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Sheath rot of rice is one of the most devastating diseases of rice due to its ability to reduce the yield significantly in all rice cultivating areas of India. The purpose of this study was to assess the effectiveness of Bacillus cereus strain RBS-57 against sheath rot disease of rice. In addition, it enables us to understand the molecular mechanism of the host–pathogen-bioagent interactions using a proteomic approach. A combination of seed treatment, seedling dip, and foliar spray with RBS-57 liquid formulation has recorded the lowest sheath rot disease index, both under pot experiment (21.33%) and field conditions (15.33% in trial I and 12.42% in trial II, respectively). In addition to that, RBS-57 application enhanced the plant growth and yield attributes. Moreover, a 2D-PAGE study uses protein profiling to illustrate the molecular response of the tripartite interaction between host–pathogen-bioagent. MALDI-TOF mass spectrometry (MS/MS) analysis identified a total of 20 differentially expressed proteins, primarily implicated in plant metabolism and development, defense response, transcription and signalling. Selected genes were validated by quantitative Real-Time PCR (qRT-PCR) analysis. The alterations in protein abundance and transcripts were positively correlated for all the genes. The present study provides initial insights into the molecular mechanism that underlies the tripartite interaction between the host–pathogen-bioagent in rice plants. [ABSTRACT FROM AUTHOR]

Sheath rot and dirty panicle are some of the major diseases of rice in Thailand. The diseases are traditionally considered to be caused by the pathogen Sarocladium oryzae and damage and lower both the quantity and quality of rice grain. In this study, 32 fungal isolates collected from the central and northeastern regions of Thailand were analysed phylogenetically using three molecular markers (ITS, D1/D2 of 28S rDNA and ACT) and physiological races were determined on 10 differential rice cultivars. We found that S. oryzae is not the only causal agent of sheath rot in Thailand, but S. attenuatum was also found. Despite having similar morphological features, the phylogenetic analysis recognised 11 of 32 isolates as S. attenuatum and the remaining isolates as S. oryzae. This is the first report of S. attenuatum causing sheath rot of rice in Thailand in addition to S. oryzae. Evaluation of physiological races revealed high pathogenic diversity of the two species. Thus, 16 and 11 physiological races were recorded from 21 isolates of S. oryzae and 11 isolates of S. attenuatum, respectively. These results indicate that both S. oryzae and S. attenuatum are the causal agents of rice sheath rot and dirty panicle in Thailand and that they are pathologically diverse. [ABSTRACT FROM AUTHOR]

Sheath rot and dirty panicle are some of the major diseases of rice in Thailand. The diseases are traditionally considered to be caused by the pathogen Sarocladium oryzae and damage and lower both the quantity and quality of rice grain. In this study, 32 fungal isolates collected from the central and northeastern regions of Thailand were analysed phylogenetically using three molecular markers (ITS, D1/D2 of 28S rDNA and ACT) and physiological races were determined on 10 differential rice cultivars. We found that S. oryzae is not the only causal agent of sheath rot in Thailand, but S. attenuatum was also found. Despite having similar morphological features, the phylogenetic analysis recognised 11 of 32 isolates as S. attenuatum and the remaining isolates as S. oryzae. This is the first report of S. attenuatum causing sheath rot of rice in Thailand in addition to S. oryzae. Evaluation of physiological races revealed high pathogenic diversity of the two species. Thus, 16 and 11 physiological races were recorded from 21 isolates of S. oryzae and 11 isolates of S. attenuatum, respectively. These results indicate that both S. oryzae and S. attenuatum are the causal agents of rice sheath rot and dirty panicle in Thailand and that they are pathologically diverse.

