Category Archives: Volume 30 No. 2 (2008)

Research Note: Floristic inventory of monocots in Mt. Pangasugan, Baybay, Leyte, Philippines


Author(s): Pamela M. Po-Abit

Abstract

Mt. Pangasugan which lies up to an elevation of 1,158 m ASL on the western slope of the Central Cordillera of Leyte is one of the unexplored mountains. Since directory of Philippine flora is still incomplete, a floristic inventory of the country’s remaining forest is imperative. The study was conducted to provide a checklist of existing monocot flora in Mt. Pangasugan.
A total of 76 species belonging to 14 families and 51 genera were recorded. Family Araceae had the most number of genera while Family Palmae had the most number of species.

Keywords : flora, floristic composition, rainforest

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Growing tropical tree planting stock in root trainers: Cell volume, seedling density and growing media


Author(s): Sanjay Singh1, N. P. S. Nain2 and S. P. Tripathi2

Abstract

The influence of root trainer cell volume and seedling density, and composition of growing media was examined in relation to morphological, biomass and seedling quality parameters of four-month old planting stock of three tropical broadleaved tree species viz., Acacia catechu, Azadiractha indica and Pongamia pinnata. The study revealed that a cell volume of 90 cm3 was not sufficient for proper seedling growth of A. catechu and A. indica. However, clear-cut superiority of 300 cm3 cell volume was evident only in the case of A. indica. It appeared that root trainer pots of 150 cm3 cell volume were suitable for growth of planting stock of A. catechu and P. pinnata and 300 cm3 cell volume for A. indica. Significant differences in the growth of planting stocks were observed among growing media treatments. Overall the tree species exhibited fast growth and high biomass as well as favorable seeding quality in growing media containing 80% compost with either sand (A. catechu and A. indica) or soil (P. pinnata) than the other treatments having 50%, 60% or 100% compost.

Keywords : biomass, height and root collar diameter, hiko pots, seedling quality

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Gmelina Boom, Farmers’ Doom: Tree growers’ risks, coping strategies and options


Author(s): Paulo N. Pasicolan1 and Damasa M. Macandog2

Abstract

A strong belief by Clavaria farmers that there is ‘gold in Gmelina growing’ turned out to be a huge frustration among tree out growers in southern Philippines in the late 1990s. The lack of a market study and appropriate government support system to address farmers’ tree growing risks resulted in a great loss, not only financially but also in terms of local people’s confidence in tree growing in the area. A large number of tree growers returned to subsistence farming while others opted to have their land rented out to multi-nationals for high value crops production (including bananas and pineapples). However, the majority shifted to fruit bearing trees. Ten farmers were interviewed using Problem in Context analysis, and they made various recommendations for government to improve the financial performance and regulatory environment for tree farming. These recommendations included the removal of the cutting permit requirements for timber grown in private woodlots, setting the wood price regulatory system to safeguard the interest of small tree growers, providing wood market information and strategic networks for tree growers to find alternative markets or use for their timber produce, and encouraging the private sector to establish small wood processing plants in every municipality in order to provide ready markets for timber produce. It was also suggested that government initiate contract tree growing between the private sector and farmers’ groups, provide more planting area for interested tree growers, and assist small tree farmers to form or strengthen local cooperatives.

Keywords : market uncertainties, tree growing risks, coping strategies, policy measures, institutional safeguards

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Somatic embryogenesis and plant regeneration in purple food yam (Dioscorea alata L.)


Author(s): Marilyn M. Belarmino1 and Jocelyn R. Gonzales2

Abstract

A study was conducted to establish a reliable procedure for somatic embryogenesis and plant regeneration from callus cultures of purple food yam (Dioscorea alata L.). The procedure involved three steps; (1) culture of nodal stem segments from greenhousegrown plants to generate in vitro plantlets; (2) induction of callus from the leaf, petiole and nodal stem tissues; and (3) initiation of somatic embryo from callus. Results showed that the agar-solidified Murashige and Skoog (MS) medium containing 30 gl-1 sugar, 0.1 gl-1 α-cysteine , 10 mgl-1 calcium pantothenic acid, 2.0 mgl-1 asparagine, 2.0 mgl-1 arginine, 80.0 mgl-1 adenine sulfate (AdSO4) and 0.1 mgl-1 naphthalene acetic acid (NAA) effectively broke dormancy of lateral buds of nodal stem cultures from both ‘VU-2’ and ‘Kinampay‘ varieties. Production of multiple adventitious shoots occurred after transfer of in vitro nodal pieces to the same medium added with 1.0 mgl-1 benzylamino purine (BAP) or, MSA medium. Callus was effectively induced from the vegetative tissues in MS medium added with 1.0 mgl-1 2,4-Dichlorophenoxy acetic acid (2,4-D) or, with picloram. Among the three types of explants, the nodal stem was the most suitable which produced purplish nodular embryogenic callus. A higher percentage of nodal stem-derived calli produced globular embryos in MS medium containing 1.0 mgl-1 2,4-D and 0.5 mgl-1 BAP, or in 1.0 mgl-1 picloram and 0.5 mgl-1 BAP than, in the plant growth regulator-free medium (control). The maturation of embryos was facilitated by one-month culture in MS medium containing 0.1 mgl-1 ABA and 100 mgl-1 glutamine. This step improved the germination of somatic embryos in one-half strength PGR-free MS medium containing 100 mgl-1 glutamine (regeneration medium). All somatic embryoderived plantlets were morphologically normal and established well in soil.

Keywords : callus, multiple adventitious shoots, nodal stem explant, plantlet, somatic embryo

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Development of bacterial blight resistant Mestizo hybrid maintainer and restorer lines through marker-aided backcrossing


Author(s): Lucia M. Borines1, Emilie O. Espejo1, Robelyn T. Piamonte1, Casiana M. Vera Cruz2 and Edilberto Redoña2

Abstract

This study was conducted to: 1) evaluate the reaction of Mestizo hybrids, their maintainer and restorer lines to Philippine Xanthomonas oryzae pv. oryzae races, 2) incorporate bacterial blight resistance genes to these lines via marker-aided backcrossing and 3) confirm the presence of introgressed Xa genes in the progeny of each backcross generation through phenotyping and molecular marker analysis.
Mestizo hybrids, their maintainer and restorer lines, IRBB62 donor, and checks were inoculated with ten Xoo races (12 isolates). Marker-aided backcrossing from IRBB62 donor (with Xa4/7/21) to each line was done to introgress target genes. The resistance genes in the advanced lines were confirmed using diagnostic Xoo races and analyses of linked DNA markers.
Mestizo 1,2 and 3, their maintainer and restorer lines (IR68888B, IR68897B, IR34686R, IR62161R, IR60819R) except IR58025B were similar to IRBB4 indicating the presence of Xa4 resistance gene in these lines. All the lines however, did not contain the Xa7 and Xa21 genes. Resistance genes Xa7 and Xa21 were incorporated in addition to Xa4 to BC5F2 progeny (BC5F3 seeds) of IR34686-179-1-2-1R, IR60819-34-2R, IR62161184-3-1-3-2R and IR6888B. Resistance genes were also incorporated to BC4F1 progeny (BC4F2 seeds) of IR58025B and IR68897B. The presence of the genes was confirmed through linked markers.
The lines containing gene pyramids had increased resistance to bacterial blight and a wider resistance spectrum to Xoo races. Advanced backcross progeny were phenotypically similar to their recurrent B and R lines.

Keywords : rice, hybrid, maintainers, restorers, resistance

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