Potential of Exserohilum Monoceras (Drechsler) Leonard and Suggs Isolated from Echinochloa P. Beauv. Species as a Bioherbicide

Echinochloa spp is widespread in the warm temperate, sub tropical and tropical regions. It is ubiquitous in the Malaysia rice fields and serious weedy pest to the crop, especially after the adoption of double cropping, more rapidly maturing cultivars and a shift from transplanting to direct sowing. The problem worsens by the contamination of farm machineries such as tractors and combined harvester and also through seeds contamination. Chemical herbicides are widely used to control the grass which has a negative implication to the environment and public health. Several fungal pathogens have been reported to be potential biocontrol agents of this weed. This study was conducted to identify potential indigenous fungal pathogens for the control of Echinochloa spp and its requirements to be developed as bioherbicide. Exserohilum monoceras isolate 1125 was identified to be the potential fungus to control Echinochloa spp. Studies on the efficacy of the fungus indicated that it was effective at concentration of 10 6 spores/mL, and plant was sensitive at their 4 leaves stage. The fungus attacked E. crus-galli var crus galli, E. crus-galli var formosensis, E.colona and E. orizycola but with different disease intensity. The fungus was safe to all modern rice varieties, turf grasses and the selected vegetable crops tested, indicated that it was highly selective. Before it developed into a bioherbicide, the fungus need to mass produced. This study indicated that carbon source enhance, mycelium and production also disease efficacy. Addition of Nitrogen source does not increase the mycelium production however the spore production was significantly increased. The CN ratio found to be good for the mycelium and spore production range from 9:1 to 24:1. Exserohilum monoceras infection was influence by availability of dew and temperature. The fungus needed a minimum 12 hrs of humidity to caused severe disease on the host. The best temperature for infection is within the range 25OC to 35OC. Exserohilum monoceras was also effective in field condition. Spore concentration at the rate of 106 spore/mL and 107 spore/mL produced 45% and 50% control of Echinochloa in the field respectively. At the rate 108 spore/mL the fungus caused toxic effect on rice plants but recovered after sometimes. Disease severity also increased with spray frequency. The apparent infection rate at 107 spore/mL (rL = 0.14 logit/day) was highest followed by 108 spore/mL (rL = 0.13 logit/day) and 106 spore/mL (rL =0.12 logit/day). At the end of the trial, tillers production and dry weight of Echinochloa was also reduced. The result of this research indicated that E. monoceras has potential as a candidate for bioherbicide in the control of Echinochloa in rice field but need some improvement in the formulation

Preliminary screening of endophytic fungi isolated from medicinal plants in MARDI Sessang, Sarawak for their bioactivity

A total of 100 isolates of endophytic fungi were isolated from 19 species of medicinal plants collected at MARDI Station Sessang, Sarawak. A total of 55% of the endophytic fungi were isolated from the leaves while 45% from the branches. Screening of isolates for enzymatic secretion found that 15, 28 and 12 isolates were able to hydrolyze cellulose, xylan and mannan respectively. All 100 isolates were also tested for their antimicrobial activity towards selected phytopathogenic and human pathogenic microbes. The test indicated that only one isolate showed positive result when tested against Xanthomonas campestris. The results indicate that the endophytic fungi isolated from medicinal plant at MARDI Research Station Sessang, Sarawak may have the potential to be further exploited for its bioactivity

Isolation and screening of actinomycetes from Malaysian soil for their enzymatic and antimicrobial activities

Actinomycetes, a slow growing gram positive bacteria, are known as an organism that is useful in the search for bioactive compounds. In this study, 212 isolates of actinomycetes were isolated from soil samples collected in the area of Serdang, Bangi, Petaling Jaya and Putrajaya. From the total of 212 isolates, 91 showed the ability to degrade cellulose; 16 for mannan and 90 for xylan. The 212 isolates were then subjected to anti-microbial testing, where they were tested for their ability to produce anti-microbial activity against selected phytopathogens. From the test, only two strains of isolates (strain 161 and 176) showed positive result towards Xanthomonas campestris. These two isolates were then identified using research microscope

Efficacy of Exserohilum monoceras, a potential fungi for biocontrol of Echinochloa spesies