Sarocladium and Fusarium species are commonly identified as causal agents of rice sheath rot disease worldwide. However, limited knowledge exists about their genetic, pathogenic, and toxigenic diversity in sub-Saharan African (SSA) countries, where an increasing incidence of this disease has been observed. In this study, seventy fungal isolates were obtained from rice plants displaying disease symptoms in rice research programs and farmer fields in Mali, Nigeria, and Rwanda. Thus, an extensive comparative analysis was conducted to assess their genetic, pathogenic, and toxigenic diversity. The Fusarium spp. were characterized using the translation elongation factor (EF-1α) region, while a concatenation of Internal Transcribed Spacer (ITS) and Actin-encoding regions were used to resolve Sarocladium species. Phylogenetic analysis revealed four Fusarium species complexes. The dominant complex in Nigeria was the Fusarium incarnatum-equiseti species complex (FIESC), comprising F. hainanense, F. sulawesiense, F. pernambucatum, and F. tanahbumbuense, while F. incarnatum was found in Rwanda. The Fusarium fujikuroi species complex (FFSC) was predominant in Rwanda and Mali, with species such as F. andiyazi, F. madaense, and F. casha in Rwanda and F. annulatum and F. nygamai in Mali. F. marum was found in Nigeria. Furthermore, Fusarium oxysporum species complex (FOSC) members, F. callistephi and F. triseptatum, were found in Rwanda and Mali, respectively. Two isolates of F. acasiae-mearnsii, belonging to the Fusarium sambucinum species complex (FSAMSC), were obtained in Rwanda. Isolates of Sarocladium, which were previously classified into three phylogenetic groups, were resolved into three species, which are attenuatum, oryzae, and sparsum. S. attenuatum was dominant in Rwanda, while S. oryzae and S. sparsum were found in Nigeria. Also, the susceptibility of FARO44, a rice cultivar released by Africa Rice Centre (AfricaRice), was tested against isolates from the four Fusarium species complexes and the three Sarocladium species. All isolates evaluated could induce typical sheath rot symptoms, albeit with varying disease development levels. In addition, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine variation in the in vitro mycotoxins of the Fusarium species. Regional differences were observed in the in vitro mycotoxins profiling. Out of the forty-six isolates tested, nineteen were able to produce one to four mycotoxins. Notably, very high zearalenone (ZEN) production was specific to the two F. hainanense isolates from Ibadan, Nigeria, while Fusarium nygamai isolates from Mali produced high amounts of fumonisins. To the best of our knowledge, it seems that this study is the first to elucidate the genetic, pathogenic, and toxigenic diversity of Fusarium species associated with the rice sheath rot disease complex in selected countries in SSA. [ABSTRACT FROM AUTHOR]

Sheath rot, caused by Sarocladium oryzae, is an emerging serious threat in rice cultivating regions especially in Union Territory of Jammu & Kashmir, causing yield losses of 20%–85%. Little and scattered information is available on the epidemiology of the disease. Hence, the field experiments were conducted during the cropping seasons of 2019 and 2020 to find out the effect of weather factors on the development of the disease as well as computation of predictive model for its initiation and spread in the field in five popular and commercially grown rice varieties viz. PB‐1509, PB‐1401, PR‐114, PB‐1121 and Arize 6444 Gold. The higher mean percent disease index (PDI) of 37.3% was recorded during 2019, whereas it was 33.8% during 2020. The effect of cropping seasons (years) on PDI, area under disease progress curve (AUDPC) and infection rate (r) was significant. Significant and negative correlation was observed between PDI and selected meteorological parameters, that is maximum and minimum temperature and relative humidity in the evening during both the cropping seasons The PDI had positive and significant correlation with relative humidity in the morning during the cropping season 2020. Rainfall showed significant and negative correlation with PDI in all the varieties during 2019 whereas it was non‐ significant and positive during 2020 in all the varieties except PR‐114 where, it was positive and significantly correlated. Minimum temperature, morning and evening relative humidity and sunshine hours resulted in ~92%–95% and 97%–99% variation for PDI in all the varieties during the cropping seasons 2019 and 2020, respectively. Sheath rot was the maximum recorded at minimum temperature (11.5–20.0°C), high morning relative humidity (74.0%–94.0%) and moderate evening relative humidity (26.0%–75.0%) and sunshine hours of 2.8–9.3 h, respectively. All the assumptions related to the developed model were acceptable as the global stat, skewness, kurtosis, link function and heteroscedasticity tests had the least p‐values in all the varieties during both the cropping seasons. Hence the model may be used for the prediction of sheath rot, which would be helpful in the early adoption, precise and judicious management practices. [ABSTRACT FROM AUTHOR]

Sheath rot is one of the most destructive emerging diseases of rice in Asia and a significant loss (20–85%) to rice production is caused by this disease under temperate agro-climatic conditions of Kashmir. Disease is more prevalent in higher belts of valley where Japonica rice cultivation is more common. Also, late-maturing varieties are more likely to be attacked by sheath rot disease of rice. Information regarding the occurrence and distribution of any pathogen and its variability in the field is very much essential to devise a suitable disease management programme against the particular pathogen. The isolates of Sarocladium oryzae tested in the present study exhibited considerable variation in cultural characteristics, morphology and pathogenicity. The resistant sources for sheath rot disease of rice were identified among the temperate germplasm of rice under a relatively high inoculum concentration and disease pressure of all the variable isolates of S. oryzae. Among 219 rice genotypes screened for resistance against S. oryzae under field conditions, 42 genotypes were further evaluated under controlled epiphytotic conditions against all the 18 isolates of S. oryzae. Four genotypes (SKUA-354, ORN-V4, GS-183, GS357) were finally selected with high resistance against sheath rot disease of rice which can be utilized as potential donors for the development of disease-resistant varieties of rice against sheath rot. [ABSTRACT FROM AUTHOR]

