Category Archives: Volume 32 No. 1 (2010)

Organic Agriculture: The logical sequence to modern chemical agriculture in the Philippine context

Author: Teodoro C. Mendoza


Organic agriculture, which is also described as less fossil fuel-dependent and agrochemical-free agriculture, is now perceived as the logical sequence to the food production systems which are dependent on agro-chemical inputs from production to processing. This paper discusses the situations and factors that should be considered in the crucial process of shifting approaches to food production systems to achieve food security in the new millennium.
In the past, farmers shifted with government support to chemical agriculture to produce the food requirements of the burgeoning population. Soils are badly degraded from the use of chemical fertilizer and pest populations are so complex and crop failures associated with no application of pesticides are widely known. Withdrawal from agrochemical use will mean huge yield reduction without soil fertility restoration and any further yield decline is unacceptable both to the farmers and the consumers. The shift to organic agriculture requires soil fertility restoration, breeding/selection of seeds for organic agriculture, adoption of cultural management practices and shifting monocropping to diverse planting, integrated nutrient management and ecological pest management systems, among others.
Farmers need full government support to shift to organic agriculture. Moreover, the society or the consumers need to realize that the shift to organic agriculture is for their own benefit, hence, they need to appreciate, understand, cooperate, patronize and put premium value to organic agriculture products. The superior quality of organic products should be appreciated and should be translated to higher price. Organic agriculture production should be complemented with a change in consumer preferences or consumption patterns. It should be translated into a demand that will lead to changes in the supply side thereby changing the agricultural production systems that our Filipino farmers currently adopt.

Keywords : Organic agriculture, chemical agriculture, monocropping, biodiverse farming, fertilizer, pesticides, agroecosystems

Annals of Tropical Research 32(1):112-129(2010)

Isozyme polymorphism to detect genetic diversity of Jatropha curcas (L.) in India

Author(s): Rekha R. Warrier, P. Priyadharshini, S. Senthil Vadivu, B. Devika Nagalakshmi, C. Savitha, R. Anandalakshmi,
A. Nicodemus, and B. Gurudev Singh


The Indian Government identified Jatropha curcas L. as the most suitable treeborne oilseed for the production of bio-diesel. The species has spread to many parts of India due to its ability to withstand adverse conditions. Breeding of inter and intra specific Jatrophas for the exploitation of hybrid vigour is one of the most economical means of tree improvement. To study the genetic base of the species distributed in India, 55 accessions of J. curcas from Jammu to Kanyakumari and Jodhpur to Kolkata were assessed using isozyme markers. Fifteen enzyme systems were evaluated for their efficacy in distinguishing the accessions. While three (formate dehydrogenase, malate dehydrogenase and peroxidase) were found useful, twelve did not exhibit any variation and had fixed monomorphic alleles. Each polymorphic enzyme system produced one well resolved polymorphic region except peroxidase which had three. On an average 4 loci (26.67%) were found to be polymorphic (P) and mean observed number of alleles per locus (A) was 1.533. Average observed heterozygosity (Ho) was 0.1082 and expected value (He) was 0.0993 with and gene flow Nm = 0.2177 showing low level of genetic variation among different accessions suggesting poor segregation of genes over generations. The isozyme variation was measured by standard gene diversity measures using POPGENE v. 1.32. Dendrograms revealed very low heterozygosity leaving little scope for exploitation of hybrid vigour and suggesting that initiating breeding programmes with Indian land races may not lead to substantial genetic gain, vigorous seed set and higher volumes of oil yield.

Keywords : Jatropha curcas, isozymes, genetic variability, dendrogram, heterozygosity

Annals of Tropical Research 32(1):92-111(2010)

Nitrogen mineralization and phosphorus solubilization due to rewetting of forest and paddy soils

Author(s): Marco Rodel J. Aragon and Victor B. Asio


Rewetting of soils may cause an increase in phosphorus solubilization and nitrogen mineralization resulting in the release of bioavailable phosphates and nitrates which are vital for crop growth but are also associated with eutrophication of surface waters. The study was conducted to evaluate P solubilization and N mineralization due to drying and rewetting of forest and paddy soils under laboratory conditions. Forest and paddy soils were tested for water extractable P and mineralizable N (NH4+ and NO3) after being subjected to drying and rewetting cycles for 7 and 14 days of drying. Soil samples were also analyzed for pH, OM, total N, total P, available P, and clay contents. Results indicated a significant increase in water-extractable P and total mineralized N for all the samples tested. N mineralization and P solubilization were correlated with OM, total N, available P, and clay. Findings also revealed that NH4+ concentration increased while that of NO3 decreased significantly for all the samples tested. The amounts of water-extractable P and NO3 released due to rewetting could potentially accelerate eutrophication if transported to bodies of water. They could also however benefit the growing plant.

