Ovary culture has been widely used to overcome the fertilization barrier of interspecific hybridizations. In order to understand the relation between ovary culture and the growth temperature of hybrid siliques, three sets of interspecific hybridization were carried out in the field. Hybrid siliques in each set of hybridizations were excised at 10, 15, and 20 days after pollination and temperature from pollination to excision was recorded. No significant correlation was found between hybrid embryo yield in ovary culture and the average temperature. However, a significant quadratic correlation between the efficiency of ovary culture and the effective accumulated temperature (EAT) was observed. It indicated a rise-andfall relation between the optimal excision time and the growth temperature of hybrid siliques. Our data suggested that EAT is a more reliable indicator than silique age to determine the optimal time for excisinghybrid B. napus 9 B. oleracea siliques for ovary culture.
Polyploidization causes ‘genomic shock’ at the genetic and epigenetic levels relative to the parental species. However, few studies have compared the genetic and epigenetic alterations during the process of polyploidization by interspecific hybridization in Brassica species. In the present study, the early generations of hexaploid derived from a triploid hybrid between Brassica napus cv. ‘Zhongshuang 9’ and B. oleracea cv. ‘SWU01’ were developed, and used to detect genetic and epigenetic alterations together with triploid and two parental lines using simple sequence repeats (SSRs) and methylation-sensitive amplified polymorphisms (MSAPs). The derived hexaploids had relatively stable karyotype (69.84% euploid chromosome segregation in S0, 100% and 72.7% hexaploid karyotype in S1 and S2, respectively) and good fertility (88.75% ± 5.43% for pollen fertility, 4.68 ± 3.25 seeds/pod for self pollination and 13.55 ± 3.66 seeds/pod for open pollination), but wide morphologic characters. Compared with the parental lines, the triploid exhibited 13.08% new SSR alleles (17 of 130) and up to 26.45% new MSAP alleles (65 of 246), indicating that interspecific hybridization caused genetic and epigenetic alterations. No change in SSRs and 33.74% alterations in MSAP alleles (83/246) was observed between the triploid and hexaploid S0, suggesting chromosome doubling only caused epigenetic alteration. On average of 39.23% ± 5.78% of DNA methylation alterations and 6.35% ± 3.69% of SSR alterations occurred among the S2, S1, and S0 generations. It indicated that genetic alteration was caused by interspecific hybridization and generation descent of hexaploid, whereas epigenetic alteration resulted from interspecific hybridization, chromosome doubling and generation descent. It is interesting to find stronger epigenetic changes than genetic changes brought on during the processes of hexaploidization between B. napus and B. oleracea. It also found the average genetic distance between hexaploid S2 and hexaploid S1 (SSR 0.056 ± 0.029, MSAP 0.337 ± 0.201) was further than that between hexaploid S1 and hexaploid S0 (SSR 0.023 ± 0.009, MSAP 0.178 ± 0.126), suggesting more genetic variance in the hexaploid S2 generations than hexaploid S1.
In order to improve the utilization of the steelmaking byproduct steel slag in the concrete industry, this paper mainly studied the cementitious and hydration properties of converter steel slag. X-ray diffraction (XRD), non-evaporable water amount, strength, and particle size distribution were measured and analyzed. The paste with steel slag and water can be slowly hardened, which indicates the weak cementitious capacity of steel slag. The hydration of steel slag is similar to that of cement. The hydration rate of steel slag is much slower than that of cement at the early age, while its rate is higher than cement at the curing age of 90 days. The hydration rate of steel slag increases as its specific surface area (SSA) increases, and the degree of hydration becomes similar in steel slag with varying SSA at the curing age of 180 days. The early-age hydration of cement can be inhibited to some extent when steel slag is added. And the inhibition effect increases as the replacement level of steel slag increases. There is a slow strength development of steel slag blend concrete with a low water-to-binder ratio at the early age, while this influence decreases as age increases. The mineral phases of steel-slag-blend hardened paste mainly includes hydration products (Ca(OH)₂ and C-S-H), inert components (C₂F, magnetite, and RO phase), and unhydrated phases (C₃S, C₂S, gehlenite, and C₁₂A₇).
Fly ash and ground iron ore tailings with fineness similar to cement were used as active and inert mineral admixtures in this study. This paper examines the compressive strength development of plain mortar and blend mortar containing fly ash and ground iron ore tailing. The mortar was cured at the same curing regime and a different water to cementitious material ratio was used. The autogenous shrinkage is also detected in the first seven days. At the early stage of hydration, fly ash and ground iron ore tailings played a role as physical filler during the hydration of the cementitious composites. As age increases, the pozzolanic reaction of fly ash became dramatic. Concrete with fly ash and ground iron ore tailings has a similar trend of autogenous shrinkage. As the amount of fly ash and ground iron ore tailings increases, autogenous shrinkage linearly decreases and their autogenous shrinkage is similar to each other. The autogenous shrinkage of concrete in one day is more than the total shrinkage of 80% in seven days.
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