Biopesticides are recognized as an efficient alternative to synthetic pesticides for pest and disease crop management. However, their commercial production processes use grains, generating large amounts of organic waste, even when agriculture waste or byproducts are the feedstock of choice. Frequently, these organic wastes are rich in nutrients that, after adequate treatment, can be used as nitrogen and carbohydrate sources for secondary metabolite production produced by microorganisms during submerged fermentation. In this sense, this study aimed to prove the concept that biopesticides could be produced under a full biorefinery process, using the entire biomass of an underexplored agroindustrial waste—damaged bean—as the main feedstock. A combination of sequential processes, including solid state fermentation, hydrolysis, and submerged fermentation, were designed for the production of two biopesticides (conventional—fungal conidia and second-generation secondary metabolite—cerulenin) from a high potential biological control agent strain Sarocladium oryzae BRM 59907. The combined processes, using damaged common bean grain as the main feedstock, provided biopesticides and organic fertilizer production that successfully controlled common bean root rot disease. This work proved to be possible the biopesticide production using a full biorefinery concept, inside the same productive chain, contributing to a sustainable environment and economy, together with animal and human health safety. [ABSTRACT FROM AUTHOR]

Sarocladium oryzae is a widely prevalent seed-borne pathogen of rice. The development of a rapid and on-site detection method for S. oryzae is therefore important to ensure the health of rice seeds. Loop-mediated isothermal amplification (LAMP) is ideal for field-level diagnosis since it offers quick, high-specific amplification of target template sequences at a single temperature. We designed primers based on the β-tubulin region of S. oryzae. The LAMP technique devised was extremely sensitive, detecting the presence of the S. oryzae template at concentrations as low as 10 fg in 30 minutes at 65°C. The assay specificity was confirmed by performing the experiment with genomic DNA isolated from 22 different phytopathogens. Through the addition of hydroxy naphthol blue in the reaction process prior to amplification, a colour shift from violet to deep sky blue was seen in the vicinity of the target pathogen only. Finally, the LAMP assay was validated using live infected tissues, weeds and different varieties of seeds collected from different locations in Tamil Nadu, India. If developed into a detection kit, the LAMP assay developed in this study has potential applications in seed health laboratories, plant quarantine stations, and on-site diagnosis of S. oryzae in seeds and plants. [ABSTRACT FROM AUTHOR]

Rice sheath rot caused by some pathogens. It occurs in the upper leaf sheath that wraps the rice panicle, its major features are rotting, discoloration, sometimes affecting rice grain production. Lampung is an important rice-producing area in Indonesia. Currently, rice sheath rot in the area is reportedly caused by Fusarium sulawesiense and Fusarium hainanense. This study aimed to identify the rice sheath rot pathogen accurately by sampling locations at varying altitudes, plant ages, and varieties in Lampung Sampling was conducted in Lampung, infected plants were collected and the pathogen isolates were molecularly characterized on the basis of DNA sequence data for the internal transcribed spacer and translation elongation factor 1-α. Pathogenicity test results showed that 16 fungal isolates caused rice sheath rot. These isolates were identified as Sarocladium oryzae, Fusarium bubalinum, F. hainanense, Setophoma poaceicola, Curvularia geniculata, and Alternaria padwickii. This study is the first to report that S. poaceicola is a pathogen of rice sheath rot. [ABSTRACT FROM AUTHOR]

Sarocladium oryzae is a widely prevalent seed-borne pathogen of rice. The development of a rapid and on-site detection method for S. oryzae is therefore important to ensure the health of rice seeds. Loop-mediated isothermal amplification (LAMP) is ideal for field-level diagnosis since it offers quick, high-specific amplification of target template sequences at a single temperature. We designed primers based on the β-tubulin region of S. oryzae. The LAMP technique devised was extremely sensitive, detecting the presence of the S. oryzae template at concentrations as low as 10 fg in 30 minutes at 65°C. The assay specificity was confirmed by performing the experiment with genomic DNA isolated from 22 different phytopathogens. Through the addition of hydroxy naphthol blue in the reaction process prior to amplification, a colour shift from violet to deep sky blue was seen in the vicinity of the target pathogen only. Finally, the LAMP assay was validated using live infected tissues, weeds and different varieties of seeds collected from different locations in Tamil Nadu, India. If developed into a detection kit, the LAMP assay developed in this study has potential applications in seed health laboratories, plant quarantine stations, and on-site diagnosis of S. oryzae in seeds and plants.

