Novel cereal bran based low-cost liquid medium for enhanced growth, multifunctional traits and shelf life of consortium biofertilizer containing Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.

The present study was carried out to valorise cereal (rice and wheat) bran for the development of low-cost liquid consortium bioformulation. Different concentrations of bran-based liquid media formulations were evaluated for the growth of consortium biofertilizer cultures (Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.). Among the bran-based formulations, wheat bran-based formulation WB5, exhibited the highest viable cell of 10.68 ± 0.09 Log10 CFU/ml and 12.63 ± 0.04 Log10 CFU/ml for Azotobacter chroococcum and Bacillus subtilis whereas for Pseudomonas sp., rice bran based bioformulation RB5 recorded maximum viability (12.71 ± 0.05 Log10 CFU/ml) after 72 h of incubation. RB51 and WB52liquid formulations were further optimized for enhanced shelf life using 5, 10 and 15 mM of trehalose, 0.05 and 0.1% carboxymethyl cellulose, and 0.5 and 1.0% glycerol. Following the peak growth at 72 h of incubation, a gradual decrease in the viable population of consortium biofertilizer cultures was observed in all the liquid formulations. The WB5 and RB5 formulations with 15 mM trehalose and 0.1% CMC, not only recorded significantly highest cell count of consortium biofertilizer cultures, but also maximally supported multi-functional traits i.e., phosphate and zinc solubilization, ammonia and IAA production up to 150 days. Further evaluation of seedling emergence and growth of wheat (PBW 826) under axenic conditions recorded WB5 amended with 15 mM trehalose-based consortium bioformulation to exhibit maximum emergence and growth of wheat seedlings. This low-cost liquid formulation can be used for large-scale biofertilizer production as a cost-effective liquid biofertilizer production technology.

Assessment of copper (Cu) nanoparticle for their biocontrol activity against Xanthomonas oryzae pv. oryzae, growth promotion, and physiology of rice (Oryza sativa L.) plants.

Among the various biotic factors that disrupt crop yield, Xanthomonas oryzae pv oryzae (Xoo) is the most ruinous microbe of rice and causes bacterial leaf blight (BLB) disease. The present study focused on the utilization of copper nanoparticles (Cu-NPs) to control BLB. The copper nanosuspension (259.7 nm) prepared using Na-CMC, CuSO4·7H2O, and NaOH showed effectively inhibited Xoo (65.0 µg/ml). The performance of Cu-NPs in vivo showed enhanced plant attributes (127.9% root length and 53.9% shoot length) compared to the control and CuSO4 treated seedling. Furthermore, Cu-NPs treated seedlings showed 23.01% disease incidence (DI) compared to CuSO4 (85.71%) treated and control plants (91.83%). In addition to enhancing the growth parameters and reducing DI, seed priming with Cu-NPs improved the total chlorophyll content to 36.0% compared to the control. The assessment of antioxidant enzymes such as superoxide dismutase (1.9 U), polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase (two- to three-fold) in roots and shoots of rice plants revealed significant enhancement in Cu-NPs treated seedlings (P < 0.05). The present study suggests that Cu-NPs can be used to control Xoo and enhance rice growth.

Comparative assessment of multi-trait plant growth-promoting endophytes associated with cultivated and wild Oryza germplasm of Assam, India.