Keywords : soil rewetting, nitrogen mineralization, phosphorus solubilization, eutrophication

Annals of Tropical Research 32(1):72-91(2010)

Cassava grates processing wastes as source of electrical energy

Author(s): Mark Anthony R. Atanacio1, Daniel Leslie S. Tan2 and Felix J. Amestoso3


The study aimed to generate electricity from cassava (Manihot esculenta) extract using an improvised microbial fuel cell (MFC). In the development of the MFC, screening experiment using 8-run Plackett-Burman (PB) technique and optimization procedure following response surface methodology (RSM) were employed. More cassava extract concentration significantly increased the generated voltage and the significance exhibited by salt ratio was inversely proportional to the voltage generated. One of the treatments in the 3×3 factorial experiment reached the maximum voltage of 546 mV.
Response surface regression analysis of all the response studied revealed that linear, quadratic, and cross product regression of cassava extract concentration and salt ratio in the salt bridge significantly affected the voltage which further developed a regression model represented as ∆E=106+1318x-4829y-850x2-787xy+18032y2.
The canonical analysis of the voltage showed minimum response at the stationary point inside the factor level space equal to 211 mV. Salt ratio level lower than 15% and cassava extract concentration not less than 60% generated a higher voltage value. T-test showed no significant difference of voltage between days, and between the predicted mean and the observed mean, which had % accuracy of 92.54, and 93.28%.“

Keywords : Cassava grates processing waste, microbial fuel cell, electricity, response surface methodology

Annals of Tropical Research 32(1):55-71(2010)

Floral biology of Jatropha curcas L.

Author(s): Angelo Jay M. Noriel1 and Othello B. Capuno2


This study was conducted at the existing plantation of Jatropha curcas within the campus of Visayas State University, Visca, Baybay, Leyte from April 2006 to June 2006 with the following objectives: 1) to study the floral morphology and flowering behavior of J. curcas; 2) to determine the time and duration of flower opening, anther dehiscence, and stigmatic receptivity of J. curcas; and 3) to test for pollen viability.
Male and female flowers of J. curcas were borne on the same plant with an average numbers per inflorescence of 55.03 and 1.926, respectively. Male flowers were more numerous than the females without definite relationship on number per inflorescence. It took an average of 9.56 days for all florets to full bloom. Anther dehiscence was observed to start at the time of opening of male flowers at around 0500 to 0600 hours and remained so for 24 to 72 hours. Stigmatic receptivity started about 12 hours after full bloom and lasted for about 24 hours. Based on observations, opening of floret buds, anther dehiscence, and stigmatic receptivity were all greatly influenced by the environment. Early sunrise, longer sunshine duration, and less amount of rainfall enhanced flowering of J. curcas. Pollen viability was relatively high, ranging from 88.12% to 98.55%.

Keywords : Jatropha curcas, anther dehiscence, stigmatic receptivity, pollen viability, flower opening

Annals of Tropical Research 32(1):31-54(2010)

Delayed yellowing of broccoli florets by ethanol: Some physio-biochemical changes during storage

Author(s): Dewoowoogen P. Baclayon1 and Toshiyuki Matsui2


due to complex metabolic processes occurring in tissues. Specifically, abrupt increase in ethylene and decline in sucrose were reported. To elucidate further these changes, 25% ethanol was applied in heads prior to storage. The relationship between postharvest yellowing of florets and ethylene production, 1-aminocyclopropane-1carboxylate oxidase (ACO) activity, sugar contents and respiration rate are determined. Results revealed that the onsets of climacteric rise in ACO activity and ethylene production were a day delayed by ethanol application. These results may suggest that ethanol inhibits ethylene synthesis by slowing down the activity of ACO at earlier storage period only. It is likely that due to volatilization of ethanol, the dilute concentration could be much less effective at overcoming its inhibitory effect on ethylene synthesis during the later stage of storage. Furthermore, the almost constant levels of sucrose from days 1 to 3 in the treated florets could be attributed to less consumption of respiratory substrate as exhibited by lower CO2 production. It is, therefore, likely that the relatively higher level of sucrose in treated florets has influenced the responsiveness of the floral tissue to ethylene. Overall, ethanol application appears to delay the metabolic processes which lead to the climacteric rise in ethylene, thereby delaying the onset of floret yellowing in broccoli. Prior to the appearance of visual sign of quality deterioration, significant changes in ACO activity and sucrose level have occurred. Thus, it is considered that yellowing is a late event in broccoli postharvest senescence preceded by significant physio-biochemical changes.

Keywords : ACO, ethylene, respiration and sugar

Annals of Tropical Research 32(1):17-30(2010)

Purification and partial characterization of white radish (Raphanus sativus L. var. Long white) peroxidase from cell suspension culture extract

Author(s): Sri Pudjiraharti and Andi Tenri Adjeng Karossi


Peroxidase mainly Horseradish peroxidase (HRP) has been widely used as a component of clinical diagnostic reagent for Enzyme Linked Immunosorbent Assay (ELISA) technique. White radish (Raphanus sativus L.) was found as another source of peroxidase . In this study, white radish was used for the production of peroxidase by cell suspension culture technique. Isolation of the enzyme was conducted by ammonium sulfate precipitation followed by purification using DEAE-Cellulose column chromatography eluted with 0.01 M phosphate buffer, pH 7.5 and 0-0.5 M NaCl gradient. A major peak of protein having the highest activity and purity 25 folds compared to the crude enzyme was observed. This protein was partially characterized. SDS-Polyacrilamide gel electrophoresis showed one main band with molecular weight of 47.000 Da. This white radish peroxidase (WRP) is a very efficient enzyme with demonstrated maximum activity at temperature 55°C and pH 7.5 as well as a Km 76.6 μg/mL and Vmax 275 μg/mL/ minute toward hydrogen peroxide as substrate and pyrogallol as hydrogen donor.

Keywords : Peroxidase, white radish, cell suspension culture, purification, characterization

Annals of Tropical Research 32(1):1-16(2010)