Intraspecific Comparative Analysis Reveals Genomic Variation of Didymella arachidicola and Pathogenicity Factors Potentially Related to Lesion Phenotype.

Didymella arachidicola is one of the most important fungal pathogens, causing foliar disease and leading to severe yield losses of peanuts (Arachis hypogaea L.) in China. Two main lesion phenotypes of peanut web blotch have been identified as reticulation type (R type) and blotch type (B type). As no satisfactory reference genome is available, the genomic variations and pathogenicity factors of D. arachidicola remain to be revealed. In the present study, we collected 41 D. arachidicola isolates from 26 geographic locations across China (33 for R type and 8 for B type). The chromosome-scale genome of the most virulent isolate (YY187) was assembled as a reference using PacBio and Hi-C technologies. In addition, we re-sequenced 40 isolates from different sampling sites. Genome-wide alignments showed high similarity among the genomic sequences from the 40 isolates, with an average mapping rate of 97.38%. An average of 3242 SNPs and 315 InDels were identified in the genomic variation analysis, which revealed an intraspecific polymorphism in D. arachidicola. The comparative analysis of the most and least virulent isolates generated an integrated gene set containing 512 differential genes. Moreover, 225 genes individually or simultaneously harbored hits in CAZy-base, PHI-base, DFVF, etc. Compared with the R type reference, the differential gene sets from all B type isolates identified 13 shared genes potentially related to lesion phenotype. Our results reveal the intraspecific genomic variation of D. arachidicola isolates and pathogenicity factors potentially related to different lesion phenotypes. This work sets a genomic foundation for understanding the mechanisms behind genomic diversity driving different pathogenic phenotypes of D. arachidicola.

Development of 1,5-Diaryl-Pyrazole-3-Formate Analogs as Antifungal Pesticides and Their Application in Controlling Peanut Stem Rot Disease.

Stem rot disease caused by Sclerotium rolfsii is one of the destructive diseases in peanut and poses a big risk to peanut production. Current fungicides in the market have not provided satisfactory control efficacy and thus called for novel fungicides with different structures as an alternative treatment strategy. Our previously developed phenylpyrazole compound 3c demonstrated modest inhibitory effect against S. rolfsii. The following structure modification identified an unreported compound 6, which bears a 3-chloropyridinyl moiety as the most prominent derivative with an IC50 of 12 µg/ml in potato dextrose agar (PDA) assay, higher than those of 0.8 and 1.8 µg/ml associated with thifluzamide and tebuconazole, respectively. However, compound 6 showed similar controlling effects to those of thifluzamide and tebuconazole in field study. This study underscores the potential of 1,5-diaryl-pyrazole-3-formate as an antifungal candidate for stem rot disease management.

The complete mitochondrial genome of Psylliodes balyi Jacoby (Coleoptera: Chrysomelidae).

The complete mitogenome of Psylliodes balyi Jacoby (GenBank accession number MT644112) is 14,561 bp in length, and contains 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes, and a putative control region. The gene content and orientation of P. balyi were identical to other beetle mitogenomes. ATT, ATA, and ATG were initiation codons and TAA, TAG, and T were termination codons. All the 22 tRNAs have the typical cloverleaf secondary structure, except for trnS1 which lacked the dihydrouracil (DHU) arm. The phylogenetic relationship based on the neighbor-joining method showed that P. balyi is closely related to Agasicles hygrophila, which agrees with the conventional classification.