This paper presents a comparative study of endophytic bacteria from cultivated (Oryza sativa) and wild rice (Oryza rufipogon) plants and their functional traits related to plant growth promotion. A total of 70 bacterial isolates were characterized by both biochemical and molecular identification methods. Taxonomic classification showed dominance of three major phyla, viz, Firmicutes (57.1%), Actinobacteria (20.0%) and Proteobacteria (22.8%). Screening for in vitro plant growth-promoting activities revealed a hitherto unreported endophytic bacterium from wild rice germplasm, Microbacterium laevaniformans RS0111 with highest indole acetic acid (28.39 ± 1.39 µg/ml) and gibberellic acid (67.23 ± 1.83 µg/ml) producing efficiency. Few other endophytic isolates from cultivated rice germplasm such as Bacillus tequilensis RHS01 showed highest phosphate solubilizing activity (81.70 ± 1.98 µg/ml), while Microbacterium testaceum MKLS01 and Microbacterium enclense MI03 L05 showed highest potassium (53.42 ± 0.75 µg/ml) and zinc solubilizing activity (157.50%). Fictibacillus aquaticus LP20 05 produced highest siderophore (64.8%). In vivo evaluation of plant growth-promoting efficiencies of the isolates showed that Microbacterium laevaniformans RS0111, Microbacterium testaceum MKLS01 and Bacillus tequilensis RHS 01 could increase rice grain yield by 3.4-fold when compared to the control group. This study indicates the potentiality of rice endophytes isolates as an effective bioinoculants.

Assessment of chemically characterised Myristica fragrans essential oil against fungi contaminating stored scented rice and its mode of action as novel aflatoxin inhibitor.

The study reports chemically characterised Myristica fragrans essential oil (MFEO) as plant based food preservative against fungal and aflatoxin B1 (AFB1) contamination of scented rice varieties. The chemical profile of MFEO revealed elemicin (27.08%), myristicine (21.29%) and thujanol (18.55%) as major components. The minimum inhibitory and minimum aflatoxin inhibitory concentrations of MFEO were 2.75 and 1.5 mg/ml, respectively. The MFEO was efficacious against a broad spectrum of food deteriorating fungi. MFEO caused decrease in ergosterol content of fungal plasma membrane and enhanced leakage of cellular ions, depicting plasma membrane as the site of action. The MFEO caused reduction in cellular methylglyoxal content, the aflatoxin inducer. This is the first report on MFEO as aflatoxin suppressor. The essential oil may be recommended as plant based food preservative after large scale trials and reduction in methylglyoxal suggests its application for development of aflatoxin resistant varieties through green transgenics.

TargeTALE: A Web Resource to Identify TALEs in Xanthomonas Genomes and Their Respective Targets.

The Xanthomonas genus, comprises more than 30 species of gram-negative bacteria, most of which are pathogens of plants with high economic value, such as rice, common bean, and maize. Transcription activator-like effectors (TALEs), which act by regulating the host gene expression, are some of the major virulence factors of these bacteria. We present a novel tool to identify TALE genes in the genome of Xanthomonas strains and their respective targets. The analysis of the results obtained by TargeTALE in a proof-of-concept validation demonstrate that, at optimum setting, approximately 93% of the predicted target genes with available expression data were confirmed as upregulated during the infection, indicating that the tool might be useful for researchers in the field.

A quantitative microbiological exposure assessment model for Bacillus cereus in pasteurized rice cakes using computational fluid dynamics and Monte Carlo simulation.

The objective of this study was to develop quantitative microbial exposure assessment models for Bacillus cereus in packaged rice cakes (PRC). Probability distribution for growth of B. cereus in PRC was estimated and effects of thermal processing and acidification on extending the shelf-life of PRC were quantitatively assessed. Heat penetration curves at cold point of pasteurized PRC were successfully predicted using heat transfer simulation model and nonlinear regression model (root mean squared errors (RMSE) < 1.64 °C). The final contamination level in PRC of slab-shape package (>-0.85 log CFU/g at 95% percentile) was lower than that in oval-shape package (>3.41 log CFU/g at 95% percentile). This is due to the shorter come-up time at the cold point in the slab-shape in comparison with the oval package. Acidification significantly inhibited the growth of B. cereus and decreased the thermal resistance of B. cereus, which resulted in a decrease of the median values (1.82 log CFU/g for both B2C and B2B products). Results of quantitative microbial exposure assessment for Bacillus cereus in PRC showed that a combination of acidification and low temperature pasteurization could improve the safety of PRC (<-2.43 log CFU/g at 95% percentile).

