Vascular Streak Dieback of Cocoa in West Malaysia

A detailed study into vascular streak dieback (VSD), the most serious pathological problem of cocoa in Malaysia was carried out. The causal pathogen was isolated and the symptomatology relating to infection of mature cocoa and seedling in the nurseries has been described. Morphological studies of the local isolates have confirmed the close similarity of the VSD fungus to Oncobasidium theobromae Talbot and Keane, described as the primary causal agent of VSD in Papua New Guinea. Techniques useful for isolation of the pathogen in routine and sequential samplings were investigated. The use of nutrient poor medium, surface treatment of infected materials and plating samples within 48 hours after collection from the field had improved the efficiency of isolation of the VSD pathogen. The leaf isolation technique developed is a rapid and non-destructive method for isolation of the pathogen and confirmation of VSD incidence especially in seedlings in the nursery. A survey of the disease undertaken confirmed incidence of VSD in mature plantings in the states of Trengganu, Johor, Perak and Malacca; cocoa nurseries in Perak and Johor; and clonal plantings in Negeri Sembilan. In all cases, the percentage incidence and severity varied from locality to locality. Generally, the survey of clonal plantings had provided information On the relative susceptibility within clones. The fungus hitherto recorded to grow poorly On artificial media, had been found to grow satisfactorily on Corticium culture medium and On Leonian's solution agar

Morphological characteristics and pathogenicity of Synchytrium psophocarpi (Rac.) Baumann associated with false rust on winged bean

Problem statement: Winged bean (Psophocarpus tetragonolobus L.) is an important tropical legume in countries like Malaysia due to its potential as a high protein value crop. However, bright-orange pustules observed on the veins of young leaves, stems, pods and sepals depict symptoms of false rust disease on beans. The causal agent of this disease has been found to be Synchytrium psophocarpi. Currently, there is no published literature of this or other related species in Malaysia. Thus, there is a very serious lack of knowledge on the taxonomic characterization and pathogenicity of the local fungus. Therefore, there is an important need for this microorganism to be documented. Approach: This study was reported based from samples obtained from infected winged bean plants found in the fields around the University Putra Malaysia campus in Serdang, Selangor, Malaysia. The morphological characteristics were studied using dark field and scanning electron microscope. Meanwhile, pathogenicity test was carried out using two methods which were moist chamber and on Petri dish. Results: The sporangia were spherical to ovoid in shape and approximately 20.69 μm in diameter. The average diameter for spore measured was 2.02 μm and the flagella were 10.75 μm in length. Positive disease development with false rust disease symptoms was observed in both methods of inoculation practiced. It confirmed the pathogenicity of the fungus as the causal pathogen with the appearance of clear disease symptoms. Conclusion: This research finding is the first detailed report for Synchytrium psophocarpi associated with false rust disease of winged bean in Malaysia. It described the morphology, zoospore production and pathogenicity of the causal fungal organism. This information would be very useful for the studies involving this pathogen in future

Effect of Endophytic bacteria on growth and suppression of ganoderma infection in oil palm.

Basal stem rot (BSR) caused by Ganoderma boninense is an important disease of oil palm in Malaysia. Control of BSR is complex, because the disease occurs in the dynamic environment at the interface of the roots with soil. Endophytes as biocontrol agents offer possible advantages as they invade and proliferate in the plants to await the pathogens and they are insulated from any adverse conditions in the soil. Burkholderia cepacia (B3) and Pseudomonas aeruginosa (P3) isolated from symptomless oil palm root tissues have shown potential to inhibit the spread of G. boninense. They play a role in keeping the G. boninense population below threshold for BSR initiation by restricting its entry and movement in the palm. When tested on 4 month-old oil palm seedlings inoculated with G. boninense, the bacteria singly and in a mixture suppressed the spread of the pathogen with an epidemic rate of 0.10 - 0.24 units compared to 0.52 units in the control. At 8 months after inoculation, BSR incidence was reduced by 76% in seedlings pre-inoculated with P. aeruginosa (P3). B. cepacia (B3) reduced incidence by 42% and the mixture of P. aeruginosa and B. cepacia by 54%. Inoculation of endophytic bacteria also improved vegetative growth of oil palm seedlings

Altered lignin in oil palm : a novel approach to Ganoderma control.

Oil palm (OP) is an economically-significant crop in the tropics that is prone to a rot caused by Ganoderma: a white rot fungus. Fungi that rot in this manner are extraordinary organisms which degrade lignin, and leave white cellulose exposed. Surprisingly, there are no data concerning the biochemical basis of how Ganoderma rots oil palm in terms of lignocellulose biodegradation. It is necessary to consider this mode of attack for integrated control. The existing literature is concerned particularly with the mode of spread and molecular biology of Ganoderma, which are indirect ways in which to understand and control the disease. The white rot perception opens up new fields such as: (a) especially selecting/transforming for resistant cultivars of oil palm with high lignin content, (b) ensuring that the conditions for lignin decomposition are reduced, and (c) simply sealing damaged oil palm specifically to stop decay. In conclusion, the control of Ganoderma on oil palm will benefit greatly from consideration of the process as one of white rot

First report of cabbage soft rot caused by Pectobacterium carotovorum subsp carotovorum in Malaysia.

