Screening of fluorescent bacteria for growth promotion and biocontrol potential against Pyricularia oryzae on aerobic rice (MARDI Aerob 1)

Aims@#This study aimed to screen the plant growth-promoting fluorescent bacteria (FLB) which isolated from the healthy rice rhizophere and to evaluate its biocontrol and growth promotion properties against Pyricularia oryzae on aerobic rice seedling of MARDI Aerob 1. @*Methodology and results@#King’s B agar with glycerol was used as the selective medium to isolate FLB from the healthy rice rhizosphere soil. All FLB obtained were in vitro screened for antagonistic activities against P. oryzae using dual culture, volatile substances and hydrogen cyanide productions. The potential FLB isolates were further evaluated on rice seedling early growth promotion before identified using 16S rRNA gene sequencing. A total of 24 FLB were isolated from the healthy rice rhizosphere soil in Setiu, Terengganu, Malaysia. Isolates: FLB4, FLB5, FLB7 and FLB10 scored the total of percentage inhibition radial growth (PIRG) values ranged 99.5-105.0%. Further seedling growth promotion screening revealed that FLB4, FLB7 and FLB10 were significantly improved seedling growth with vigor index of 378.32%, 461.53% and 335.60% over control (133.31%). 16S rRNA sequencing identified that FLB7 as Bacillus subtilis and the FLB4 and FLB10 as Pseudomonas putida.@*Conclusion, significance and impact of study@#The selected FLB isolates (FLB4, FLB7 and FLB10) are potential to be developed as biological control agents against P. oryzae with growth promoting property on aerobic rice seedling.

Isolation and characterization of Pyricularia oryzae isolated from lowland rice in Sarawak, Malaysian Borneo

@#Aims: Rice blast disease caused by Pyricularia oryzae is one of the major biotic diseases of rice in Sarawak, Malaysian Borneo. This study aims to isolate and characterize rice blast fungus obtained from infected leaf collected from four different divisions in Sarawak, viz, Miri, Serian, Sri Aman, and Kuching. Methodology and results: Twelve succeeded isolates were pre-identified as P. oryzae by morphological characteristics of spores, followed by verification through (internal transcribed spacer) ITS sequencing. The isolates were evaluated for morphological characteristics, growth rate and sporulation rate, which were grown on two types of media, (filtered oatmeal agar) FOMA and (potato dextrose agar) PDA. Morphological characterization showed that the colony surface of the different isolates varied from smooth and fluffy to rough and flattened mycelia; some were with the present of concentric rings, and some with aerial mycelia. The growth rate and sporulation rate of each isolate varied based on types of media used. Most of the isolates grew faster on PDA than on FOMA but produced higher number of spores on FOMA as compared to PDA. Conclusion, significance and impact of study: This preliminary study showed that there were variations observed based on morphological and physiological characterization for the different isolates collected in Sarawak, Malaysian Borneo. This study is the first step towards understanding variation in the population of P. oryzae from Sarawak.

The pathogen and control management of rice blast disease

Abstracts@#Outbreak of rice blast disease is a serious problem in all rice growing regions worldwide and is a threat to rice production. In Malaysia, the outbreak of rice blast is a recurrent problem where rice plant remain vulnerable to the disease. Nowadays, the generic name of rice blast pathogen is Pyricularia oryzae and Magnaporthe oryzae is the synonym. Rice pathogen infects mainly aerial parts of rice plant causing rotting and blast on the leaves, stems, peduncles, panicles and seeds leading to crop failure. Rice blast pathogen population is regarded as highly variable and consisted of multiple pathotypes which contribute to genetic diversity as well virulence diversity of the pathogen. The pathotypes can only be determined through pathogenicity test using a set of differential rice cultivars which generally differ by one or more resistance genes. Knowledge on the rice blast virulence and host resistant is important to manage the disease. Among the control methods, utilizing resistant cultivars is considered as the most effective approach to manage rice blast disease. Therefore, development of blast resistant cultivar becomes a priority.

