Okinawa Island had old mango trees of unknown cultivars before the introduction of ‘Irwin’ which is the most important cultivar for commercial production. The continuous wet climate in Okinawa during the flowering season requires roof protection for stable fruit production, however, local Okinawa mango trees set fruit without protection. To identify these old mango trees, the morphological and physiological characteristics were recorded and their backgrounds of the introductions were interviewed to the local people. Their distributions were intensive around Nago and southern area from Urazoe, with thin distribution from Yomitan to Urazoe. Trees of about 100 years old were found such as in gardens and private homes. Some set fruit out of roof protection, and some set fruit off-season. ISSR analysis found that Okinawa mango trees exceeded the international standard cultivars in both the number of bands and polymorphism ratio, indicating wider diversity than the world major commercial cultivars. Interviews to the local people on the background of introduction and the result of ISSR suggest the relevance between most local Okinawa mango trees and Taiwanese resources.
We carried out experiments to determine the optimal rate and timing of fertilizer application to macadamia (Macadamia integrifolia Maiden & Betche) in Wakayama Prefecture, Japan. To determine the optimal rates of fertilizer application, fertilizer was applied once a year in a macadamia orchard lying on gray lowland soils after converts in from paddy fields. The fertilizer was applied in April, at a rate of 150, 300 or 450 kg N/ ha. The maximum yield was obtained with a fertilizer application rate of 150 kg N/ ha/ year. The timing of fertilizer application was studied in a macadamia orchard lying on brown earth in the upland soils of Susami, southern Wakayama Prefecture. Fertilizer (300 kg N/ ha) was applied in three different ways: total amount applied in spring (April); half-amount applied in spring (April) and half-amount applied in autumn (October); or total amount applied in autumn (October). The highest yield was obtained when the total amount was applied in spring (April).
We investigated the changes in the amount and composition of essential oil in the leaf blades and sheaths during the growth of two different strains of lemongrass (citral-dominant strain and geraniol-rich strain). Lemongrass plants were grown in pots, and the aerial parts of the plants (leaf blades and sheaths) were harvested at 15, 30, 45, and 60 days after the first fertilizer application. The leaf essential oil was extracted and purified by a solvent-based method that we newly developed for lemongrass leaves. The two strains of lemongrass grew with similar patterns during the experimental period, and the aboveground biomass increased exponentially after 30 days. In both lemongrass strains, the concentration of essential oil in the whole leaves decreased with growth as a result of a significant decrease in the leaf blades, whereas the amount of essential oil per hill increased rapidly with increasing aboveground biomass. These results indicated that the yield of essential oil per hill depended mainly on the biomass of the aerial parts, regardless of lemongrass strains. We also found that there were significant differences in the composition of the essential oil in the leaf blades and in the sheaths, and that the proportion of the constituents appeared to vary during the experimental period, particularly in the geraniol-rich strain of lemongrass. These results suggest that the ability of lemongrass leaves to synthesize and accumulate essential oil constituents varies depending not only on the strains of lemongrass, but also on the part of the leaf and the developmental stage of the plant.
Multi-location yield trials in sugarcane were conducted in the central and western regions of Thailand. Twelve genotypes grown at 15 locations were used. Thirteen traits including sugar yield, cane yield, number of stalks, stalk height at 6 months after planting (MAP) and at harvest, stalk diameter, single stalk weight, number of tillers at 6 MAP, number of died-tiller, Brix value, Pol (sucrose content), fiber content and CCS (commercial cane sugar) value, were used to analyze the genotype x trait (GT) biplot. All the traits except for the sugar yield and CCS value were used to analyze the trait covariate-effect biplot. In all the crop-cycles, several traits showed large variations among genotypes, whereas some other traits showed small variations. The GT-biplot clearly revealed these relationships between genotypes and traits. The GT-biplot enabled to analyze not only the relationship between each genotype and each trait, but also to compare these relationships among genotypes. In addition, the GT-biplot also displayed the relationships among traits. In all the crop-cycles, the trait covariate x environment biplots clearly showed 4 positively correlated traits with cane yield (number of stalks, stalk height at 6 MAP, that at harvest and stalk weight) at most locations, and there were 4 negatively correlated traits (Brix value, Pol, fiber content and number of died-tiller). Although yearly variations were found, some associations between the contribution of traits to cane yield and locations were confirmed. Therefore, it was suggested that the GT biplot is an efficient and powerful technique to analyze the relationship among traits and their association with genotypes, and that the trait covariate biplot is a useful indicator of the traits correlated with cane yield in association with tested locations.