Accurate and timely disease detection plays a critical role in achieving sustainable crop protection. Globally, rice has been a staple crop for centuries plagued by the diseases that greatly hamper its productivity. Sheath rot, an emerging disease of rice caused by the seed-borne pathogen Sarocladium oryzae, has reportedly caused heavy losses to agricultural produce in recent years. Our study has led to the development and validation of a LAMP assay for early detection of S. oryzae, the causal agent of sheath rot from the live-infected tissues, seeds, weeds, and environmental samples. The assay could detect as low as 1.6 fg/ml of the pathogen in 15 min. The assay was implemented to bio-surveil the presence of this pathogen by testing it on three weed species (Echinochloa colona, Echinochloa crus-galli, and Cyperus teneriffae) growing around the rice fields. The results showed the presence of the pathogen in two of the weed species viz. E. colona and E. crus-galli. The assay was used to test 13 different rice varieties for the presence of S. oryzae in seeds. In total, three of the varieties did not show the presence of S. oryzae in their seeds while the rest were found to harbor the pathogen. The developed assay can effectively be used to detect and screen the presence of S. oryzae in live samples including seeds and field soil. [ABSTRACT FROM AUTHOR]

La pudrición de la vaina causada por Sarocladium oryzae, es una enfermedad que afecta al cultivo de arroz (Oryza sativa L.), se relaciona por presencia del ácaro Steneotarsonemus spinki y aplicaciones excesivas de nitrógeno ya que en cantidades elevadas atrae al ácaro. El objetivo fue determinar la población de ácaros en dos variedades de arroz bajo la incidencia de la pudrición de la vaina, fertilización nitrogenada más la aplicación con y sin acaricida más rendimiento. Se utilizó un diseño de parcelas divididas con dos variedades de arroz, tres dosis de nitrógeno y dos aplicaciones de acaricida lo que totalizó 12 tratamientos con tres repeticiones para un total de 36 parcelas evaluadas. Las variables fueron números de ácaros tetraníquidos, predatores y tarsonémidos, porcentajes de espigas afectadas y rendimiento kg ha-1. Los resultados demostraron que la mayor cantidad de ácaros encontrados fueron 124 predatores en tres evaluaciones realizadas, el porcentaje de espigas afectadas 12% y rendimientos superaron 2500 kg ha-1, además no se pudo relacionar la presencia de la enfermedad con el ácaro Steneotarsonemus spinki debido a que solo se encontró un individuo. Palabras clave: Sarocladium oryzae; Steneotarsonemus spinki; rendimiento.

Accurate and timely disease detection plays a critical role in achieving sustainable crop protection. Globally, rice has been a staple crop for centuries plagued by the diseases that greatly hamper its productivity. Sheath rot, an emerging disease of rice caused by the seed-borne pathogen Sarocladium oryzae, has reportedly caused heavy losses to agricultural produce in recent years. Our study has led to the development and validation of a LAMP assay for early detection of S. oryzae, the causal agent of sheath rot from the live-infected tissues, seeds, weeds, and environmental samples. The assay could detect as low as 1.6 fg/μl of the pathogen in 15 min. The assay was implemented to bio-surveil the presence of this pathogen by testing it on three weed species (Echinochloa colona, Echinochloa crus-galli, and Cyperus teneriffae) growing around the rice fields. The results showed the presence of the pathogen in two of the weed species viz. E. colona and E. crus-galli. The assay was used to test 13 different rice varieties for the presence of S. oryzae in seeds. In total, three of the varieties did not show the presence of S. oryzae in their seeds while the rest were found to harbor the pathogen. The developed assay can effectively be used to detect and screen the presence of S. oryzae in live samples including seeds and field soil.

