Category Archives: Volume 29 No. 2 (2007)

Optimization of the factors affecting the drying rate of cassava grates in a rotary drum dryer

Author(s): Daniel Leslie S. Tan1, Gener G. Sebial2 and Felix J. Amestoso3


This study determined the optimum effects of temperature, drum rotation and loading rate on the drying rate of cassava grates using the rotary drum dryer in removing moisture from cassava grates. A Central Composite Design was employed to evaluate a total of 15 fractional treatments derived from the 27 treatment combinations of temperature (75, 94 and 113°C), drum rotation (15, 20 and 25 RPM) and loading rate (5, 15, and 25 kg/h). The response surface regression obtained optimum conditions of the factors and predicted values on the stationary point on water loss as well as the rate of water removal.

Results from the canonical analysis of response surface on plain water loss show an optimum combination of temperature of 107°C, drum rotation of 23 RPM and loading rate of 24 kg/h. At 25 kg/h loading rate regardless of any variation of temperature and drum rotation, the rotation of the drum could not be sustained due to heavy load caused by the accumulated weight of the grates inside the drums. The optimum conditions and predicted response values for rate of plain moisture loss were observed to be: temperature of 108°C, drum rotation of 23 RPM, loading rate of 26 kg/h. Response surface plots show the opposite effects between loading rates and temperature on the plain water loss as well as the rate of moisture loss. Response surface plots also revealed that RPM has no effect on the plain water loss and rate of moisture removal

Keywords: dried cassava grates, rotary drum dryer, response surface

Research Note: Abundance and prey spectrum of web spiders in rice agroecosystems of Pangasugan, Leyte, Philippines

Author(s): Sarwshri Gangurde1, Konrad Martin1 and Maria Juliet C.Ceniza2


The cultivation of tropical Asian rice, which may have originated 9,000 years ago, created an agricultural ecosystem of unrivalled ecological complexity. A complex arthropod communitiy is inhabiting in the rice ecosystem, including pest and beneficial species. Concerning beneficials, the spiders are among the very commonly encountered species. A study was conducted in the irrigated tropical rice fields of Leyte, Philippines on the abundance and their potential for natural biological control. the objective of this study was to record, identify and count individuals of selected web building spider species and evaluate the prey spectrum at different stages of rice growth. It was observed that abundance of spiders in the rice ecosystems occurred only starting at the tillering stage when the preferred host plant stage for the prey species was reached. the most dominant species of spiders encountered were Tetragnatha species. However, in the latest stage of rice development, Argiope species were the most dominant spiders. Prey species included mainly the pest species of the rice plants, such as the hoppers, rice bugs and other smaller insects and in addition the other predatory species such as the coccinellid beetles, dragonflies and parasitic hymenopterans were also observed. The web building spiders showed more activity in the late afternoon than in early morning.

Keywords : Tetragnatha, Argiope, prey spectrum, ricefields, spider fauna

Research Note: Effect of tidal inundation on some chemical properties of soil of the Sundarbans (India)

Author(s): Tanumi Kumar and Monoranian Ghose


Soil samples from twenty seven sites of Indian Sundarbans were analysed for some chemical parameters, These sites were divided into three inundation types namely, diurnal, usual springtide and summer springtide. The study demonstrated that most of the soil properties significantly varied with inundation type. Sites inundated by usual springtides exhibited lowest concentrations of pH, salinity (Sal), available phosphorus (I)), and exchangeable potassium (K), sodium (Na) and magnesium (Mg), whereas summer springtide inundated sites had the highest concentrations of Sal, organic carbon (OC), available nitrogen (N), Na, K and Mg. Highest level of P and lowest N in the diurnally inundated sites could be attributed to increased mobility of phosphates and denitrification or volatilization losses of inorganic nitrogen in the soils respectively, Highest concentration of in summer springtide inundated sites could be attributed to increased ammonium ion mobility in the soils.

Keywords : Indian Sundarbans, tidal inundation, soil parameters, relationship.

