Genetic diversity and morphological variations of goosegrass [Eleusine indica (L.) Gaertn] ecotypes in Malaysia

Goosegrass [Eleusine indica (L.) Gaertn] has been a nuisance to growers in Malaysia due to its increased resistance to commercial herbicides, rapid growth and dissemination, and interference with agricultural practices. In the course of developing an apt integrated management to control goosegrass, more information of this weed is needed. The aim of this study was to look into variations among the goosegrass ecotypes sampled throughout Malaysia from the aspects of genotype and phenotype. Sequence-related amplified polymorphism (SRAP) markers were employed in investigating the genetic diversity and relationships among the 18 goosegrass ecotypes. Consequently, 5 primer combinations amplified 13 fragments with the polymorphism rate of 69.23%. At 74% similarity, the ecotypes were clustered into 6 groups. Phenotypic variability of the goosegrass ecotypes was assessed by observing their morphology, growth and seed traits. Goosegrass ecotypes were sorted into 3 major groups at the genetic distance (DIST) of 0.37. Concurrences of the evaluated genetic distance, ecotypes with the closest and most distant relationships were assembled together in Group I which showed high variation even among ecotypes in the same group. Results obtained thus implied high molecular and morphological variations of the goosegrass ecotypes in Malaysia

Controlling Musa AAA Berangan crown rot disease using UV-C irradiation

Crown rot, caused by complex pathogen, is the most serious postharvest problem in bananas. UV-C irradiation has the potential to be used as an alternative method to reduce our dependence on postharvest agrochemicals due to its germicidal properties. It could also promote resistance against pathogens. The aim of this work was to evaluate the in vitro effects of UV-C on three major fungi isolated from Berangan banana, namely: Lasiodiplodia theobromae, Colletotrichum musae and Fusarium spp., and to evaluate the potential of UV-C in controlling crown rot disease on naturally infected banana. The applied UV-C doses varied from 0.01 to 0.30 kJ m-2 and the treatment condition was under the ambient temperature (28±2°C). Mycelial growth, sporulation intensity and conidial germination of each fungus were evaluated in vitro after fungal exposure to different UV-C doses. Mature green banana was exposed to UV-C to examine the effects of UV-C on disease incidence, severity, colour and texture of the fruit crowns. The disease incidence and severity were carried out after ripening initiation using 1 mL L-1 ethylene for 24 h. The fruits were then allowed to ripen at 27°C/85% relative humidity and observations were carried out at day 0 (before ripening initiation), 1, 3, 5 and 7 (after ripening initiation). UV-C irradiation effectively controlled the mycelial growth, sporulation and conidial germination of the isolated fungal pathogen at dose 0.015 kJ m-2. UV-C irradiation was able to control the severity of crown rot disease on Berangan banana at a satisfactory level when irradiated at dose of 0.01 kJ m-2. Hence, UV-C irradiation could be used as an alternative to chemical fungicides for management of crown rot disease

Histological study of the interaction between Exserohilum Longirostratum, barnyard grass, and rice var. MR219

The course of infection and the development of Exserohilum longirostratum (Subramanian) Sivanesan on barnyardgrass (Echinochloa crus-galli (L.) Beauv. spp. crusgalli) and rice (Oryza sativa L. var. MR219) were studied under light microscopy (LM) and scanning electron microscopy (SEM). Observation under SEM indicated similarity of the gross anatomy of both rice and barnyard grass leaves. Meanwhile, germination of the conidium of E. longirostratun was found to be not influenced by inoculation time as the conidia started to germinate 4 hours after the inoculation on both leaf surfaces. However, the patterns and number of germ tubes and appressoria formation were influenced by host plants. On barnyard grass, the primary infection process consisted of the conidial germination, elongation of the germ tube, formation of the appresorial initials, maturation of the appressoria, and formation of secondary hyphae. Successful penetration was followed by an extensive colonization of the invaded epidermal cell wall. Observation of the cross section revealed that the infection hyphae expanded into a spherical vessel and colonized the cells, causing the collapse of the epidermal cells and resulting in the formation of necrotic lesions of infected and adjacent tissue. Although fungus successfully grew and produced germtube on rice, both the primary infection process and the successful penetration of the cuticle were not observed on rice. The conidia germinated and produced slender and thin germ tube, with occasional appressorium formation. Germ tubes and appressoria formation on the barnyard grass (70% and 92%, respectively) were significantly higher as compared to rice leaves (51% and 10%). It was observed that the mycelium infected barnyard grass much faster (less than 24 h) than the conidia as it immediately formed appressorium without having the need, like the conidia, to germinate first. These results suggest that it may be possible to utilize E. longirostratum as a bioherbicide to control barnyard grass under rice production in Malaysia

Microbial starter for the enhancement of biological activity of compost tea.

