Characterization of Pyricularia oryzae and Screening the Qualitative Resistance of Sarawak Rainfed Lowland Rice Landraces Against the Pathogen

Rice blast disease caused by Pyricularia oryzae is one of the major diseases of rice in Sarawak, Malaysian Borneo. Unfortunately, the documentation and characterization of P. oryzae in Sarawak, resistance of Sarawak rainfed lowland landraces against P. oryzae and crucial information on the population genetics of P. oryzae in the Sarawak paddy fields are still lacking. This study aims to: 1) isolate and characterize rice blast fungus from infected paddy leaves collected from four divisions in Sarawak, viz, Miri, Sri Aman, Serian and Kuching, 2) screen the selected Sarawak lowland rice landraces (Bubuk, Pandan, Semanggang, Bario (Bintung), Entangor, Entaba (Lembut), Brunei, Bario Hitam, Perintah, Sebuti, Bario Putih, Sabak Hitam, Kuning, Rendah and Saga) for resistance against different isolates of P. oryzae at seedling stage and 3) analyse the genetic relatedness of P. oryzae in Sarawak with isolates from Peninsular Malaysia. Fifteen succeeded isolates were pre-identified as P. oryzae by morphological characteristics of spores, followed by verification through internal transcribed spacer (ITS) sequence. The isolates were evaluated for morphological characteristics, growth rate and sporulation rate, which were grown on six types of media, oatmeal agar (OMA), potato dextrose agar (PDA), malt extract agar (MEA), cornmeal agar (CMA), rice agar (RA) and barley agar (BA). 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. There were no morphological characters that are unique to a specific location. The growth rate and sporulation rate of each isolate varied based on types of media used. In general, among the six media, four media, viz; OMA, PDA, CMA and BA were found favourable for mycelial growth and sporulation for most of the isolates. Disease test screening were done by inoculating 15 lowland rice landraces against five different isolates of P. oryzae, viz; isolate POK3, POK6, POS2, POMI1 and POSA2. The results showed that all rice landraces were resistance against four P. oryzae isolates namely, POK3, POK6, POS2 and POMI1. Nine rice landraces showed mild resistance against isolate POSA2. Isolate specificity resistance was observed. Phylogenetic tree analysis based on Internal transcribed spacer (ITS) region was constructed by using maximum-likelihood method involving eight isolates from Sarawak and seventeen different isolates from five different states in Peninsular Malaysia. The results found that all isolates from Sarawak except isolate POSA1 were genetically related to isolates from Peninsular Malaysia

Antifungal Properties of Elephantopus scaber L. (Asteraceae) Against Crop Pathogenic Fungi

Harmful effect of synthetic fungicides towards environment and other organisms have become important issues nowadays. Research on the plant product to be developed as an alternative for synthetic fungicides has attracted interest of many scientists. The aim of this study is to determine the effect of antimicrobial properties of Elephantopus scaber L. from the family Asteraceae against six crop pathogenic fungi viz., Glomerella cingulata (Stoneman) Spauld. & H. Schrenk, Fusarium oxysporum Schltdl., Pyricularia oryzae Cavara, Fusarium solani (Mart.) Sacc., Pestalotiopsis sp., and Colletotrichum sp. Three different concentrations of E. scaber crude extract- 1%, 5% and 15%, were used in fungal growth inhibition test. At 15% (w/v) concentration, the mycelia growth of Colletotrichum sp., F. solani, and P. oryzae were significantly retarded. It indicates that the extract of E. scaber could potentially be used as a biofungicide

Qualitative Resistance of Sarawak Rice Landraces Against Pyricularia oryzae

Malaysia rice production is threatened by rice blast disease, caused by Pyricularia oryzae. Yield can be greatly reduced by this disease as it can attack all the aerial parts of rice including leaves, node, neck, and collar. The use of resistant cultivar, which can be produced from resistance breeding, can control the disease effectively. Sarawak, in Malaysian Borneo, has diverse rice landraces, which can be genetic resources for resistance breeding. Study on the resistance of Sarawak rice landraces against P. oryzae, is still limited. In this study, diseased leaf samples were collected from rice fields in Serian division, Sarawak. One isolate was successfully obtained and designated as B2PG. The morphological characteristics were documented. Six Sarawak rice landraces were challenged with isolate B2PG. Four of the rice landraces were resistant and might carry resistance gene(s), which can be utilised in future breeding program

Morphological and Physiological Development of Pyricularia oryzae Isolates from North-western Region of Sarawak on Different Media under Laboratory Conditions Laboratory Conditions