Influence of waterlogging stress and benzyladenine application on tomato grafted to eggplant

Author(s): Mary Ann Jully B. Regis1 and Misael T. Diputado, Jr.2


Under waterlogged conditions, the non-grafted tomato plants had significantly lower survival rate (53%), compared to the 100% survival rating of grafted plants. Both grafted and non-grafted plants while under waterlogged conditions had high leaf stomatal resistance, low transpiration rate and high stress rating, compared to the non-waterlogged plants. However, one week after resumption of aerobic soil conditions, both stomatal resistance and transpiration as well as stress rating returned to normal in grafted plants unlike in the non-grafted plants which continued to show high stomatal resistance, low transpiration rates and high stress rating. The morphological changes associated with stress in the plant regardless of treatments were cupping, drooping and eventual wilting of leaves. Due to severe stress under waterlogged conditions, the non-grafted plants had significantly lower yield which was just about 41% that in grafted plants. The grafted, non-waterlogged plants had comparable yield with the non-grafted, non-waterlogged plants.
Application of benzyladenine was not effective in alleviating waterlogging stress effects on both grafted and non-grafted tomato.

Keywords : grafted tomato, eggplant, waterlogging, benzyladenine, stomatal resistance, transpiration

Reaction of hybrid rice and component lines to rice black bug [Scotinophara coarctata (Fabricius), Hemiptera: Pentatomidae]

Author(s): Brian S. Sinangote1, Reny G. Gerona1, Ma. Dinah M. Reformina1, Ma. Gina M. Babb2 and Lucia M. Borines1


A limiting factor to hybrid rice production in the Philippines is the susceptibility of hybrid rice component lines to diseases and insect pests. Rice black bug (Scotinophara coarctata Fabr.) is among the insect pests and is the newest addition to the list of major pests of rice. This study aims to determine the reaction of hybrid rice component lines to rice black bug (RBB).
Eighty-four (84) hybrid rice componet lines were evaluated for their reacton to RBB. Two batches of unreplicated preliminary screening of the lines were done. Two sets of re-evaluation were also conducted. The standard evaluation system for rice (SE) was followed.
No lines showed resistance to RBB during the preliminary screening. Twentysix (26) lines which showed a moderately susceptible reaction were re-evaluated in a replicated experiment. Among them, R2-6 and IR60819R showed resistance, PR4B showed an intermediate reaction and GUI99 showed a moderatley susceptible reaction. These promising lines were further valueated against RBB and results showed thatR2-6 was rated highly resistant (HR), IR60819R was resistant (R), PR4B was moderately resistant (MR) and GUI99 was moderately susceptible (MS). Most of the hybrid rice component lines are susceptible to RBB.

Keywords : Hybrid rice, component lines, reaction, rice black bug

Comparative suitability of two culture media to the in vitro growth of embryos of three coconut types

Author: Tessie C. Nuñez


Using a suitable medium for specific plant genotype greatly improves the efficiency of the in vitro culture method. The Visayas State University (VSU)-based National Coconut Research Center -Visayas (NCRC-V) evaluated the comparative suitability of the COGENT medium and VSU-modified Y3 (mY3) as in vitro culture media for coconut embryos using Albuera Dwarf (ALD), Baybay Tall (BAYT),and the VSU-developed Coconiño x Makapuno (VMAC1) hybrid. These two media differ in vitamin components, iron concentration and state during the first two stages of culture, namely germination and first subculture.
Results showed that mY3 was more suitable for the in vitro germination and development of the coconut embryos than the COGENT medium. Significantly higher germination rates were observed in BAYT, ALD, and VMAC1 cultured in the semi-solid mY3 than those in the liquid COGENT medium from the first week until the fourth week of initial culture. Germination rates of 100%, 85.8% and 84.5% were obtained from CÑO x MAC, ALD, and BAYT, respectively. Furthermore, significantly higher percentages of germinating embryos with developing shoot and root were observed in the semi-solid mY3 than in the liquid COGENT. Likewise, better growth of plantlets in liquid mY3 was noted during the fourth and fifth months of culture.
Among coconut types, VMAC1 had the highest germination rates in the two media and the best growth in mY3. BAYT had better growth in the COGENT medium while ALD had better shoot development in mY3.

