Monthly Archives: May 2022

Insect vectors transmitting Phytoplasma to vegetables in Eastern Visayas Philippines

Authors: Lucia M. Borines1*, Nickie D. Duero1, Joy Adeline C. Nuñez1, Rezel Sagarino-Borines2, Reny G. Gerona1 and Sandra McDougall3


Phytoplasma diseases are found affecting vegetables in Eastern Visayas, Philippines. Identifying the insect vectors that transmit phytoplasma in the field is necessary for the management of this disease. This study was conducted to identify the vectors of phytoplasma affecting bitter gourd, loofah, and string beans. Insects associated with these vegetables that had shown phytoplasma symptoms in the field were collected, mass-reared, and the progenies of mass reared insects were used for transmission to healthy host plants. Phytoplasma detection was done through PCR and nest PCR assays. Phytoplasma was positively transmitted to healthy bitter gourd plants by a cicadellid leafhopper, Hishimonus sp. and brown planthopper, Ricania speculum. The ~ 1.25Kb phytoplasma-specific band was amplified in these insects. The phytoplasmas transmitted by the Hishimonus sp. and R. speculum produced two different types of symptoms to the bitter gourd, and rDNA sequence analysis separated them into two clusters which confirmed that the phytoplasmas belong to two different strains. Although the Aphis gossypii and Aphis craccivora also produced symptoms in bitter gourd and string beans, and the pathogen was detected in the insects, whether they vectored phytoplasma to their respective hosts needs further study, since the symptoms produced were quite different from the ones produced by the cicadellid leafhopper and Ricania speculum.

Keywords: Hishimonus sp., Ricania speculum, bitter gourd, witches broom

Annals of Tropical Research 44(1):46-60(2022)
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Conventional biotyping revealed Mycoplasma and antimicrobial resistant Escherichia coli and Salmonella isolates during disease outbreak in broiler farms and hatcheries in Leyte, Philippines

Authors: Eugene B. Lañada1*, Harvie P. Portugaliza1, Analyn I. Blanza2, Mercy Cheryll C. Espejo3 and Ma. Delia A. Pagente1


A respiratory disease outbreak investigation was carried out from October to December 2015 in three broiler farms and two hatcheries in Leyte. Three- to seven-day-old chicks from farms were initially brought to CVM diagnostic laboratory for necropsy and microbial analyses. Subsequent visits to hatcheries and farms were made for random swabbing and sampling of physical facilities, equipment, vehicle, unhatched eggs, 18-day old eggs, eggshells, and day-old chicks. Chick necropsy, embryo examination, and bacteriological method for Mycoplasma, Escherichia coli, Salmonella, and Aspergillus were performed. Antimicrobial sensitivity testing was conducted for Salmonella and E. coli isolates. The main clinical sign observed in chicks was dyspnea. Necropsy revealed consistent bilateral fibrinous airsacculitis and perihepatitis with few cases of pericarditis, wherein sampled organs consistently showed the presence of E. coli. Out of 83 samples collected, 19 (22.89%) Salmonella, 40 (48.19%) E. coli, and no Aspergillus were isolated. Most E. coli were isolated from chick embryos and necropsied chickens, while Salmonella isolates were mostly from the environment. Mycoplasma was isolated from 63.64% (7/11) of sampled lungs, air sacs, and liver from unhatched embryos (100%), 18-day old embryos (50%), and day-old chicks (33.33%). The majority of Salmonella and E. coli isolates showed multidrug resistance against amoxicillin, chloramphenicol, erythromycin, trimethoprim/sulfamethoxazole (TMPS), and tetracycline. Few isolates were sensitive to ciprofloxacin. Our results should raise awareness on the occurrence of antimicrobial-resistant E. coli and Salmonella, and coinfection with Mycoplasma among broilers in Leyte. Therefore, proper selection and usage of antibiotics should be advocated in all poultry farms.

