus oil (T2) showed highest yield of 49.03q ha-1 as against 39.11 q ha-1 in control and was statistically significant. Treatment T2 recorded 25.36% increase in yield over control. This was followed by T5 (46.85%) and T4 (43.40%).

The in vivo experiment was conducted at Agricultural Research Station, Vizianagaram against pearl millet blast revealed that all the treatments showed significant reduction in blast disease incidence in pearl millet. Among all the treatments T3i.e., foliar application of Pseudomonas fluorescens at 20 DAS and Trifloxystrob in + Tebuconazole at 35 DAS was found effective with least disease intensity of blast (14.1%), highest grain (26.0 q/ha) and fodder yield (60.9 q/ha). While the highest disease intensity (94.8) was noticed in the treatment T6i.e., control with lowest grain (9.3 q/ha) and fodder yiled (26.3 q/ha). The highest cost benefit ratio (2.5) was obtained in treatment T3.

Keeping in view the importance of rice blast disease, an experiment was conducted in the Laboratory of the department of Plant Pathology & Seed Science, Sylhet Agricultural University, and at the field of regional BADC Seed Production farm, Khadimnagar, Sylhet, Bangladesh, to evaluate see health status of the collected samples and effectiveness of fungicides against the blast disease of rice. Treatments viz T1: Edifen 50 EC (Edifenphos), T2: Karisma 28 SC (Azoxystrobin 20% + Cyproconazole 8%), T3: Nativo 75 WP (Tebuconazole 50% +Trifloxystrobin 25%), T4: Trooper 75WP (Tricyclazole), T5: Stanza 75WP (Imidazole), T6: Amister top (Azoxystobin 20% + Difenoconazole 12.5%), T7: Control (water) were used both in laboratory and field condition. In laboratory, different seed borne fungi, like Aspergillus, Fusarium, Curvularia, Penicillium, Pyricularia, Bipolaris, Alternaria, were detected from the collected seed sample by blotter method. In the field, treatments were applied as foliar sprays for three times with ten days interval. The lowest blast disease incidence (34.0%), lowest severity (31.6%) was found in T2: Karisma 28 SC treated plots, and gave best result in term of yield (6.3 ton/ha) in comparison to other treatments. The results of the present studies suggested that use of Karisma 28 SC is the best choice against rice blast with lowest disease incidence and highest yield.

Blast disease is a disease that attacks rice plants. The control of this disease is still using a synthetic fungicide that is very harmful to the environment. The purpose of this research is to know the effect of the combination of Piper caninum leaf extract with compost to blast disease and rice plant growth. This research was conducted in vivo in the glasshouse of Senganan village, Penebel Tabanan. Bali. This study used a randomized block design. In this study, the extracts were combined with organic fertilizer which was made by biotechnology stater starmic ok. Fo = control (soil 100%). F1= (soil 90% + compost 10% + extract 0,5%) .F2 = (soil 80% + compost 20% + extract 1%) F3 = (soil 70% + 30% + extract 1.5%). F4 = (soil 60% + compost 40% + 2% extract), do repeat 4 times. The results show that the formulas F3 effectively reduce the intensity of blast disease by inhibition of 79.09%, significantly affect the number of rice leaves, and the number of rice tillers increases but in treatment, F4 decreased. The height of the rice plant from F1 to F4 decreases, it is great because it reduces the fall when the rice is fruitfull. This is due to the disruption of growth hormone by the extract.

Rice blast caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating diseases in rice production worldwide. Information on rice varieties with the blast disease resistance gene is important for rice cultivar development. This study identified rice blast resistant genes in 226 rice cultivars including 203 Thai landrace rice cultivars (19 upland rice cultivars from the North, 99 lowland rice cultivars from the Northeast, 45 floating rice cultivars from the Northeast and 40 cultivars from the South), 21 recommended rice varieties and two susceptible varieties ‘KDML105’ and ‘Nipponbare’ by using gene-specific markers for the blast resistant genes Pid3, Pi54 and Pigm. Results showed that 159 cultivars have at least one resistant gene and four cultivars have all three resistant genes. These results indicate that Thai landrace rice is a valuable source of rice blast resistant genes for rice breeding programmes.