Rapid detection of rice disease using microscopy image identification based on the synergistic judgment of texture and shape features and decision tree-confusion matrix method.

BACKGROUND: Rice smut and rice blast are listed as two of the three major diseases of rice. Owing to the small size and similar structure of rice blast and rice smut spores, traditional microscopic methods are troublesome to detect them. Therefore, this paper uses microscopy image identification based on the synergistic judgment of texture and shape features and the decision tree-confusion matrix method. RESULTS: The distance transformation-Gaussian filtering-watershed algorithm method was proposed to separate the adherent rice blast spores, and the accuracy was increased by about 10%. Four shape features (area, perimeter, ellipticity, complexity) and three texture features (entropy, homogeneity, contrast) were selected for decision-tree model classification. The confusion-matrix algorithm was used to calculate the classification accuracy, in which global accuracy is 82% and the Kappa coefficient is 0.81. At the same time, the detection accuracy is as high as 94%. CONCLUSIONS: The synergistic judgment of texture and shape features and the decision tree-confusion matrix method can be used to detect rice disease quickly and precisely. The proposed method can be combined with a spore trap, which is vital to devise strategies early and to control rice disease effectively. © 2019 Society of Chemical Industry.

Presence of Zearalenone in Cereal Grains and Its Exposure Risk Assessment in Indian Population.

Zearalenone (ZEA) is a toxic metabolite of Fusarium genera that frequently contaminates cereal grains. India being a tropical country provides suitable conditions for fungal invasion to the cereals. In the absence of any regulatory limits for ZEA in India, the present study was carried out to analyze the contamination levels of ZEA in different cereal samples consumed by Indian population and its exposure assessment through intake. Out of 117 cereal samples comprising of wheat, rice, corn, and oats, 70 (84%) were found to be positive for ZEA contamination, among which 24 (33%) samples exceeded the permissible limits proposed by European Union when analyzed by high-performance liquid chromatography. The positive samples were further validated by Liquid Chromatography-Mass Spectroscopy (LC-MS) analysis. Based on the quantitative estimation of ZEA contamination in cereals and their daily consumption values, the probable daily intake of ZEA was found to be 16.9- and 7.9-fold higher in rice and wheat samples, respectively, than the tolerable daily intake prescribed by European Food Safety Authority. The presence of ZEA at high levels indicates a higher exposure risk for Indian population as wheat and rice are staple foods in India. Thus, there is an immediate need to set the permissible levels of ZEA in India to safeguard the health of 1.34 billion people. PRACTICAL APPLICATION: High levels of ZEA contaminated wheat and rice samples suggest that the consumers are at a greater exposure risk. The study will help the Indian regulatory bodies to set the permissible level of ZEA in different cereal grains so as to safeguard the health of common masses. This can happen by simply adopting to European Food Safety Authority standards or depending on the consumption pattern of food and its occurrence, the new safe limit can be prescribed in India like in other Asian countries.

In vivo assessment of plant extracts for control of plant diseases: A sesquiterpene ketolactone isolated from Curcuma zedoaria suppresses wheat leaf rust.

As an alternative to synthetic pesticides, natural materials such as plant extracts and microbes have been considered to control plant diseases. In this study, methanol extracts of 120 plants were explored for in vivo antifungal activity against Rhizoctonia solani, Botrytis cinerea, Phytophthora infestans, Puccinia triticina, and Blumeria graminis f. sp. hordei. Of the 120 plant extracts, eight plant extracts exhibited a disease control efficacy of more than 90% against at least one of five plant diseases. In particular, a methanol extract of Curcuma zedoaria rhizomes exhibited strong activity against wheat leaf rust caused by P. triticina. When the C. zedoaria methanol extracts were partitioned with various solvents, the layers of n-hexane, methylene chloride, and ethyl acetate showed disease control values of 100, 80, and 43%, respectively, against wheat leaf rust. From the C. zedoaria rhizome extracts, an antifungal substance was isolated and identified as a sesquiterpene ketolactone based on the mass and nuclear magnetic resonance spectral data. The active compound controlled the development of rice sheath blight, wheat leaf rust, and tomato late blight. Considering the in vivo antifungal activities of the sesquiterpene ketolactone and the C. zedoaria extracts, these results suggest that C. zedoaria can be used as a potent fungicide in organic agriculture.