Indigenous Exserohilum monoceras isolate 1125 was evaluated for its efficacy on different Echinochloa species. Exserohilum monoceras spores, prepared at 103, 104, 105, 106 and 107 spores/ml concentrations and sprayed onto E. crus-galli, showed increased infectivity with increasing spore concentration. Disease progress of E. crus-galli at various leaf development stages revealed the highest area under the disease progress curve (AUDPC) was at the 4-leaf stage (535.69 unit2), followed by the 3-leaf (446.75 unit2), 2-leaf (377.22 unit2) and 6-leaf stage (263.72 unit2). The fungus was also tested on 4 species of Echinochloa. The results showed that the AUDPC was highest for E. crus- galli var formosensis (693.33 unit2), followed by E. crus-galli var crus-galli (638.33 unit2), E. oryzicola (470 unit2) and E. colona (447 unit2). The study illustrated that E. monoceras is a potential fungus for biological control that can be further developed into bioherbicide

Host range of Exserohilum monoceras 1125, a potential biological control agent for Echinochloa spp.

A total of 54 plant species, including varieties and breeding lines from 14 families and 33 genera were screened against Exserohilum monoceras, a fungal pathogen with potential as biocontrol agent for barnyard grass, Echinochloa crus-galli. The selected plant species were treated with spore suspensions at about 2.5 x 107 spores/ml concentration in glasshouse conditions supplemented with 24 h dew. The ability of the fungus to infect the plants was evaluated by disease incidence and disease severity which translated into disease index (DI). The disease index of Echinochloa crus-galli var. crus-galli, E. crus-galli var. formosensis and E. stagnina were 4 (dead) while those for E. colona and E. oryzicola were 3 (severely damage). Among the economic plants tested, only Zea mays was infected with a disease index of 2 (tolerant). Young Imperata cylindrica was dead (DI = 4), however the older plant showed hypersensitive reaction (DI = 2). Other plants that were infected were Cymbopogon sp. (DI = 1), Paspalum sp. (DI = 3) and Rhynchelytrum repen (DI = 3). Exserohilum monoceras did not infect selected varieties of rice in Malaysia, such as MRQ 50, MRQ 74, MR 219, MR 220 and MR 84. Vegetables and medicinal plants used in the test were also not infected

Survey and evaluation of native fungal pathogens for biocontrol of barnyard grass (Echinochloa crus-galli complex)

Echinochloa crus-galli is reported to be among the three most serious weeds of rice in many countries in Asia. In Malaysia, yield loss by E. crus-galli was about 41%. Selective chemical herbicides are primary means to control the grass. However, the extended use of the herbicides may develop negative implication to the environment and public health. Several fungal pathogens have been reported to attack barnyard grass (E. crus-galli complex) in various parts of the world. This study was to isolate, identify and evaluate the native fungi from diseased barnyard grass in paddy field, for potential as bioherbicide. From surveys carried out in 2003 to 2004 throughout the Peninsular Malaysia, several fungi species were identified to be associated with the diseases. A total of 82 isolates from 12 fungus genera have been isolated. Among the fungi were E. monoceras, E. longirostratum and Curvularia lunata. The fungus, E. monoceras, was consistently found associated with the disease, virulent, stable and has the ability to produce spores profusely in culture. These characteristics suggest that it can be used as biological control agent for the grass

Effects of moisture duration and temperature on infection of Exserohilum monoceras on Echinochloa crus-galli at different growth stages

The effects of moisture duration and temperature on the infectivity of Exserohilum monoceras on Echinochloa crus-galli, an important weed in Malaysian granaries, were investigated. The results showed that E. monoceras infections were influenced by the availability of moisture and temperature. The fungus needed a minimum of 12 h of humidity to cause severe disease on the host. The apparent disease infection rate was also influenced by moisture duration exposed to the plants. The fastest apparent infection rate was observed at 24 h of moisture exposure for 2-leaf plants (rL = 0.74 logit/day) and 6-leaf plants (rL = 0.72 logit/day). The optimum temperature for infection was within the range of 25 – 35 °C. The study indicated that temperature also influenced the ability of the fungus to infect E. crus-galli. The apparent infection rate for 4-leaf plants at 25 °C was rL = 1.05 logit/day, 30 °C at rL = 1.0 logit/day and 35 °C at rL = 0.77 logit/day. It could be taken as an advantage particularly in Malaysia where the temperature in granary areas usually ranges from 27 – 37 °C. Based on the results of this study, E. monoceras can be exploited as a bioherbicide, if the constraints related to moisture dependency can be solved

