Role of Human-Mediated Dispersal in the Spread of the Pinewood Nematode in China

Background: Intensification of world trade is responsible for an increase in the number of alien species introductions. Human-mediated dispersal promotes not only introductions but also expansion of the species distribution via long-distance dispersal. Thus, understanding the role of anthropogenic pathways in the spread of invading species has become one of the most important challenges nowadays. Methodology/Principal Findings: We analysed the invasion pattern of the pinewood nematode in China based on invasion data from 1982 to 2005 and monitoring data on 7 locations over 15 years. Short distance spread mediated by long-horned beetles was estimated at 7.5 km per year. Infested sites located further away represented more than 90% of observations and the mean long distance spread was estimated at 111–339 km. Railways, river ports, and lakes had significant effects on the spread pattern. Human population density levels explained 87% of the variation in the invasion probability (P,0.05).Since 2001, the number of new records of the nematode was multiplied by a factor of 5 and the spread distance by a factor of 2. We combined a diffusion model to describe the short distance spread with a stochastic,individual based model to describe the long distance jumps. This combined model generated an error of only 13% when used to predict the presence of the nematode. Under two climate scenarios (stable climate or moderate warming), projections of the invasion probability suggest that this pest could expand its distribution 40–55% by 2025. Conclusions/Significance: This study provides evidence that human-induced dispersal plays a fundamental role in the spread of the pinewood nematode, and appropriate control measures should be taken to stop or slow its expansion. This model can be applied to Europe, where the nematode had been introduced later, and is currently expanding its distribution. Similar models could also be derived for other species that could be accidentally transported by humans

Grain Yield and Nitrogen Use Efficiency of Late-cropping Rice in Response to Delayed Application of Nitrogen and Altered Plant Spacing in South China

【Objective】In order to further enhance grain yield of rice and nitrogen (N) use efficiency (NUE), N fertilizer was reduced and topdressing was delayed, together with alteration in row and plant spacing and planting density.【Method】In two late seasons, comparison trials were conducted with 8 treatments, including zero applied N (T1), farmers' practice (T2, control), 3 moderately-delayed N topdressing (T3-T5) and 3 highly-delayed N topdressing (T5-T8). T3-T8 also had alteration in N application rate, planting density and row and plant spacing.【Result】In comparison to T2, the average grain yields under T3-T5 were increased by 29.7% and 15.9%, and those of T6-T8 were increased by 26.4% and 18.6% in two late seasons, respectively. In both late seasons, nitrogen uptake and plant growth under T3-T5 and T6-T8 were slower before panicle initiation and they were both increased or accelerated thereafter. Based on average results in two late seasons, leaf area indexes at heading stage were enhanced by 8.5% and 11.8% respectively under T3-T5 and T6-T8 compared with that under T2. Leaf nitrogen contents at heading stage were enhanced by 16.8% and 23.5%, respectively. The numbers of panicles per hectare were increased by 14.5% and 15.2%, panicle size remained unchanged or was increased by 12.5%, sink sizes were increased by 13.6% and 29.3%, seed setting rate was enhanced by 9.0% or remained the same, 1000-grain weight remained identical or was decreased by 9.0%, biomasses were increased by 14.8% and 15.5%, and harvest indexes were increased by 7.2% and 6.4%, respectively. The total amounts of N uptake were increased by 27.6% and 40.7%, N uptake efficiencies were increased by 85.9% and 124.2%, agronomical efficiencies were increased by 99.1% and 102.5%, and partial factor productivity was increased by 32.1% and 36.2%, respectively. Additional N input, dense planting and alteration in row and plant spacing had little effect on yield and NUE. Highly-delayed N topdressing could further expand sink size and improve NUE, but could not enhance grain yield anymore.【Conclusion】With reduced N input, both source and sink of rice were substantially enlarged, and the yield and NUE were dramatically increased under moderately-delayed and highly-delayed N topdressing