Assessment of the Virulence Spectrum and Its Association with Genetic Diversity in Magnaporthe oryzae Populations from Sub-Saharan Africa.

A collection of 122 isolates of Magnaporthe oryzae, from nine sub-Saharan African countries, was assessed for virulence diversity and genetic relatedness. The virulence spectrum was assessed by pathotype analysis with a panel of 43 rice genotypes consisting of differential lines carrying 24 blast resistance genes (R-genes), contemporary African rice cultivars, and susceptible checks. The virulence spectrum among isolates ranged from 5 to 80%. Five isolates were avirulent to the entire rice panel, while two isolates were virulent to ∼75% of the panel. Overall, cultivar 75-1-127, the Pi9 R-gene donor, was resistant to all isolates (100%), followed by four African rice cultivars (AR105, NERICA 15, 96%; NERICA 4, 91%; and F6-36, 90%). Genetic relatedness of isolates was assessed by single nucleotide polymorphisms derived from genotyping-by-sequencing and by vegetative compatibility tests. Phylogenetic analysis of SNPs of a subset of isolates (n = 78) revealed seven distinct clades that differed in virulence. Principal component analysis showed isolates from East Africa were genetically distinct from those from West Africa. Vegetative compatibility tests of a subset of isolates (n = 65) showed no common groups among countries. This study shows that blast disease could be controlled by pyramiding of Pi9 together with other promising R-genes into rice cultivars that are adapted to East and West African regions.

Economic and Environmental Impact of Rice Blast Pathogen (Magnaporthe oryzae) Alleviation in the United States.

Rice blast (Magnaporthe oryzae) is a key concern in combating global food insecurity given the disease is responsible for approximately 30% of rice production losses globally-the equivalent of feeding 60 million people. These losses increase the global rice price and reduce consumer welfare and food security. Rice is the staple crop for more than half the world's population so any reduction in rice blast would have substantial beneficial effects on consumer livelihoods. In 2012, researchers in the US began analyzing the feasibility of creating blast-resistant rice through cisgenic breeding. Correspondingly, our study evaluates the changes in producer, consumer, and environmental welfare, if all the rice produced in the Mid-South of the US were blast resistant through a process like cisgenics, using both international trade and environmental assessment modeling. Our results show that US rice producers would gain 69.34 million dollars annually and increase the rice supply to feed an additional one million consumers globally by eliminating blast from production in the Mid-South. These results suggest that blast alleviation could be even more significant in increasing global food security given that the US is a small rice producer by global standards and likely experiences lower losses from blast than other rice-producing countries because of its ongoing investment in production technology and management. Furthermore, results from our detailed life cycle assessment (LCA) show that producing blast-resistant rice has lower environmental (fossil fuel depletion, ecotoxicity, carcinogenics, eutrophication, acidification, global warming potential, and ozone depletion) impacts per unit of rice than non-blast resistant rice production. Our findings suggest that any reduction in blast via breeding will have significantly positive impacts on reducing global food insecurity through increased supply, as well as decreased price and environmental impacts in production.

Stability assessment of hydro dispersive nanometric permethrin and its biosafety study towards the beneficial bacterial isolate from paddy rhizome.

