Search

Blast of rice caused by Pyricularia grisea (Cooke.) Sacc. (Teleomorph :Magnaporthe oryzae) is a serious disease of rice and causes considerable reduction in yield. Overdose and untimely application of chemical fungicides disturb the rice ecosystem, pollute the environment and induce resistant mutants of the pathogen. An ecofriendly integrated disease management programme should be implemented to avoid overuse of a single control method and fight against genetic resistance. Salicylic acid (0.01ml/ l) and Benzoic acid (0.01ml/ l) proved superior in inducing disease resistance among different inducers tested at Regional Agricultural Research Station, Pattambi, Palakkdad district, under Kerala Agricultural University under green house conditions. As an integrated approach, Palmarosa oil + Carbendazim and Palmarosa oil+ Salicylic acid were the most effective treatments .Compatibility studies under in vitro conditions showed that Trichoderma harzianum and fluorescent pseudomonad were compatible to each other, and also palmarosa oil and Neemazal were compatible with Trichoderma harzianum and Fluorescent pseudomonad. For the management of blast disease under field conditions with high B:C ratio, Palmarosa oil (0.1%) + Carbendazim (0.1%)was the best treatment followed by Trichoderma (2%) + Fluorescent pseudomonad (2%)+ Palmarosa oil (0.1%).

Global food security is threatened by rice blast disease caused by the filamentous fungus Magnaporthe oryzae. An understanding of rice resistance mechanisms is fundamental to developing strategies for disease control. In this review, we summarize recent advances in pathogen-associated molecular pattern-triggered immunity, effector-triggered immunity, defense regulator-mediated immunity, and effects of nutrient elements on rice blast resistance. We outline strategies used for breeding rice cultivars with improved disease resistance. We also present the major research challenges for rice blast disease resistance and propose approaches for future investigation.

This article presents the results of the development of a methodology for describing the main morphological and cultural traits of the Pyricularia oryzae Cav. strains widespread in the south of Russia. At the same time, the types of traits are identified and listed, which make it possible to unambiguously determine the uniqueness and variety of the pathogen. The relationships and patterns established using cluster and statistical analysis make it possible to identify the conditions for the development of a pathogen that determine its predominant forms. Thus, research shows that leaf forms of P. oryzae strains isolated from rice plants with leaf form of blast disease have an equally directional growth pattern of a colony with a felt structure, and strains isolated from neck-affected plant form often produce a zone of a colony with a clumpy structure. The classification of cultural traits will make it possible to obtain scientifically grounded and comparable data that can be used in the analysis of the interaction of P. oryzae strains with rice plants on various varieties and in various agro-technological conditions in order to improve and rationalize agricultural activities. The study opens up the possibility of using data in breeding, making it possible to identify forms of a pathogen that infect certain varieties.

The study was conducted to know the knowledge and adoption level of plant protection measures against blast disease among 80 respondent paddy growers in the blocks of North and South 24 Parganas of Sundarbans. About 48.75% of the respondents had medium knowledge. Majority of the respondents (75%) knew about blast disease of rice and its key identifying symptom. The 67.5% farmers were having the knowledge about the fungicides used against the disease (Tricyclazole 75 WP, Carbendazim 50 WP, Hexaconazole 5EC), and 22.5% of the farmers knowing about the recommended dose of fungicide application. The 28.75% of the respondents also knew that the fungicide should be applied at the first appearance of the disease. Further, it has been found that the adoption level of plant protection measures against blast disease of rice was medium (47.5%). Nearly 53.75% of the respondents practicing rice cultivation were in the middle age group of 31-50 years. Most of the respondent had either 0.13-0.27ha (22.5%) or 0.40-0.67ha (37.5%) landholding wherein they were practicing rice cultivation. Almost all the respondents (100%) possessed Knapsack or hand sprayer for fungicide application. Climatic vagaries, lack of knowledge about to the number of sprays and concerning technology application, non-availability of fungicide on time, lack of facility at the nearby place were the major constraints as expressed by 95, 83.75, 85, 90, and 95 per cent of respondents, respectively. The high cost of chemicals and expensiveness and non-availability of labour during peak cropping period were also the major constraints as expressed by 60 and 83.75 per cent of the respondents, respectively. There was a significant relationship between age, education, landholding, social, mass media and participation in extension activities with knowledge and adoption levels of the farmers of the Indian Sundarbans.

Rice blast disease is one of the major constraints to rice production, threatening food security globally. Rice grain production losses due to the disease leads economic losses to the farmers, and to an increase in global rice price as a result of the supply that is far below the consumer demand. The losses from the disease annually was estimated to feed over 60 million individual. The disease has been studied comprehensively by researchers due to the importance attached to rice and its vast spread and destructiveness across the globe. A good understanding of the pathogen causing the disease, its life cycle and development, epidemiology, symptoms, management strategy will offer a good insight into the disease incidence and give an appropriate and effective decision-making in its management. Different control measures have been adopted managing the disease, including the use of resistant varieties. Integrated disease management strategies coupled with good agronomy practices are required for successful control of rice blast for food security. This review, therefore, examined the fundamentals of rice blast disease (Magnaporthe oryzae) and offered strategies to minimize the disease activities to ensure proper production and increase the supply of rice grains.

