Category Archives: Volume 42 No. 2 (2020)

Planktonic algae as bioindicators of water quality in Pagbanganan River, Baybay City, Leyte

Authors: Eunice Kenee L. Seriño1* and Beatriz S. Belonias

ABSTRACT Submitted: 11 September 2019 | Accepted: 9 June 2020

Biological monitoring is a valuable method used in conservation studies to protect and preserve the biological integrity of natural ecosystems. This study was conducted to assess the water quality of the Pagbanganan River using planktonic algae as bioindicators of organic pollution. Horizontal tows were made in three selected stations (upstream, midstream & downstream) using a Wisconsin plankton net with 80pm mesh size. Collected samples were preserved with Lugol’s solution and 70% ethyl alcohol. Identified phytoplankton genera were analyzed using Palmer’s Pollution Index. Out ofthe 20 pollution indicator genera identified by Palmer (1969), 10 were present in Pagbanganan River, namely; Ankistrodesmus, Closterium, Cyclotella, Gomphonema, Melosira, Navicula, Nitzschia, Oscillatoria, Stigeoclonium and Synedra. Four of these were among the most abundant algae in the river. Mean Palmer’s Pollution Index Scores indicate that there is “less” organic pollution existing in the river. Results imply that the river is still relatively safe for general household use, but effective conservation measures should be done to preserve the integrity ofthe river ecosystem.

Keywords: planktonic algae, bioindicators, water quality, Palmer’s pollution index

Annals of Tropical Research 42(2):43-51(2020)
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Application of Mitscherlich-Bray equation to formulate fertilizer recommendations for sweetpotato in Leyte, Philippines

Authors: Luz G. Asio1* and Nenita E. dela Cruz2

ABSTRACT Submitted: 23 March 2020 | Accepted: 28 July 2020

Until now, no studies have been conducted in the Philippines on the use of the Mitscherlich-Bray equation to formulate NPK fertilizer recommendation for sweetpotato. This study used the Mitscherlich-Bray equation to formulate NPK requirements for sweetpotato. Independent experimental set-ups of N (7 application levels), P (6 levels), and K (9 levels) arranged in RCBD with three replications were simultaneously conducted. Theoretical maximum yield, NPK constants c, and c, NPK fertilizer recommendations for sweetpotato at different soil fertility levels, and optimum fertilizer rates were calculated. Fertilizer recommendations for a common range of soil test values were developed but needed further field verification trials. Theoretical maximum yields determined by the Mitscherlich-Bray equation were 19.05, 12.66, and 14.88t ha-1 for NPK, respectively. The study showed that inherent soil fertility is vital in the development of fertilizer recommendation for sweetpotato not only to increase root yield but likewise to increase overall productivity. It showed that 30, 50, and 60 percent of the maximum possible yield was attributed to the inherent soil N, P, and K, respectively. N, P2O5, and K2O recommendations for sweetpotato were computed based on a common range of soil test values ranging from 50 to 300, 5to 40, and 200 to 700kg ha-1 NPK, respectively.

Keywords: sweetpotato, Mitscherlich-Bray equation, NPK, fertilizer recommendations

Annals of Tropical Research 42(2):30-42(2020)
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Detection and molecular characterization of phytoplasma affecting vegetables in Eastern Visayas, Philippines

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

ABSTRACT Submitted: 13 June 2019 | Accepted: 9 June 2020

Phytoplasma-like diseases were observed affecting bitter gourd, Loofah, string bean, “Baguio” bean, cucumber, and tomato in Eastern Visayas, Philippines. The infected vegetables commonly show little leaf/witches’ broom symptoms. The study aimed to detect and confirm phytoplasmas presence in these vegetables through PCR and nest PCR assays using universal primers, electron microscopy, and 16srDNA sequence analysis. Loofah little leaf had the highest prevalence (50% of the surveyed farms), followed by bitter gourd (45%) and string beans (31%). The disease had an approximate mean incidence of 27% for bitter gourd, 38.0% for Loofah, and 42.5% for string bean, in farms where plants showed infections. Electron micrographs of bitter gourd and Loofah samples showed phytoplasma cells in the phloem sieve tubes. Nest PCR assays using R1 6F2n/R16R2 primer linked to phytoplasmal6srDNA amplified a ~1.25Kb band in the majority of DNA samples. rDNA sequence analysis using Blastn showed that phytoplasmas in bitter gourd, Loofah, and one cucumber samples shared 98-99% identity with Loofah’s reference gene phytoplasma clones. More than one phytoplasma strain infected the vegetables based on Rsai enzyme digestion and phylogenetic analysis.

Keywords: witches broom, PCR, bitter gourd rDNA sequence

Annals of Tropical Research 42(2):1-20(2020)
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