The study was conducted to evaluate the effects of different wheat varieties against blast disease and to observe the status of seed health of collected wheat varieties. The study was carried out under experimental field and laboratory condition at the Plant Pathology and Seed Science Department, Sylhet Agricultural University, Sylhet during October to March (2016-2017). The seeds collected from the Regional Agricultural Research Station, Jessore including ten different varieties, viz., BARI Gom19, BARI Gom22, BARI Gom23, BARI Gom24, BARI Gom25, BARI Gom26, BARI Gom27, BARI Gom28, BARI Gom29, BARI Gom30 were used in both laboratory and field conditions. In the laboratory, different fungal pathogens like Fusarium oxysporum, Bipolaris sorokiniana, Aspergillus sp., Alternaria sp., Rhizophus sp., Curvularia sp. and Magnaporthe oryzae Triticum were detected using a standard blotter method. In the field, it was found that BARI Gom28 was moderately resistant against blast. It had the lowest disease incidence (21.66%), lowest severity (30%) and also highest result in term of grain yield (5.5 t ha-1). The highest blast disease incidence (66.67%), highest severities (78.33%) and lowest grain yield (1.6 t ha-1) were found in BARI Gom26.

Fearsome wheat blast disease expanded its radius from Latin America to Bangladesh in 2016 with higher degrees of destruction efficiency. In 1985, Brazil was the first hotspot and consecutively Paraguay, Argentina, Bolivia were affected by the wheat blast fungus. Blast fungus Magnaporthe oryzae is under pyriculariaceae family with three-celled, pyriform, hyaline conidia. Not only wheat and rice are affected by the blast pathogen but also around 50 grass species can be affected and act as host, but the fungus pathotype is specific and distinct for each plant species. Morpho-biometrical analysis revealed similarity between the Magnaporthe oryzae pathotype Tritici (MoT) strain of Bangladeshi and Brazil. Through extensive molecular genetics and genomics study unfolded five resistant genes, among those Rmg2, Rmg3, and Rmg7 lost viability but Rmg8 and RmgGR119 still have resistance. In addition, 2NS translocation from Aegilops ventricosa in wheat reports resistance against MoT. CIMMYT based Milan variety is regarded as a resistant variety and plant breeders are trying to develop new resistant varieties. But the main problem regarding blast pathogen is breakdown of resistance and evolving virulent races consecutively which is fueled by global warming. A wide range of molecular markers can potentially be used for blast resistance study. Utilization of medium to high-throughput markers like SSR, InDel and SNP gave pace in blast resistance study. Along with that, allele mining has potentiality for finding out source of resistance. In addition, gene pyramiding will play a vital role in introgression of multiple resistant genes into a superior wheat linage. In future, high-throughput marker technology along with cutting-edge gene editing technology will play a pivotal role. Furthermore, the collaborative research in Bangladesh indicates that international scientific community has taken wheat blast as a serious issue. J. Bangladesh Agril. Univ. 17(2): 122–132, June 2019

Background Rice blast disease is a major restriction in rice production. That is usually managed using chemical pesticides, which are expensive in terms of cost and environment hazards. Use of blast-resistance genes to develop resistant varieties may therefore be a more economical and environmentally friendly method for effective control. Results In this study, we improved the blast resistance of four sterile lines, Y58S, GuangZhan63S (GZ63), C815S and HD9802S, by introgression of 9 cloned broad-spectrum blast resistance genes Pi37, Pit, Pid3, Pigm, Pi36, Pi5, Pi54, Pikm and Pb1. Through molecular marker-assisted selection and backcross breeding, 31 single-gene derived lines and 20 double-gene combination lines were obtained. When infected naturally, single-gene lines with Pigm or Pid3 showed significantly enhanced resistance during whole growth period relative to their recurrent parent. Single-gene lines with Pi37, Pi5, Pit, Pi36, Pi54 or Pikm showed significantly enhanced resistance in some of the four backgrounds. No obviously enhanced resistance was observed in single-gene line with Pb1 for the whole growth period. Compared with recurrent parents, most of the double-gene lines showed improved resistance. Among these double-gene lines, lines with Pi37/Pid3, Pi5/Pi54, Pi54/Pid3 or Pigm/Pi37, exhibited significantly enhanced resistance and observable additive effects. Conclusions Two blast resistance genes, Pigm and Pid3, showed significantly enhanced resistance for the whole rice growth period, and six blast resistance genes Pi37, Pi5, Pit, Pi36, Pi54 or Pikm showed significantly enhanced resistance for some of the four backgrounds. Double-gene lines with Pi37/Pid3, Pi5/Pi54, Pi54/Pid3 and Pigm/Pi37 exhibited significantly enhanced resistance and observable additive effects. These lines could be used in rice hybrid and production. Electronic supplementary material The online version of this article (10.1186/s12284-019-0292-z) contains supplementary material, which is available to authorized users.

