Identification,pathogenicity and control of powdery mildew caused by Erysiphe elevata on Eucalyptus pellita in Sumatra,Indonesia

Powdery mildews are biotrophic ascomycetes that do not typically kill their hosts, but instead interfere with normal plant growth. In Indonesia, white powdery spots were observed forming on the upper part of fully developed leaves of Eucalyptus pellita planted in sand beds of a clonal nursery. Thus, this study aimed to identify the causal agent of eucalypt powdery mildew in Indonesia as well as to develop control strategies to better manage the disease. Pathogen identification was based on morphology, molecular characterization of DNA sequencing the ITS region and pathogenicity test. In addition, considering that some powdery mildews are inhibited by free moisture on leaves, efficacy of foliar watering was tested for disease control. Phylogenetic analyses showed that isolates collected from infected eucalypt plants grouped together with other sequences of the Erysiphe elevata clade with bootstrap support of 99%; a similar result was also confirmed by morphological observations. Pathogenicity of powdery mildew on eucalypt plants was confirmed through artificial inoculation, thus fulfilling the Koch's postulates. For disease control, foliar watering reduced the incidence of powdery mildew on mother plants. The reduction of the disease incidence began to be more evident at 2 weeks after trial establishment, and in the fourth week, the incidence was below 10% in all three treatments, while the control was above 20%. Therefore, we concluded that E. elevata is the causal agent of powdery mildew in Indonesia and that one application of foliar watering per week was enough to minimize the disease impact in the nursery.     

Design considerations of variable rate liquid fertilizer applicator for mature oil palm trees

Precision Agriculture - This research study focuses on the design of variable rate liquid fertilizer applicator which can measure the NPK status of soil and applies N, P and K nutrients...     

Effects of habitat type, vegetation structure, and proximity to forests on bird species richness in a forest–agricultural landscape of West Java, Indonesia

To halt biodiversity loss in the humid tropics of developing countries, it is crucial to understand the roles and effects of human-modified landscapes with fragmented forest remnants in maintaining biodiversity while fulfilling the demands of local communities and reducing poverty. To implement appropriate landscape planning for conserving biodiversity and ecosystem functioning, appropriate information is required about parameters of habitat suitability among various anthropogenic habitats with a range of distances to forests and vegetation characteristics, but such information is limited. We examined differences in avian communities between a remnant forest and four types of man-made forest (two mature plantations and two agroforests) in a forest–agricultural landscape of West Java, and we analyzed the effects of both local and landscape factors on various types of species richness in this landscape. The results from non-metric multidimensional scaling revealed avifauna in the two types of agroforest was clustered separately from that in the remnant forest, mainly because drastic declines in the abundance of forest specialists (including IUCN red-listed species) and their replacement with open-habitat generalists. The mixed-tree agroforests were colonized by 30 % of forest specialists and forest-edge species found in the remnant forest, and maintained the highest richness of species endemic to Indonesia among man-made forests, implying that some forest specialists and endemics might have adapted to ancient landscape heterogeneity. High proportion of insectivorous birds was found in the remnant forest (more than 50 %) and drastically decline in man-made forests, although the species richness of insectivores did not decline significantly in broad-leaved plantations. We concluded that protection of remnant forests should be prioritized to conserve forest bird diversity. However, as different environmental factors affected the richness values of different ecological groups, appropriate landscape design and habitat management could improve functional diversity in forest–agricultural landscapes in the tropics.     

Isolation of alginate lyase‐producing bacteria and screening for their potential characteristics as abalone probionts.

This study is aimed at the isolation and screening of alginate lyase‐producing bacteria from the gastrointestinal tracts of hybrid abalone, Haliotis rubra x H. laevigata, as probiotic candidates. Six bacterial isolates were detected to produce alginate lyase. Of these, the isolate with the highest alginate‐lyase activity was identified as Enterobacter ludwigii strain EN‐119, displaying 99% similarity of 16S rDNA sequence. Further assays indicated that E. ludwigii showed good viability and stability when it was incorporated into manufactured pellets and stored at 4°C for 7 days. The isolate also had high tolerance of high salinity (35 mg/L), low pH in simulated stomach juice (5) and to simulated intestinal juice containing surfactants such as bile salts and gastric enzymes (pepsin and trypsin). Additionally, a short, preliminary study indicated that supplementation of E. ludwigii via manufactured pellets improved the total weight gain and specific growth rate of hybrid abalone. These results suggest that E. ludwigii is a potential probiont for shortening the culture period of hybrid abalone.     

Development of sensory organs and changes of behavior in larvae of the sutchi catfish, <Emphasis Type="Italic">Pangasianodon hypophthalmus</Emphasis>

Larvae of the sutchi catfish Pangasianodon hypophthalmus hatch with morphologically immature features, but sensory organs develop rapidly as the fish grow. By 1 day old, yolk-sac larvae showed notochord flexion, and by 2 days old larvae were observed to have consumed a large part of the yolk sac. At this stage, larvae had well-developed eyes, olfactory organs with ciliated receptor cells, inner ears with semicircular canals, and numerous taste buds, and they commenced ingestion of rotifers, Artemia nauplii, and artificial compound feed. Two-day-old larvae had many free neuromasts on the surface of the head and flanks and clearly showed rheotaxis. By 20 days old, free neuromasts in postflexion larvae had sunk under the skin. At this later stage, larvae swam against a water current and schooled along the side of the fish tank. Rapid development of sensory organs and notochord flexion would be an adaptation for survival in conditions of flowing water, as in the Mekong River. In this study, we show that development of the lateral line in the postflexion stage seems to be closely related to larval behavior, suggesting that these developments could be essential for sutchi catfish larvae survival.     