Sheath rot disease is an emerging fungal disease in rice, whose infection causes severe yield loss. Sarocladium oryzae (S. oryzae) is the major causal agent. Previous study has demonstrated that rice deficiency in potassium (K) aggravates S. oryzae infection. However, the effects of S. oryzae infection on the nutrient-uptake process, endophyte communities, and hormone level of host plant under K-deficiency condition remain unclear, the mechanism of K mediated S. oryzae infection needs to be further study. The present study analyzed alterations in the endophytic community and nutrient-uptake process of host plants through an exogenous inoculation of S. oryzae in pot and hydroponics experiments. S. oryzae infection sharply increased the relative abundance of Ascomycota and decreased the Shannon and Simpson index of the endophytic community. Compared with the K-sufficient rice infected with S. oryzae , K-starved rice infected with S. oryzae (−K + I) increased the relative abundance of Ascomycota in leaf sheaths by 52.3%. Likewise, the −K + I treatment significantly decreased the Shannon and Simpson indexes by 27.7 and 25.0%, respectively. Sufficient K supply increased the relative abundance of Pseudomonas spp. in the host plant. S. oryzae infection profoundly inhibited the nutrient uptake of the host plant. The accumulation of oleic acid and linoleic acid in diseased rice decreased the biosynthesis of jasmonic acid (JA), and the content of JA was lowest in the −K + I treatment, which suppressed K+ uptake. These results emphasize the importance of K in resistance to S. oryzae infection by modulating endophyte community diversity and enhancing the nutrient-uptake capacity of the host plant. [ABSTRACT FROM AUTHOR]

The observation conducted from 2000 to 2018 found that rice sheath rot has become an emerging disease in several regions. The disease was able to reduce quality and quantity of rice yield. This research objective was to study the history and status of rice sheath rot caused by Sarocladium oryzae. Data was obtained from literature study, farmer interview, and field survey. Data were used to calculate disease incidence followed by visual observation of the symptoms caused by this disease. Identification of sheath rot pathogen was done using microscopic and molecular techniques using specific primers. Rice sheath rot was first reported in Indonesia as a minor disease in 1987 and has only currently become an important disease. This fungus generally causes rice sheath rot in Karawang and Cianjur Regency. Disease incidence of rice sheath rot was 12.56% without considering the varieties at all generative growth stages. Average disease incidence on all rice varieties observed was 12.64%, except for IR 42 (0%). The level of rice plants damage due to rice sheath rot in Cianjur was higher than Karawang with average disease incidence of 11.58% and 9.27%, respectively. Rice sheath rot symptoms have often been found in the last 10 years with average level of damage of 3%‒18% and yield loss of 10%-15%. This disease has proven to be important and has become a challenge in rice cultivation. The fungus that infect rice plants in Karawang and Cianjur had different morphotypes, namely KP, KP2, KP3, PW3, and PW03. The amplification results showed that all fungal isolates were S. oryzae.

Sheath rot disease is an emerging fungal disease in rice, whose infection causes severe yield loss. Sarocladium oryzae (S. oryzae) is the major causal agent. Previous study has demonstrated that rice deficiency in potassium (K) aggravates S. oryzae infection. However, the effects of S. oryzae infection on the nutrient-uptake process, endophyte communities, and hormone level of host plant under K-deficiency condition remain unclear, the mechanism of K mediated S. oryzae infection needs to be further study. The present study analyzed alterations in the endophytic community and nutrient-uptake process of host plants through an exogenous inoculation of S. oryzae in pot and hydroponics experiments. S. oryzae infection sharply increased the relative abundance of Ascomycota and decreased the Shannon and Simpson index of the endophytic community. Compared with the K-sufficient rice infected with S. oryzae, K-starved rice infected with S. oryzae (−K + I) increased the relative abundance of Ascomycota in leaf sheaths by 52.3%. Likewise, the −K + I treatment significantly decreased the Shannon and Simpson indexes by 27.7 and 25.0%, respectively. Sufficient K supply increased the relative abundance of Pseudomonas spp. in the host plant. S. oryzae infection profoundly inhibited the nutrient uptake of the host plant. The accumulation of oleic acid and linoleic acid in diseased rice decreased the biosynthesis of jasmonic acid (JA), and the content of JA was lowest in the −K + I treatment, which suppressed K+ uptake. These results emphasize the importance of K in resistance to S. oryzae infection by modulating endophyte community diversity and enhancing the nutrient-uptake capacity of the host plant.