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.

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.

Blast is one of the devastating diseases of rice which cause significant yield losses. Blast is mainly managed by the use of fungicides. However, this approach is not eco-friendly and causes health hazards. Basmati is the specialty rice of India with great export potential. However, the importing nations have increased the stringency in maximum permissible limits of pesticide residues in the grain, which has led to rejection of several Basmati rice consignments. Therefore, developing genetic resistance is one of the most pragmatic approaches to address this issue. More than 100 blast resistance genes have been identified which can be effectively deployed into the high-yielding rice varieties through marker-assisted backcross breeding. In India the major blast resistance genes, namely Pi9, Pi2, Pi54, Pita, and Pi1, are widely used to develop blast resistance in popular rice varieties. Until recently, blast-resistant varieties developed in India are Pusa Basmati 1637, Pusa Basmati 1609, Pusa 1612, and Pusa Samba 1850. Effective adoption of these varieties would significantly reduce the use of chemical pesticides, thereby producing consumer-safe rice with eco-friendly approach.

By 2030, global rice production will need to increase to meet the demand of the growing world population. However, rice is severely affected by blast disease caused by the fungus Pyricularia oryzae, which accounts for 10–30% yield losses per year globally, thus posing a threat to the world’s most important food crop. The fungus can infect all parts of the rice plant, including leaves, nodes and panicles. In the early stages of the infection process, P. oryzae forms an infection structure called appressorium to break the plant cuticle. After an initial biotrophic phase, the fungus kills plant cells thus leading to visible symptoms. Currently, several methods for the management of rice blast disease, such as agronomic practices, use of resistant cultivars and synthetic fungicides, are available and can be exploited in an integrated management approach. However, despite some resistant rice varieties that have been developed by breeding programs, P. oryzae is able to rapidly develop new races that overcome resistance genes. Furthermore, the continuous use of fungicides may be harmful to humans and environment and can increase the risk of appearance of resistant fungal races. Biological control using microbial agents or plant extracts with antimicrobial activity is therefore considered a possible alternative and sustainable approach to control rice blast disease. However, biological protection is difficult to achieve in the field as its effectiveness is variable, highly depending on formulations and climatic conditions. Because of these drawbacks, durable control of rice blast still represents a substantial challenge. Innovative strategies for the identification of new molecules for the sustainable protection of rice are thus highly desirable.

Wheat blast disease pathogen, Magnaporthe oryzae Triticum (MoT) pathotype, is posing a serious threat to wheat production in Southern America and Bangladesh. Specially under the changing climatic conditions, traditional wheat-growing regions are experiencing favourable weather conditions for thriving of MoT. Management of this disease is becoming even more challenging due to lack of complete resistance in wheat germplasm. However, availability of wheat genome sequence along with recently published MoT genome could enhance the understanding of wheat-MoT interaction and enable speedier identification and characterization of novel resistance genes. The future management strategies could also be largely benefitted by the recent genome editing tools such as CRISPR-Cas9.

Paddy is a major agricultural crop. But the production of paddy is hindered by various kinds of diseases. Some of those diseases are leaf blast disease, brown spot disease, bacterial blight disease, etc. Amidst of all these diseases influencing the paddy production, leaf blast disease had a great influence and it is the most destructive diseases that are effecting on paddy crop. Leaf blast is risen by the fungus Magnaporthe oryzae. It will affect all the above-ground parts of a paddy crop: leaf, collar, node, neck, parts of panicle, and sometimes leaf sheath. Thus, examining and accurate forecasting for the development of blast disease are significant and early forecasting of the disease is very beneficial. Many former blast disease prediction models were only considering the attribute values but not their correlations. In this paper, logistic regression algorithm is applied for forecasting the occurrence of leaf blast disease for Adilabad district of Telangana state in India during 2007–2017 in order to prevent the paddy fields from disease. With the help of the correlation mining and clustering process among the attributes, we are classifying the attribute sets based on their impact on disease occurrence. Finally, the logistic regression algorithm calculates the leaf blast disease occurrence probability.

Significance Crops carrying broad-spectrum resistance loci provide an effective strategy for controlling infectious disease. Despite their importance, few broad-spectrum resistance loci have been reported, and the underlying mechanisms controlling the trait remain largely unknown. This report describes the identification of a gene, called “bsr-k1,” conferring broad-spectrum resistance and demonstrates that the encoded protein regulates immunity-related genes. Loss of function of BSR-K1 in rice leads to enhanced broad-spectrum resistance to two serious rice diseases with no major penalty on yield. This report provides insights into broad-spectrum resistance and offers an efficient strategy to breeding durably resistant rice., Crops carrying broad-spectrum resistance loci provide an effective strategy for controlling infectious disease because these loci typically confer resistance to diverse races of a pathogen or even multiple species of pathogens. Despite their importance, only a few crop broad-spectrum resistance loci have been reported. Here, we report the identification and characterization of the rice bsr-k1 (broad-spectrum resistance Kitaake-1) mutant, which confers broad-spectrum resistance against Magnaporthe oryzae and Xanthomonas oryzae pv oryzae with no major penalty on key agronomic traits. Map-based cloning reveals that Bsr-k1 encodes a tetratricopeptide repeats (TPRs)-containing protein, which binds to mRNAs of multiple OsPAL (OsPAL1–7) genes and promotes their turnover. Loss of function of the Bsr-k1 gene leads to accumulation of OsPAL1–7 mRNAs in the bsr-k1 mutant. Furthermore, overexpression of OsPAL1 in wild-type rice TP309 confers resistance to M. oryzae, supporting the role of OsPAL1. Our discovery of the bsr-k1 allele constitutes a significant conceptual advancement and provides a valuable tool for breeding broad-spectrum resistant rice.

