Toshihiro Hasegawa

Growth and yield of potato plants grown from microtubers in fields

Despite many reports of thein vitro production of microtubers, little is known about plant growth and yield from microtubers planted in the field. This study clarified differences in growth and yields between potato plants grown in the field from microtubers and from conventional seed tubers. The experiments were performed at Hokkaido University, Japan, over four years. Conventional seed tubers of about 50 g and microtubers of two sizes (0.5–1.0 g and 1.0–3.0 g) of the latematurity cultivar Norin 1 were planted, and plant growth and tuber yields were analyzed. The microtuber plants had a lower initial increase in root and leaf area index than conventional seed tuber plants, but had the same leaf area index after about 40 days from emergence. The first tuber formation in microtuber plants was about 7 days later than in conventional seed tuber plants, while tuber bulking occurred about 14 days later in microtuber plants. Consequently, the onset of tuber weight increase was later in microtuber plants, but the rate of increase thereafter was similar between conventional seed tuber and microtuber plants. At harvest the tuber fresh weight of microtuber plants was 82% that of conventional tuber plants, suggesting a potential for using microtubers for field planting.ResumenA pesar de los muchos reportes sobre producción de microtubérculosin vitro, se conoce muy poco acerca del desarrollo y rendimiento de las plantas provenientes de microtubérculos en el campo. Este estudio pone en claro las diferencias en desarrollo y producción en el campo de plantas provenientes de microtubérculos con las provenientes de tubérculo semilla convencional. Los experimentos se realizaron en la Universidad de Hokkaido, Japón durante cuatro años. Se sembraron tubérculos de semilla convencional de unos 50 g y microtubérculos de dos tamaños (0.5 a 1.0 g y 1.0 a 3.0 g) del cultivar de maduración tardía Norin 1, y se analizó tanto el desarrollo de las plantas como el rendimiento de los tubérculos. Las plantas provenientes de microtubérculos mostraron un incremento inicial del índice en área de raíces y hojas menor que las plantas provenientes de tubérculo semilla convencional, pero 40 días después de la emergencia, el índice de área foliar fue la misma. Las plantas de tubérculo semilla convencional y las plantas de microtubérculos mostraron muy poca diferencia en cuanto al numéro de días en que se produjo el inicio de la formación de tubérculos, pero el aumento en el volumen del tubérculo se produjo 10 dias después, en las plantas provenientes de microtubérculos. El incremento en tubérculos y peso seco total desde el comienzo de la formación de tubérculos hasta el maximo crecimiento de los vástagos fue mayor en las plantas originadas de tubérculo semilla convencional que en las plantas provenientes de microtubérculos. Al momento de la cosecha, el peso fresco de tubérculos de plantas provenientes de microtubérculos fue 82% de aquel proveniente de plantas de tubérculos convencionales, lo cual sugiere que los microtubérculos tienen potencial para su uso en el campo.

Phosphorus Solubilizing Microorganisms in the Rhizosphere of Local Rice Varieties Grown without Fertilizer on Acid Sulfate Soils

Local farmers who living in South Kalimantan (Banjarese farmers) apply almost none of phosphatic (P) fertilizers to grow local rice varieties. This practice has been adopted for many years. We have investigated the mechanisms involved in P availability for the crop. This study focuses on identifying microorganisms involved in solubilizing insoluble P. The study was conducted in Balandean District, South Kalimantan, Indonesia. The soil was classified as acid sulfate soil. Three out of 8 rice varieties grown were selected for net P balance in the soil-plant system and the microbial studies. We found that the P uptakes by the rice crop was much higher than the sum of P released from soil, water and soil microbial biomass P. It was also observed that these soils harboured bacteria and fungi that have the capability of dissolving aluminium phosphate (AIPO4) and tricalcium phosphate [Ca3(PO4)2]. Based on the area of clear zone on plates, it seem that there were variations of ability in dissolving Al-P or Ca-P. DNA sequence analysis shown that Burkholderia sp. was the common P solubilizing bacterium found in the rhizosphere of rice varieties Siam Unus, Siam Ubi and Siam Puntal. The presence of other bacteria was specific for each rice variety grown.