Compost tea is gaining importance as an alternative to chemical fertilizers and pesticides. The microbial population in the compost tea contributes toward its effectiveness. An attempt was made to enhance the biological activity of compost tea by fortification with microbial substrates. Humic acid and yeast extract (4:7 w/w 100 g-1 compost) when used as microbial starter during brewing of compost tea significantly (P less than or equal to 0.05) enhanced the microbial population. There was a ten to hundred fold percentage increase for total bacteria, fungi and actinomycetes compared to control. The stability of microbial enriched compost tea was maintained up to four months of storage based on significantly higher number of viable cell counts when compared to compost tea without substrates (control). The viable microbial cell counts over a storage period of six months was 8.5x10(9), 4.6x10(6), 3.5x10(4), 3.9x10(4), 1.4x10(5), 4.8x10(4) and 7.3x10(5) for other bacteria

ANTAGONISTIC BACTERIA AGAINST SCHIZOPHYLLUM COMMUNE FR. IN PENINSULAR MALAYSIA

Schizophyllum commune Fr., is one of the important fungi, causes brown germ and seed rot of oil palm. Biodiversity of antagonistic bacteria from oil palm plantations in Peninsular Malaysia is expected to support in development of biopesticide. Isolation with liquid assay and screening antagonistic bacteria using dual culture assay were carried out in the bioexploration. A total of 265 bacterial isolates from plant parts of oil palm screened 52 antagonistic bacterial isolates against 5. commune. Bacterial isolates were identified by using Biolog* Identification System i.e. Bacillus macroccanus, B. thermoglucosidasius, Burkholderia cepacia, B. gladioli, B. multivorans, B pyrrocinia, B. spinosa, Corynebacterium agropyri, C. misitidis, Enterobacter aerogenes, Microbacterium testaceum, Pseudomonas aeruginosa, P. citronellolis, Rhodococcus rhodochrous, Serratia ficaria, Serratia sp., S. marcescens, Staphylococcus sciuri, Sternotrophomonas maltophilia.Key words : Schizophyllum commune, biodiversity, antagonistic bacteri

Effect of Exserohilum monoceras (Drechslera) leonard & suggs on the competitiveness of Echinocloa cruss-galli (L.) P. Beauv

The use of bioherbicide to reduce interference by barnyard grass in rice cropping system has been suggested but has not been reported. Against this conceptual background, a mini-plot study was conducted to simulate the efficacy of Exserohilum monoceras to reduce competitiveness of barnyard grass in rice using replacement series experiment. The effect of E. monoceras on rice was negligible, as it did not cause any infection. Severe infection was observed on barnyard grass inoculated with this fungus at all plant densities as indicated by high AUDPC values (ranges from 610.35-468.28 unit2) and fast disease progress rates (r L= 0.48 logit/day). Rice biomass in mixture with diseased weed was higher than in the presence of healthy weed, and is not significantly different from rice biomass in the non-weedy control. In the inoculated experiment, at lower weed density, competition between barnyard grass and rice was not apparent despite the fact that the weed growth was reduced. As the weed density increased, rice continued to grow, but barnyard grass was suppressed; the growth difference was bigger and more measureable. In the non-inoculated control, the interaction between barnyard grass and rice was observed at 2:2 ratio, but at 3:1 in the inoculated experiment, indicating that rice was more competitive over barnyard grass. It took three barnyard grass to equal the shoot dry weight of one rice plant. This study provides strong evidence of the ability of E. monoceras in reducing the competitive ability of barnyard grass and thus provides new opportunities for the future of biological weed control in Malaysia

First report of Lasiodiplodia theobromae causing stem Canker of Jatropha curcas in Malaysia.

