Search

Abstract: Many rice breeding programs have currently reached yield plateaus as a result of limited genetic variability in parental strains. Dongxiang common wild rice (Oryza rufipogon Griff.) is the progenitor of cultivated rice (Oryza sativa L.) and serves as an important gene pool for the genetic improvement of rice cultivars. In this study, heterotic loci (HLs) associated with six yield-related traits were identified in wild and cultivated rice and investigated using a set of 265 introgression lines (ILs) of O. rufipogon Griff. in the background of the Indica high-yielding cultivar Guichao 2 (O. sativa L.). Forty-two HLs were detected by a single point analysis of mid-parent heterosis values from test cross F1 offspring, and 30 (71.5%) of these HLs showed significantly positive effects, consistent with the superiority shown by the F1 test cross population in the six yield-related traits under study. Genetic mapping of hsp11, a locus responsible for the number of spikelets per panicle, confirmed the utility of these HLs. The results indicate that favorable HLs capable of improving agronomic traits are available. The identification of HLs between wild rice and cultivated rice could lead to a new strategy for the application of heterosis in rice breeding. [Copyright &y& Elsevier]

• Distribution of forest fire was concentrated in the southern region near the border. • There was an increasing trend of forest fire crossing national and provincial borders. • Forest fire policy is the main driver, followed by biophysics and human intervention. • Human interventions via policy significantly affected the forest fire occurrences. • Fire prevention publicity and education near the national border should be improved. Forest fire is a recurrent and serious problem which stirs major environmental, economic, and social concerns. Information on the temporal–spatial distribution of ignition probability and identifying the factors that drive the pattern of forest fire occurrences are the most challenging issues over the world. In this study, the spatial distribution and temporal variation in forest fire occurrence were examined by applying the Maximum Entropy (Maxent) algorithm. Redundancy analyses were used to determine the contributions of driving factors (forest fire policy, human interventions, and biophysical variables) to the forest fire occurrences. In addition, the strength of the relationship between the forest fire policy, human interventions, and biophysical variables and their direct and indirect effects on forest fire occurrences were determined using structural equation models (SEMs). Our results showed the Maxent model was suitable for predictive modeling of the distribution of forest fire occurrences in southwestern China. The predicted area of forest fire occurrences in southwestern China during 2000–2017 was 3.25 × 105 km2 which mostly concentrated in the southern region. There was an increasing trend of forest fire crossing national and provincial borders. According to the temporal pattern of forest fire occurrences, additional ignition probability areas including the central Yunnan and the eastern Sichuan were found in spring when compared to those in winter. Moreover, forest fire policy is the main driver underlying the ignition, followed by biophysical factors and human interventions. These should be considered as key elements in the design of forest fire prevention programmes. Although the explanatory power of driving factors varied, national border distance (NBD) and conductive index (CI) that represented effects of forest fire policy were constantly the key driving variables. In addition, there is heterogeneity among the biophysical factors. The meteorological factors significantly affected on ignition probability in different temporal scale, while the effects of topographic factors were smaller. Human interventions had no significant direct effect on ignition probability, while they via fire policy had a significant positive indirect effect on the probability of fire occurrence. The results suggest that we should strengthen the administrative capacities to prevent forest fires, and improve the fire prevention publicity and education on the residents living near the national border and/or in low population density areas to get higher awareness and compliance of forest fire policies for local residents. [ABSTRACT FROM AUTHOR]