Wheat blast disease, caused by Magnaporthe oryzae Triticum pathotype, was first reported in 1985 from Brazil, and since then it has emerged as a major threat to global wheat production. Unlike rice blast disease, where many rice lines are known to provide nearly complete resistance to M. oryzae, the resistance response of wheat germplasm to blast pathogen is rather limited to a few isolated lines with low to moderate level of resistance. Considering this aspect along with the limited success achieved in managing wheat blast using chemical fungicides, it is going to be a very challenging task to manage this disease. Therefore, it is imperative on the part of the wheat breeders and agricultural scientist to visit and explore the knowledge and genomic and genetic resources gained by concomitant molecular biology research over decades while dealing with rice-Magnaporthe pathosystem and devise strategies to effectively manage wheat blast disease.

The introduction and use of foreign germplasms have played an important role in the improvement of crop varieties in China. Based on published materials and scientist interviews, we collected data on the sown area, morphological characteristics, and pedigree of the popular rice varieties grown in the 15 major rice production provinces and 1 autonomous region in China, from 1982 to 2011. Results showed that China's scientists developed the largest number of rice varieties worldwide, and that rice yield potential and grain quality have substantiality improved during the studied period. In contrast, resistance of newly-released varieties to diseases and insect pests has decreased since the 1990s. Germplasms from the International Rice Research Institute (IRRI) and from Japan have contributed 16.4 and 11.2% of genetic materials to China's rice varieties developed between 1982 and 2011, respectively. While IRRI's materials contributed to the improvement of yield potential, growth duration, and blast and bacterial blight resistance, Japanese materials contributed to the improvement of grain quality. Materials from other countries contributed to the improvement of resistance to diseases and insect pests, particularly to rice blast disease, brown planthoppers, white-backed planthoppers, and striped stem borers.

Grain productivity of rice is significantly reduced by dangerous disease blast. Therefore, the development of resistant high yielding rice varieties with the Pi group of genes is important. Use of molecular markers linked with the loci of resistance significantly optimizes the breeding process. The purpose of the research is to develop rice lines combining 2-6 loci of resistance to blast: Pi-1, Pi-2, Pi-33, Pi-ta, Pi-b, Pi-40 by molecular marking. Materials and Methods. As donors of resistance genes foreign samples were used, recipient Russian varieties. In the studies we used micro-satellites markers and PCR analysis. Results. In the first stage of the research as a result of hybridization domestic lines with genes Pi-l, Pi-2, Pi-33 were obtained. At the second stage hybrids with all 3 genes were developed. In the third stage genes Pi-b and Pi-ta and on the fourth Pi-40 were introduced. Conclusion. As a result, rice genotypes, combining 6 loci of blast resistance were developed with use of marker assisted selection.

We genotyped 74 rice germplasms including Tripura's local landraces, improved varieties, cultivars and breeding lines and other rice varieties using molecular markers for genetic diversity, drought QTLs, and blast resistance genes. The number of alleles per locus ranged from 2 to 5 with an average of 2.9. The polymorphic information content value per locus ranged from 0.059 (RM537) to 0.755 (RM252) with an average of 0.475. Cluster analysis based on 30 simple sequence repeat markers revealed 5 clusters and also indicated the presence of variability within the rice accessions. The drought QTL qDTY2.1 was found in 56.0% of germplasms and qDTY1.1 was detected in only 6.8% of the germplasms. Out of seven rice blast resistance genes screened, only two rice varieties, RCPL-1-82 and Buh Vubuk (Lubuk), were positive for four blast resistance genes while only Releng possessed two blast resistance genes. Among 74 rice germplasms, only three accessions, Releng, RCPL1-82 and Buh Vubuk (Lubuk), possessed both drought-related QTLs and blast resistance genes. Overall, the 74 indigenous rice genotypes showed low level of genetic diversity, which is in contrast to high level of genetic diversity among rice varieties in northeast India, where highlights the good farming practice, conservation of germplasms and the limitation of molecular markers employed in this study. The presence of both drought related QTLs and blast resistance genes in some of the germplasms can be useful in future breeding programmes.

