Abstract. Xanthone in mangosteen fruit hull has antioxidant activities. The objective of this experiment was to determine xanthones content, physical and chemical characters, and antioxidant potentials of several groups of mangosteens qualities. The experiment was carried out from January 2008 to August 2008. The research used a randomized complete block design with four replications. The treatments were four physical fruit conditions: large size mangosteens (# 100 g), small size mangosteens (min. 50 g), yellow sap dotted fruits, and scabbed fruit. The parameters being observed were physical and chemical characteristics, xanthone content, and radical scavenging activity of mangosteen fruit hull extract. The results demonstrated that the physical condition of fruit signifi cantly affected physical fruit hull characters and chemical fruit characters. Characters of fruit hull, thickness, fresh weight, and dry weight, differed among fruit qualities. The physical condition of fruit hull also signifi cantly infl uenced total soluble solid and vitamin C content, but did not affect total titrable acid and degree of acidity of the fruits. Fruit hulls of all groups of mangosteen qualities had similar antioxidant properties with the IC50 value of 5.57-6.11 ppm.

Keywords: benzophenone, scab, vitamin C, yellow sap

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Abstract. Eggplant, yard long bean, and kangkong, were grown with polyethylene mulch with a drip irrigation system on Podzolic soil with low pH (4.5), low C-Organic (0.97%), very low total-N (0.17 %), low K content (0.15 me (100 g)-1), but had a high soil P2O5 concentration (13.7 ppm) to evaluate the best crop management practices under this soil condition. Combination of polyethylene mulch treatments (with and without), fertilizer (with and without), number of irrigation lines (0, 1, and 2 lines), and methods of fertilizer applications (preplant, split, and drip) were arranged in a Randomized Completely Block Design with four replications. The results showed that the use of mulch and fertilizer signifi cantly increased yield of all crops. One line irrigation system also resulted in the best yield. Preplanting application of 100% P, 50% N and K in addition to 50% N and K applied 10 times weekly was the best methods to produce Eggplant, Yard Long Bean, Kangkong under polyethylene mulched and drip irrigation system.

Keywords: Solanum melongena L, fertilization, fertigation, Ipomoea reptans L, micro-irrigation, polyethylene-mulched, Vigna unguilata L.

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Abstract. Biological control of bacterial wilt pathogen (Ralstonia solanacearum) of tomato using endophytic bacteria is one of the alternative control methods to support sustainable agriculture. This study was conducted to select and characterize endophytic bacteria isolated from healthy tomato stems and to test their ability to promote plant growth and suppress bacterial wilt disease. Among 49 isolates successfully isolated, 41 were non-plant pathogenic. Green house test on six selected isolates based on antagonistic effect on R. solanacearum or ability to suppress R. solanacearum population in dual culture assays obtained BC4 and BL10 isolates as promising biocontrol agents. At six weeks after transplanting, plants treated with BC4 isolate showed significantly lower disease incidence (33%) than that of control (83%). Plants height was not significantly affected by endophytic bacterial treatments. Based on 16S rRNA sequence, BC4 isolate had 97% similarity with Staphylococcus epidermidis (accession number EU834240.1), while isolate BL10 had 98% similarity with Bacillus amyloliquefaciens strain JK-SD002 (accession number AB547229.1).

Key words: biological control, endophytic bacteria, Ralstonia solanacearum, Staphylococcus epidermidis, tomato

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