Heterosis-associated genes confer high yield in super hybrid rice.

KEY MESSAGE: Heterosis QTLs, including qSS7 and qHD8, with dominance effects were identified through GBS and large-scale phenotyping of CSSLs and hybrid F1 populations in a paddy field. Heterosis has contributed immensely to agricultural production, but its genetic basis is unclear. We evaluated dominance effects by creating two hybrid populations: a B-homo set with a homozygous background and heterozygous chromosomal segments and a B-heter set with a heterozygous background and homozygous segments. This was achieved by crossing a set of 156 backcrossed-derived chromosome segment substitution lines (CSSLs) with their recurrent parent (9311), the male parent of the first super-high-yield hybrid Liangyoupei9 (LYP9), and with the female parent (PA64s) of the hybrid. The CSSLs were subjected to a genotyping-by-sequencing analysis to develop a genetic map of segments introduced from the PA64s. We evaluated the heterotic effects on eight yield-related traits in the hybrid variety and F1 populations in large-scale field experiments over 2 years. Using a linkage map consisting of high-density SNPs, we identified heterosis-associated genes in LYP9. Five candidate genes contributed to the high yield of LYP9, with qSS7 and qHD8 repeatedly detected in both B-hybrid populations. The heterozygous segments harboring qSS7 and qHD8 showed dominance effects that contributed to the heterosis of yield components in the hybrid rice variety Liangyoupei9.

Influence of Ultraviolet Light and Alternating Wet-Dry Environments on the Corrosion Behavior of Weathering Steels.

The corrosion behaviors of two bridge steels (Q345q and Q500q) under simulated ultraviolet irradiation and a wet-dry alternating (UVWD) environment were studied. Weight loss measurement, stereomicroscope observation, SEM, XRD, and electrochemical impedance spectroscopy (EIS) were performed to investigate the influence of the coupled environment. The results revealed that the corrosion rates of Q345q and Q500q were significantly accelerated by the synergistic effect of UV light exposure and alternating wet-dry conditions. Numerous voids and cracks could be observed throughout the thickened rust layers, enabling the corrosive substances to easily penetrate through the rust layer. Q500q exhibited better corrosion resistance than Q345q due to the addition of Mo, Cr, and Ni as corrosion-resistant elements, which tended to transform the rust layer into α-FeOOH rather than γ-FeOOH during later stages of corrosion.