Rice blast disease caused by Pyricularia oryzae is the most destructive disease of rice worldwide. It kills seedlings or plants up to the tillering stage. The most common practice controlling method is using chemical fungicide, however there are several negative impact of using synthetic chemicals to the human consumption as well as to the environment. In order to solve this problem, this study was conducted to find other alternative methods to control blast disease by using plant extracts from family Zingiberaceae which are Alpinia galangal, Curcuma longa and Zingiber officinale. Screening for antifungal activities of these plant extracts were done in vitro on Potato Dextrose Agar (PDA). After 7 days of treatment, result showed that crude extracts of Alpinia galangal hexane crude extract exhibited strong inhibitory against Pyricularia oryzae with the highest percentage of inhibition 52.9%, followed by Curcuma longa hexane crude extract with 49.1% and Zingiber officinale methanol crude extract with 43.5% inhibition. The antifungal activities may be due to the presence of some chemical compounds such as alkaloids, saponins, tannins, phenols, gylcosides, flavonoids and terpenes that been proved thru phytochemical test. However, further trial such as field trial is necessary to be done to evaluate the effectiveness of these extracts to control rice blast disease under field condition.

Rice blast is a damaging disease caused by Magnaportheoryzae. Marker-assisted selection of blast resistance genes could help develop cultivars with blast resistance. Pigm is a broad-spectrum blast-resistant gene. However, few rice resources contain Pigm. In this study, the Pigm gene donor Gumei4 (GM4) was investigated. By analyzing different regions of Pigm sequences, we found that marker G8900 was a specific molecular marker of Pigm gene in GM4. Correlation analysis between molecular marker detection and identification of rice blast disease nursery revealed that G8900 could be used in marker-assisted selection (MAS) of Pigm. Furthermore, we introduced Pigm gene into the KT27S line (a blast-susceptible yellow-green-leaf-color mutant) in G8900-assisted breeding and identified three new yellow-green-leaf-color marker lines that are resistant to blast. The agronomic and economic traits of the three new lines are similar to those of their parental lines. The identification and application of Pigm-specific molecular marker in breeding of yellow-green-leaf-color marker line could play an important role in the production of disease-resistant hybrid rice.

Effective control of blast, a devastating fungal disease of rice caused by Pyricularia oryzae, is an important breeding objective to increase and stabilize worldwide rice production. Use of quantitative resistance to blast is considered a promising strategy because such resistance is more durable than race-specific qualitative resistance. Quantitative resistance is under complex genetic control, with each contributing gene having a smaller individual effect than those conveying qualitative resistance. This characteristic decreases selection pressure, thereby slowing the counter-evolution of the pathogen, but also makes it difficult for breeders to select the required traits in practical breeding programs. Extensive genetic studies of quantitative resistance during the last two decades have identified several relevant genes and have contributed to our understanding of the genetic control of quantitative resistance. Such studies will accelerate marker-assisted gene pyramiding of resistance alleles to confer strong, non-race-specific, and environmentally stable resistance to blast disease; this achievement would contribute substantially to global food security.

Development of resistant cultivars has been an effective method for controlling rice blast disease caused by Magnaporthe oryzae. Quantitative blast resistance genes may offer durable resistance because the selection pressure on M. oryzae to overcome resistance is low as a result of the genes’ moderate susceptibility. Because the effects of individual resistance genes are relatively small, pyramiding these genes in rice cultivars is a promising strategy. Here, we used near-isogenic and backcross lines of rice cultivar Koshihikari with single- or two-gene combinations of blast resistance genes (pi21, Pi34, and Pi35) to evaluate the suppression of leaf blast. The severity of the disease was assessed throughout the infection process. Resistance varied among the lines: Pi35 conferred the strongest resistance, while Pi34 showed the weakest effects. Two types of combined-gene interactions were observed, and they varied on the basis of gene combination and characteristic of the infection: (i) the combination of two resistance genes was more effective than either of the genes individually or (ii) the combination of two resistance genes was similar to the level of the most effective resistance gene in the pair. The most effective gene combination for the suppression of leaf blast was pi21 + Pi35.

Isolates of the rice blast fungus show a range of tissue-specificities infecting leaves, nodes, neck and panicles. Although neck and panicle blast cause significantly greater yield losses than the leaf blast, virulence tests of the blast isolates have been performed only rice leaves instead of neck and panicles. In this study, we have developed a virulence test method for neck and panicle blast. We selected three representative isolates from each of leaf, neck, and panicle blast. We observed that severe disease lesions developed on the neck and the panicles when the infected rice plants were incubated in a dew chamber for 48 h instead of 24 h when tested on leaves. Unlike the leaf blast, a typical lesion on the neck and panicles appeared after 14 days post-infection as opposed to 7 days with leaf blast. This method will be applied to examine tissue-specificity of the rice blast fungus isolates.