Physic nut (Jatropha curcas L.) is an important biofuel crop worldwide. Although it has been reported to be resistant to pests and diseases (1), stem cankers have been observed on this plant at several locations in Peninsular Malaysia since early February 2008. Necrotic lesions on branches appear as scars with vascular discoloration in the tissue below the lesion. The affected area is brownish and sunken in appearance. Disease incidence of these symptomatic nonwoody plants can reach up to 80% in a plantation. Forty-eight samples of symptomatic branches collected from six locations (University Farm, Setiu, Gemenceh, Pulau Carey, Port Dickson, and Kuala Selangor) were surface sterilized in 10% bleach, rinsed twice with sterile distilled water, air dried on filter paper, and plated on water agar. After 4 days, fungal colonies on the agar were transferred to potato dextrose agar (PDA) and incubated at 25°C. Twenty-seven single-spore fungal cultures obtained from all locations produced white, aerial mycelium that became dull gray after a week in culture. Pycnidia from 30-day-old pure cultures produced dark brown, oval conidia that were two celled, thin walled, and oval shape with longitudinal striations. The average size of the conidia was 23.63 × 12.72 μm with a length/width ratio of 1.86. On the basis of conidial morphology, these cultures were identified as Lasiodiplodia theobromae. To confirm the identity of the isolates, the internal transcribed spacer (ITS) region was amplified with ITS1/ITS4 primers and sequenced. The sequences were deposited in GenBank (Accession Nos. HM466951, HM466953, HM466957, GU228527, HM466959, and GU219983). Sequences from the 27 isolates were 99 to 100% identical to two L. theobromae accessions in GenBank (Nos. HM008598 and HM999905). Hence, both morphological and molecular characteristics confirmed the isolates as L. theobromae. Pathogenicity tests were performed in the glasshouse with 2-month-old J. curcas seedlings. Each plant was wound inoculated by removing the bark on a branch to a depth of 2 mm with a 10-mm cork borer. Inoculation was conducted by inserting a 10-mm-diameter PDA plug of mycelium into the wound and wrapping the inoculation site with wetted, cotton wool and Parafilm. Control plants were treated with plugs of sterile PDA. Each isolate had four replicates and two controls. After 6 days of incubation, all inoculated plants produced sunken, necrotic lesions with vascular discoloration. Leaves were wilted and yellow above the point of inoculation on branches. The control plants remained symptomless. The pathogen was successfully reisolated from lesions on inoculated branches. L. theobromae has been reported to cause cankers and dieback in a wide range of hosts and is common in tropical and subtropical regions of the world (2,3). To our knowledge, this is the first report of stem canker associated with L. theobromae on J. curcas in Malaysia

Effect of dactylaria higginsii on purple nutsedge (Cyperus rotundus) interference with pepper (Capsicum annuum L)

Greenhouse studies were conducted to evaluate the effect of the fungal pathogen, Dactylaria higginsii, on purple nutsedge interference with 'Capistrano' pepper (Capsicum annuum). Purple nutsedge plants established from tubers were planted at initial densities of 40, 80,160, and 320 plants m-2with pepper in 35-cm diam pots with a commercial potting medium, under nonlimiting fertilization and irrigation conditions. Three to four-leafstage purple nutsedge and four-leafstage pepper plants were inoculated by spraying D. higginsii in 0.5% Metamucil, a carrier; the treatments were carrier only, 104 conidia ml1 carrier, or 106 conidia conidia ml1 carrier. Purple nutsedge at all tuber densities significantly reduced pepper yield in the absence of D. higginsii. Percentage yield loss of pepper was greater in treatment with 104 conidia ml1• However, percentage yield loss of pepper was negligible in treatments with D. higginsii at 106 conidia ml1 when compared to the non-weedy control. The disease progress rate was significantly faster in treatments with 1(1 conidia ml1 (rc = 0.113 - 0.123) compared to 104 conidia mlJ (rc = 0.049 - 0.050). At 106 conidia ml1 , D. higginsii reduced nutsedge interference, provided greater nutsedge control, and increase pepper yield compared to weedy checks

Producing transgenic rice with improved traits and yield – how far have we come?

Improving rice production is of current global concern so that food security is maintained especially in developing nations where rice remains as the staple food. With the aid of molecular biology, various isolated genes conferring to abiotic, biotic and herbicide stress tolerance has been successfully transferred into rice. Attempts have also been made to enhance grain yield, nutritional characteristics, fragrance and photosynthetic capacity of rice. The success of a commercialized transgenic rice largely depends on the biosafety and environmental risks assessments as these information translates into consumers’ acceptance towards genetically modified (GM) rice. As the renowned Golden Rice has received the green light for field trial in the Philippines and Bangladesh, this would serve as a catalyst for better acceptance of GM food crops. A brief case study on the commercialization of transgenic BT rice in China will also be discussed. The review aims to bring useful insights for future endeavors in improving traits for rice through genetic engineering

Effect of Selected Pesticides on Survivality of Exserohilum longirostratum, A Bioherbicide for Itchgrass

Four commercial formulations of herbicides and four fungicides were evaluated for their toxic effects on germination of Exserohilum longirostratum.  At the recommended rates, one of the herbicides recommended for grassy weed control was compatible with E. longirostratum.  E. longirostratum conidia germination was not affected by Paraquat but was totally inhibited by Glufosinate, Glyphosate and Fenoxyaprop-p-ethyl. At lower concentrations, most herbicides were less toxic except Rumpas. The fungicide Benlate at recommended rate has no effect on E. longirostratum. Score and Topper reduced germination more than 50% at recommended rate and growth was distorted. Spore germination was totally inhibited at all concentrations with Dithane.  Based on high germination and appresorium development, Sapol and Tween 20 is suitable as carrier for this fungus.  Paraquat and Bentazone can be used with E. longirostratum either with tank mixing or as split applications but at concentration less than the recommended rate