Prestine marine ecosystem surrounded by Paleozoic limestone rocks (El Nido, Palawan)

Prestine marine ecosystem surrounded by Paleozoic limestone rocks (El Nido, Palawan)

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Traditional rice production system (Borongan, Eastern Samar)

Traditional rice production system (Borongan, Eastern Samar)

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 Diverse crop production systems in the middle central highlands (Cebu)

Diverse crop production systems in the middle central highlands (Cebu)

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Coastal and Marine Ecosystems (Bangui, Ilocos Norte)

Coastal and Marine Ecosystems (Bangui, Ilocos Norte)

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Agricultural Landscape (Biliran)

Agricultural Landscape (Biliran)

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Marginal Upland (Inopacan, Leyte)

Marginal Upland (Inopacan, Leyte)

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Rainforest Ecosystem (Leyte Central Highlands)

Rainforest Ecosystem (Leyte Central Highlands)

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Polluted Sites (Abandoned Bagacay Mine, Samar)

Polluted Sites (Abandoned Bagacay Mine, Samar)

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Volcanic Landscape (Mt. Mayon, Bicol)

Volcanic Landscape (Mt. Mayon, Bicol)

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Fate of phosphorus fertilizer in acidic Cambisol assessed using 33P isotope labeling technique


DOI: Not yet available
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Author(s): Deejay Maranguit1*,2 and Yakov Kuzyakov2,3

Abstract

Direct 33P labeling approach is a very powerful technique that has high sensitivity in tracing the fate of added phosphorus (P) fertilizers across various P pools. Nonetheless, only a few studies have used this approach. This study traced the fate of applied P fertilizer in acidic P-limited soil using the 33P labeling approach.The incorporation of 33P-labeled KH2PO4 in available P (PAEM), microbial biomass P (Pmic) and Fe/Al-bound P (PNaOH) pools was followed in Cambisol as influenced by C and N sources applied as glucose and ammonium sulfate, respectively.Results showed that not all of the added P fertilizer remains in available pool; instead, it was distributed to poorly-available pools. Fast, almost instantaneous P fixation by the Fe and Al oxides and immobilization by microbial uptake were recorded.Applying glucose boosts microbial growth and demand for P, resulting in increased 33P recovery. High 33P recovery in Pmic (20% of the applied 33P) and in PNaOH (45% of applied 33P) showed the dominance of P immobilization by microorganisms and adsorption by Fe and Al oxides on the fate of P in an acidic soil. Nevertheless, these can contribute to long-term P availability after the turnover of microbial biomass and desorption of fixed P.

Keywords: 33P isotopic labeling; Phosphorus dynamics; Phosphorus availability; Phosphorus fractions; Microbial biomass P; P-limited soil

In vitro growth response to bacterial wilt pathogen of banana (var. lakatan, Musa acuminata Colla) plantlets regenerated from ethyl methanesulfonate-treated shoot explants


DOI: Not yet available
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Author(s): Nonna Fatima H. Abello1and Tessie C. Nuñez1*

Abstract

Bacterial wilt caused by Ralstonia solanacearum leads to death of infected suckers and reduces the yield of commercially important banana varieties like Lakatan. Among the many varieties of banana, no germplasm with bacterial wilt resistance has been identified yet (Tripathi et al 2004).
Mutation induction in plants to develop disease resistance genes using physical or chemical mutagens has been used as alternative to harmful pesticides. To induce mutation for the possible development of resistance to bacterial wilt, shoot tips of Stage 2 in vitro-grown Lakatan plantlets were exposed to 0.1% and 0.2% ethyl methanesulfonate (EMS) for 12 and 24h. Treated and untreated explants were cultured in-vitro to regenerate plantlets.
Shoots emerged two days after in vitro inoculation of explants treated with – 0.1% EMS for 12h. Significantly longer shoots also developed from the cultures compared to the untreated explants. The other explants exposed to other treatments had shoot emergence one to three days later. Falcate, curled, irregularly-shaped, and yellowish leaves and pseudostems also developed in EMS-treated cultures.
Untreated plantlets exhibited at least one bacterial wilt symptom such as leaf spots, necrosis at pseudostem base, and death six days from the introduction of Ralstonia solanacearum in vitro. Plantlets from explants exposed to 0.1% EMS for 12h did not exhibit disease symptoms even after ten days of exposure to the pathogen and had 100% survival. Seventy one percent of plantlets from explants exposed to 0.1% EMS for 24h and 55% from explants treated with 0.2% EMS for 24h also survived without infection. The surviving plantlets need to be studied further for their ex vitro responses to the pathogen and determine possible genetic changes due to the chemical mutagen treatment.

Keywords : in vitro growth of banana, Ethyl methanesulfonate, Bacterial wilt screening, Ralstonia solanacearum