Nanopesticides such as nanopermethrin can serve as an alternative to conventional pesticides causing eco-toxicity. The nanoformulation of this pyrethroid pesticide was carried out by solvent evaporation of pesticide-loaded microemulsion. The Z average for the nanopermethrin dispersion in paddy field water was found to be 169.2 ± 0.75 nm with a polydispersity index of 0.371 that exhibits uniform dispersion. Further, the nanopermethrin (NP) dispersion exhibited an effective stability in the paddy field water for a duration of 48 h with a Z average of 177.3 ± 1.2 nm and a zeta potential of -30.7 ± 0.9 mV. The LC50 of the nanopermethrin against Culex tritaeniorhynchus in the field condition was found to be 0.051 µg/mL. In addition to the stability assessment, the biosafety of the nanopermethrin was commenced on the beneficial bacterial isolate Enterobacter ludwigii (VITSPR1) considered as plant growth-promoting rhizobacteria. The toxic effect of nanopesticide was compared to its bulk counterpart, i.e. bulk permethrin (BP) at a concentration of 100 µg/mL, and the nanopesticide was found to be potentially safe. The results of biomarker enzymatic assays (lipid peroxidase, glutathione reductase, lactate dehydrogenase) displayed insignificant (p < 0.05) toxicity of NP towards the bacterial cells compared to BP. The live-dead cell staining and SEM analysis illustrated negligible toxicity of NP towards the bacteria. The non-toxic behaviour of the NP towards the non-target species was studied which displayed the eco-safe property of NP.

Tissue-specific expression of Arabidopsis NPR1 gene in rice for sheath blight resistance without compromising phenotypic cost.

Rice sheath blight disease, caused by the fungus Rhizoctonia solani, is considered the second most important disease of rice after blast. NPR1 (non expressor of PR1) is the central regulator of systemic acquired resistance (SAR) conferring broad spectrum resistance to various pathogens. Previous reports have indicated that constitutive expression of the Arabidopsis thaliana NPR1 (AtNPR1) gene results in disease resistance in rice but has a negative impact on growth and agronomic traits. Here, we report that green tissue-specific expression of AtNPR1 in rice confers resistance to the sheath blight pathogen, with no concomitant abnormalities in plant growth and yield parameters. Elevated levels of NPR1 activated the defence pathway in the transgenic plants by inducing expression of endogenous genes such as PR1b, RC24, and PR10A. Enhanced sheath blight resistance of the transgenic plants was evaluated using three different bioassay systems. A partially isolated toxin from R. solani was used in the bioassays to measure the resistance level. Studies of the phenotype and yield showed that the transgenic plants did not exhibit any kind of phenotypic imbalances. Our results demonstrate that green tissue-specific expression of AtNPR1 is an effective strategy for controlling the sheath blight pathogen. The present work in rice can be extended to other crop plants severely damaged by the pathogen.

Food system consequences of a fungal disease epidemic in a major crop.

Fungal diseases are major threats to the most important crops upon which humanity depends. Were there to be a major epidemic that severely reduced yields, its effects would spread throughout the globalized food system. To explore these ramifications, we use a partial equilibrium economic model of the global food system (IMPACT) to study a hypothetical severe but short-lived epidemic that reduces rice yields in the countries affected by 80%. We modelled a succession of epidemic scenarios of increasing severity, starting with the disease in a single country in southeast Asia and ending with the pathogen present in most of eastern Asia. The epidemic and subsequent crop losses led to substantially increased global rice prices. However, as long as global commodity trade was unrestricted and able to respond fast enough, the effects on individual calorie consumption were, to a large part, mitigated. Some of the worse effects were projected to be experienced by poor net-rice importing countries in sub-Saharan Africa, which were not affected directly by the disease but suffered because of higher rice prices. We critique the assumptions of our models and explore political economic pressures to restrict trade at times of crisis. We finish by arguing for the importance of 'stress-testing' the resilience of the global food system to crop disease and other shocks.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.

Assessment of endophytic yeast diversity in rice leaves by a culture-independent approach.

