The contrasting effects of local environmental conditions on tree growth between populations at different latitudes

To forecast future forest productivity and function it is critical to account for forests’ responses to current environmental conditions. Current widely used climate envelope approaches, i.e., correlations between climatic variables and the presence of a species, simulate responses for the whole species and predict future range based solely on climatic suitability. However, most tree species will not be able to migrate to environmentally suitable locations fast enough to cope with climate change. Furthermore, short-term tree responses to climate change will take place within current populations, and these populations, acclimated to their local environments, are not likely to respond similarly to climate change. Thus, to develop reliable forecasts of forest responses to climate change, we need to consider this variability among populations. In this study, we tested the effect of environmental conditions on the growth of two common maples species (Acer rubrum L. and Acer saccharum Marshall) at two different latitudes within their northern distributional range. We collected tree growth data, i.e., increment cores, and analyzed year to year variability in tree growth as a function of temperature and precipitation. We identified the times of the year with a stronger association with tree growth, indicating phenological differences between the two latitudes, and quantified growth as a function of those variables. Results showed divergent responses between species and between populations of the same species. Acer rubrum had a positive response to increasing summer temperature and precipitation in the north, but a negative association to increasing summer temperature in the south. Acer saccharum only showed significant responses in the south, negative to summer temperature increases and positive to higher precipitation. Predicted growth under difference climate scenarios predicted for the region, showed that northern populations and southern populations did not significantly differ from current range of growth variability but, still, reflected future trends of decreased growth under a forecasted climate, i.e., higher temperatures and lower precipitation. These results document population level responses to environmental conditions of these two species providing latitude-specific guidance for future forest management.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/168567/1/Wang_Xiaomao_Thesis.pd

Visualization of the entire process of rice spikelet infection by Ustilaginoidea virens through nondestructive inoculation

IntroductionRice false smut caused by Ustilaginoidea virens, is a destructive fungal disease encountered in many rice-producing areas worldwide. To determine the process by which U. virens infects rice spikelets in the field.MethodsThe green fluorescent protein-labeled U. virens was used as an inoculum to conduct artificial inoculation on rice at the booting stage via non-destructive panicle sheath instillation inoculation.ResultsThe results showed that the conidia of U. virens germinated on the surface of rice glumes and produced hyphae, which clustered at the mouth of rice glumes and entered the glumes through the gap between the palea and lemma. The conidia of U. virens colonized in rice floral organs, which led to pollen abortion of rice. U. virens wrapped the whole rice floral organ, and the floral organ-hyphae complex gradually expanded to open the glumes to form a rice false smut ball, which was two to three times larger than that observed in normal rice.DiscussionPanicle sheath instillation inoculation was shown to be a non-destructive inoculation method that could simulate the natural infection of U. virens in the field. The entire infection process of U. virens was visualized, providing a theoretical reference for formulating strategies to control rice false smut in the field

Narrowing the Agronomic Yield Gaps of Maize by Improved Soil, Cultivar, and Agricultural Management Practices in Different Climate Zones of Northeast China

Citation: Liu, Z. J., Yang, X. G., Lin, X. M., Hubbard, K. G., Lv, S., & Wang, J. (2016). Narrowing the Agronomic Yield Gaps of Maize by Improved Soil, Cultivar, and Agricultural Management Practices in Different Climate Zones of Northeast China. Earth Interactions, 20, 18. doi:10.1175/ei-d-15-0032.1Northeast China (NEC) is one of the major agricultural production areas in China, producing about 30% of China's total maize output. In the past five decades, maize yields in NEC increased rapidly. However, farmer yields still have potential to be increased. Therefore, it is important to quantify the impacts of agronomic factors, including soil physical properties, cultivar selections, and management practices on yield gaps of maize under the changing climate in NEC in order to provide reliable recommendations to narrow down the yield gaps. In this study, the Agricultural Production Systems Simulator (APSIM)-Maize model was used to separate the contributions of soil physical properties, cultivar selections, and management practices to maize yield gaps. The results indicate that approximately 5%, 12%, and 18% of potential yield loss of maize is attributable to soil physical properties, cultivar selection, and management practices. Simulation analyses showed that potential ascensions of yield of maize by improving soil physical properties PAY(s), changing to cultivar with longer maturity PAY(c), and improving management practices PAY(m) for the entire region were 0.6, 1.5, and 2.2 ton ha(-1) or 9%, 23%, and 34% increases, respectively, in NEC. In addition, PAY(c) and PAY(m) varied considerably from location to location (0.4 to 2.2 and 0.9 to 4.5 ton ha(-1) respectively), which may be associated with the spatial variation of growing season temperature and precipitation among climate zones in NEC. Therefore, changing to cultivars with longer growing season requirement and improving management practices are the top strategies for improving yield of maize in NEC, especially for the north and west areas

The changes of T lymphocytes and cytokines in ICR mice fed with Fe3O4 magnetic nanoparticles