Rice blast is the main disease of rice plants in Indonesia and several countries worldwide. Controlling this disease using chemical fungicides has harmful effects on the environment. Therefore, we need biocontrol agents which are more environmentally friendly such as rice phyllosphere bacteria. This study aimed to explore bacteria producing bioactive compounds from the rice phyllosphere environment to control blast disease. A total of 88 isolates were successfully isolated from rice leaves in Sukabumi, Situgede, and Jasinga (West Java, Indonesia). From them, we obtained 22 bacteria isolates with antifungal activity against Pyricularia oryzae in vitro assay. In addition, seven non-pathogenic bacteria were obtained from further screening in hypersensitivity, hemolysis and pathogenicity assays, namely STGG 3, STGG 7, STGG 8, STGG 14, SKBV 1, STGV 8, and SKBG 78. To show their antifungal activity, we tested crude extracts of these seven isolates and the results revealed that all the crude extracts can inhibit the growth of P. oryzae. Based on a genetic approach, isolates STGG 3, STGG 7, and STGG 14 were found to have both nonribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) genes, while isolate SKBV 1 only had the NRPS gene. The NRPS and PKS genes from potential isolates were similar to NRPS and PKS genes of Bacillus sp. in different strains. Furthermore, molecular identification based on the 16S rRNA gene revealed that the seven potential isolates belong to three genera, i.e. Bacillus (STGG 3, STGG 7, STGG 8, STGG 14, SKBV 1), Enterobacter (STGV 8) and Brachybacterium (SKBG 78). We suggest that the seven isolates found in this study have potency and could be recommended as biocontrol agents of blast disease caused by P. oryzae.

Hybrid Napier (Pennisetum purpuriam) is the best nutritive crop to suit small farmer’s field to produce around the year green cattle feed. The present study confirms the occurrence of fungal blast disease caused by Pyricularia grisea in India in hybrid Napier. The disease incidence, disease severity, coefficient of disease index, area under disease progress curve are calculated to evaluate the different age group’s host response. It was observed Napier grass allowed to cut once, before rainy season, is more prone to be attacked by the pathogen having disease incidence (89.4% and 91.8%) followed by crop developed from newly planted slips (37.5% and 37.8%), in 2017 and 2018, interestingly hybrid Napier field of 2-year-old were unaffected, surprisingly the paddy crop grown in the nearby field was also free from the disease. Average Plant Disease severity of 5-month-old Napier was (24.1 in 2017 and 21.7 in 2018) and Napier grass allowed to cut (33.6 in 2017 and 31.5 in 2018) and coefficient of disease index was in Napier grass allowed to one cut (3003.84 in 2017 and 2897.2 in 2018) and newly grown Napier grass (903.75 in 2017 and 820.26 in 2018). Area under disease progress curve was in grass allowed to one cut 2555.25 in 2017 and 2172 in 2018 and in the newly grown Napier grass was 1047 in 2017 and 1023.75. Application 1 g/l water Tricylazole has recovered the crop from the disease.

Decrease in production and quality of grain due to neck blast disease in some lowland rice varieties. Neck blast disease of rice causes a decrease in yields both in quantity and quality. The study was conducted to see the effect of neck blast disease on the characteristics of grain and yields of several high yielding varieties of lowland rice. The varieties used were Ciherang, Inpari 4, Inpari 7, Inpari 8, and Inpari 9. The parameters observed were the incidence and severity of neck blast disease, the ratio of the size of the seeds of healthy and sick panicles and the estimated production. The analysis showed that all varieties planted were infected by neck blast disease, but based on Disease Incident rate in the Necks, Ciherang and Inpari 8 varieties reacted susceptible to neck blast disease, Inpari 7 and 9 were moderate and Inpari 4 was resistant to neck blast disease. The quality of panicle grain infected by neck blast disease has decreased the size of grain width and was significantly different from grain of healthy panicles in all varieties. The highest estimated productivity was Inpari 4 variety of 10,378 kg/ha which experienced a decrease in production by 35.86% and the lowest was Ciherang variety of 8,367 kg/ha which experienced a decrease in production by 48.37% when they were infected by neck blast disease.