Keywords: Antimicrobial-resistant, E. coli, Mycoplasma, Poultry outbreak, Salmonella

Annals of Tropical Research 44(1):74-85(2022)
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PCR optimization for the detection of bunchy top virus of abaca (Musa textilis Nee) in Eastern Visayas Philippines

Authors: Jofil A. Mati-om*, Meriam B. Mati-om and Robelyn T. Piamonte


The bunchy top virus in Eastern Visayas has serverly reduced abaca production. Early and accurate detection of plant viral pathogens is an essential and crucial component for disease management. At present, there are no standard PCR conditions in the Eastern Visayas region for detecting the bunchy top virus at an early stage using PCR. Thus, optimization for the detection was carried out to assist in disease management. Different annealing temperatures (57, 60 and 65oC), gel concentrations (1, 1.5 and 2%), and running conditions (80, 90 and 100 volts) were tested using My TaqTM DNA Polymerase (Bioline, USA). The annealing temperatures of 57oC and 60oC resulted in DNA amplification as indicated by the presence of bands but absence of bands at 65oC. The higher voltages of 90 and 100 volts resulted in smears and distorted DNA bands with 1% and 1.5% agarose; thus 2% agarose gel was used to resolve small DNA fragments (100bp to 3kb). Electrophoresis using 80 volts for 45min successfully separated the DNA bands. The amplification of the product with internal control primers indicated the absence of PCR inhibitors in the abaca-extracted DNA samples. This confirmed the negative PCR reaction as indicative of the absence of the virus. The optimized PCR conditions could be applied by students and researchers for the early detection of bunchy top virus in the National Abaca Research Center Germplasm collection and the region.

Keywords: bunchy top virus, PCR, Manila hemp, detection, abaca hybrid

Annals of Tropical Research 44(1):61-73(2022)
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Assessment of sesquioxides status of some uplands soils in humid southwest Nigeria

Authors: Julius Olayinka Ojetade1*, Ruth Oluwakemi Adegbenro1, Emmanuel Adeboye Adesemuyi2, Sikiru Adekoya Muda1 and Alani Adeagbo Amusan1


Assessment of some sesquioxides in the upland soils in southwestern Nigeria was undertaken to evaluate their degree of weathering under humid tropical conditions. Samples were taken from genetic horizons of eight soil profile pits sited at different physiographic positions along two toposequences in southwestern Nigeria. The samples were analyzed for gravel content, particle size distribution, bulk density, pH, organic carbon, total nitrogen, available P, exchangeable bases, crystalline and amorphous forms of Fe and Al, using standard procedures. Sand fraction ranged from 31–76% (54.49±11.34), silt from 3–19% (10.21±3.61) and clay from 10–55% (35.3±9.7). Bulk density increased with profile depth, ranging between 1.12 and 1.64g cm-3 (1.39±0.13). The pH was low (4.2–6.1; 5.0±0.55), organic carbon content ranged from 0.75–15.99g kg-1 (5.79±3.49) with higher values in the surface horizons. Total nitrogen content ranged from low to medium (0.13–2.75g kg-1; 1.16±0.49) while available phosphorus ranged from 0.49–11.63mg kg-1 (4.30±3.57) across the horizons. Crystalline forms of Fe (Fed) and Al (Ald) ranged from 10.26–39.82g kg-1 and 0.41–1.80g kg-1, respectively while the amorphous forms (Feo and Alo) ranged from 0.41–2.60g kg-1 and 0.83–1.64g kg-1, respectively. The crystalline forms of Fed and Ald were more dominant over the amorphous forms of Feo and Alo. The argillic (Bt) horizons of pedons had significant accumulation of clay particles and free iron. The weathering indices of clay and free iron accumulation in argillic (Bt) horizons of the pedons indicated that the soils of the study area were well-drained, deeply weathered and intensely leached with few weatherable minerals available for plant uptake.

Keywords: Sesquioxides, Upland Soils, Nigeria

Annals of Tropical Research 44(1):1-16(2022)
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