In Kenya rice is the third most important cereal crop after maize and wheat. However production is constrained by rice blast disease (Pyricularia grisea (Cooke) Sacc). In order to develop viable pest management practices for rice blast disease we need to understand rice farmers' knowledge of the disease. A study was set up to determine the level of farmer knowledge on rice blast disease. A formal questionnaire was administered to a random sample of 119 farmers at Mwea irrigation scheme on 17-22 February 2011. Farmers were requested to provide information about rice, its importance and rice blast disease. Logit regression model was used to identify factors which influence farmer knowledge of rice blast disease. Logit analysis revealed that age had significant influence on rice blast disease knowledge (p

The blast fungus Magnaporthe oryzae ( Pyricularia oryzae ) destroys rice crops worldwide (see the photo) ( 1 ) and now threatens global wheat production as well. Wheat blast disease has been spreading in South America since 1985, and last year it devastated wheat crops in Bangladesh ( 2 , 3 ). Incorporation of resistance (R) genes into rice presents an effective, economical, and environmentally sound way to control blast ( 4 ). However, it takes years to move an R gene into a rice variety, whereas the highly variable fungus can overcome the R gene effects within 2 or 3 years after planting. Also, many R genes are associated with yield losses, so farmers often prefer rice varieties without R genes. On page 962 of this issue, Deng et al. ( 5 ) report a new R gene that comes with a homologous partner to counteract the yield penalty.

Drought and rice blast disease caused by Magnaporthe oryzae are two of the most serious threats to global rice production. To explore the mechanisms underlying gene expression induced in rice by stresses, studies involving transcriptome analyses have been conducted over the past few years. Thus, it is crucial to have a reliable set of reference genes to normalize the expression levels of rice genes affected by different stresses. To identify potential reference genes for studies of the differential expression of target genes in rice under M. oryzae infection and drought conditions, the present study evaluated five housekeeping genes for the normalization of gene expression. The stability of the expression of these genes was assessed using the analytical software packages geNorm and NormFinder. For all samples analyzed, the stability rank was UBQ5 > GAPDH > eIF-4α > β-TUB > 18S rRNA. The data showed that the UBQ5, GAPDH, and eIF-4α genes are appropriate, high-performing reference genes and will be highly useful in future expression studies of fungal infections and drought in rice.

Rice production and grain quality are severely affected by blast disease caused by the ascomycetous fungus Magnaporthe oryzae. Incorporation of genes that confer broad-spectrum resistance to blast has been a priority area in rice breeding programs. The blast resistance gene Pi9 sourced from Oryza minuta has shown broad spectrum and durable resistance to blast world-wide. In the present study co-dominant gene-based markers were developed for the precise marker-assisted tracking of Pi9 in breeding programs. The developed markers were validated across a diverse set of cultivars including basmati, indica and japonica varieties. Two markers, Pi9STS-1 and Pi9STS-2, effectively differentiated Pi9 donors from all the indicas and commercial basmati varieties tested. However, these markers were monomorphic between Pi-9 donors (IRBL9-W and Pusa 1637) and japonica type varieties. An additional gene-derived CAPS marker Pi91F_ 2R was developed to differentiate Pi9 donors from japonicas and traditional basmati lines. The co-dominant markers developed in the present study will be of immense utility to rice breeders for precise and speedy incorporation of Pi-9 into susceptible rice varieties through marker-assisted selection.

Situ Patenggang is an elite upland rice variety well-accepted by farmers, but recently this variety started to be attacked by blast disease (Pyricularia grisea) that causes yield loss up to 50%. To overcome this problem, Bio Patenggang variety has been developed through molecular breeding using blast-resistant monogenic lines as donor parents. The aim of this research was to present molecular breeding approach of Bio Patenggang development, including steps from the phenotypic selection on candidate lines to the genotypic analysis assisted by molecular markers. The phenotypic performances were assessed using Distinctness, Uniformity, and Stability (DUS) testing by following the standard method stated in the rice test guidelines. The genotypic analyses were performed using foreground and background markers. Four BC3F7 lines were selected as the candidates of the Situ Patenggang-derived variety. Based on ANOVA and Principal Component Analysis (PCA), phenotypic performances of the four lines demonstrated no significant differences with that of Situ Patenggang. The selected lines have also passed the foreground analysis confirming that the lines contained Pita, Pii, Pik-p, and Pia last resistance genes. Background analysis showed that the selected lines demonstrated agronomic perfomances very similar to that of Situ Patenggang. Association analyses showed that 14 markers were associated with the target traits and 10 out of the 14 markers were identified as co-segregation markers. The four selected lines, therefore, were proposed to be released as Situ Patenggang-derived variety. One of the lines (Sta-8-S15-TB16) has been approved to be released as a new variety, namely ‘Bio Patenggang Agritan’.