There are three types of paddy leaf disease that have similar symptoms, making it difficult for farmers to identify them, namely Blast Disease, Brown-Spot Disease, and Narrow Brown-Spot Disease. This paper aims to develop an application to identify paddy leaf disease automatically. Several important aspects of the development of software engineering such as usability, interactivity, and simplicity have been considered. Image processing techniques, namely Blobs analysis and color segmentation are used to get the characteristics of diseased leaf; these characteristics are then used to identify the type of diseases using a rule-based expert system. The results obtained indicate that the developed system recognition capability is considered satisfactory with an accuracy of 94.7%.

Multi-feature fusion of morphology and texture featuresStepwise regression analysis to distinguish disease areas from natural brown areasCalculate the ratio of the total area of the diseased area to the area of the leaf area to obtain the disease level Abstract. In this research, an evaluation method involving digital image processing and stepwise regression was studied to establish an efficient and accurate rating system for studying rice blast disease. For this purpose, the R-G image was segmented by using maximum interclass variance method in which the lesion and naturally withered region was extracted from the leaves. Then, 240 lesion areas and 240 natural yellow areas were selected as samples. During the experiment, ten morphological features and five texture features were extracted. Subsequently, for lesion identification, stepwise regression analysis, SVM and BP neural network were used. In the results, regression analysis of naturally yellow areas showed the highest accuracy in lesion identification, reaching 93.33% for disaster-level assessment of identified lesion areas. On the basis of the results, it is evident that 153 samples were correctly classified into divisions of 160 tested different rice blast leaves, with 95.63% classification accuracy. This study has introduced a new method for objective assessment of leaf blast disease. Keywords: Disease classification, Lesion identification, Maximum interclass variance method, Rice blast, Stepwise regression.

Magnaporthe oryzae Triticum causing blast a devastating disease of wheat. An attempt was taken to study the morphological, pathological and cultural characteristics of M. oryzae Triticum and its in-vitro fungicidal control. Four isolates were isolated from infected wheat inflorescence. Conidia of the isolates were solitary, pyriform to obclavate, pale brown, smooth, granular to guttulate, 2-septate; hilum truncate, protruding and not darkened. Isolates were positive in pathogenicity test on wheat and caused characteristic eye shape lesions on leaves. The wheat blast isolates did not produce any blast symptom in rice. M. oryzae Triticum showed consistently better mycelial growth at pH 5.5, 29°C and in Oat Meal Agar medium. Efficacy of six fungicides such as Autostin 50WGD, Nativo 75WG, Diathane M 45, Khowin 50WP, Ridomil Gold MZ 68WG and Provax 200WP at concentrations of 50 ppm, 100 ppm and 150 ppm was evaluated against M. oryzae Triticumin in-vitro. Autostin 50WGD, Nativo 75WG and Knowin 50WP inhibited the growth of M. oryzae Triticum completely at all three concentrations. Therefore, these three fungicides may be suggested to control blast disease of wheat.

A field experiment was conducted at Prime Minister Agriculture Modernization Project (Zone office), Bijuwar, Pyuthan from 18th April, 2017 to 12nd September, 2017 to evaluate the efficacy of Trichoderma viride in the management of leaf blast diseases of rainy season rice under field conditions. The experiment was laid out in two factors factorial Randomized Complete Block Design with five replications. The treatment consisted of two varieties of rice of which one is improved and resistant to blast disease (Sabitri) and another is local (Radha 7) and two rates of Trichoderma viride (5 ml/lit. and 0 ml/lit.). The leaf blast disease was scored three times using the disease rating scale 0-9 given by IRRI, 2002 from 75 DAT to 85 DAT at 5 days interval. The disease incidence, severity and AUDPC value were calculated and analyzed by using RSTAT. The variety factor and Trichoderma viride factor varied significantly for leaf blast incidence, severity and AUDPC, however, the interaction of variety and Trichoderma viride factor varied significantly only in AUDPC value. Disease incidence, severity and AUDPC were found least in Sabitri in comparison to Radha 7. T. viride had significant role in reducing the disease incidence, severity and AUDPC value. The interaction of Sabitri and Trichoderma viride treatment was found best with the mean AUDPC value being the least 3.228. So, the application of Trichoderma viride was found efficient for leaf blast management and it is more effective when applied along with an improved and resistant variety.

