A New Rice Disease, Black Sheath Spot, Caused by Curvularia fallax in China

The impact of the rice production system (irrigated vs lowland) on root-associated microbiome from farmer's fields in western Burkina Faso

Due to their potential applications for food safety, there is a growing interest in rice root-associated microbial communities, but some systems remain understudied. Here, we compare the assemblage of root-associated microbiota in rice sampled in 19 small farmer's fields from irrigated and rainfed lowlands in Burkina Faso, using an amplicon metabarcoding approach of the 16S rRNA gene (prokaryotes, three plant sample per field) and ITS (fungi, one sample per field). In addition to the expected structure by root compartments (root vs. rhizosphere) and geographical zones, we showed that the rice production system is a major driver of microbiome structure. In irrigated systems, we found a higher diversity of prokaryotic communities from the rhizosphere and more complex co-occurrence networks, compared to rainfed lowlands, while fungal communities exhibited an opposite pattern (higher richness in rainfed lowlands). Core taxa were different between the two systems, and indicator species were identified: mostly within Bacillaceae in rainfed lowlands, and within Burkholderiaceae and Moraxellaceae in irrigated areas. Finally, a higher abundance in rainfed lowlands was found for mycorrhizal fungi (both compartments) and rhizobia (rhizosphere only). Our results highlight deep microbiome differences induced by contrasted rice production systems that should consequently be considered for microbial engineering applications.

Diseases of Cymbopogon citratus (Poaceae) in China: Curvularia nanningensis sp. nov

Five Curvularia strains isolated from diseased leaves of lemongrass (Cymbopogoncitratus) in Guangxi Province, China, were examined. NCBI-Blast searches of ITS sequences suggested a high degree of similarity (99–100%) to Curvulariaakaii, C.akaiiensis, C.bothriochloae, C.heteropogonis and C.sichuanensis. To accurately identify these strains, we further analysed their morphology and phylogenetic relationships based on combinations of ITS, GAPDH, and tef1 gene sequences. Morphological observations indicated that the key character differing from similar species was conidial size, whereas phylogenetic analyses indicated that the five strains represent one species that is also distinct from C.akaii, C.akaiiensis and C.bothriochloae by conidial size and conidiophore length. Thus, the strains examined are found to represent a new species described herein as Curvulariananningensis. The pathogenicity test on the host and detached leaves confirmed the new species to be pathogenic on Cymbopogoncitratus leaves. Standardised requirements for reliable identification of Curvularia pathogens are also proposed.