Cabbage plants with symptoms of soft rot were sampled from commercial fields in Malaysia during the winter of 2010. Disease symptoms were a grey to pale brown discoloration and expanding water-soaked lesions on leaves. Several cabbage fields producing white cultivars were investigated and 27 samples were collected. The bacteria reisolated from rotted cabbage slices resembled P. carotovorum cultural characteristics and could cause soft rot in subsequent tests. PCR amplification with Y1 and Y2 primers, which are specific for P. carotovorum, produced a 434-bp band with 15 strains. Analysis by ITS-PCR and ITS-restriction fragment length polymorphism identified all the isolates as P. carotovorum subsp. carotovorum. This is thought to be the first report of P. carotovorum subsp. carotovorum in cabbage from Malaysia

First report of Exserohilum rostratum as pathogen of rice brown spot in Malaysia

Leaves with brown spot symptoms were sampled from rice planting areas in the Malaysian peninsula, including Kelantan, Penang, Kedah, Perak, and Selangor, over the planting season from November 2012 to December 2013. The disease was observed on the glumes and leaves of rice plants. Mature lesions were brown with a gray or whitish centre, whereas younger lesions were small, circular, and dark brown or purplish brown. Thirteen isolates were recovered from 100 diseased leaf samples that were plated on PDA medium. The mycelia were white in early stages but after 3 to 4 days, they turned gray or dark gray. Based on morphological characteristics, molecular data (polymerase chain reaction assay and nucleotide sequence analysis) and pathogenicity tests, the causal agent was identified as Exserohilum rostratum [Setosphaeria rostrata]. This is thought to be the first report of E. rostratum as pathogen of rice brown spot in Malaysia

Pathogenicity of Colletotrichum truncatum and its influence on soybean seed quality

Pathogenicity of Colletotrichum truncatum and its influence on soybean seed quality were evaluated by artificial inoculation. C. truncatum enabled to establish as latent infection without showing any visible symptom in all seed components with maximum frequency values of 100% for seed coat, 43.0% for cotyledon and 30.0% for embryonic axes after 4 days of incubation period. The infection level remained the same in all seed components until the end of the incubation period. Fungal infection reduced seed germination by 29.2% and viability by 26.9% than un-inoculated seeds in vitro. Moreover, infection increased the electrolyte leakages compared with control. Under glasshouse conditions, pathogenicity of C. truncatum on seeds and seedlings was more virulent than that of controlled conditions. In the glass house, C. truncatum reduced seed germination and seedling survival by 46.4% and 75.8%, respectively and caused pre- and post-emergence damping-off of seedlings. However, fungal infection by C. truncatum increased protein and oleic acid content and reduced linoleic acid content, but did not change in extracted oil and other fatty acids when compared with un-inoculated seeds after 4 days of incubation

Characterisation of Pectobacterium carotovorum causing soft rot on Kalanchoe gastonis-bonnierii in Malaysia

Soft rot disease can be found worldwide on fleshy storage tissues of fruits, vegetables and ornamentals. The soft rot Pectobacterium carotovorum subsp. carotovorum (Pcc) is an important pathogen of Kalanchoe spp. and other ornamental plants. The disease occurs on crops in the field, greenhouses and during transit, resulting great economic damages. The economic importance of crop loss by soft rot bacteria varies by severity of the disease and value of the crop. A destructive disease on Kalanchoe gastonis-bonnierii was observed in commercial ornamental plant greenhouses in Cameron highland and Melaka, Malaysia in 2011. Samples suspected to be infested with Pectobacterium spp. were brought to the laboratory. In pathogenicity test, a suspension of 106 CFU/ml of strains was able to cause soft rot on leaves and stems. A 434 bp banding pattern on 1% agarose gel was produced in polymerase chain reaction (PCR) amplification of pectate lyase encoding gene (Pel gene). PCR amplification of the intergenic transcribed spacer (ITS) (16S–23S rRNA) ITS region with G1 and L1 primers produced two main bands at about 540 and 570 bp. The ITS-PCR products were digested with RsaI restriction enzyme. For discrimination of the P. carotovorum subsp. carotovorum (Pcc) from P. carotovorum subsp. odoriferum (Pco), all isolates subjected to α-methyl glucoside test. All isolates were identified as Pcc based on phenotypic and molecular methods. This is the first report of soft rot disease caused by P. carotovorum subsp. carotovorum on K. gastonis-bonnierii, in Malaysia

Effect of carrier and temperature on the viability of Burkholderia sp (UPMB3) and Pseudomonas sp (UPM P3) during storage.

This study was aimed at to determine the ability of different carriers to sustain the viability and efficacy of endophytic bacteria: Burkholderia sp (UPMB3) and Pseudomonas sp(UPMP3) during storage. UPMB3 and UPMP3 were formulated as dry formulation using vermiculite and coir dust as carriers and liquid formulation with Luria broth (LB) as the culture substrate. These bacterial formulations developed were assessed for the viability and efficacy as fresh preparations and after nine months stored at 10, 20 and 30°C. Formulations stored at 10 and 20°C provided a longer shelf-life than those stored at 30°C based on viability at monthly intervals over a 9-month storage period. At 10 and 20°C, the LB-based and vermiculite-based formulations were found to be the most stable by sustaining 86% of viable bacteria cells after 6 months of storage. However, at the end of 9 months, the number of viable bacteria cells in both formulations declined to 71 and 57%, respectively. Coir dust-based formulation was the least stable at 10 and 20°C storage, when only 43 and 29% viable cells were detected at the end of 9-months storage