Rice blast (causal agent: Pyricularia oryzae) is an important disease of rice in Sarawak. Understanding the pathogen’s morphological characteristics, genetic diversity and pathogenicity is important. Having a suitable medium for culturing and maintaining P. oryzae is important to ensure the availability of inoculum or materials under laboratory conditions. Oatmeal agar (OMA) and potato dextrose agar (PDA) are common media used for growing P. oryzae. OMA allows better mycelial growth and better sporulation as compared to PDA. There are also other alternatives such as fresh rice leaf agar and rice straw agar. Although OMA seems to be the best medium, unfortunately the opaqueness of the medium causes difficulty in observing the morphology and growth of mycelia. In addition, it is known that different isolates of P. oryzae will respond differently to different media. This study aims to identify the best media for culturing and maintaining P. oryzae isolates from Sarawak. A total of 14 P. oryzae isolates were characterised for their morphological characteristics, growth rate and sporulation rate using seven growing media. These 14 isolates included seven newly identified isolates in this study and seven isolates from a previous study, which were verified using internal transcribed spacer DNA sequence. The colony surface of the 14 P. oryzae isolates varied on different growing media. The pigmentation of colony surface varied from different shades of grey, translucent light brown, white and colourless. Pyricularia oryzae isolates grew better on OMA and PDA, while OMA was the best for sporulation. These two media can be recommended for culturing and maintaining different P. oryzae isolates under laboratory conditions

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

New variants of AvrPiz-t identified in Pyricularia oryzae from Malaysia

Rice blast disease (causal agent: Pyricularia oryzae) is an important rice disease worldwide as it can cause significant yield loss. Resistance genes in rice can recognise the corresponding avirulence genes (Avr-gene) of P. oryzae and suppress the attack of the pathogen as proposed in ‘gene-for-gene’ interaction. This interaction is highly specific. The resistance will be rapidly breakdown owing to the plasticity of Avr-gene. The breaking down of disease resistance can cause problem in managing the disease as well as sustaining a resistant rice variety. This paper aimed to study and analyse the sequence variation of AvrPiz-t gene from P. oryzae isolates in Malaysia (Sarawak) together with AvrPiz-t sequences available from National Centre for Biotechnology Information (NCBI). This study compared the AvrPiz-t haplotype found with previously reported haplotypes. A total of 20 Malaysian P. oryzae isolates were obtained from six divisions of Sarawak and were verified using internal transcribed spacer. Together with seven Malaysian P. oryzae isolates from a previous study, a total of 27 AvrPiz-t gene sequences from Malaysian isolates were successfully amplified and verified. The AvrPiz-t open reading frame (ORF) of 27 Malaysian isolates were aligned with 123 AvrPiz-t ORF from other countries that were available in NCBI database and 100 AvrPiz-t ORF from a previous study (Total = 250 sequences). Unique sequences were identified and translated into amino sequence. The amino acid sequences were aligned with haplotype sequences from previous studies. In total, there were 19 AvrPiz-t haplotypes, with eight newly identified haplotypes. The AvrPiz-t haplotypes were distributed across 14 countries with haplotype H9 as the dominant haplotype. Neutrality tests were performed for the 250 AvrPiz-t ORF sequences. The 250 isolates of P. oryzae were undergoing directional natural selection.. Detached leaf inoculation using filter paper method of selected Malaysia (Sarawak) P. oryzae isolates carrying one of the new AvrPiz-t haplotypes showed different level of pathogenicity towards Sarawak rice landraces. The data obtained serves as baseline information for disease management in Malaysia, especially for Sarawak state. Additionally, the information is also a reference for future rice breeding program in Sarawak

Thermal Degradation And Mechanical Characteristics Of Sugarcane Bagasse Reinforced Biodegradable Potato Starch Composites

Global pollution due to the overwhelming usage of non-biodegradable plastics is getting severe nowadays. Hence, the aim of this paper is to develop an environmentally friendly composite material from potato starch and sugarcane bagasse. The composites were prepared by hot pressing at 145℃ for 60 min. The composites were characterized for their mechanical and thermal properties. In terms of thermal properties, thermogravimetric analysis shows that incorporation of sugarcane fiber has improved the thermal stability of the composites. Meanwhile, incorporation of sugarcane fibre from 0 to 15 wt.% has significantly improved the tensile (202.7%) and flexural (198%) strength of the composites. Scanning electron micrograph of the tensile fracture showed the fibre fracture and fibre “pull-out” from the composite. Overall, the biodegradable composites have shown improved functional characteristic than the origin material. This finding shows that this Sugarcane/Potato starch composites are potential alternative material for biodegradable product i.e. biodegradable plastic packaging

Antimicrobial Properties of Elephantopus Scaber Against Crop Pathogenic Fungi

Harmful effect of synthetic fungicides towards environment and other organisms have become important issues nowadays. Research on the plant product to be developed as the alternative for synthetic fungicides has attracted interest of many scientists. Elephantopus scaber previously was reported to contain antimicrobial properties. The aim of this study is to determine the effect of antimicrobial properties of Elephantopus scaber against six crop pathogenic fungi viz., Glomerella cingulata, Fusarium oxysporum, F. solani, Pestalotiopsis sp, Colletotrichum sp and Pyricularia oryzae. 80% of methanols were used as solvent to extract the phytochemical content of E. scaber. Different concentrations of the methanol crude extracts were used in fungal growth inhibition test. Result showed methanol crude extract at 15% concentration retard the mycelia growth on four crop pathogenic fungi, P. oryzae, F. solani, G. cingulata and Colletotrichum sp. F. oxysporum and Pestalotiopsis sp. did not showed growth retardation at any concentration used