Endophytic microorganisms inhabit internal plant tissues in the host plant without causing any symptoms or negative effects. Although the diversity of endophytes has been evaluated by both culture-dependent and culture-independent methods, less information is available on yeast communities. Therefore, in this study a culture-independent method was used to examine endophytic yeasts associated with rice leaves based on the large subunit of ribosomal DNA using a semi-nested PCR technique. Sequence analysis indicated that the colonization frequency and the relative species frequency (RF) of endophytic yeast phylotypes were 0.41 and 0.06, respectively, and the majority of the yeast phylotypes were basidiomycetous yeasts. The phylotypes were designated as five known species (Cryptococcus victoriae, Debaryomyces hansenii, Debaryomyces vindobonensis, Meyerozyma guilliermondii and Pseudozyma antarctica), together with seventeen phylotypes closest to Candida metapsilosis, Cryp. foliicola, Cryp. laurentii, Pseudozyma abaconensis, Pseudozyma aphidis and Trichosporon asahii, among which some could be novel species. The most prevalent phylotypes were those closest to Cryp. foliicola (47.5 % RF) followed by D. hansenii (22.8 % RF) and P. antarctica (16.8 % RF). The presence of the phylotypes related to species known for their potential applications as biocontrol agents and plant growth promoting hormone producers suggests that they may have valuable applications. In addition, our findings revealed the occurrence of novel phylotypes at high frequency, which should encourage extensive studies to discover novel yeast species and to understand their roles in the rice leaves.

Assessment of epiphytic yeast diversity in rice (Oryza sativa) phyllosphere in Thailand by a culture-independent approach.

The epiphytic yeast diversity in rice phyllosphere in Thailand was investigated by a culture-independent technique based on the RFLP pattern and the sequence of the D1/D2 domain of the large subunit rRNA gene. Forty-four samples of rice leaf were collected randomly from six provinces. The DNA was extracted from leaf washing samples and the D1/D2 domain was amplified using PCR technique. The PCR products were cloned and then screened by colony PCR. Of total 1121 clones, 451 clones (40.2 %) revealed the D1/D2 domain sequences closely related to sequences of yeasts in GenBank, and they were clustered into 45 operational taxonomic units (OTUs) at 99 % homology. Of total yeast related clones, 329 clones (72.9 %) were identified as nine known yeast species, which consisted of 314 clones (8 OTUs) in the phylum Basidiomycota including Bullera japonica, Pseudozyma antarctica, Pseudozyma aphidis, Sporobolomyces blumeae, Sporobolomyces carnicolor and Sporobolomyces oryzicola and 15 clones (6 OTUs) in the phylum Ascomycota including Metschnikowia koreensis, Meyerozyma guilliermondii and Wickerhamomyces anomalus. The D1/D2 sequences (122 clones) that could not be identified as known yeast species were closest to 3 and 14 species in Ascomycota and Basidiomycota, respectively, some of which may be new yeast species. The most predominant species detected was P. antarctica (42.6 %) followed by B. japonica (25.9 %) with 63.6 and 22.7 % frequency of occurrence, respectively. The results of OTU richness of each sampling location revealed that climate condition and sampling location could affect epiphytic yeast diversity in rice phyllosphere.

Characterization of leaf blade- and leaf sheath-associated bacterial communities and assessment of their responses to environmental changes in CO2, temperature, and nitrogen levels under field conditions.

Rice shoot-associated bacterial communities at the panicle initiation stage were characterized and their responses to elevated surface water-soil temperature (ET), low nitrogen (LN), and free-air CO2 enrichment (FACE) were assessed by clone library analyses of the 16S rRNA gene. Principal coordinate analyses combining all sequence data for leaf blade- and leaf sheath-associated bacteria revealed that each bacterial community had a distinct structure, as supported by PC1 (61.5%), that was mainly attributed to the high abundance of Planctomycetes in leaf sheaths. Our results also indicated that the community structures of leaf blade-associated bacteria were more sensitive than those of leaf sheath-associated bacteria to the environmental factors examined. Among these environmental factors, LN strongly affected the community structures of leaf blade-associated bacteria by increasing the relative abundance of Bacilli. The most significant effect of FACE was also observed on leaf blade-associated bacteria under the LN condition, which was explained by decreases and increases in Agrobacterium and Pantoea, respectively. The community structures of leaf blade-associated bacteria under the combination of FACE and ET were more similar to those of the control than to those under ET or FACE. Thus, the combined effects of environmental factors need to be considered in order to realistically assess the effects of environmental changes on microbial community structures.

