Category Archives: Volume 31 No. 1 (2009)

Morphological characterization of selected papaya (Carica papaya L.) inbreds and hybrids

Author(s): Florence Lasalita-Zapico1 and Violeta N. Villegas2


Morphological analysis was undertaken to assess the degree of genetic relatedness and to characterize selected papaya (Carica papaya L.) inbreds and hybrids. Transmission of phenotypic traits from inbred parents to hybrid progeny followed the Mendelian pattern (complete dominance). The clustering mechanism separated the papaya genotypes into two groups. It was also revealed that some inbred lines presumably of very diverse origins exhibited similar morphological characteristics, raising the possibility that they have phylogenetic affinities and/or common origins. Screening for morphological traits with a high degree of polymorphism and with invariable expressions of the phenotypes would help in the identification of markers for hybrid identification and also in the accurate estimation of genetic relatedness among these hybrids and their parents.

Keywords : Carica papaya, morphological characterization, cluster analysis

Annals of Tropical Research 31(2):102-112(2009)

Nutrient characteristics of aggregates and rhizosphere of a degraded upland soil: Implication for soil fertility evaluation

Author(s): Ian A. Navarrete1,2, Salfe O. Macalde1 and Victor B. Asio1


The influence of aggregates and rhizosphere on nutrient availability of degraded tropical soils is not yet well understood. The study evaluated differences in the nutrient characteristics between rhizosphere and non-rhizosphere soils, aggregated and homogenized soil samples, and inner and outer portions of aggregates. Soil samples were collected from a degraded upland soil in Pinabacdao, Samar, Philippines, and analyzed for selected soil properties. Results revealed that rhizosphere soil had higher organic matter (OM), available P contents, and exchangeable Ca and Mg contents than the non-rhizosphere soil but with no considerable variation in soil pH. Results also showed no differences in the chemical properties between the outer and inner portions of aggregates and that the aggregated samples slightly differed from the homogenized soil samples in terms of some chemical characteristics. Findings suggest that the standard practice of homogenizing soil sample for analysis may have limitations for fertility evaluation of degraded soils.

Keywords : degraded soil, soil aggregates, rhizosphere soil, soil fertility evaluation

Annals of Tropical Research 31(2):90-101(2009)

Antimicrobial property of chitosan and induction of systemic acquired resistance for the control of rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Swings et al.)

Author(s): Ivy M. Modina1, Candelario L. Calibo2 and Lucia M. Borines3


Chitosan has been reported to have antimicrobial property to some pathogen species as well as an elicitor of resistance in plants , particularly Systemic Acquired Resistance (SAR). A bioassay of chitosan against Xanthomonas oryzae pv. oryzae (Xoo) was conducted to determine its antimicrobial property against bacterial blight pathogen and the optimum concentration that is most inhibitory to the pathogen. Chitosan was also tested as foliar spray to rice plants to evaluate its potential to induce SAR against bacterial blight disease.
Chitosan treatments (300 ppm, 400 ppm, and 500 ppm) possessed antimicrobial property against Xoo in vitro, producing zones of inhibition which were generally significantly bigger than those of the control (streptomycin, acetic acid, and sterile distilled water) at 2, 4, and 6 days after inoculation. Chitosan-sprayed plants showed significantly shorter bacterial blight lesions which were comparable to the plants sprayed with streptomycin, and Boost, a commercial plant defense activator and a known inducer of SAR. Chitosan is found effective in reducing bacterial blight lesions in rice plants due to its antimicrobial property and also most likely due to the induction of SAR.

Keywords : Rice, bacterial blight, resistance, induction, chitosan, antimicrobial, systemic acquired resistance (SAR)

Annals of Tropical Research 31(1):69-89(2009)

Allelochemicals from the leaves of Tamarindus indica L.