Typing of Ralstonia solanacearum isolated from tomato by antibiotic susceptibility, plasmid profiling and PCR-based techniques of RAPD and ERIC

The epidemiological characteristics of Ralstonia solanacearum isolated from tomato plants in Sarawak and Selangor were studied. The epidemiological analysis of the strains was carried out through antibiotic resistant pattern, plasmid profiles, randomly amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) methods. Six strains were susceptible to all antibiotics tested, whereas the 10 strains that were resistant to one or more antibiotics were grouped into six antibiotic resistance patterns. Small single plasmid of 7.2 Mda and 9.2 Mda were detected among the nine plasmid containing strains, enabling them to be grouped into only two plasmid patterns. In the polymerase chain reaction, based methods using RAPD and ERIC, two strains were untypable by RAPD, whereas all were typable by ERIC. In this study, a wide diversity of R. solanacearum strains was examined. ERIC analysis demonstrated the clonal relationship between isolates from tomato plants in Sarawak and Selangor. The existence of similar R. solanacearum strains in tomato plants from two very distant locations should be considered if tomato strain fingerprint results were to be used to help trace the vehicles for transmission

Local practices for production of rice husk biochar and coconut shell biochar: production methods, product characteristics, nutrient and field water holding capacity

Application of biochar is widely reported to enhance soil quality and decrease leaching of nutrients. In this study, biochar from rice husk and coconut shells were used to determine physico-chemical characteristics, ability on nutrients and water holding capacity in soil. These biochars were produced using conventional processes of rotary husk (for rice husk) and kiln-drum furnaces (for coconut shells). It was found that coconut shell biochar (CSB) was very effective in retaining nitrogen compared to rice husk biochar (RHB). Leaching analysis over 19 days (100 ml each day) has identified 15 g/kg of CSB in Bungor series soil to consistently maintain a leaching rate of nitrogen at below 5 mg/litre as compared to other samples. Meanwhile, RHB was very effective in retaining water compared to CSB with highest water retention at 31.2%. Overall results indicate that conventionally made biochar has great potential to reduce nutrient leaching and improve water holding capacity in soil. CSB is more effective in reducing nutrient leaching, particularly nitrogen while RHB was most effective in increasing field water holding capacity. Further research is required to study its effectiveness on nutrient plant uptake

Effects of Gliricidia sepium residue vermicompost on the yield and dry matter biomass of organic choy sum mustard

As the population grows and resource consumption increases, waste management has become a significant environmental challenge. A more sustainable approach to waste management is essential to maximize the recovery of materials acquired from nature. Vermicomposting is one of the answers to sustainable waste management. A study was conducted to determine the viability of vermicomposting Gliricidia sepium leaves and office scrap paper with matured compost as feedstock and to determine the vermicompost characteristics and suitability as potting mixtures for vegetable cultivation. The choy sum mustard was selected as the test crop. The plants were grown in the pots in a netted nursery in Serdang, Selangor. Treatments were mixtures of vermicompost to soil ratio by volume: control (0% no vermicompost), T1 (20% vermicompost), T2 (40% vermicompost), T3 (60% vermicompost), T4 (80% vermicompost) and T5 (100% vermicompost). Physicochemical properties of the potting media mix were determined and compared to an established growth media concentration and other ASEAN standards. Crop growth was evaluated by measuring plant height, the number of petioles, and fresh and dry weights at harvest. A significant improvement in the physicochemical properties of the media was observed, where the optimum ratio of potting media was 60% to 80% (T3 & T4). The number of petioles was 20-46% higher, plants were 39-46% taller, and dry matter accumulation was three-fold higher than controls. Crop yields were 200% higher in media treatments consisting of 60-80% vermicompost. In conclusion, G. sepium based vermicompost could be used in media mixtures for potting plants