Assessment of sensitivity and virulence fitness costs of the AvrPik alleles from Magnaporthe oryzae to isoprothiolane.

The in vitro sensitivity of AvrPik allele isolates of Magnaporthe oryzae to isoprothiolane was examined and the virulence fitness costs of AvrPik allele isolates to isoprothiolane were assessed. Isoprothiolane was found to suppress the radial growth of AvrPik allele isolates at all concentrations (1, 5, 10, 15, and 20 µg/mL). Generally, a higher isoprothiolane concentration has a stronger inhibitory effect on mycelial growth in AvrPik allele isolates at 6 and 10 days after inoculation. The inhibitory effect of isoprothiolane also increased with treatment time. To determine whether a correlation existed between the in vitro sensitivity of AvrPik allele isolates and virulence, the half-maximal inhibitor concentration and 75% of the maximum inhibitor concentration were calculated for each mutation isolate and wild-type isolate. Based on these values and virulence, no significant correlation between the susceptibility of AvrPik allele isolates and virulence was detected. In summary, no fitness costs were associated with sensitivity of blast isolates carrying specific AvrPik alleles to different virulence.

Early diagnosis of blast fungus, Magnaporthe oryzae, in rice plant by using an ultra-sensitive electrically magnetic-controllable electrochemical biosensor.

As one of the most destructive and widespread disease of rice, Magnaporthe oryzae (also called Magnaporthe grisea) has a significant negative impact on rice production. Therefore, it is still in high demand to develop extremely sensitive and accurate methods for the early diagnosis of Magnaporthe oryzae (M. oryzae). In this study, we developed a novel magnetic-controllable electrochemical biosensor for the ultra sensitive and specific detection of M. oryzae in rice plant by using M. oryzae's chitinases (Mgchi) as biochemical marker and a rice (Oryza sativa) cDNA encoding mannose-binding jacalin-related lectin (Osmbl) as recognition probe. The proposed biosensor combined with the merits of chronoamperometry, electrically magnetic-controllable gold electrode and magnetic beads (MBs)-based palladium nano-particles (PdNPs) catalysis amplification, has an ultra-high sensitivity and specificity for the detection of trace M. oryzae in rice plant. It could be used to detect M. oryzae in rice plant in the initial infection stage (before any symptomatic lesions were observed) to help farmers timely manage the disease. In comparison with previous methods, the proposed method has notable advantages such as higher sensitivity, excellent specificity, short analysis time, robust resistibility to complex matrix and low cost etc. The success in this study provides a reliable approach for the early diagnosis and fast screening of M. oryzae in rice plant.

Multi-commutated fluorometric optosensor for the determination of citrinin in rice and red yeast rice supplements.

Citrinin is a toxic secondary metabolite first isolated from Penicillium citrinum, although is also produced by other species of Penicillium and Aspergillus. It has highly toxic, mutagenic, teratogenic and carcinogenic properties and is often found in crops, vegetables and fruit. To our knowledge there is no specific legislation on maximum levels permitted for citrinin, so no official analytical method is currently available for its determination. Our laboratory developed a fluorometric flow-through optosensor using Sephadex SPC-25 as solid support. Multi-commutated flow injection analysis was used for the construction of the manifold and for handling solutions. In this way, we minimised waste generation and human intervention, which are critical aspects when dealing with highly toxic compounds such as citrinin. The optimum excitation/emission wavelengths were set at 330/494 nm; the calibration curve was linear in the concentration range 35-900 ng ml⁻¹. A detection limit of 10.5 ng ml⁻¹ and relative standard deviations (RSDs) lower than 3% were obtained. The developed optosensor was applied to the determination of citrinin in rice and dietary supplements containing red yeast rice.