Rice sheath rot has become a highly destructive rice disease with a high variability in yield loss levels varying from 20 to 85%. It is caused by many pathogenic agents varying depending on the area, grown varieties, prevailing environmental conditions, the farming system, other pests, etc. Therefore, sheath rot disease can be effectively managed through crop improvement strategies viz., discovery of resistance sources from varieties, germplasm, landraces, wild genetic resources and further deploying them in breeding programmes. In this study, the level of resistance to sheath rot in 43 rice germplasm accessions were screened and the results were grouped using Darwin 6.0 statistical package from dissimilarity analysis. The percent disease index (PDI) was calculated and varietal reactions were presented. Out of 43 lines screened against sheath rot, six entries viz., Gowri, NLR 3449, Navara, Soorakkuruvai, Keralakandasala, krishnahemavathi were categorised as moderately resistant. Most of the lines and varieties viz., JGL 348, Abhya, LFR293, MDU5, Kalinga, Annada, Kodaikannan, TP-100008, TP-10106, Kuruvaikalanjium, Kalyani, Maranella, Seeragasamba, Thondi, Kavara, TPS-4, TPS-5, TP 08053 were found as moderately susceptible. However, the germplasm lines Swarna, Kattanur, Dhalaheera and JGL 3855 have been reported to be resistant to sheath rot. Sixteen germplasm lines viz., Bharathi, Uma, CO 39, Neikuruvai, CO 50, Rajalakshmi, Karsamba, JGL 1798, CO 51, BPT 5204, Virendra, JGL 1798, CO 51, BPT 5204 and Aman were designated as susceptible and three germplasm lines viz., Athira, Malampunchan, Adukan were found as highly susceptible. None of the entry in the present study was recorded as immune. The present investigation revealed that the resistant and moderately resistant genotypes viz., Swarna, Kattanur, Dhalaheera, JGL 3855, Gowri, NLR3449, Navara, Soorakuruvai, Keralakandasala, and Krishnahemavathi can be utilised in resistant breeding programmes for the development of sheath rot resistant lines in rice.

Rice sheath rot, caused by the fungus Sarocladium oryzae , poses a major threat to rice crops. This pathogen exhibits substantial variability in the field, yet limited information on its genetic diversity and population structure hampers the development of effective disease management strategies. In this study, hyper-variable Simple Sequence Repeats (HV-SSR) markers were employed for the first time to assess the genetic diversity of Sarocladium oryzae , collected from various rice cultivating regions in Odisha, Eastern India. The isolates were identified using both morphological and molecular criteria. A pathogenicity test was performed for all the isolates. A total of 2558 HV-SSRs with more than 10 repeat units were identified in the genome of S. oryzae. The most prevalent types of repeats were dinucleotides (26.8%), followed by trinucleotides (22.8%), tetranucleotides (8.67%), pentanucleotides (2.83%), and hexanucleotides (1.83%). A total of 150 HV-SSR primers were designed and 24 were randomly selected and validated, of which ten of them demonstrating polymorphism in the 87 isolates. These ten polymorphic hyper-variable SSR markers were subsequently used to assess the genetic diversity and population structure of Sarocladium oryzae isolates. The markers revealed a total of 32 alleles, with the number of alleles per locus varying from 2 to 4. Gene diversity ranged from 0.409 to 0.641, while the major allele frequency varied from 0.448 to 0.736. The Polymorphic Information Content (PIC) values ranged from 0.325 to 0.569, with an average of 0.457. Cluster analysis categorized the sheath rot isolates into three distinct major clusters. Principal coordinate analysis and structure analysis identified two genetic clusters within S. oryzae isolates. Analysis of molecular variance indicated that there was more genetic variation within populations (55%) and less variation among populations (45%). The findings of this study provide insights into the genetic diversity of S. oryzae in the rice-cultivating regions of Odisha, which can be used to develop more effective disease management strategies. • We isolated 87 Sarocladium oryzae isolates from rice-cultivating areas of Odisha, Eastern India. • All the Sarocladium oryzae isolates were identified at the molecular level. • First report on the genetic diversity and population structure of S. oryzae isolates using genome-specific HV-SSR markers. [ABSTRACT FROM AUTHOR]

Sheath rot, caused by Sarocladium oryzae (Sawada) W. Gams & D. Hawksw, is an important seed borne fungal disease of paddy (Oryza sativa L.). In the present investigation, diseased specimens were collected in kharif 2016 and 2017 from more than 55 different geographical locations spread across 15 states of the country and variability in 30 isolates of Sarocladium oryzae was studied by molecular methods. The molecular characterization using two marker systems, i.e. Inter-Simple Sequence Repeat (ISSR) and Random Amplified Polymorphic DNA (RAPD) was carried out which revealed differences in isolates collected from different geographical locations. After preliminary screening, out of 22 ISSR and 24 RAPD primers, 8 ISSR and 7 RAPD primers were used against all the isolates. Percent polymorphic ranging between 53.1–100% in ISSR and 61.4–100% in RAPD was recorded with all the isolates. The average number of bands in ISSR markers was 63.3, and 71.8 in RAPD markers. All RAPD primers showed 100% polymorphism except OPS13 (61.4%) and OPD5 (74%). Among ISSR primers ISSR5 and ISSR18 showed 100% polymorphism. Cluster analysis of individual and combined primers was done. In the combined cluster analysis of RAPD and ISSR markers, the isolates from same geographical region were in same cluster as evident from the cluster I that includes Kadapa, Ragolu, Maruteru, West Godavari and Adutharai, which are from southern plain region of the country. Similar observations were recorded when data analysis of individual marker system was carried out which revealed that the two different marker systems applied complement each other in characterizing various isolates.