Thai jasmine rice, RD 15 variety is well known for its fragrance, cooking and eating qualities. However, it is susceptible to blast disease, a major rice disease caused by the fungus Pyricularia oryzae. The aim of this research was to transfer blast disease resistant QTLs from KD4-14 line into RD15 variety by using phenotype and genotype selections by the aid of markers. In this study, the two resistant QTLs were transferred from KD4-14 rice line into a RD15. Our analysis led to the breeding of elite lines with two resistant QTLs for blast disease by phenotype and foreground selections. The background genome recovery of the lines expressed more than 92.4% by using genome wide SSR markers analysis. The pathogenicity assays of the five resistant-QTL-derived lines were validated under greenhouse conditions with 17 blast isolates, prevalent in Thailand. These lines exhibited resistant reaction to all isolates with agronomic and grain quality traits similar to those of the RD15. The strategy of simultaneous phenotype and genotype selections to introduce multiple resistant QTLs is very useful for reducing the cost and time required for the isolation of desirable recombinants with target resistant genes in rice. The resistant-QTL-derived lines have practical breeding value in providing broad spectrum resistance, without a yield penalty, against most of the existing races of blast in Thailand. These lines could have a great impact on the yield stability and sustainability of rice productivity.

This study was conducted to elucidate the performance of varieties with known resistance genes of rice at two sites and assess the efficiency of the two sites for screening rice genotypes for blast resistance. Thirty-four (34) varieties plus one local check were screened for resistance to rice blast disease caused by a fungus (Magnaporthe oryzae) at Ibadan and Ikenne under natural infection for two years. The experiment was laid out using randomized complete block design with four replicates. Data were collected on disease development and severity using standard evaluation scale. Data were subjected to analysis of variance and the effect of genotype, environment, and their interaction were further analyzed using genotype main effect plus genotype-by-environment (GGE) biplot. Results revealed that the thirty-five varieties responded differently to blast infection and the two sites were significantly different from each other. Genotype-by-environment interaction was significant and had the highest contribution to the total sum of squares for disease development and severity scores. GGE biplot revealed that only Moroberekan was resistant to blast fungus across years and sites. In conclusion, although, the two sites are found in the same agroecology, Ibadan was identified as a better site for screening rice genotypes for blast resistance than Ikenne.

Background Rice blast is one of the most damaging disease of rice. The use of resistant cultivars is the only practical way to control the disease in developing countries where most farmers cannot afford fungicides. However resistance often breaks down. Genome wide association studies (GWAS) allow high resolution exploration of rice genetic diversity for quantitative and qualitative resistance alleles that can be combined in breeding programs to achieve durability. We undertook a GWAS of resistance to rice blast using a tropical japonica panel of 150 accessions genotyped with 10,937 markers and an indica panel of 190 accessions genotyped with 14,187 markers. Results The contrasted distribution of blast disease scores between the indica and tropical japonica groups observed in the field suggest a higher level of quantitative resistance in the japonica panel than in the indica panel. In the japonica panel, two different loci significantly associated with blast resistance were identified in two experimental sites. The first, detected by seven SNP markers located on chromosome 1, colocalized with a cluster of four NBS-LRR including the two cloned resistance genes Pi37 and Pish/Pi35. The second is located on chromosome 12 and is associated with partial resistance to blast. In the indica panel, we identified only one locus associated with blast resistance. The three markers significantly detected at this locus were located on chromosome 8 in the 240 kb region carrying Pi33, which encompasses a cluster of three nucleotide binding site-leucine-rich repeat (NBS-LRRs) and six LRR-kinases in the Nipponbare sequence. Within this region, there is an insertion in the IR64 sequence compared to the Nipponbare sequence which also contains resistance gene analogs. Pi33 may belong to this insertion. The analysis of haplotype diversity in the target region revealed two distinct haplotypes, both associated with Pi33 resistance. Conclusions It was possible to identify three chromosomal regions associated with resistance in the field through GWAS in this study. Future research should concentrate on specific indica markers targeting the identified insertion in the Pi33 zone. Specific experimental designs should also be implemented to dissect quantitative resistance among tropical japonica varieties. Electronic supplementary material The online version of this article (doi:10.1186/s12284-016-0131-4) contains supplementary material, which is available to authorized users.

A new pyriculol-related phytotoxin, designated as pyricuol (1), was isolated from a liquid culture of Magnaporthe grisea, the causal fungus of rice blast disease, together with two known metabolites, pyriculol (2) and dihydropyriculol. Its structure was determined on the basis of physicochemical and spectroscopic data to be 2-(3-hydroxymethyl-1,4-hexadienyl)-6-hydroxybenzaldehyde.

Background The most sustainable approach to control rice blast disease is to develop durably resistant cultivars. In molecular breeding for rice blast resistance, markers developed based on polymorphisms between functional and non-functional alleles of resistance genes, can provide precise and accurate selection of resistant genotypes without the need for difficult, laborious and time-consuming phenotyping. The Pi2 and Pi9 genes confer broad-spectrum resistance against diverse blast isolates. Development of allele-specific markers for Pi2 and Pi9 would facilitate breeding of blast resistant rice by using the two blast resistance genes. Result In this work, we developed two new markers, named Pi9-Pro and Pi2-LRR respectively, targeting the unique polymorphisms of the resistant and susceptible alleles of Pi2 and of Pi9. The InDel marker Pi9-Pro differentiates three different genotypes corresponding to the Pi2/Piz-t, Pi9 and non-Pi2/Piz-t/Pi9 alleles, and the CAPS marker Pi2-LRR differentiates the Pi2 allele from the non-Pi2 allele. Based on the two newly developed markers and two available markers Pi2SNP and Pi9SNP, the presence of Pi2 and Pi9 was assessed in a set of 434 rice accessions consisting of 377 Chinese indica cultivars/breeding materials and 57 Chinese japonica cultivars/breeding materials. Of the 434 accessions tested, while one indica restorer line Huazhan was identified harboring the Pi2 resistance allele, no other rice line was identified harboring the Pi2 or Pi9 resistance alleles. Conclusions Allele-specific marker-based assessment revealed that Pi2 and Pi9 have not been widely incorporated into diverse Chinese indica rice cultivars. Thus, the two blast resistance genes can be new gene sources for developing blast resistant rice, especially indica rice, in China. The two newly developed markers should be highly useful for using Pi2 and Pi9 in marker-assisted selection (MAS) breeding programs. Electronic supplementary material The online version of this article (doi:10.1186/s12284-016-0091-8) contains supplementary material, which is available to authorized users.

