I. Van den Bergh

Purity control of oxytetracycline by capillary electrophoresis

Abstract The applicability of capillary electrophoresis for the purity control of oxytetracycline (OTC) was investigated. OTC is a broad-spectrum antibiotic belonging to the group of the tetracyclines. Several related substances can be present due to fermentation or degradation, such as 4-epioxytetracycline, α-apooxytetracycline, β-apooxytetracycline, anhydrooxytet racycline, 2-acetyl-2-decarboxamidooxytetracycline, tetracycline and 4-epitetracycline. Using fused-silica capillaries, the influence of buffer type, buffer pH and buffer concentration were investigated. In all cases 1 m M EDTA was added to prevent metal-ion complexation. The influence of the buffer counter-ion type was examined. Consequently, some instrumental parameters were changed such as capillary length and diameter as well as capillary temperature and applied voltage. The following method is finally proposed: fused-silica capillary, l (effective length) = 38 cm, L (total length) = 44 cm, 50 μm I.D.; buffer, sodium carbonate 20 m M -EDTA 1 m M , pH 11.25; voltage, 10 kV; temperature, 10°C. Linearity, limit of detection and limit of quantitation were determined as well as the relative standard deviations for all the analytes involved. This method is less selective then existing liquid chromatographic methods but it may be used as a complementary tool in purity control and stability studies.

Screening of Vietnamese Musa germplasm for resistance to root knot and root lesion nematodes in the greenhouse

Twenty-six Vietnamese banana accessions, from the AA, AAA, AAB, ABB, AB genome groups and some wild accessions, were evaluated for resistance and/or tolerance to Meloidogyne spp. and Pratylenchus coffeae under greenhouse conditions. No source of resistance to Meloidogyne spp. was found. All the tested genotypes were found to be at least as susceptible to Meloidogyne spp. as the susceptible reference cv. Grand Nain (AAA) and the final nematode population in the roots was always much higher than the initial inoculum. The intensity of galling was less in the cvv. Man (AAB), Tay (ABB), Ngu Thoc (AA) and Yangambi Km 5 (AAA). Possible sources of resistance/tolerance to P. coffeae were found in cw. Yangambi Km 5 (AAA), Tieu Xanh (AAA), Tieu Mien Nam (AA), Gros Michel (AAA), Com Chua (AAB), Com Lua (AA), Man (AAB), Ngu Thoc (AA) and Grand Nain (AAA).

Studies of Ploidy Assessment in Some Synthetic Hybrids of Banana (Musa spp.)

Bananas are among the largest herbs in the world. They are perennials with tall aerial shoots that arise from swollen, fleshy corms. Polyploidy in banana makes breeding a difficult process owing to complexities resulting from parthenocarpy and sterility. Besides, the degree of sterility is particularly high in edible cultivars, breeding of banana is complicated and time consuming Shepherd (1954, 1960). A minimum of two years is required to complete a seed-to-seed crop cycle. Even after thousands of crosses, very few viable seedlings were obtained from a limited percentage of seed set and each plant occupied 6m 2 in the field for evaluation by Rowe (1984).

A comparative study of the reproductive fitness and pathogenicity of a population of Radopholus similis from Davao, Philippines, on banana (Musa spp.)

The in vitro reproductive fitness on carrot discs and the in vivo pathogenicity on selected FHIA (Fundación Hondureña de Investigaciónes Agrícola) banana hybrids of a population of Radopholus similis isolated from banana in Davao, Philippines, were investigated at the Bureau of Plant Industry, Davao City, Philippines. It was shown that on carrot discs following inoculation with 25 females, the Davao population had the highest population density and multiplication rate compared with two other R. similis populations from the Philippines (Los Baños and Quezon) and two exotic populations of R. similis (from Uganda and Indonesia). According to the Gompertz model, the Davao population also had a short lag phase and a high maximum specific growth. Following inoculation with one single female, the Davao population also had the highest multiplication rate and the highest proportion of juveniles and females compared with the other four populations included in the experiments. Nine weeks after inoculation with 1000 vermiforms, the R. similis population from Davao had reduced the plant height of the FHIA hybrids included in the experiment (FHIA-3, FHIA-4, FHIA-5, FHIA-18 and FHIA-23) on average by 37%, plant girth by 5.3–40.9%, shoot weight by 20.1–65.8% and root weight by 31.7–69.7%, indicating the high pathogenicity of this population on banana. FHIA-4 was tolerant to R. similis infection.