Highlights • WRKY 13 plays regulatory role in mediating resistance against rice sheath blight and sheath rot. • Differential expression of WRKY 13 in susceptible and resistant varieties. • WRKY 13 influences the MAPK cascade with TIFY 9 as mediator. Abstract OsWRKY 13 TF gene is known to play a regulatory role of signaling in physiological pathways related to either development or disease resistance in rice plants. Rice cultivars IR 50 and TRY 3, resistant and susceptible respectively to sheath blight, TRY 3 and CO 43 resistant and susceptible respectively to sheath rot were challenged with fungal pathogens and disease scoring was carried out. Percent Disease Index (PDI) was significantly higher in susceptible varieties than resistant varieties. RT-PCR and qPCR analyses of WRKY 13 using RNA extracted from the plant tissues revealed higher WRKY 13 expression in resistant varieties (both diseases) upon pathogen challenge compared to uninfected control and also the susceptible varieties. To compute and evaluate the possible molecular mechanism for observed resistance correlated to WRKY 13 gene expression, rice gene expression profiles against bacterial leaf blight and leaf blast disease from ROAD database were used to prioritize the locus IDs that were used as input in RiceNet v2 tool. The expression of WRKY 13-regulated TIFY 9 gene was predicted and validated using RT-PCR and qRT-PCR along with WRKY 12 and PR 2. All three genes showed induced expression in R. solani challenged sheath blight resistant variety. WRKY 12 and PR 2 expression in S. oryzae challenged sheath rot resistant variety was higher. Agrobacterium mediated transformation was carried out in rice plants using overexpression construct of WRKY 13 (agroinfection in seeds of varieties susceptible to sheath blight and sheath rot, followed by selection in antibiotic media, germinating and hardening of putative transgenic lines). Based on qPCR analysis, the expression level of WRKY 13 and the co-expression levels of WRKY 12, TIFY 9 and PR 2 were found higher in PCR-positive T 1 plants compared to wild-type. Infection bioassays in the transgenic plants of both varieties revealed enhanced resistance to the pathogens. A mechanism by which WRKY 13 would influence the MAPK cascade with TIFY 9 acting as a mediator, is proposed. [ABSTRACT FROM AUTHOR]

Three new helvolic acid derivatives (named sarocladilactone A (1), sarocladilactone B (2) and sarocladic acid A (3a)), together with five known compounds (6,16-diacetoxy-25-hy- droxy-3,7-dioxy-29-nordammara-1,17(20)-dien-21-oic acid (3b), helvolic acid (4), helvolinic acid (5), 6-desacetoxy-helvolic acid (6) and 1,2-dihydrohelvolic acid (7)), were isolated from the endophytic fungus DX-THL3, obtained from the leaf of Dongxiang wild rice (Oryza rufipogon Griff.). The structures of the new compounds were elucidated via HR-MS, extensive 1D and 2D NMR analysis and comparison with reported data. Compounds 1, 2, 4, 5, 6 and 7 exhibited potent antibacterial activities. In particular, sarocladilactone B (2), helvolinic acid (5) and 6-desacetoxy-helvolic acid (6) exhibited strongly Staphylococcus aureus inhibitory activity with minimum inhibitory concentration (MIC) values of 4, 1 and 4 μg/mL, respectively. The structure–activity relationship (SAR) of these compounds was primarily summarized.

