ABSTRACT The enhancement of rice production numbers can be achieved by using quality rice cultivars and fertilizers. The double rice cropping model has given rise to an important rice production system in southern China. Exploring the possibility of whether hybrid vigor could make a substantial contribution to early and late season rice production, and how the heterosis expression of hybrid rice functions under different levels of fertilizer application is of great significance. The objective of this study was to evaluate the grain yield and associated plant traits of popular hybrid and inbred rice varieties with large–scale promotion under conditions of customary (high) and combined (low) fertilization in the early and late seasons of 2017–18 in Changsha County, Hunan Province, China. We found that hybrid rice varieties displayed their respective advantages in the early and late rice seasons, but the advantages in their relative yield traits varied. The leading advantages of early season rice were effective panicle number per hill (EPN), 1000–grain weight (KGW), harvest index (HI), yield, and nitrogen use efficiency (NUE), whereas in late season rice, the foremost advantages were grain number per panicle (GNP), HI, yield, and NUE. The EPN was the prime advantage of early season hybrid rice with a short growth period, and the GNP was the main advantage of late season hybrid rice with a long growth period. Notably, the main yield advantage of hybrid rice was stronger under combined (low) fertilization than under customary (high) fertilization. Hence, high yield can be achieved by selecting the best hybrid rice varieties supported by combined fertilization (lower fertilizer use with higher efficiency).

Osteogenesis imperfecta (OI) is a family of genetic disorders associated with bone loss and fragility. Mutations associated with OI have been found in genes encoding the type I collagen chains. People with OI type I often produce insufficient α1-chain type I collagen because of frameshift, nonsense, or splice site mutations in COL1A1 or COL1A2. This report is of a Chinese daughter and mother who had both experienced two bone fractures. Because skeletal fragility is predominantly inherited, we focused on identifying mutations in COL1A1 and COL1A2 genes. A novel mutation in COL1A1, c.700delG, was detected by genomic DNA sequencing in the mother and daughter, but not in their relatives. The identification of this mutation led to the conclusion that they were affected by mild OI type I. Open reading frame analysis indicated that this frameshift mutation would truncate α1-chain type I collagen at residue p263 (p.E234KfsX264), while the wild-type protein would contain 1,464 residues. The clinical data were consistent with the patients’ diagnosis of mild OI type I caused by haploinsufficiency of α1-chain type I collagen. Combined with previous reports, identification of the novel mutation COL1A1-c.700delG in these patients suggests that additional genetic and environmental factors may influence the severity of OI.