Design of Sphingomonad-Detecting Probes for a DNA Array, and Its Application to Investigate the Behavior, Distribution, and Source of Rhizospherous Sphingomonas and Other Sphingomonads Inhabiting an Acid Sulfate Soil Paddock in Kalimantan, Indonesia

Throughout Central and South Kalimantan, Indonesia, strongly acidic soil (pH 2.1–3.7) is widely distributed, and the local acidic soil-tolerant plants, including local rice varieties, often possess sphingomonads in their rhizosphere and rhizoplane. To investigate the behavior of sphingomonads inhabiting the rhizosphere of such acid-tolerant plants, we designed 13 different DNA array probes (each of 72 mer) specific to a group of sphingomonads, using a hypervariable V6 region of the 16S rRNA gene. This DNA array system was used preliminarily for an analysis of microfloral dynamisms, particularly of sphingomonads, in acidic paddock ecosystems, and the results suggest that the acid-tolerant local rice shares rhizospherous sphingomonads with wild Juncus sp., a predominant weed that thrives in acidic paddocks during the off-season for rice farming. This tentative conclusion supports the bio-rationality of the traditional rice farming system with respect to functional rhizobacteria.

Extreme High Yield of Tropical Rice Grown Without Fertilizer on Acid Sulfate Soil in South Kalimantan, Indonesia

Land Characteristics of Batang Pelepat Watershed In Bungo District, Jambi (Sunarti): Land characteristics describe biophysics characteristics of watershed. But, land has been used for economic oriented. The objective of this research is to identify land characteristics of Batang Pelepat watershed. Data collection was carried out by survey based on land unit map and analyzed by descriptive analysis. The results showed that land in Batang Pelepat watershed consist of 23 land units and some land use types (forest, rubber and oil palm farming, settlement and shrub), soil parent materials variously (alluvium, granite, tuff andesite, basalt, and clay rock), soil depth ranges from 88 to 160 cm and soil texture is classified moderate fine to fine. Lands were dominated by slope of >15–30% and >45–65% and dystrudepts of soil group with soil fertility level very low to low because its pH about 3.80-6.20, base saturation about 7.86-32.79% and P- available about 2.80-25.00 ppm. Various land use has also caused different erosion and permeability levels.

Effects of root pruning and root zone restriction on spikelet fertility of paddy rice (Oryza sativa L.) under cool water condition

Various field observations suggested that rice plants with a deep and sound root system showed a relatively small yield loss due to spikelet sterility caused by the cool injury. The role of the vertical root distribution in susceptibility to a cool injury, however, has rarely been tested experimentally under field conditions. Three cultivars with different sensitivity to sterile-type cool injury were provided for the experiments. Roots were pruned at the panicle initiation and booting stages in 1998, and the root zone restriction treatment was imposed by placing unwoven cloth horizontally in a shallow soil layer (8–9 cm) before flooding in 1999 and 2000. Two levels of water temperature (Tw) were set during the reproductive periods (high, 23–24 °C; low, 19–20 °C). Low Tw substantially decreased spikelet fertility by 10–78% for all cultivars, and its magnitude differed largely between cultivars according to the cold tolerance ranks of the cultivars tested. Root pruning at the panicle initiation and booting stages did not decrease spikelet fertility of any cultivars under either Tw regime. The root zone restriction treatment gave no negative influence on spikelet fertility under both Tw regimes in both years. Bleeding rates were decreased by low Tw, but no difference was found between cultivars with largely different sensitivity to the sterile-type cool injury. The bleeding rate was not significantly affected by the root zone restriction treatment, suggesting that the limited root zone had a small influence on root activity. The results did not support an association between vertical root distribution and spikelet fertility under cool temperatures.