No abstract

Heterosis refers to the superior performance of hybrids relative to the parents. Utilization of heterosis has contributed tremendously to the increased productivity in many crops for decades. Although there have been a range of studies on various aspects of heterosis, the key to understanding the biological mechanisms of heterotic performance in crop hybrids is the genetic basis, much of which is still uncharacterized. In this study, we dissected the genetic composition of yield and yield component traits using data of replicated field trials of an "immortalized F 2 " population derived from an elite rice hybrid. On the basis of an ultrahigh-density SNP bin map constructed with population sequencing, we calculated single-locus and epistatic genetic effects in the whole genome and identified components pertaining to heterosis of the hybrid. The results showed that the relative contributions of the genetic components varied with traits. Overdominance/pseudo-overdominance is the most important contributor to heterosis of yield, number of grains per panicle, and grain weight. Dominance × dominance interaction is important for heterosis of tillers per plant and grain weight and has roles in yield and grain number. Single-locus dominance has relatively small contributions in all of the traits. The results suggest that cumulative effects of these components may adequately explain the genetic basis of heterosis in the hybrid. epistasis | recombinant inbred intercross H eterosis, or hybrid vigor, refers to the superior performance of the hybrids relative to the parents (1). Utilization of heterosis has tremendously increased productivity of many crops globally. However, the understanding of the underpinning biological mechanism is still fragmentary after a century of debate and quest. Although there have been a range of studies on various aspects of heterosis (2-5), the key to understanding the biological mechanisms of heterotic performance in crop hybrids is the genetic basis (6), much of which is still uncharacterized (7).Three classic genetic hypotheses-dominance (8-11), overdominance (12-15), and epistasis (16, 17)-were proposed as explanations for the genetic basis of heterosis. Although there have been a large number of genetic analyses in plants with results favoring one hypothesis or another (18-31), genetic composition pertaining to heterotic performance of crop hybrids has not been fully characterized in an experimental population. There has been no assessment about the relative contributions of these genetic components to heterosis in a crop hybrid.The following conditions should be met for complete genetic characterization of heterosis relevant to crop production: (i) the genetic materials are based on elite hybrids that have shown timehonored superiority in crop production; (ii) the targets are key traits of agronomic performance; (iii) the experimental population allows identification of all of the genetic components concerned, including dominance (d/a ≤1, where d is the dominant effect and a is the additiv...

The primary aim of this study was to examine associations between problematic Internet use, depression and sleep disturbance, and explore whether there were differential effects of problematic Internet use and depression on sleep disturbance. A total of 1772 adolescents who participated in the Shantou Adolescent Mental Health Survey were recruited in 2012 in Shantou, China. The Chinese version of the Internet Addiction Test (IAT) was used to evaluate the prevalence and severity of Internet addiction. The Chinese version of the Pittsburgh Sleep Quality Index (PSQI), a 10-item version of the Center for Epidemiologic Studies Depression Scale (CESD-10), and other socio-demographic measures were also completed. Multiple regression analysis was used to test the mediating effect of problematic Internet use and depression on sleep disturbance. Among the participants, 17.2% of adolescents met the criteria for problematic Internet use, 40.0% were also classified as suffering from sleep disturbance, and 54.4% of students had depressive symptoms. Problematic Internet use was significantly associated with depressive symptoms and sleep disturbance. The correlation between depressive symptoms and sleep disturbance was highly significant. Both problematic Internet use (β = 0.014; Sobel test Z = 12.7, p < 0.001) and depression (β = 0.232; Sobel test Z = 3.39, p < 0.001) had partially mediating effects on sleep disturbance and depression was of greater importance for sleep disturbance than problematic Internet use. There is a high prevalence of problematic Internet use, depression and sleep disturbance among high school students in southern China, and problematic Internet use and depressive symptoms are strongly associated with sleep disturbance. This study provides evidence that problematic Internet use and depression have partially mediating effects on sleep disturbance. These results are important for clinicians and policy makers with useful information for prevention and intervention efforts.

Short-term CBT group intervention seems to be a robust intervention for natural disaster victims. Short-term CBT group intervention was more effective than the general supportive intervention and the no-treatment group in enhancing psychological resilience and reducing PTSD and depression among adolescents who had lost parents in the earthquake. The general supportive intervention was effective only in improving psychological resilience.

Menopause might have a negative impact on QOL independent of age in community-based women in China. There seemed to be a potential model of the relationship of menopause status to change in QOL, but this needs supporting evidence from longitudinal studies. The association of QOL with age and other factors also should be considered.