Rice production is affected by several plant pathogens, including the fungus Pyricularia oryzae, which causes blast disease. This disease is a major constraint to the intensification of rice production in the world. To improve integrated pest management, it is necessary to know the sources of inoculum and useful information on the diversity of the pathogen. However, presently, the disease prevalence and the relative importance of inoculum sources have not been assessed in West Africa and, more specifically, in Mali. Similarly, the genetic diversity and population structure of P. oryzae are poorly documented in Africa.The general objective of this thesis is, therefore, to contribute to filling this knowledge gap, and the specific objectives are 1) to assess the incidence and severity of rice blast in different rice-growing areas in Mali, 2) to determine whether seeds, straw, and/or wild rice are sources of inoculum for cultivated rice, and 3) to determine the population structure of P. oryzae in Africa.Surveys conducted in farmers' and experimental plots in 2018 allowed to observe leaf and panicle blast in 10 out of 17 sites surveyed. In symptomatic fields, leaf incidence ranged from 24 to 72% and leaf severity from 2 to 15%. The highest values of panicle incidence and severity reached 94% and 52%, respectively. In 2019, leaf blast was observed on 3 out of 4 sites surveyed, and incidence and severity were much lower (maximum of 7% and 1%, respectively). Incidence and severity were not significantly different between irrigated and rainfed-lowland agrosystems. The highest values for panicle blast incidence and severity confirm that blast is a potential cause of high yield losses.The analysis of seed mycoflora showed the presence of the genera Bipolaris and Curvularia in 17 of the 20 plots with averages of 4.6 and 4.3% of contaminated seeds, respectively. The third pathogen observed was a fungus of the genus Fusarium. P. oryzae was not detected on the seeds. In contrast, P. oryzae was observed in straw lots from Niono (3%) and Sélingué (6%). The hypothesis that wild rice (Oryza longistaminata) is a source of inoculum for Asian cultivated rice (O. sativa) was also tested. Under controlled conditions, wild rice isolates are pathogenic to cultivated rice. But, on average, these isolates have a narrower range of compatibility than isolates collected from cultivated rice. Results of pathogenicity tests suggest that P. oryzae isolates from wild rice have the potential to attack cultivated rice in the field. However, the populations of P. oryzae on cultivated and wild rice are genetically differentiated. Thus, although physically close, each host plant harbors a different population of the pathogen, and our results suggest that wild rice is not a source of blast inoculum for cultivated rice. Seeds do not appear to either be a source of inoculum for blast epidemics in Mali. The role of infected straws needs to be further studied.The analysis of the population structure of P. oryzae with microsatellite markers revealed four genetic groups in Africa and Madagascar. These groups correspond to the four groups identified at the worldwide level. The populations of West Africa, East Africa, and Madagascar are highly differentiated. The geographic structure is consistent with limited dispersal and with some migratory events between neighboring countries. Both sexual compatibility groups (Mat1.1 and Mat1.2) are present in Africa with a dominance of Mat1.2, but no fertile female strains were detected, confirming the absence of sexual reproduction on this continent. This study showed an unsuspected high level of genetic diversity of P. oryzae in Africa and suggests several independent introductions.; La production du riz est affectée par des agents phytopathogènes dont le champignon Pyricularia oryzae, agent de la pyriculariose. Pour améliorer la lutte intégrée, il est nécessaire de connaître les sources d’inoculum et utile de disposer d’informations sur la diversité de l’agent pathogène. Toutefois, actuellement la prévalence de la maladie et l’importance relative des sources d'inoculum n’ont pas été évaluées en Afrique de l’Ouest, et plus spécifiquement au Mali. De même, la diversité et la structure des populations de P. oryzae sont peu documentées en Afrique.Cette thèse a donc pour objectif général de contribuer à combler ce déficit de connaissances et pour objectifs spécifiques 1) d’évaluer l’incidence et la sévérité de la pyriculariose du riz dans les différentes zones rizicoles au Mali, 2) de déterminer si les semences, les pailles et/ou le riz sauvage sont sources d’inoculum pour le riz cultivé et 3) d’établir la structure des populations de P. oryzae en Afrique.Les prospections conduites sur des parcelles paysannes et expérimentales en 2018, ont permis d’observer la pyriculariose foliaire et paniculaire dans 10 des 17 sites prospectés. Dans les champs symptomatiques, l'incidence foliaire allait de 24 à 72 % et la sévérité foliaire de 2 à 15 %. Les valeurs les plus élevées d'incidence et de sévérité paniculaires atteignaient respectivement 94 % et 52 %. En 2019, la pyriculariose a été observée sur 3 des 4 sites prospectés et l’incidence et la sévérité étaient beaucoup plus faibles (respectivement 7 % et 1% au maximum). L’incidence de la maladie n’était pas significativement différente entre culture irriguée et bas-fond. Les valeurs maximales d’incidence et de sévérité paniculaire confirment que la pyriculariose est un risque potentiel de pertes de rendement élevées.L'analyse de la mycoflore des semences a montré la présence des genres Bipolaris (ou Exserohilum) et Curvularia dans 17 des 20 lots examinés avec des moyennes de 4,6 et 4,3% de semences contaminées respectivement. Le genre Fusarium a également été observé fréquemment. P. oryzae n'a pas été détecté sur les semences. Par contre, nous avons observé la présence de P. oryzae dans les lots de paille de Niono (3%) et de Sélingué (6%). L’hypothèse que le riz sauvage (Oryza longistaminata) soit une source d’inoculum pour le riz cultivé asiatique (O. sativa) a aussi été testée. Dans des conditions contrôlées, les isolats de riz sauvage sont pathogènes pour le riz cultivé. Ces résultats suggèrent donc que les isolats de P. oryzae provenant du riz sauvage ont le potentiel d'attaquer le riz cultivé dans les champs. Cependant, les populations de P. oryzae sur le riz cultivé et le riz sauvage sont génétiquement différenciées. Ainsi, bien que physiquement proches, chaque plante hôte abrite une population différente de l'agent pathogène et nos travaux suggèrent que le riz sauvage n’est pas une source d'inoculum de pyriculariose pour le riz cultivé. Les semences ne semblent pas non plus être une source d'inoculum au Mali. Le rôle des pailles infectées doit faire l'objet d'une étude plus approfondie.L’analyse de la structure des populations de P. oryzae avec des marqueurs microsatellite a mis en évidence quatre groupes génétiques en Afrique et à Madagascar. Ces groupes correspondent aux quatre groupes identifiés à l’échelle mondiale. Les populations d'Afrique de l'Ouest, d'Afrique de l'Est et de Madagascar sont très différenciées. La structure géographique est cohérente avec une dispersion limitée et avec quelques événements migratoires entre pays voisins. Les deux signes de compatibilité sexuelle sont présents en Afrique mais aucune souche fertile femelle n'a été détectée, ce qui confirme l'absence de reproduction sexuée sur ce continent. Cette étude montre un niveau élevé insoupçonné de diversité génétique de P. oryzae en Afrique et suggère plusieurs introductions indépendantes.