Relationship between blast severity on seedlings and panicles of Brazilian oat cultivars / Relação entre a severidade de brusone em plântulas e panículas de cultivares brasileiras de aveia

ABSTRACT: Blast, caused by Pyricularia oryzae, threats black (Avena strigosa) and white (A. sativa) oats in Brazil. Little is known about the reaction of Brazilian oat cultivars to blast and if there is a relationship between the response of cultivars to the disease at seedling and adult plant stages. The goals of this research were to verify (a) the reaction of black and white Brazilian oat cultivars to infection of P. oryzae and (b) if the response to blast on seedling leaves and panicles was correlated. Seedlings and adult plants of 13 oat cultivars were inoculated with a conidial suspension of one P. oryzae isolate obtained from a black oat cultivar. The cultivars were classified according to blast severity on the leaf seedlings and panicles estimated by visual estimation. Two experiments were conducted for each one of the two evaluated stages. Cultivars with lower value to blast severity on seedling leaves were 'UPFA Gaudéria' (25.82%) and 'UPF 18' (24.88%) and, on panicles, 'BRS Centauro' (31.63%). Coefficients of Pearson, Spearman, and Kendall obtained from correlation analyses between blast severity on seedling leaves and panicles were -0.21232, -0.35714, and -0.30769, respectively (non-significant at 0.05). Lack of correlation between the responses of these oat cultivars to blast on seedling leaves and panicles be considered in the management of the disease in the field and the generation of new oat cultivars.

RESUMO: A brusone, causada por Pyricularia oryzae, ameaça as culturas da aveia preta (Avena strigosa) e branca (A. sativa) no Brasil. Sabe-se pouco sobre a reação das cultivares brasileiras de aveia à brusone e se existe relação entre a resposta destas cultivares à doença nos estádios de plântula e de planta adulta. Os objetivos deste trabalho foram: (a) verificar a reação de cultivares brasileiras de aveia à infecção de P. oryzae e; (b) se existe relação entre a resposta à brusone dessas cultivares nos estádios de plântula e de planta adulta. Plântulas e plantas adultas de 13 cultivares de aveia foram inoculadas com uma suspensão de conídios de um isolado de P. oryzae obtido de uma planta de uma cultivar de aveia preta. As cultivares foram classificadas de acordo com a estimativa visual da severidade da doença nas folhas das plântulas e nas panículas das plantas adultas. Dois experimentos foram conduzidos para cada um dos estádios avaliados. As cultivares com menor severidade de brusone nas plântulas foram a 'Gaudéria UPFA' (25,82%) e a 'UPF 18' (24,88%) e, nas panículas, foi a 'BRS Centauro' (31,63%). Os coeficientes de Pearson, Spearman e Kendall obtidos da análise de correlação entre os dois estádios avaliados foram -0,21232, -0,35714 e -0,30769, respectivamente (todos sem significância estatística à 0,05). A falta de correlação entre as respostas das cultivares de aveia à brusone, em plântulas e panículas, constitui-se em informação a ser considerada no manejo da doença, no campo e na geração de novas cultivares de aveia.

Isolation of antagonistic Trichoderma spp. against selected phytopathogenic fungi from the field soils in Kelantan

Aims: Trichoderma is a soil borne mycoparasitic fungus which comprises a number of fungal strains that act as biocontrol agent. In this present study have investigated the diversity of Trichoderma in different cultivated soils in state of Kelantan. The effectiveness of biocontrol agent of isolated Trichoderm species was evaluated against the phytopathogen of Pyricularia oryzae, Fusarium oxysporum, and Ganoderma boninense. Methodology and results: The identification experiment was carried out on the basis of morphological characteristics as colony appearance, shapes and size of conidia, the branching patterns of conidiophores and phialides. Then, the effectiveness of biocontrol agent of Trichoderma species against the pathogens was tested in plate assay experiment. A total of 11 isolates were obtained from three different cultivated soils from Jeli (J), Machang (M) and Pasirmas (P). Morphological studies data identified as two groups of Trichoderma species as Trichoderma harzianum, and T. koningii. All the isolates showed the antagonistic activity against the pathogens while T. harzianum strain THMPA1 showed highest antagonistic activity of 80.00% against P. oryzae and in T. koningii strain TKMPA3 group showed highest antagonistic activity of 69% against P. oryzae. Conclusion, significance and impact of study: Among the 11 isolates of Trichoderma, the species of T. harzianum strain THMPA1 was the best as biocontrol agent against P. oryzae. Thus, diversity of Trichoderma species study is important to find promising species isolation of Trichoderma species which will be influenced in future to sustainable crop production and maintain green environment.