Keywords : coconut, Cocos nucifera L., coconut embryo culture, in vitro culture media, in vitro growth

Screening of endophytic microorganisms from sweetpotato for the production of antimicrobial compounds

Author(s): Julie D. Tan1, Edmundo L. Sanchez, Jr.1, Michiko Tanaka2, Taiki Katayama2, Kozo Asano2 and Fusao Tomita2


This study was an attempt to isolate endophytic microorganism with antimicorbial properties from sweetpotato that are grown in the Philippines. Endophytic microorganims were isolated from surface-sterilized stem cuttings of selected Philipine sweetpotato varieties such as BSP-SP-17, BSP-SP-22, and NSIC-SP-25. The isolates were purified and tested for antimicrobial activities using spot and streak inoculation methods against Lasiodiplodia theobromae (sweetpotato rot-causing mold), Colletotrichum gloesporoides (yam anthracnose-causing mold)

Keywords : sweetpotato, endophytes, zone of inhibition, bacteria, fungi, screening

Species and structure of forests in Tampakan Highlands, South Cotabato, Philippines

Author(s): Justino M. Quimio and N. L. Quilario


The study was conducted in a logged-over forest of Tampakan Highlands that has an elevation of about 1,350 m. It was aimed to assess the timber stocking rate and level of floristic diversity of the forests that may be influenced by future mining operation in the area. Data collection and data presentation were undertaken following the BraunBlanquet methodology.
Results indicate that Tampakan forests are highly productive, with relatively large trees and highly diverse species despite past logging. Forty-nine (49) timber species and timber stocking rate of 69cu m/ha were recorded in the forests. A total of 312 plant species had been listed in the 73 plots or in a combined area of 1.93 ha. The forest still contained most species of the original old-growth forest. The pioneer vegetation dominated by Piper aduncum was very low in species richness. This indicated the importance of natural forest in preserving native flora.
It was recommended that zoning plan be prepared to demarcate areas that need to be reserved as permanent forest and more effective forest protection schemes be devised. Enrichment planting in pioneer areas should also be undertaken, with active participation of the B’laan tribe.

Keywords : Braun-Blanquet, floristic inventory, Philippine forest

Toxic heavy metal biosorption by some marine bacteria isolated from the sediments of industrial effluents of Iligan Bay

Author(s): Arvin C. Balala1 and Jose M. Oclarit2


Heavy metal-resistant marine bacteria were isolated from the sediments of Iligan Bay near the effluents outlets of certain factories. Isolation was done using marine agar fortified with corresponding different heavy metal concentrations. Isolates were grouped using their morphological and colonial growth characteristics. Among the purified isolates(61), 19 were cadmium-resistant, 29 were lead-resistant and 13 were mercury-resistant. These isolates were tested for their absorptive capability using marine broth added with metal ions: 23.20 µg of Cd, 250.24 µg of Pb and 495.66 µg of Hg, and consequently analyzed using Atomic Absorption Spectrophotometric(AAS) method. From these isolates, 10 heavy metal-resistant species with relatively high absorptive efficiency were identified using conventional method and API 20E Test Kit. Out of ten isolates, 3 were Gram-positive and 7 were Gram-negative rods. All Gram-positive bacteria belong to the genus Bacillus and were found to absorb lead metals at 94% absorptive efficiency. However, Enterobacter sp. 2 had the highest absorptive efficiency for Cd at 99% among Gram negative bacteria followed by Chryseomonas sp. 2 with 96% biosorption. Furthermore, among the mercury resistant isolates, Pseudomonas sp. had the highest absorptive efficiency at 79%. Only those heavy metal-resistant isolates which exhibited the highest absorptive efficiency were able to form a zone of growth promotion around a heavy metal-containing filter paper disk which suggests that these bacteria have accumulated heavy metals in their cells. The presence of heavy metal-resistant bacteria is helpful in cleaning up or remediating metal contaminated environments released from industrial effluents.

Keywords : absorptive efficiency, zone of growth promotion, atomic absorption spectrophotometer, heavy metal-resistant bacteria

Guide to the fresh water fishes in Tubod River, Lake Danao and its outlet, Inawasan River in Leyte, Philippines.

Author(s): Wasantha S. Weliange1, Jimmy Pogosa2, Chandima Lankaadikara1, Maria Leichtfried3 and
Friedhelm Göltenboth4


Description and key for the identification of 21 fresh water fish species occur Tubod River (18 species), Lake Danao (4 species); and its outlet; Inawasan River (1species) in Leyte Main Island in Philippines are presented together with notes and ecology of the species.