Stability in and Correlation between Factors Influencing Genetic Quality of Seed Lots in Seed Orchard of Pinus tabuliformis Carr. over a 12-Year Span

Coniferous seed orchards require a long period from initial seed harvest to stable seed production. Differential reproductive success and asynchrony are among the main factors for orchard crops year-to-year variation in terms of parental gametic contribution and ultimately the genetic gain. It is fundamental in both making predictions about the genetic composition of the seed crop and decisions about orchard roguing and improved seed orchard establishment. In this paper, a primary Chinese pine seed orchard with 49 clones is investigated for stability, variation and correlation analysis of factors which influence genetic quality of the seed lots from initial seed harvest to the stable seed production over a 12 years span. Results indicated that the reproductive synchrony index of pollen shedding has shown to be higher than that of the strobili receptivity, and both can be drastically influenced by the ambient climate factors. Reproductive synchrony index of the clones has certain relative stability and it could be used as an indication of the seed orchard status during maturity stage; clones in the studied orchard have shown extreme differences in terms of the gametic and genetic contribution to the seed crop at the orchard's early production phase specifically when they severe as either female or male parents. Those differences are closely related to clonal sex tendency at the time of orchard's initial reproduction. Clonal gamete contribution as male and female parent often has a negative correlation. Clone utilization as pollen, seed or both pollen and seed donors should consider the role it would play in the seed crop; due to numerous factors influencing on the mating system in seed orchards, clonal genetic contribution as male parent is uncertain, and it has major influence on the genetic composition in the seed orchard during the initial reproductive and seed production phase

Growth of oxide particles in FeCrAl- oxide dispersion strengthened steels at high temperature

The growth of oxide particles in FeCrAl-oxide dispersion strengthened steel (ODSS) considering an accident condition of the light-water reactor at above 1500 K was studied by using a high-temperature annealing. Oxide particles grew from 9 nm to more than 50 nm as maximum at 1623 K for 27 h, with decreasing their number density in two orders of magnitude. Most of the oxide particles in 15Cr-7Al were identified as YAM or YAP, while the oxide particles in 15Cr-7Al-0.4Zr were identified trigonal Y4Zr3O12. Zr addition to 15Cr-7Al ODSS accelerated the growth of the oxide particles, which is quite contrary to the effect of Zr addition during sintering as suggested in the literature. The kinetics of coarsening was characterized by an equation of Ostwald ripening. The diffusion activation energies obtained in the present materials were quite larger than the conventional diffusion activation energy of Y in alpha-iron. Gibbs free energy of oxides should be considered to discuss the coarsening. (C) 2017 Elsevier B.V. All rights reserved

Oxide particle coarsening at temperature over 1473K in 9CrODS steel

The oxide particle coarsening was evaluated at temperature over 1473K by means of transmission electron microscopy (TEM). After annealing of the 9CrODS extruded bar, the size of oxide particles increases while the number density decreases, indicating that the oxide particles coarsen through Ostwald ripening. The growth rate of the oxide particles follows the fifth-power law, which is in the region of dislocation ‘pipe’ diffusion. The activation energy for pipe diffusion, however, was remarkably high, derived as 891KJ/mole. The stability of oxide particles and the difference of the diffusion velocity in between bcc-δ phase and fcc-γ phase should be considered as the contributions to the activation energy

Grain boundary sliding associated with low strain rate at 1000°C in recrystallized ODS ferritic steel

The high-temperature deformation process of the recrystallized 16CrODS ferritic steel was investigated at 1000°C for the stress loading perpendicular to the elongated grain structure. The strain rate was varied in the range from 1.0×10−2 to 1.0×10−5s−1. At the strain rate over 1.0×10−4s−1, deformation is dominated by the conventional dislocation creep. Decreasing strain rate from 1.0×10−4s−1, grain boundary sliding becomes prominent. Accommodation process for the localized stress induced by grain boundary sliding could be dislocation creep at 1.0×10−4s−1, and by diffusional creep at 1.0×10−5s−1 or less. These were verified through the observation of void formation and localized strain accumulation by KAM map