Multi-temporal analysis of terrestrial laser scanning data to detect basal stem rot in oil palm trees

Terrestrial laser scanning technology is an advanced active remote sensing ranging method that is well suited for yielding high-resolution scans of the morphology of a tree, which is an indicator of the health of the plant. The Ganoderma boninense fungus causes basal stem rot (BSR), which threatens the oil palm industry in Malaysia. To date, the current practice of inspection in a plantation is conducted every 6 months. Monitoring the progress with a closer gap is required to comprehend if any changes can be seen earlier than 6 months. Therefore, the objectives of this study were to identify the most suitable parameters of the oil palm trees to detect the BSR disease based on temporal laser scanning data and to identify suitable time frames for monitoring the progress of the symptoms of the disease. Terrestrial laser scanning data was used to analyse changes in the crown and frond metrics of oil palm trees with two different scan durations i.e., 2- and 4-months after the first scan. This spatio-temporal data is important in the precision agriculture field for better oil palm management, to understand the disease development for long-term solutions and also to provide a fast response so that appropriate treatment can be given to the palm as early as possible. Statistical analyses, i.e., the Kruskal–Wallis test with α?=?0.05 and the Wilcoxon post-hoc test, were conducted to determine significant differences in the parameters at different points in time. The results show that crown strata number 17 (850 cm from the top) and the crown area were the most suitable parameters to be used. Furthermore, the oil palm trees with BSR can be detected by comparing the 4-month scan or the second 2-month scan. The results have shown that the effect of Ganoderma boninense infection can be differentiated at the later stage. In conclusion, the changes can be measured at 4-months after the first inspection, thus helping to preventing crop losses.

     

An experimental study of search in global social networks

We report on a global social-search experiment in which more than 60,000 e-mail users attempted to reach one of 18 target persons in 13 countries by forwarding messages to acquaintances. We find that successful social search is conducted primarily through intermediate to weak strength ties, does not require highly connected "hubs" to succeed, and, in contrast to unsuccessful social search, disproportionately relies on professional relationships. By accounting for the attrition of message chains, we estimate that social searches can reach their targets in a median of five to seven steps, depending on the separation of source and target, although small variations in chain lengths and participation rates generate large differences in target reachability. We conclude that although global social networks are, in principle, searchable, actual success depends sensitively on individual incentives.     

Evaluating vegetation recovery following large-scale forest fires in Borneo and northeastern China using multi-temporal NOAA/AVHRR images

This study evaluated whether a normalized difference vegetation index (NDVI), derived from 8-km-resolution National Oceanic Atmospheric Administration (NOAA) Pathfinder AVHRR (advanced very high resolution radiometer) land (PAL) data, is appropriate for monitoring recovery following large-scale forest fires. Recovery processes were examined after fires on the island of Borneo and in northeastern China in 1983 and 1987, respectively. Based on pre- and post-fire NDVI differences (NDVId), six damage classes were established. Post-fire changes in land cover were monitored using (1) the average NDVI of all pixels corresponding to each damage class (A-NDVI) and (2) the ratio of a fire-affected A-NDVI to a non-fire-affected A-NDVI (QNDVI). Burn areas located by an NDVId threshold value were similar to reported burn areas. Both A-NDVI and QNDVI values signaled vegetation recovery, but the QNDVI gave much better results. For both the 1983 Borneo and 1987 northeastern China fires, QNDVI values dropped at the time of the fire and increased for about 4 years afterwards, although a 4-year period is obviously less than the time required for biomass recovery. Trends at the two study sites diverged after this period, however. The QNDVI values for multiple fire events in Borneo (in 1983, 1987, 1991, 1997, and 1998) showed that recovery times varied with the size of the burn area, but not with the damage class of the same event, whereas the severe-class QNDVI values for the fire in northeastern China in 1987 were still lower than the control value 10 years after the fire.     

Facing the peat CO2 threat: digital mapping of Indonesian peatlands—a proposed methodology and its application

Journal of Soils and Sediments - We conducted this project to develop a feasible method for mapping tropical peat lands of Bengkalis Island—as a test site—in Indonesia. The method based...     

Effects of electrolyte enhanced water on culturing giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

In this work, electrolyte enhanced water (EW) was used to determine the effect of EW in culturing freshwater prawns. The giant freshwater prawn juvenile, Macrobrachium rosenbergii, was exposed to different concentrations of EW in experiment 1. The EW was added into the water and labeled as treatment A1 which consists of 1% anolyte and 0.5% catholyte. In the respective treatments, the proportion of anolytes and catolytes are as follows: treatment B1 (1% anolyte and 1% catholyte), treatment C1 (2% anolyte and 0.5% catholyte), treatment D1 (2% anolyte and 1% catholyte), and control (without EW). All these treatments were run in three replicates for each treatment including the control. In the first experiment, the growth of the M. rosenbergii under treatment A1 showed an increased in growth as compared to the control after 56 days of exposure with a significant difference of p?<?0.05. The survival rate of prawns is higher in treatments A1 (73%), B1 (70%), and control (63%) as compared to treatments C1 (53%) and D1 (50%). In the second experiment, the treatment using EW concentration of 1% anolyte and 0.5% catholyte was used as the most suitable concentration for the prawn culturing tested with recirculating aquaculture system (RAS). The treatments used in the second experiment was labeled as A2 (EW), B2 (EW and RAS), C2 (RAS), and control. Treatment B2 showed a higher growth and survival rate and was significantly different to the other treatments. The colony-forming unit (CFU) showed a lower count of bacteria in all experiments that used EW as compared to the control. The concentration of 1% of anolyte and 0.5% of catholyte has shown to improve the growth and survival rate of the M. rosenbergii culture when combined with the RAS. This study showed a potential use of electrolyte enhanced water in culturing giant freshwater prawn.