Evolution of the rice blast pathogen on spatially structured rice landraces maintains multiple generalist fungal lineages.

Traditional agrosystems, where humans, crops and microbes have coevolved over long periods, can serve as models to understand the ecoevolutionary determinants of disease dynamics and help the engineering of durably resistant agrosystems. Here, we investigated the genetic and phenotypic relationship between rice (Oryza sativa) landraces and their rice blast pathogen (Pyricularia oryzae) in the traditional Yuanyang terraces of flooded rice paddies in China, where rice landraces have been grown and bred over centuries without significant disease outbreaks. Analyses of genetic subdivision revealed that indica rice plants clustered according to landrace names. Three new diverse lineages of rice blast specific to the Yuanyang terraces coexisted with lineages previously detected at the worldwide scale. Population subdivision in the pathogen population did not mirror pattern of population subdivision in the host. Measuring the pathogenicity of rice blast isolates on landraces revealed generalist life history traits. Our results suggest that the implementation of disease control strategies based on the emergence or maintenance of a generalist lifestyle in pathogens may sustainably reduce the burden of disease in crops.

Heterogeneity of the rice microbial community of the Chinese centuries-old Honghe Hani rice terraces system.

The Honghe Hani rice terraces system (HHRTS) is a traditional rice cultivation system where Hani people cultivate remarkably diverse rice varieties. Recent introductions of modern rice varieties to the HHRTS have significantly increased the severity of rice diseases within the terraces. Here, we determine the impacts of these recent introductions on the composition of the rice-associated microbial communities. We confirm that the HHRTS contains a range of both traditional HHRTS landraces and introduced modern rice varieties and find differences between the microbial communities of these two groups. However, this introduction of modern rice varieties has not strongly impacted the overall diversity of the HHRTS rice microbial community. Furthermore, we find that the rice varieties (i.e. groups of closely related genotypes) have significantly structured the rice microbial community composition (accounting for 15%-22% of the variance) and that the core microbial community of HHRTS rice plants represents less than 3.3% of all the microbial taxa identified. Collectively, our study suggests a highly diverse HHRTS rice holobiont (host with its associated microbes) where the diversity of rice hosts mirrors the diversity of their microbial communities. Further studies will be needed to better determine how such changes might impact the sustainability of the HHRTS.

Inhibitory mechanism of 6-Pentyl-2H-pyran-2-one secreted by Trichoderma atroviride T2 against Cylindrocarpon destructans.

Root rot caused by Cylindrocarpon destructans is one of the most devastating diseases of Panax notoginseng, and Trichoderma species are potential agents for the biocontrol of fungal diseases. Thus, we screened a total of 10 Trichoderma isolates against C. destructans and selected Trichoderma atroviride T2 as an antagonistic strain for further research. 6-Pentyl-2H-pyran-2-one (6PP) was identified as an important active metabolite in the fermentation broth of the strain and exhibited antifungal activity against C. destructans. Transcriptome and metabolome analyses showed that 6PP significantly disturbed the metabolic homeostasis of C. destructans, particularly the metabolism of amino acids. By constructing a gene coexpression network, ECHS1 was identified as the hub gene correlated with 6PP stress. 6PP significantly downregulated the expression of ECHS1 at the transcriptional level and combined with the ECHS1 protein. Autophagy occurred in C. destructans cells under 6PP stress. In conclusion, 6PP may induce autophagy in C. destructans by downregulating ECHS1 at the transcriptional level and inhibiting ECHS1 protein activity. 6PP is a potential candidate for the development of new fungicides against C. destructans.

External Factors Impacting Residents' Participation in Waste Sorting Using NCA and fsQCA Methods on Pilot Cities in China.

Recycling waste is important as it can help to reduce environmental pollution caused by "waste siege". Source classification is an important part of the municipal solid waste (MSW) sorting process. The factors that prompt residents to participate in waste sorting have been debated by scholars in recent years; however, there are not many papers that focus on the complex relationships between them. This study reviewed the literature that concerns residents' participation in waste sorting, and it summarized the external factors that might influence residents' participation. Then, we focused on 25 pilot cities in China, and we analyzed the configuration impact of external factors on residents' participation using a necessary condition analysis (NCA) and a fuzzy-set qualitative comparative analysis (fsQCA). We found no consistency between variables, nor was there one single condition that caused residents to participate in waste sorting. There are two main methods (environment-driven and resource-driven) that can help achieve a high participation rate, and three methods that can cause a low participation rate. This study provides suggestions for the implementation of waste sorting in other cities in China, as well as developing countries, with an emphasis on the importance of public participation.

Emergence of Southern Rice Black-Streaked Dwarf Virus in the Centuries-Old Chinese Yuanyang Agrosystem of Rice Landraces.

Southern rice black-streaked dwarf virus (SRBSDV), which causes severe disease symptoms in rice (Oriza sativa L.) has been emerging in the last decade throughout northern Vietnam, southern Japan and southern, central and eastern China. Here we attempt to quantify the prevalence of SRBSDV in the Honghe Hani rice terraces system (HHRTS)-a Chinese 1300-year-old traditional rice production system. We first confirm that genetically diverse rice varieties are still being cultivated in the HHRTS and categorize these varieties into three main genetic clusters, including the modern hybrid varieties group (MH), the Hongyang improved modern variety group (HY) and the traditional indica landraces group (TIL). We also show over a 2-year period that SRBSDV remains prevalent in the HHRTS (20.1% prevalence) and that both the TIL (17.9% prevalence) and the MH varieties (5.1% prevalence) were less affected by SRBSDV than were the HY varieties (30.2% prevalence). Collectively we suggest that SRBSDV isolates are freely moving within the HHRTS and that TIL, HY and MH rice genetic clusters are not being preferentially infected by particular SRBSDV lineages. Given that SRBSDV can cause 30-50% rice yield losses, our study emphasizes both the need to better monitor the disease in the HHRTS, and the need to start considering ways to reduce its burden on rice production.

[Isolation and identification of root endophytic and rhizosphere bacteria of rice landraces in Yuanyang Terrace, China].

ABSTRACT: To reveal root endophytic and rhizosphere bacteria constitution of rice landraces in Yuanyang Terrace, isolation was carried out by tissue isolation method and soil dilution plate method for two landraces of Yuelianggu and Hongjiaolaojing. A total of 399 bacterial strains isolated were identified by morphological characteristics, physiological and biochemical identification. The results showed that there were 8 genera isolated from the root of Yuelianggu and 5 genera from its rhizosphere soil, and 5 genera were same. For Hongjiaolaojing, there were 10 genera isolated from its root and 7 genera from its rhizosphere soil, and 6 genera were same. By molecular biology, identification, a total of 11 species and 5 genera were isolated from the root of Yuelianggu, 8 species and 4 genera from its rhizosphere soil, and 5 species and 4 genera were same. As for Hongjiaolaojing, there were 9 species and 5 genera isolated from its root, and 10 species and 3 genera from its rhizosphere soil, and 4 species and 2 genera were same. The results of physiological and biochemical characteristics identification method and molecular identification method were basically same at the genus level, while most of the strains could be identified to species by molecular identification. There were certain species homology and specificity in the root endophytic and rhizosphere bacteria of Yuanyang rice landraces.