Differential behaviour of sheath blight pathogen Rhizoctonia solani in tolerant and susceptible rice varieties before and during infection

This study characterized the early infection and establishment of the sheath blight pathogen Rhizoctonia solani on a tolerant rice variety, Swarnadhaan (IET 5656), and a susceptible variety, Swarna (MTU 7029). Assays using whole plants showed that disease severity was higher in Swarna than Swarnadhaan. In a detached leaf assay, Swarnadhaan showed a disease index that was 50% less than that with Swarna. Rhizoctonia solani exhibited different growth behaviour in the tolerant and susceptible varieties. The pathogen showed more hyphal growth in the susceptible host than in the tolerant variety. It also showed profuse branching, making intimate contact with the host surface to form more inter‐ and intracellular structures, and greater sclerotial development in the susceptible host compared to the tolerant one. Using light and scanning electron microscopy, it was observed for the first time that the pathogen could intercept host surface structures and use these for anchorage or penetration. Transformed R. solani, expressing green fluorescent protein, was observed using confocal laser scanning microscopy to investigate pathogen behaviour, including the formation of infection cushions and subsequent colonization of the host tissues. This is the first ultrastructural report to characterize the differential behaviour of the sheath blight pathogen in the vicinity and within tolerant and susceptible rice plants.     

Relationship Between Seed Mass and Young-Seedling Growth and Morphology Among Nine Bluebunch Wheatgrass Populations

To better match plant materials to ecological sites for the purpose of rangeland seedling establishment, we examined the relationship between seed size and growth and morphological traits in young seedlings of bluebunch wheatgrass (BBWG) (Pseudoroegneria spicata [Pursh.] Á. Löve), a perennial Triticeae bunchgrass native to the Intermountain West. Traits examined included onset of germination, seedling biomass traits, and seedling surface-area traits. We grew seeds of nine BBWG populations that varied for seed size and were produced in a common environment under 2 contrasting d/n temperature regimes (20/15°C; 10/5°C). Lighter-seeded populations germinated and initiated shoots earlier. Heavier-seeded populations displayed high levels of biomass-related traits (e.g., shoot and root biomass and shoot length), while lighter-seeded populations displayed high levels of surface area ? related traits (e.g., specific leaf area and specific root length [SRL]). Correlations between seed size and young-seedling traits were mostly similar under the two temperature regimes. However, root length ? related traits showed more positive correlations with seed size under the low-temperature regime, which is more similar to actual field-emergence conditions during early spring. P-24, a light-seeded population, originated from the most arid site and exhibited the highest SRL at low temperature, while T-17t, a heavy-seeded population, originated from the most mesic site and exhibited moderate SRL. Three populations used for rangeland revegetation, “Whitmar,” “Goldar,” and Anatone Germplasm, all exhibited low seed mass and high SRL. However, only Anatone displayed high root-to-shoot length ratio under both temperature regimes, perhaps explaining its wide and successful use in rangeland seedings.     

猪流行性腹泻病毒S2基因B细胞表位嵌入型S-层蛋白在副干酪乳杆菌中的表达与鉴定

【目的】构建新型猪流行性腹泻病毒(Porcine epidemic diarrhea virus, PEDV)乳酸菌活菌疫苗载体。【方法】应用DNA重组技术将嗜酸乳杆菌S-层蛋白(SLP)基因及PEDV S2基因B细胞表位(EpitopeS2)融合基因(SLP-EpitopeS2)克隆到乳酸杆菌表达载体pTRK892中,构建重组载体pTRK-SLP-EpitopeS2,通过电转化方法将重组质粒导入副干酪乳杆菌中,获得重组副干酪乳杆菌。分别用SDS-PAGE、Western blotting和免疫荧光试验(IFA)鉴定目的蛋白在副干酪乳杆菌中的表达。【结果】PCR结果显示,成功扩增出大小为1 400 bp的目的条带,与插入融合基因大小一致,双酶切结果出现大小分别为1 400和4 700 bp的2条带,基因测序结果显示无碱基缺失和突变等,从而确定重组质粒pTRK-SLP-EpitopeS2构建正确。SDS-PAGE、Western blotting结果显示,在48 ku处出现与理论值大小一致的目的蛋白条带,表明融合基因SLP-EpitopeS2在副干酪乳杆菌中得到有效表达。IFA结果显示,...     

Effects of long-term phosphorus fertilizer inputs and seasonal conditions on organic soil phosphorus cycling under grazed pasture

Soil microbes and phosphatase enzymes play a critical role in organic soil phosphorus (P) cycling. However, how long-term P inputs influence microbial P transformations and phosphatase enzyme activity under grazed pastures remains unclear. We collected top-soil (0–75 mm) from a grazed pasture receiving contrasting P inputs (control, 188 kg ha⁻¹ year⁻¹ of single super phosphate [SSP], and 376 kg ha⁻¹ year⁻¹ of SSP) for more than 65 years. Olsen P, microbial biomass P, and acid and alkaline phosphatase enzyme activities were measured regularly over a 2-year period. Pasture dry matter and soil chemical properties were also investigated. Results showed that long-term P inputs significantly increased pasture dry matter, total N, and the concentrations of ${\mathrm{NO}}_3^{–}$–N but significantly decreased soil pH and the concentrations of ${\mathrm{NH}}_4^{+}$–N. Total C was not affected by P fertilization. Although Olsen P significantly increased with increasing long-term P inputs, microbial biomass P was similar under P fertilized treatments. Long-term P inputs decreased acid phosphatase activity but increased alkaline phosphatase activity. Microbial biomass P was similar across seasons in the control but decreased in spring and autumn while increased in summer and winter under P fertilized treatments. Acid and alkaline phosphatase activities were significantly affected by season and followed similar seasonal trends being maximum in summer and minimum in winter regardless of P treatment. Correlation and principal component analysis revealed that acid and alkaline phosphatase activities were significantly positively correlated with soil temperature and significantly negatively correlated with soil moisture. In contrast, Olsen P and microbial biomass P were weakly correlated with environmental conditions. The findings of this study highlight the intertwined relationship between organic P cycling and the availability of C and N in soil systems and the need to integrate both soil moisture and temperature in models predicting organic P mineralization, especially in the context of global climate change.