Author(s): Suparna Mandal Biswas1, Nasrin Begam1, Sunanda Chanda1 and Lalit Kumar2


Potent biopesticides with strong antimicrobial activity as well growth inhibitory activity has been isolated and purified from the Ethyl Acetate Fraction (TrEAF) of tamarind leaves. Chromatographic analyses (TLC, UV, MS, NMR, and IR) indicated the presence of putative caffeic acid derivative in Tamarind leaves. Aspergillus tamarii was highly sensitive to TrEAF compound at all concentrations (500 ppm, 1000 ppm, 1500 ppm and 2000 ppm) than Aspergillus fumigatus, Aspergillius niger. In Aspergillus tamarii and Aspergillius niger, 1500ppm concentration was very much sensitive to TrEAF compound. Cercina lutia, Staphylococcus aureus, Micrococcus roseus and Pseudomonas sp were much more sensitive to TrEAF compound than Escherichia coli. No effect of TrEAF compound was detected in E.coli at concentration of 1000ppm. When isolated and purified by fractionation and column chromatography, this active TrEAF compound showed concentration-dependent inhibitory/stimulatory activity on rice seeds. At concentration of 1000ppm, it showed 53.81% inhibition on shoot length and 58.85% inhibition in root length. At 500ppm concentration, 29.01% inhibition in shoot length and 38.82% inhibition in root length have been detected. Very slight stimulation on shoot length was observed at 7.81ppm. It showed no effect on the germination of rice seed.

Keywords : Tamarindus indica L., allelochemicals, caffeic acid derivative, agrochemicals, antimicrobial activity

Annals of Tropical Research 31(1):47-68(2009)

Carbohydrate status of sucrose-fed broccoli head during storage and the activity and gene expression of sucrose synthase

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


Quality deterioration in broccoli is associated with rapid loss of sucrose after harvest. Hence, this study was conducted to investigate the influence of exogenous application of 10% (w/v) sucrose to broccoli heads during storage at 20oC on the activity and gene expression of sucrose synthase. The level of sucrose in the branchlets and florets tissues was improved only within a day and 2 days, respectively, from treatment. The enzyme activity in both portions was inconsistent with SS gene expression thereafter. The decline in sucrose could be a consequence of concerted actions of other harvest related genes in addition to SS. It is possible that SS could be encoded by multi-genes as exhibited in other plant species. Further characterization or isolation of different SS isoforms and their expressions during postharvest senescence would be helpful in the regulation of sugar metabolism in harvested heads during storage.

Keywords : BoSS, enzyme, fructose, glucose, postharvest life, senescence, sugar

Annals of Tropical Research 31(1):34-46(2009)

Food security implications of biofuel production

Author(s): Teodoro C. Mendoza


Producing liquid biofuel for cars to address the declining oil supply requires the same resources or inputs (land, water, initial energy or oil, fertilizer and machineries) as in producing food for humans. As early as the 1980s, all the prime lands in the world are already used for agri-and-aquaculture (1970s for the Philippines. Biofuel production consumed water (up to 10,000L of water/L ethanol). At present, 74% of water is used to irrigate food crops. Only 1% water is now used for biofuel but this water consumption will increase to 80% if the biofuel production plan materializes. One out of three individuals in the world is now suffering from water scarcity. Global warming/ global climate change, droughts, more forest fires and high evaporation triggered by high temperature will further magnify the diminishing supply of fresh water both for agriculture and domestic use (household and industries).

The simple linear thought is…..more crops for food or biofuel = more lands and water use = more fertilizer or oil use = more erosion = more greenhouse gas emission.

Biofuels have forced global food prices up by 75%, a World Bank study showed. In 2007, 100 metric tons (Mt) of grains were processed into biofuel. This precipitated to food price spikes in the following year. It is clear that without biofuel in the food equation, there will be enough food. As more money is spent for food, food price spikes have caused 100 million people to be below poverty line and food riots in 36 countries. About 3 billion people are now affected especially those who spend 6070% of their income on food. There aremany options other than biofuel such as solar, wind, and wave. The technology is now in place for solar- powered and battery/electric or hybrid cars for transport. In the Philippines (a tropical country), geothermal, hydroelectric, wind and solar power, are so abundant. They remain to be tapped.

Keywords : Food security, biofuel, ethanol, biodiesel, distillery slop, biodiversity, erosion, greenhouse gas, global warming/climate change, food miles, globalization, cheap food, cheap oil

Annals of Tropical Research 31(1):1-33(2009)