The aim of this article is to study the changes inhibited T lymphocytes and cytokines related to the cellular immunity in ICR (imprinting control region) mice fed with Fe3O4 magnetic nanoparticles (Fe3O4-MNPs). The Fe3O4-MNPs were synthesized, and their characteristics such as particle size, zeta potential, and X-ray diffraction patterns were measured and determined. All ICR mice were sacrificed after being exposed to 0, 300, 600, and 1200 mg/kg of Fe3O4-MNPs by single gastric administration for 14 days. Splenocytes proliferation was indicated with stimulate index by MTT assay; release of cytokines in the serum of ICR mice was detected by enzyme-linked immunosorbent assay, and the phenotypic analyses of T-lymphocyte subsets were performed using flow cytometry. Our results indicated that there were no significant differences in splenocyte proliferation and release of cytokines between exposed and control groups. Furthermore, there was no significant difference in the proportions of T-lymphocyte subsets in the low-dose Fe3O4-MNPs group when compared to the control group, but the proportions of CD3+CD4+ and CD3+CD8+ T-lymphocyte subsets both in the medium- and high-dose Fe3O4-MNPs groups were higher than those in the control group. It is concluded that a high dose of Fe3O4-MNPs, to some extent, could influence in vivo immune function of normal ICR mice

Ambiguity-Resistant Semi-Supervised Learning for Dense Object Detection

With basic Semi-Supervised Object Detection (SSOD) techniques, one-stage detectors generally obtain limited promotions compared with two-stage clusters. We experimentally find that the root lies in two kinds of ambiguities: (1) Selection ambiguity that selected pseudo labels are less accurate, since classification scores cannot properly represent the localization quality. (2) Assignment ambiguity that samples are matched with improper labels in pseudo-label assignment, as the strategy is misguided by missed objects and inaccurate pseudo boxes. To tackle these problems, we propose a Ambiguity-Resistant Semi-supervised Learning (ARSL) for one-stage detectors. Specifically, to alleviate the selection ambiguity, Joint-Confidence Estimation (JCE) is proposed to jointly quantifies the classification and localization quality of pseudo labels. As for the assignment ambiguity, Task-Separation Assignment (TSA) is introduced to assign labels based on pixel-level predictions rather than unreliable pseudo boxes. It employs a "divide-and-conquer" strategy and separately exploits positives for the classification and localization task, which is more robust to the assignment ambiguity. Comprehensive experiments demonstrate that ARSL effectively mitigates the ambiguities and achieves state-of-the-art SSOD performance on MS COCO and PASCAL VOC. Codes can be found at https://github.com/PaddlePaddle/PaddleDetection.Comment: Accepted to CVPR 202

Exploring Valid Reference Genes for Quantitative Real-time PCR Analysis in \u3cem\u3ePlutella xylostella\u3c/em\u3e (Lepidoptera: Plutellidae)

Quantitative real-time PCR (qRT-PCR), a primary tool in gene expression analysis, requires an appropriate normalization strategy to control for variation among samples. The best option is to compare the mRNA level of a target gene with that of reference gene(s) whose expression level is stable across various experimental conditions. In this study, expression profiles of eight candidate reference genes from the diamondback moth, Plutella xylostella, were evaluated under diverse experimental conditions. RefFinder, a web-based analysis tool, integrates four major computational programs including geNorm, Normfinder, BestKeeper, and the comparative ΔCt method to comprehensively rank the tested candidate genes. Elongation factor 1 (EF1) was the most suited reference gene for the biotic factors (development stage, tissue, and strain). In contrast, although appropriate reference gene(s) do exist for several abiotic factors (temperature, photoperiod, insecticide, and mechanical injury), we were not able to identify a single universal reference gene. Nevertheless, a suite of candidate reference genes were specifically recommended for selected experimental conditions. Our finding is the first step toward establishing a standardized qRT-PCR analysis of this agriculturally important insect pest

Reference Gene Selection for qRT-PCR Analysis in the Sweetpotato Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae)

BACKGROUND: Accurate evaluation of gene expression requires normalization relative to the expression of reliable reference genes. Expression levels of classical reference genes can differ, however, across experimental conditions. Although quantitative real-time PCR (qRT-PCR) has been used extensively to decipher gene function in the sweetpotato whitefly Bemisia tabaci, a world-wide pest in many agricultural systems, the stability of its reference genes has rarely been validated. RESULTS: In this study, 15 candidate reference genes from B. tabaci were evaluated using two Excel-based algorithms geNorm and Normfinder under a diverse set of biotic and abiotic conditions. At least two reference genes were selected to normalize gene expressions in B. tabaci under experimental conditions. Specifically, for biotic conditions including host plant, acquisition of a plant virus, developmental stage, tissue (body region of the adult), and whitefly biotype, ribosomal protein L29 was the most stable reference gene. In contrast, the expression of elongation factor 1 alpha, peptidylprolyl isomerase A, NADH dehydrogenase, succinate dehydrogenase complex subunit A and heat shock protein 40 were consistently stable across various abiotic conditions including photoperiod, temperature, and insecticide susceptibility. CONCLUSION: Our finding is the first step toward establishing a standardized quantitative real-time PCR procedure following the MIQE (Minimum Information for publication of Quantitative real time PCR Experiments) guideline in an agriculturally important insect pest, and provides a solid foundation for future RNA interference based functional study in B. tabaci