In order to study the function of blast resistance gene and estimate resistance scale to Pyricularia grisea Sacc., the cause of Rice Blast Disease in rice, we evaluated 58 rice genotypes for phenotypic and molecular assessment. Phenotypic tests were conducted in a blast upland nursery and also in the greenhouse by using specific races of blast IA-82 and IA-90 in the greenhouse and local races for the nursery. The traits assessed consisted of infection type (IT), percent diseased leaf area (DLA) (in both nursery and greenhouse), and lesion number (LN), lesion size (LS, mm2 ) only in greenhouse conditions. Molecular assessment was done by using three STS, JJ80, JJ81, and JJ113, and four microsatellite markers, RM224, RM277, RM463, and RM179 which are linked to resistance genes on rice chromosomes. Genotypes had different reactions against blast races in the phenotypic part of experiment. Consequently, all genotypes were divided into three groups with high, intermediate, and susceptible resistance. Our results indicated that partial resistant genotypes are preferable for achieving durable control. Eventually, the association test between molecular data and phenotypic results showed that there is a significant level for some of the SSR markers. This means there is at least one race-specific resistance gene in the genetic sources of these genotypes that bring about resistance functions to the blast races. These results demonstrated the existence of functional resistance genes in Iranian rice genotypes. Thus, these functional genes are responsible for some parts of resistance that have been measured in phenotypic tests. Our results could be useful for breeding programs to make some modifications in the rice germplasm and would also be applicable for the marker-assisted selection process.

In the present study, the authors studied the interaction between 26 monogenic differentials carrying 26 blast resistance genes with 15 isolates of Pyricularia oryzae under field conditions and pathogenicity assays. The result in field conditions showed that area under disease progress curves (AUDPC) of monogenic lines was found to range from 0 to 142.3. Lijiangxintuanheigu (LTH) was susceptible in all of regions. The monogenic lines carrying Pik, Pik-p, Pik-h, Piz, Pi1, Pi7(t), Pik-m, Pi4(t), Pish, Pi9(t) and Pita were highly resistant to blast in all of regions. In plastic house net conditions, the percentage of virulent reactions of monogenic lines to 15 isolates was found to range from 23.1% to 84.6%. LTH was susceptible to all 15 isolates. All 26 monogenic lines were resistant to at least 3 isolates of P. oryzae, and the frequency of resistant reactions of the monogenic lines carrying Pik, Pik-p, Pik-h, Piz, Pi4(t), Pish, Pi1, Pi7(t), Pi9, Pik-m and Pita were 80.0%, 93.3%, 93.3%, 80.0%, 73.3%, 86.7%, 73.3%, 80.0%, 80.0%, 80.0% and 80.0%, respectively. These findings suggest that Pik, Pik-p, Pik-h, Piz, Pi4(t), Pish, Pi1, Pi7(t), Pi9, Pik-m and Pita may be important R genes for preventing blast disease in South Central Vietnam. Based on these data, a useful strategy for managing rice blast disease by stacking pyramiding blast R genes against pathogenic P. oryzae isolates at hotspot in South Central Coast of Vietnam was proposed.

This research paper focuses on implementation of image analysis algorithms on captured images for the purpose of detecting crop diseases and monitored through Mobile App. The purpose of this research is to find out the diseases in early stage, and reduce the yield loss. The system design includes sensors, controller, image analysis algorithm, Cloud storage and mobile app. Using the USB camera, images in the farm are captured and processed by controller module. This is sent to the cloud, which can be accessed by mobile App or remote user. Various image processing algorithms were used to process the images. The results are presented in this paper.

Recently organic farming practice of rice has been emerged in Korea, but one of the major limiting factor is the no effective environmental-friendly agro-materials to control major plant diseases. Bordeaux mixture has been used effectively as a preventive agro-chemical. The aim of this study was to investigate efficacy of Bordeanux mixture on control of rice blast caused by Magnaporthe grisea which is one of the disruptive rice diseases in world-wide. In greenhouse experiment, pre-treatment of 6-6 type of Bordeaux mixture before inoculation of spore suspension of M. grasea showed 71 % of control value. In field experiment, preventive applications of 4-8 and 6-6 types of Bordeaux mixture showed over 71 % of the control value. Chemical injury on rice leaves were not found in the application concentrations of all types of Bordeaux mixture, but observed in applications of Bordeaux mixtures between 30 and 100 diluted concentrations. This results indicate Bordeaux mixture can be used as an effective environmental-friendly agro-chemical to control rice blast disease in the field.

