BackgroundSugarcane mosaic virus (SCMV) is responsible for large-scale economic losses in the global production of sugarcane, maize, sorghum, and some other graminaceous species. To understand the evolutionary mechanism of SCMV populations, this virus was studied in Shanxi, China. A total of 86 maize leaf samples (41 samples in 2012 and 45 samples in 2013) were collected from 4 regions of Shanxi.ResultsDouble-antibody sandwich (DAS)-ELISA and RT-PCR showed 59 samples (30 samples in 2012 and 29 samples in 2013) to be positive for SCMV, from which 10 new isolates of SCMV were isolated and sequenced. The complete genomes of these isolates are 9610 nt long, including the 5′ and 3′ non-coding regions, and encode a 3063-amino acid polyprotein. Phylogenetic analyses revealed that 24 SCMV isolates could be divided on the basis of the whole genome into 2 divergent evolutionary groups, which were associated with the host species. Among the populations, 15 potential recombination events were identified. The selection pressure on the genes of these SCMV isolates was also calculated. The results confirmed that all the genes were under negative selection.ConclusionsNegative selection and recombination appear to be important evolutionary factors shaping the genetic structure of these SCMV isolates. SCMV is distributed widely in China and exists as numerous strains with distinct genetic diversity. Our findings will provide a foundation for evaluating the epidemiological characteristics of SCMV in China and will be useful in designing long-term, sustainable management strategies for SCMV.

Bacillus velezensis LQ-3 was previously isolated from wheat soil and has been found to exhibit strong biocontrol activity against Rhizoctonia cerealis. To better understand its biocontrol mechanism, we utilized both Illumina and Nanopore sequencing technologies to sequence the whole genome of LQ-3. Our analysis revealed that the assembled genome of strain LQ-3 was 3,929,792 bp in length and contained one chromosome with a G+C content of 46.50%. We also identified 3,747 coding sequence genes (CDSs), 86 tRNA, 27 rRNA and one tmRNA genes. The LQ-3 genome contained 12 biosynthetic gene clusters responsible for secondary metabolite production. This genome sequence analysis is crucial for understanding the biocontrol mechanism of B. velezensis LQ-3 and serves as a foundation for the development and industrialization of biocontrol agents.