Mapping of QTL for Chlorophyll Content in Rice on High-Density Bin Map

【Objective】The research explored the genetic mechanism for regulating chlorophyll content and its response to nitrogen (N) fertilizer in rice, and provide new molecular marker segments for breeding of high-yield and nitrogen- efficient rice varieties.【Method】The 113 family lines of ZS 97 × MH 63 recombinant inbred lines (RIL, F11) were adopted as tested materials for QTL analysis. Field experiments were performed with split-plot design, N fertilizer rate being the main plots and RIL being subplots. The low N (no N) and normal N (130, 135 N kg/hm2) fertilizer treatments were established in the fields. The chlorophyll meter was used to determine SPAD values of leaves at 30 days after transplanting (30 DAT) and at heading (HD) stage. By using a high-density genetic map containing 1 619 Bin markers, IciMappingv3.4 software and complete interval mapping, QTL for controlling leaf chlorophyll content at two growth stages was mapped.【Result】In two N treatments at two growth stages within two years, a total of 15 QTLs for controlling leaf chlorophyll content were detected and they were located on chromosomes 1, 2, 3, 6, 7, 10 and 11. Each single QTL could explain 1.21%-40.74% of genetic contributions to traits. Through comparison of their physical loci, 6 QTLs were found to have been cloned or have the same loci being known previously for chlorophyll content. Among them, a locus, named qHDCHL6-1, regulating the chlorophyll content of flag leaf at heading stage was detected at 8.45-9.12Mb of chromosome 6. It was stably detected under two N treatments in two years, which explained 1.55%-28.01% of contributions to traits. Through functional annotation, 4 candidate genes related to chlorophyll content of flag leaf were found in the qHDCHL6-1 chromosome interval. These genes were LOC_Os06g15370 (OsNPF3.1), LOC_Os06g15420 (OsAS2), LOC_Os06g15620 (GAS) and LOC_Os06g15590, and the first three of these genes have been cloned【Conclusion】15 QTLs controlling leaf chlorophyll content of rice at 30 DAT and HD stage are detected, and a QTL locus qHDCHL6-1 with stable expression was identified, which contains 4 candidate genes

Source-sink-flow Characteristics and Super-high Yield Potential of the Super-large-panicle Rice Line DS23 in South China

【Objective】It aims to study the yield performance and source-sink-flow characteristics of new strain of super-large-panicle rice DS23 in early season, and explore the source-flow-sink characteristics and super-high yield potential of DS23, with an aim to provide theoretical basis for high-yield breeding and cultivation of early rice in South China.【Method】The study was conducted under field conditions with the new super-large panicle type strain DS23 as test material and the medium to large panicle type variety YHSM as the control. The leaf area index, SPAD value, accumulation and transport characteristics of non-structural carbohydrate (NSC) in stems, anatomical characteristics of vascular bundles and yield component factors of different panicle types of rice were measured and compared.【Result】The number of grain per panicle, grain weight, sink capacity and yield of DS23 were increased by 37.3%, 4.0%, 33.7% and 15.9% respectively compared to those of YHSM seedlings. The effective number of panicles and seed setting rate were significantly decreased by 6.8% and 15.1% compared to those of YHSM seedlings. There was no significant difference in leaf area index and flag leaf SPAD value between the two varieties at heading stage. Compared with YHSM, total mass of NSC reserved in stem and apparent contribution of transferred NSC to grain yield of DS23 were significantly reduced by 15.3% and 19.8%, respectively, and the apparent transport rate of stem sheath NSC was significantly increased by 10.3%; The DS23 vascular bundle number was significantly increased by 17.3%, and there was no significant difference in the vascular bundle area between the two varieties; DS23 showed no significant change in grain/leaf ratio, with a significant decrease in NSC/spikelet ratio of 34.2% and an increase in vascular bundle load index of 20.4%-60.2%.【Conclusion】The super-large panicle type rice germplasm DS23 planted in early season has a large sink capacity, well-developed vascular bundles transport organization, strong material transformation ability in later stage and great potential for high yield and yield increase. Improvement in seed setting rate is a main direction for exploring its super-high yield potential. The study result lays a theoretical foundation for the breeding of super-large panicle early rice varieties and the research and development of high yield cultivation techniques

Optical temperature sensing performance of Er3+/Yb3+ co-doped TiO2–ZrO2–La2O3 glasses

Er ^3+ /Yb ^3+ co-doped TiO _2 –ZrO _2 –La _2 O _3 glasses were prepared by aerodynamic levitation method. The transmittance spectrum shows that the transmittance of the glass before and after irradiation decreases from 75.46% to 71.13% in visible and near-infrared bands. The absorption and emission cross sections of the glasses at 525 nm were studied. The glasses were thermally treated at various temperatures and then investigated by x-ray diffraction, Scanning Electron Microscope and Transmission Electron Microscope. Optical spectra were measured as a function of temperature in the range of 298–498 K. The maximum relative sensitivity was determined to be 1.47% K ^−1 at 298 K. These results imply that the obtained glass may have the potential to be the matrix material for temperature sensing that requires to employed in a complex environment

Invasion data and potential driving factors.

