QTL analysis for brown spot resistance in American rice cultivar ‘Dawn’

Rice brown spot (BS), caused by Bipolaris oryzae, causes yield loss and deterioration of grain quality. Using single-nucleotide polymorphism (SNP) markers, we conducted quantitative trait locus (QTL) analysis of BS resistance in backcross inbred lines (BILs) from a cross between an American rice cultivar, ‘Dawn’ (resistant), and ‘Koshihikari’ (susceptible). Four QTLs for BS resistance were detected in a three-year field evaluation, and ‘Dawn’ contributed the resistance alleles at all QTLs. The QTL with the greatest effect, qBSR6-kd, explained 15.1% to 20.3% of the total phenotypic variation. Although disease score and days to heading (DTH) were negatively correlated in all three years, qBSR6-kd was located near a QTL for DTH at which the ‘Dawn’ allele promoted heading. Another BS resistance QTL (qBSR3.1-kd) was unlinked to the QTLs for DTH. Therefore, these two QTLs are likely to be useful for breeding BS-resistant varieties without delaying heading. The other two BS resistance QTLs (qBSR3.2-kd and qBSR7-kd) were located near DTH QTLs at which the ‘Dawn’ alleles delayed heading. The QTLs reported here will be good candidates for developing BS-resistant cultivars.     

Performance of coated carbide tools when grooving wood-based materials: effect of work materials and coating materials on the wear resistance of coated carbide tools

This paper presents the performance of coated carbide tools when grooving various density hardboards and wood-chip cement boards. Work materials of low density (about 0.8g/cm³) and high density (about 1.2g/cm³) were tested. The coating materials studied were chromium carbide, titanium carbonitride, and titanium carbide, which were synthesized on P30 carbide substrate using a chemical vapor deposition method; titanium nitride, chromium nitride, and titanium carbonitride were synthesized using the physical vapor deposition method. Cutting tests were performed during grooving at a cutting speed of 1000m/min and a feed rate of 0.1 mm/rev. The results of the study show that the coated carbide tools are more advantageous in reducing the progression of tool wear and retaining lower normal force and noise level when cutting both hardboard and wood-chip cement board of high density than was the uncoated carbide tool. The wear rate of the coated carbide tools for the wood-chip cement board increased more rapidly than that of the hardboard with increasing densities. Though the coated carbide tools suffered more wear with the low-density wood-chip cement board than with hardboard, their normal force and noise level were always lower for the low-density wood-chip cement board.Part of this paper was presented at the 11th Annual Meeting of the Chugoku Shikoku branch of the Japan Wood Research Society, Matsue, Shimane, September 25, 1999     

Evaluation of surface smoothness by laser displacement sensor 1: effect of wood species

The best methods for determining surface roughness in an industrial environment are of the noncontact variety, with reproduction of the profile. The objective of this work was to compare the roughness profile obtained by a contact stylus with a commercial laser displacement sensor (LDS). Measurements were done using 15 wood species with different densities and colors, based on which special triangle profiles were prepared. The accuracy of the laser sensor was examined by statistical analysis of roughness parameters measured from the profiles. Experimental results show that LDS profiles were imitated correctly. However, LDS accuracy depends on the scanned wood properties (density and color), installation position of the sensor, and profile shape. It was found that evaluation of dark and high-density wooden surfaces was imperfect.Part of this work was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000; and at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001     

Improving production systems of timber-processing plants IV: Application of genetic algorithms for appropriate positioning of processing machines

The development of a layout plan for a new plant with the aid of genetic algorithms was studied to place the machines so that the plant floor was effectively utilized and the operation would not be impeded. Genetic algorithms are search algorithms based on the mechanics of natural evolution and natural genetics to solve problems in engineering fields. Simulation with the aid of genetic algorithms was undertaken step by step. The first seven hundred strings (chromosomes) were generated at random to organize an initial population. Each string consisted of 40 bits (genes), which represented characteristics of machines (x- andy-coordinates and inlet and outlet formations of materials on machines) in the binary coding. Then the simulation was undertaken by repeating selection, crossover, reproduction, and mutation of strings until all strings were saturated with the highest evaluation (fitness of chromosomes to environments in the case of creatures). Under some limitations, an acceptable layout plan of the modeled plant involving four wood-processing machines was obtained according to evaluation indices.Part III of this series appeared inMokuzai Gakkaishi 37: 702–710, 1991.Part of this report was presented at the 47^th annual meeting of the Japan Wood Research Society, Kocht, April 1997     

Effects of fiber length and orientation on elasticity of fiber-reinforced plywood

Short carbon fibers, a reinforced material in wood veneer composites, were used to investigate the effects of fiber length and orientation of fibers on the elasticity of plywood. The technical feasibility, elasticity, and strength of the reinforced plywood with short carbon fiber were evaluated. In a short fiber reinforcement system, the fiber length does not directly influence the reinforcement in Cox's theory when the fiber length exceeded a certain length. When the length of short carbon fiber is beyond 3 mm, the high reinforced result was obtained in the experiment. However, if fiber length was too long, the reinforced result was less owing to the bridge between fibers and the increase of holes. The optimum fiber length must be considered. The orientation of fibers has a strong influence on the reinforcement. Unidirectional, perpendicular, and random orientation displayed different influence on the elasticity. Experimental results were discussed with Cox's method. Reinforced plywood with short carbon fibers in random orientation has a higher shear modulus and bending strength than the controls, in addition to other mechanical properties.     

Abrasive wear properties of compressed sugi wood

We examined the abrasive wear properties and the effect of abrasive grain size on the rate of wear when sugi wood (Cryptomeria japonica D.Don), compressed to various densities, was rubbed with abrasive paper. The results showed that the wear resistance of compressed wood increased linearly with the increased compression ratio; and under the condition of a low compression ratio it tended to be higher in comparison with the strength of compressed wood. The critical grain size effect, which can be witnessed during the abrasive wear of metals and plastics, was seen when low pressure was applied to the abrasive material. At higher pressures, the wear rate of the compressed wood increased with grain size, but the critical grain size effect was not observed. The pressure required to create the critical grain size effect was found to be higher than that needed for other types of uncompressed wood with the same yield properties.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000