Research status and prospect of ratoon rice in China under mechanically harvested condition.

The proportion and area of ratoon rice planting in China have been substantially increased, due to continuous improvement of rice breeding methods and consecutive innovation of cultivation technology, which has developed into one of rice planting modes with significant production efficiency. Combining the experience in research and practice, from the perspective of crop physiology and ecology, we reviewed the current situation and prospects of high-yielding formation and physiological mechanisms of ratoon rice. We focused on four key aspects: screening and breeding of ratoon rice cultivars and the classification; suitable stubble height for mechanically harvested ratoon rice, as well as water and fertilizer management; dry matter production and allocation in ratoon rice and the relationship with yield formation; regenerative activity and vigor of ratoon rice roots and their relationship with rhizosphere micro-ecological characteristics. As for the extending of mechanized low-cut stubbles ratoon rice technique, we should properly regulate the rhizosphere system, coordinate rhizosphere nutrient supply, germination of axillary buds, and tillering regeneration, to achieve the target of "four-high-one-low", that is high regeneration coefficient, high number of regeneration panicle, high harvest index, high yield, high quality, low-carbon and safe, aiming to improve the sustainability of ratoon rice industry.

Temporal variation of antibiotic resistome and pathogens in food waste during short-term storage.

The massive food wastes pose a growing health concern for spreading of antibiotic resistance and pathogens due to food spoilage. However, little is known about these microbial hazards during collection, classification, and transportation before eventual treatment. Here, we profiled the temporal variations of antibiotic resistance genes (ARGs), pathogens, bacterial and fungal communities across four typical food wastes (vegetable, fish, meat, and rice) during storage at room temperature in summer (maximum 28-29 °C) of typical southeast city in China. A total of 171 ARGs and 32 mobile genetic elements were detected, and the absolute abundance of ARGs significantly increased by up to 126-fold with the storage time. Additionally, five bacterial pathogens containing virulence factor genes were detected, and Klebsiella pneumoniae was persistently detected throughout the storage time in all food types except rice. Moreover, fungal pathogens (e.g., Aspergillus, Penicillium, and Fusarium) were also frequently detected. Notably, animal food wastes were demonstrated to harbor higher abundance of ARGs and more types of pathogens, indicating a higher level of hazard. Mobile genetic elements and food types were demonstrated to mainly impact ARG profiles and pathogens, respectively. This work provides a comprehensive understanding of the microbial hazards associated with food waste recycling, and will contribute to optimize the food waste management to ensure biosecurity and benefit human health.

Physiological and Proteomic Analyses of Different Ecotypes of Reed (Phragmites communis) in Adaption to Natural Drought and Salinity.

Drought and salinity are the two major abiotic stresses constraining the crop yield worldwide. Both of them trigger cellular dehydration and cause osmotic stress which leads to cytosolic and vacuolar volume reduction. However, whether plants share a similar tolerance mechanism in response to these two stresses under natural conditions has seldom been comparatively reported. There are three different ecotypes of reed within a 5 km2 region in the Badanjilin desert of Northwest China. Taking the typical swamp reed (SR) as a control, we performed a comparative study on the adaption mechanisms of the two terrestrial ecotypes: dune reed (DR) and heavy salt meadow reed (HSMR) by physiological and proteomic approaches coupled with bioinformatic analysis. The results showed that HSMR and DR have evolved C4-like photosynthetic and anatomical characteristics, such as the increased bundle sheath cells (BSCs) and chloroplasts in BSCs, higher density of veins, and lower density and aperture of stomata. In addition, the thylakoid membrane fluidity also plays an important role in their higher drought and salinity tolerance capability. The proteomic results further demonstrated that HSMR and DR facilitated the regulation of proteins associated with photosynthesis and energy metabolism, lipid metabolism, transcription and translation, and stress responses to well-adapt to the drought and salinity conditions. Overall, our results demonstrated that HSMR and DR shaped a similar adaption strategy from the structural and physiological levels to the molecular scale to ensure functionality in a harsh environment.

[Effects of Low-level Nutrition and Trace Antibiotics on the Fitness Cost of Plasmids Bearing Antibiotic Resistance].

The effects of nutrition and antibiotic level on fitness costs of plasmid containing antibiotic resistance in drinking water system were investigated in this study. Three plasmids harboring different antibiotic resistances, i.e. pACYC184, RP4, and PBR322, were selected. It was found that the antibiotic resistance imposed cost on the fitness of all plasmids at different nutrition levels, which was universal. Moreover, the fitness costs were larger at lower nutrition levels. Besides, the fitness costs of plasmid bearing antibiotic resistance were also affected by trace antibiotics. In this study, when exposed to antibiotics (lower than 50% MIC), the fitness costs of plasmid imposed to the bacteria were more apparent than the injury or inhibition effect by antibiotics. The plasmids were unstable. Therefore, it was inferred that the plasmid containing antibiotic resistance imposed large fitness costs on bacteria in drinking water system (with low-level nutrition and ng·L-1 level antibiotic), and it was not stable. Thus, the risk of plasmid bearing antibiotic resistance transmission and spread in drinking water system was low.

[An analysis of genetic diversity of different ecotypes of reed (Phragmites communis Trin.) by molecular marker techniques].

ISSR (inter-simple sequence repeat) and RAPD (random-amplified polymorphic DNA) markers were used to detect genetic diversity of 4 different ecotypes of reed (Phragmites communis Trin.) growing in Hexi Corridor, Gansu province. Nine effective primers were screened from 30 ISSR arbitrary primers, and a total of 99 DNA bands were amplified, among which 51 (51.5%) were polymorphic. Thirteen effective primers were screened from 45 RAPD 10-oligonucleotide arbitrary primers, and a total of 195 DNA bands were amplified, among which 87 (44.6%) were polymorphic. Genetic identity based on ISSR and RAPD data showed a positive correlation (r=0.845, P<0.05). Based on unweighted pair-group method with arithmetic averages (UPGMA) cluster analysis on DNA bands amplified, together with the correlation analysis between genetic distance and soil water contents and soluble salt contents as well, the present results suggest that the genetic diversity occurs among the four ecotypes of reed in adaptation to long term natural drought and salinity, showing an obvious evolutional tendency from swamp reed via salt meadow reed to dune reed.