<p>The pinewood nematode invasion in China between 1982 and 2005 (Panel A). The first pinewood nematode observation in China (in Nanjing) is represented by a white star. Spatial distribution of 10 susceptible tree species (Panel B). Black dots represent locations already infested. Potential anthropogenic pathways (Panel C), and spatial distribution of human-population density in 2000 (Panel D).</p

Monitoring data set.

<p>Annual changes in the number of dead trees over fifteen years after the introduction of <i>Bursaphelencus xylophilus</i> at seven locations in China.</p

Evaluating Rice Varieties for Suitability in a Rice–Fish Co-Culture System Based on Lodging Resistance and Grain Yield

Rice–fish co-cultures have been practiced for over 2000 years, and they have tremendous potential in terms of increasing food security and economic benefits. However, little research has been conducted into achieving stable yields and high lodging resistance with regard to rice while simultaneously promoting the harmonious and healthy growth of fish in rice–fish co-culture paddy fields. We conducted a field study aimed at selecting suitable rice varieties for rice–fish co-culture systems (encompassing both ratoon and main crop). This selection process was grounded in an evaluation of lodging resistance and grain yield among 33 rice varieties used throughout the studied region. The results revealed a range of lodging indices of the main crop for the second internode, spanning from 62.43 to 138.75, and the annual grain yield (main crop and ratoon crop) ranged from 7.17 to 13.10 t ha−1 within rice–fish co-culture systems. We found that the use of rice–fish co-culture farming could improve the milling quality, nutrient quality, and appearance quality of rice, though the improvement gained through co-culturing varied across rice varieties. Moreover, the lodging index of the three basal internodes of rice plants was significantly and positively correlated with the plant height and the culm fresh weight, but it was negatively correlated with the bending strength of the rice basal internodes. Additionally, the 33 tested rice varieties were clustered in accordance with their lodging resistance (i.e., high resistance with lodging indices 62.43–75.42; medium resistance with lodging indices 80.57–104.62; and low resistance with lodging indices 113.02–138.75) according to the hierarchical cluster analysis. The 33 rice varieties were also clustered in accordance with the annual (main crop and ratoon crop) grain yield (i.e., high yield with 11.17–13.10 t ha−1; medium yield with 10.15–10.83 t ha−1; and low yield with 7.16–9.88 t ha−1). In all, 11 rice varieties were identified by a comprehensive evaluation as suitable varieties for grain production in the rice–fish co-culture system. These varieties displayed favorable traits, including a high annual rice yield, strong lodging resistance, and good grain quality. This is the first study to systematically evaluate rice varieties based on grain yield, lodging resistance, and grain quality in rice–fish co-culture systems

Pathways.

<p>Results of the Wilcoxon test to compare the effects of rivers, river ports, lakes, railways and human population density (<i>H</i>) between infested points and random points, for three neighbourhoods (<i>N</i>120, <i>N</i>60, <i>N</i>30). The sample size of both datasets (observed and random data) was <i>n</i> = 156.</p

Current Status and Strategies for the Research on Fish Pond Rice Planting in Guangdong

Fish pond rice planting is an agricultural production activity that uses aquaculture ponds to grow rice. The development of fish pond rice planting technology can keep the aquaculture area, expand the rice planting area, improve food security, and reduce pollution from aquaculture tail water. In the early season of 2022, we conducted a fish pond rice planting experiment in Guangzhou and achieved initial success. The tested rice varieties were Yuetai Youzhan, Huangguang Youzhan, Meixiangzhan No. 2, Taifengyou 208, Guanghong No. 3, Yuexiang 430, Yuenong Simiao, Wushan Simiao, and Nanjing Xiangzhan. The aquaculture varieties were largemouth black bass, Australian freshwater lobster, crucian carp and yellow catfish. The results showed that there was significant difference in grain yield among tested rice varieties under fish pond cultivation and the difference was much greater than that under field cultivation. The yield of Yuexiang 430 was the highest, reaching 390.8 kg/667m2, which was 148.6% higher than that of Taifengyou 208. The four aquaculture varieties all performed well, with high survival rate and fast growth speed, among which the Australian freshwater lobster performed the best. At present, there are still some critical problems such as high cost, lack of technical standards and lagging behind in basic research in fish pond rice planting. Coordinated efforts should be made to enhance low-cost floating bed development, improve rice and fishery matching, screen out more rice varieties, optimize fertilizer management and pest control, manufacture or adapt supporting machinery and equipment, and strengthen relevant theoretical researches. Finally, the green, high-yield and high-efficiency fish pond rice planting procedures and standards should be established through technical integration. With the deepening of research and the maturing of technologies, the fish pond rice planting technology will make increasing contributions to food security, farmers' income increase, environmental protection and beautiful countryside construction in China, especially in the southern regions