Identification of Resistance of Guangxi Oryza Rufipogon to Sogatella Furcifera with Stem Evaluation Method

White-backed planthopper (WBPH) is a devastating pest of rice, which significantly reduces production and causes millions of dollars in losses worldwide annually. Screening of germplasm resources with resistance to white-backed planthopper plays a crucial role in crop insect resistance breeding. In the present research, a total of 1080 accessions of Guangxi common wild rice(Oryza rufipogon) was screened for WBPH resistance through stem evaluation method (SEM). After preliminary screening, 49 resistance resources were identified, accounting for 4.54% of the total. After verified identification at the adult stage, 15 resistance resources with stable resistance to white-backed planthopper were finally obtained as resistant resources. The regional distribution analysis showed that the highest frequency of WBPH resistance resources appeared in Fusui county located in the upper reaches of Xijiang river(6.80%). Meanwhile, the highest frequency of the high resistance (HR and R) resources appeared in Pingnan located in lower reaches(2.79%). The 49 resistant accessions were genotyped for 43 SSR markers evenly distributed on the 12 chromosomes. The genetic diversity analysis showed a high polymorphism level of common wild rice populations. Fusui county possesses higher level of genetic diversity than the Yongning district and Pingnan county populations. The results from this study are essential to analyze resistance genes, cultivate insect-resistant varieties, and provide regional guidance for the exploration of resistance resources in the future.

New estimate of chemical weathering rate in Xijiang River Basin based on multi-model

Hydrochemistry and Sr isotope compositions were measured in water samples collected during high- and low-water periods from the main stream and tributaries of the Xijiang River Basin in southern China. The primary weathering end-members were analyzed and calculated using the multi-model combination and classic hydrogeochemical method. During the high-water period, structural factors were found to be the main factors controlling chemical weathering in the basin, whereas anthropogenic activity and other random factors had a negligible influence. During the low-water period, both structural and random factors controlled chemical weathering. Through path-model and semi-variance analyses, we determined and quantified the relationship between the main weathering sources, whose results were stable; this is consistent with the inversion model. The total dissolved substances were mainly derived from carbonate weathering, which was approximately 76% (0–96%) while silicate weathering accounted for only 14% (5–19%). The inversion model results showed that the optimum silicate weathering rate was 7.264–35.551 × 103 mol/km2/year, where carbonic acid was the main factor that induces weathering. The CO2 flux consumed by rock weathering in the basin during the study period was 150.69 × 109 mol/year, while the CO2 flux consumed by carbonic acid weathering of carbonate (CCW) and silicate rocks (CSW) was 144.47 and 29.45 × 109 mol/year, respectively. The CO2 flux produced by H2SO4 weathered carbonate (SCW) was 23.23 × 109 mol/year.

Ontogenetic Structure and Temporal Patterns of Summer Ichthyoplankton in Upper Course of the Xijiang River, SW China

The summer ichthyoplankton characteristics in the Laibin section of the Xijiang River were analyzed based on a survey during summer 2017. The ontogenetic structure and temporal patterns of ichthyoplankton and the correlation between environmental parameters and the temporal patterns were investigated. A total of 10,665 eggs and 447 larval belonging to four orders, ten families, and 28 species were collected. According to the flood regime, summer is divided into three periods (pre-flood, flood period, and post-flood). Ichthyoplankton proved to be heterogeneous between periods in summer with differences in the composition and abundance. The assemblages were distinguished by multiple analytical tools, and presented a chronological pattern of marked variability in composition of the species between the periods, and under the strong influence of flood. The assemblages were mainly represented by eggs of S. wui Fang and S. robusta in the pre-flood period, S. argentatus and S. macrops in the flood period, and H. leucisculus and S. curriculus in the post-flood period, while, the larval occurred mainly in the flood period. Understanding these temporal patterns of the upper course of the Xijiang River is useful for the recruitment of fish resources and conservation of fish community diversity.