Once thought to be a minor disease, foliar blast disease of pearl millet, caused by Magnaporthe grisea, has recently emerged as an important biotic constraint for pearl millet production in India. The presence of a wider host range as well as high pathogenic heterogeneity complicates host–pathogen dynamics. Furthermore, environmental factors play a significant role in exacerbating the disease severity. An attempt was made to unravel the genotype-by-environment interactions for identification and validation of stable resistant genotypes against foliar blast disease through multi-environment testing. A diversity panel consisting of 250 accessions collected from over 20 different countries was screened under natural epiphytotic conditions in five environments. A total of 43 resistant genotypes were found to have high and stable resistance. Interestingly, most of the resistant lines were late maturing. Combined ANOVA of these 250 genotypes exhibited significant genotype-by-environment interaction and indicated the involvement of crossover interaction with a consistent genotypic response. This justifies the necessity of multi-year and multi-location testing. The first two principal components (PCs) accounted for 44.85 and 29.22% of the total variance in the environment-centered blast scoring results. Heritability-adjusted genotype plus genotype × environment interaction (HA-GGE) biplot aptly identified “IP 11353” and “IP 22423, IP 7910 and IP 7941” as “ideal” and “desirable” genotypes, respectively, having stable resistance and genetic buffering capacity against this disease. Bootstrapping at a 95% confidence interval validated the recommendations of genotypes. Therefore, these genotypes can be used in future resistance breeding programs in pearl millet. Mega-environment delineation and desirability index suggested Jaipur as the ideal environment for precise testing of material against the disease and will increase proper resource optimization in future breeding programs. Information obtained in current study will be further used for genome-wide association mapping of foliar blast disease in pearl millet.

Among the eco-friendly products tested viz., leaf extracts of eucalyptus and henna @ (25% conc.), Sheep urine @ (10%), goat urine @ (20%) and Pseudomonas fluorescens @ (10g/kg of seed) alone and in combination, seeds treated with sheep urine was found to increase the germination percentage, vigour index and also enhance the yield parameters of rice. Among the different ecofriendly products, seeds treated with P. fluorescens retained the fungitoxicty for the longest duration of time against P. oryzae. Finally, under the pot culture studies, seed treatment with P. fluorescens and foliar spray with sheep urine on 30 and 50 DAT recorded the least leaf blast intensity in rice.