Bacillus species have been identified as effective bioagents and plant growth boosters in rice. Currently, there is limited research on the effectiveness of Bacillus strains in managing the sheath rot disease of rice caused by Sarocladium oryzae , a significant threat to rice-cultivating areas in India. The aim of this study was to evaluate the efficacy of Bacillus spp. to control the sheath rot disease and promote growth in rice plants. We investigated the in vitro antagonistic activity and growth-promoting potential of eighty-four Bacillus spp. against S. oryzae. Ten efficient strains were carefully selected and analyzed at the molecular level based on their capacity for antagonism and growth promotion. A PCR study of the potential strains has revealed the presence of lipopeptide genes that produce bacilysin, bacillomycin, iturin, surfactin, subtilin, subtilosin and fengycin. Among the strains, RBS-57 had the highest mycelial growth inhibition (74.44 %) of the pathogen as well as the highest number of antibiotic genes (6). The efficacy of talc and liquid formulations of Bacillus strains BS-5, RBS-57, and RBS-3 was further tested against sheath rot disease. Results indicated that a combined application of seed treatment + seedling dip + foliar spray of RBS-57 liquid formulation under pot culture conditions, showed a considerable reduction in the incidence of sheath rot disease, followed by BS-5 and RBS-3. Similarly, a significant increase in the plant growth attributes and yield was observed with RBS-57, when compared to the other treatments. Enzymatic activities such as PO, PPO, PAL, CAT and SOD were induced in the rice sheath by B. cereus (RBS-57) treatment. Real-time expression analysis was performed to validate the fold changes in defense enzymes and reactive oxygen species. The effectiveness of RBS-57 liquid formulation in reducing disease incidence was demonstrated when applied as a combination of seed treatment @ 10 ml/l + seedling dip @ 10 ml/l + foliar spray @ 10 ml/l. Moreover, higher defense enzyme activities, maximum plant growth promotion and higher yield were reported with RBS-57 treatment. This study has the potential to be exploited to manage sheath rot disease in an eco-friendly and sustainable manner. • We evaluated the efficacy of Bacillus spp. against Sarocladium oryzae in vitro. • Bacillus strains RBS-57, BS-5, and RBS-3 increased the rice growth in vitro. • We evaluated the presence of antibiotic biosynthetic genes using gene specific primers. • The liquid RBS-57 formulation effectively reduced sheath rot disease in rice. • We investigated the defense enzymatic activities in host-pathogen-bioagent interactions. [ABSTRACT FROM AUTHOR]

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In this work it was developed marker-free transgenic indica rice plants (cv J-104) by biolistic co-transformation and segregation approach. We attempted to express the NmDef02 antifungal defensin. Primary transformants were regenerated from embryogenic callus on culture medium with 50 mg/L hygromycin. Screening of hpt-marker-free transgenic lines was made by PCR in T1 progeny lines, germinated on semisolid medium without hygromycin. Relative expression of NmDef02 mRNA was examined by quantitative RT-PCR in marker- free T1 plants. In vitro antifungal test was performed by disk diffusion assay against Sarocladium oryzae. PCR assay verified that 15.12% of T1 plants were marker-free (NmDef02+/hpt-). RT-PCR analysis indicated that NmDef02 gene was successfully transcribed and the transgenic lines displayed different expression levels of the NmDef02 cDNA. Protein extracts of marker-free lines with high relative expression of NmDef02 inhibited fungus mycelial growth around disks. In contrast, it was confirmed fungus proliferation on disks impregnated with protein extracts of non-transgenic plants. The results of the present work demonstrated that the expression of the NmDef02 defensin in transgenic rice plants is effective against the phytopathogenic fungus Sarocladium oryzae under in vitro conditions. Thus, NmDef02 defensin could be a useful tool for J-104 rice improvement. [ABSTRACT FROM AUTHOR]

Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium spp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: Sarocladium oryzae, the Fusarium fujikuroi complex and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution and control options will be discussed.

Accurate measurement of parameters contributing to diseases and their symptoms is important for identification of resistant genotypes. Present sheath rot scoring system such as disease incidence scoring system accounts for only percentage of disease incidence and not the disease severity. Disease severity scoring system is based on combined features of panicle exertion and lesion size, very laborious and less accurate in field condition. Existing disease index requires assigning of incidence-severity scores for each and every tillers in a plant and has greater difficulties in evaluation of large number of plants or breeding pools. Hence, we propose phenotypic parameters such as proportion of panicle exertion, proportion of diseased and healthy sheath and modified disease severity scoring system for accurate measurement of disease. A high-throughput and simple disease indices (severity index, lesion index, detached lesion index and panicle discolouration index) are proposed for accurate identification of resistant-susceptible genotypes. [ABSTRACT FROM AUTHOR]

Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium sp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness, and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: S. oryzae, the Fusarium fujikuroi complex, and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution, and control options will be discussed. [ABSTRACT FROM AUTHOR]