Critical-point models to relate yield and disease intensity of the multiple pathosystem in rice leaf spots disease / Modelos de pontos críticos para relacionar o rendimento de grãos com a intensidade em patossistema múltiplo de manchas foliares em arroz irrigado

ABSTRACT: The occurrence of leaf spots in irrigated rice can reduce the yield and compromise the quality of the grain. However it is unknown the economic damage threshold (EDT) that these spots cause the yield of crop. The objective of this study was to obtain damage functions for models of critical, to relate damage by simultaneous occurrence of blast, brown spot and scald spot with grain yield harvests in 2011/12 and 2012/2013, in Rio do Oeste, Santa Catarina State, Brazil. Gradient of diseases intensity was generated by number of applications and fungicides rates. Design was a randomized block with four replications and six treatments consisting of mixing fungicide applications of triazole (difenoconazole) and strobilurin (azoxystrobin). In 2011/12 and 2012/13 growing season were made two and three tests respectively with the same experiment. Before each application it was determined the incidence and severity of fungal diseases. The critical point models were obtained by linear regression between grain yield and incidence (I) and severity (S). In 2011/12 the functions were not significant at the beginning of tillering and 2012/2013 harvest resulted in R=13.404-92.98I and R=10.685-3.804S. Respectively in each harvest resulted in tillering (R=9.141-103.6I; R=7.605-1.538 and R=8.864-73.91I; R=7.202-77S), panicle initiation (R=9.432-188.5I; R=7.,038-1.466S and R=10.176-87.33I; R=8.258-533.55S), booting (R=7.044-71.78I; R=6.881-1.296S and R=9.993-71.74I; R=8.846-763.83S), flowering (R=7.447-82.29I; R=8.731-1.398S and R=8.347-54.36I; R=7.338-681.52S) and milky grain (R=10.143-80.5I; R=7.522-1.402S and R=8.661-60.063I; R=9.754-1.465S). The generated functions allow getting the damage coefficient for use in the calculation of EDT in multiple pathossystem leaf spots in irrigated rice.

RESUMO: A ocorrência de manchas foliares na cultura do arroz irrigado pode reduzir o rendimento e comprometer a qualidade do grão. No entanto, é desconhecido o limiar de dano econômico (LDE) que essas manchas causam no rendimento da cultura. O objetivo deste trabalho foi obter funções de dano, por modelos de ponto crítico, ao relacionar o dano pela ocorrência simultânea da brusone, mancha parda e escaldadura com o rendimento de grãos nas safras de 2011/12 e 2012/2013, em Rio do Oeste, Santa Catarina (SC). O gradiente da intensidade das doenças foi gerado por número de aplicações e doses de fungicidas. O delineamento foi de blocos casualizados, com quatro repetições e seis tratamentos, constituídos de aplicações de mistura de fungicidas triazol (difenoconazole) e estrobilurina (azoxistrobina). Na safra de 2011/12 e 2012/13, foram feitos dois e três ensaios, respectivamente, com o mesmo experimento. Antes de cada aplicação, foi determinada a incidência e a severidade das doenças foliares. Os modelos de ponto crítico foram obtidos por regressão linear entre rendimento de grãos e incidência (I) e severidade (S). Em 2011/12, as funções não foram significativas no início do perfilhamento e, na safra de 2012/2013, resultou em R=13.404-92,98I e R=10.685-3.804S. Respectivamente, em cada safra, resultaram no perfilhamento (R=9.141-103,6I; R=7.605-1.538 e R=8.864-73,91I; R=7.202-77S), iniciação da panícula (9.432-188,5I; R=7.038-1.466S e 10.176-87I; R=8.258-533,55S), emborrachamento (R=7.044-71,78I; 6.881-1.296S e R=9.993-71,74I; R=8.846-763,83S), floração (R=7.447-82,29I; R=8.731-1.398S e R=8.347-54,36I; R=7.338-681,52S) e grão leitoso (R=10.143-80,5I; R=7.522-1.402S e R=8.661-60.063I; R=9.754-1.465S). As funções geradas permitem obter o coeficiente de dano para uso no cálculo do LDE em patossistema múltiplo de manchas foliares, em arroz irrigado.