Two metabolites, 2-epi-botcinin A and 3-O-acetylbotcineric acid, were isolated from Botrytis cinerea (AEM211). The former compound was new, and the latter was known but structurally revised by us. In a test for antifungal activity against Magnaporthe grisea, a pathogen of rice blast disease, 2-epi-botcinin A was 8 times less active than botcinin A (MIC 100 microM), and the MIC value for 3-O-acetylbotcineric acid being 100 microM.

The IRRI-Japan Collaborative Research Project has been developing new sets of differential varieties for resistance to blast disease (Pyricularia grisea Sacc.) in rice (Oryza saliva L.). The first international standard differential variety set composed of monogenic lines for 24 kinds of resistance genes (Pia, Pib, Pii, Pik, Pik-h, Pik-m, Pik-p, Pik-s, Pish, Pit. Pita. Pita-2, Piz, Piz-5 (= Pi2), Piz-t, Pil, Pi3 , Pi5(t), Pi7, Pi9, Pi11(t), Pi12(t), Pi19(t), and Pi20) was released and has been widely used in various countries. Furthermore, the project has been developing near-isogenic lines (NILs) for blast resistance with three kinds of genetic backgrounds, a Japonica-type variety Lijiangxintuanheigu (LTH), an Indica-type variety C039, and a newly developed 'universal susceptible' line US-2 which was derived from a cross between Indica and Japonica-type susceptible varieties. A total of 23 lines for 14 kinds of resistance genes, Pia, Pib, Pik, Pik-h, Pik-s, Pita, Pita-2, Piz-5 (= Pi2), Piz-t, Pil, Pi3, Pi5(t), Pi7, and Pi9, have been developed by the recurrent backcross method using the monogenic lines with the LTH genetic background. Twenty lines for 14 kinds of resistance genes, Pib, Pik, Pik-h, Pik-m, Pik-p, Pik-s, Pish, Pita, Pita-2, Piz-5 (= Pi2), Piz-t, Pil, Pi5(t), and Pi 7 have been developed with the CO39 genetic background. Moreover, a universal susceptible rice line, US-2, which has not been known to have any blast resistance genes in the genetic background, and can be cultivated easily under both tropical and temperate conditions, is also being used for the development of NILs as the next generation of differential varieties. These lines are offered as gene sources for breeding of blast resistance and as sets of international standard differential varieties used for the study of blast disease.

The incidence and severity of leaf and panicle blasts were efficiently reduced in the wind-treated fields. Artificially-generated wind was performed on rice paddy field in order to measure the changes in temperature and humidity during and after the blowing process and to investigate the effects of sending wind on the formation and removal of guttation and dew droplets on rice leaves. A large electric fan was used to send wind with a depression angle of 30° at 4:00 am for 30-40 min. During the blowing process, the humidity percentage was 100% in both treated and control paddy fields, the temperature was 0.8°C higher in the treated than the control field and the dew weight was rapidly decreased from 21 to 8 g in 20 min in the treated field. After the blowing process, the temperature started to rise at 6:28 am (10 min earlier than the control block). It reached 29°C at 6:48 am (30 min earlier than the control block) and remained higher than the control block till 7:20 am (1-7°C higher). The humidity decreased to 95% at 6:30 am (20 min earlier than the control block) and remained 95% till 6:42 am, then rapidly decreased to reach 68% at 6:46 am, and finally reached 60% at 7:20 am. The humidity was 5-30% lower than that in the control block. Moreover, the dew weight increased to the initial level within 10 min and then decreased rapidly in both blocks starting from 6:20 am. Using wind speed of 4.3 m/s or 3.2 m/s for 60 s per rotation at 4:00 am, almost all the guttation droplets except those of less than 0.5 mm were removed from the surfaces of the 1st and 2nd uppermost leaves after two rotations (at velocity 4.3 m/s) or three rotations (at velocity 3.2 m/s) and the dew droplets were mostly removed after five rotations (at velocity 4.3 m/s) or nine rotations (at velocity 3.2 m/s). Sending wind at a speed of 3.2 m/s or faster removed guttation and dew droplets and suppressed the subsequent dew formation. Our data indicates that the removal of dew droplets on rice hills resulted in reduction of the disease development of Pyricularia oryzea. Key words: Generated–wind, rice blast, microclimate, guttation, dew droplets.

Magnaporthe oryzae causes blast, the most serious disease on rice. The fungus is genetically diverse and hence easily develops resistance to fungicides. In Japan, it started from the resistance to kasugamycin and has continued up until MBI-D and QoI fungicide resistance experienced most recently. The history of fungicide resistance occurred on rice blast disease and research and countermeasure taken in the country are summarized in this chapter. Some related information from overseas is also introduced.