BACKGROUND Potato late blight (PLB) caused by Phytophthora infestans is one of the most devastating plant diseases. The heavy use of chemical control agents is at odds with the development of sustainable and environmentally friendly agriculture practices. It is necessary to screen the antagonistic microorganisms of P. infestans and provide a new choice of PLB biocontrol. RESULTS In vitro, eight bacterial strains (A, B, C, D, E, F, G, H) isolated from the rhizosphere of resistant potato plants had a significant inhibitory effect on the mycelium growth of P. infestans, and the inhibition rate was 35.02–79.20%. These isolates were assigned to Streptomyces, Pseudomonas, Saccharothrix and Nocardiopsis by phylogenetic analysis of 16S rRNA genes. Their physiological and biochemical characteristics suggested that they can produce cellulase and catalase, which may help to inhibit the infection of P. infestans. In vivo, each strain significantly inhibited the infection of P. infestans after individual inoculation into potato tubers, and no strains posed a pathogenic threat to tubers. In the field environment, multibacterial treatment significantly reduced the disease index. Compared with the control, multibacterial and single H treatment significantly increased the microbial species and abundance of the potato rhizosphere and enriched potential beneficial bacteria such as Rhizobiaceae. Meanwhile, multi‐bacterial and single H treatment significantly reduced the abundance of Enterobacteriaceae and Bacillaceae. CONCLUSION Our results provide some valuable native strains from the potato rhizosphere with the ability to inhibit P. infestans in vivo and in vitro, which may be a new option for PLB biocontrol. © 2021 Society of Chemical Industry.

A rare actinomycetes strain of Saccharothrix texasensis strain 6-C, has been isolated from the potato rhizosphere and it was shown to act as a biological control agent to potato late blight. It is also the first report on Saccharothrix inhibiting P. infestans. Here, we present the complete genome data of S. texasensis strain 6-C, assembled by sequencing reads obtained by both PacBio and Illumina technologies with annotation. The final assembled genome length is 9,045,220 bp, with no gaps, no plasmid, and its GC content is 72.39%. Nine non-ribosomal peptide synthetase (NRPS), five type I polyketide synthase (T1PKS), four terpene and three lanthipeptide gene clusters were identified in the genome, which would be likely to encode lots of antimicrobial active substances to help host plants against disease. This genome sequence could contribute to investigations of the molecular basis underlying the biocontrol activity of this Saccharothrix strain.

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Potato late blight, caused by Phytophthora infestans, leads to a significant reduction in the yield and value of potato. Biocontrol displays great potential in the suppression of plant diseases. Diallyl trisulfide (DATS) is a well-known natural compound for biocontrol, although there is little information about it against potato late blight. In this study, DATS was found to be able to inhibit the hyphae growth of P. infestans, reduce its pathogenicity on detached potato leaves and tubers, and induce the overall resistance of potato tubers. DATS significantly increases catalase (CAT) activity of potato tubers, and it does not affect the levels of peroxidase (POD), superoxide dismutase (SOD), and malondialdehyde (MDA). The transcriptome datasets show that totals of 607 and 60 significantly differentially expressed genes (DEGs) and miRNAs (DEMs) are detected. Twenty-one negatively regulated miRNA-mRNA interaction pairs are observed in the co-expression regulatory network, which are mainly enriched in metabolic pathways, biosynthesis of secondary metabolites, and starch and sucrose metabolism based on the KEGG pathway. Our observations provide new insight into the role of DATS in biocontrol of potato late blight.

Streptomyces sp. strain A2-16 was recently isolated from potato root zone soil and it could inhibit the hyphal growth of Phytophthora infestans. The A2-16 genome consisted of one chromosome of 9,765,518 bp and one plasmid of 30,948 bp with a GC content of 70.88% and 68.39%, respectively. A total of 8,518 predicted coding genes, 3 ncRNA,73 tRNA,18 rRNA genes and 28 secondary metabolite biosynthesis gene clusters were identified. The products of the gene clusters included bioactive polyketides, terpenes, and siderophores, which might contribute to host plants against disease. The average nucleotide identity (ANI) value (82.88-91.41%) among the genome of A2-16 and other Streptomyces species suggested it might not belong to any previously sequenced species in the Streptomyces genus.