Identification of Some Rice Genotypes Resistant to Blast Disease in Egypt.

Blast disease caused by Pyricularia oryzae, is the most important disease of rice in Egypt and in the world. Field surveys in main production regions, revealed that the highest disease incidence was recorded in El-Behera Governorate. Seven rice cultivars were screened for resistance to blast disease. Resistance to disease was studied under both artificially and naturally with local pathogen. A bioassay was developed based on (0-9) scale, Area Under the Disease Progress Curve (AUDPC), disease area and sporulation. Differential expression to pathogen was observed between cultivars. Among seven cultivars, Sakha 101 and Sakha 103 were highly resistant and Giza 175 and Giza 178 were highly susceptible to three strains of fungus P. oryzae. Meanwhile other lines showed moderate resistance and susceptible. At the same time there were great differences concerning the growth rate and yield between different rice cultivars.

Studies on the secondary metabolites from marine fungus 09-1-1-1 / 中国海洋药物

Objective To search for novel antifungal structures produced by marine fungus.Methods Using the Pyricularia oryzae (P.oryzaae) bioassay method to screen marine fungi led to the isolation of marine fungus 09-1-1-1.Active metabolites were isolated from the broth of the marine fungus 09-1-1-1.Results Two compounds were extracted from the mycelium and their structures were elucidated by various spectroscopic methods as 3a,12c-dihydro-8-hydroxy-6-methoxy-7H-furo\furo\xanthen-7-one(Ⅰ,sterigmatocystin) and 1,3,6,8-tetrahydroxy-2-(1-hydroxyhexyl)anthraquinone(Ⅱ,averantin).Conclusion The P.oryzae bioassay was a cheap,quick and convenient method for the screening of bioactive substances from marine fungi.Compound Ⅱ showed potent inhibitory activity to the mycelia of P.oryzae.The MIC of compound Ⅱagainst P.oryzae was 1.6 ?g?mL~(-1).

Studies on chemical constituents of the sea cucumber Holothuria fuscocinerea / 中国海洋药物

Objective To study the chemical constituents of the sea cucumber Holothuria fuscocinerea collected from the South China Sea.Methods The compounds were isolated by Pyricularia oryzae bioassay-guided fractionation method in combination with extraction and partition as well as multi-chromatography.Their structures were determined on the basis of spectral analysis and chemical evidence.Results Three triterpene glycosides were isolated from the n-BuOH extract and identified as: pervicoside C(Ⅰ),holothurin A(Ⅱ) and DS-holoturin B(Ⅲ);Four compounds [uracil(Ⅳ),thymine(Ⅴ),thymidine(Ⅵ) and 2'-deoxyuridine(Ⅶ)] were obtained from the CHCl_(3) extract.Conclusion All the compounds were isolated from this sea cucumber for the first time while Compound Ⅰ was first obtained as pure compound.Compound Ⅰ and Ⅱ were active compounds causing morphological abnormality of P.oryzae mycelia and exhibited cytotoxicity against two cancer cell lines.

Using conidia of Pyricularia oryzae screening for bioactive portions from marine organisms / 第二军医大学学报

Objective:To screen for the bioactive marine organisms and to study the active constituents from them.Methods:Bioactivities of marine organisms extracts were screened by Pyricularia oryzae bioassay method and the constituents were isolated and identified by a combination of multi chromatography and spectral analysis.Results:Twenty ethanolic extracts and 5 aqueous extracts of the tested marine organisms showed activities causing morphological abnormality of P.oryzae mycelia.Fifty six compounds were obtained and identified from Sargassum carpophyllum,Ishige okamurai and Natarchus leachii freeri ,among which 28 compounds showed activities against P.oryzae and exhibited cytotoxicities on various cultured tumor cell lines,eight compounds showed inhibition effects on Fonsecaea pedrosoi in vitro .Conclusion:The screening data and bioactivity evaluation suggest the P.oryzae bioassay is suitable for preliminary screening of bioactive agents from marine organisms.