Gray leaf spot is a devastating disease caused by Stemphylium lycopersici that threatens tomato-growing areas worldwide. Typically, many pathogenesis-related and unrelated secreted proteins can be predicted in genomes using bioinformatics and computer-based prediction algorithms, which help to elucidate the molecular mechanisms of pathogen-plant interactions. S. lycopersici-secreted proteins were predicted from 8997 proteins using a set of internet-based programs, including SignalP v4.1 TMHMM v2.0, big-PI Fungal Predictor, ProtComp V9.0 and TargetP v1.1. Analysis showed that 511 proteins are predicted to be secreted. These proteins vary from 51 to 600 residues in length, with signal peptides ranging from 14 to 30 residues in length. Functional analysis of differentially expressed proteins was performed using Blast2GO. Gene ontology analysis of 305 proteins classified them into 8 groups in biological process (BP), 6 groups in molecular function (MF), and 10 groups in cellular component (CC). Pathogen-host interaction (PHI) partners were predicted by performing BLASTp analysis of the predicted secreted proteins against the PHI database. In total, 159 secreted proteins in S. lycopersici might be involved in pathogenicity and virulence pathways. Scanning S. lycopersici-secreted proteins for the presence of carbohydrate-active enzyme (CAZyme)-coding gene homologs resulted in the prediction of 259 proteins. In addition, 12 of the 511 proteins predicted to be secreted are small cysteine-rich proteins (SCRPs). S. lycopersici secretory proteins have not yet been studied. The study of S. lycopersici genes predicted to encode secreted proteins is highly significant for research aimed at understanding the hypothesized roles of these proteins in host penetration, tissue necrosis, immune subversion and the identification of new targets for fungicides.

Bacillus subtilis A-5 has the capabilities of high-molecular-weight γ-PGA production, antagonism to plant pathogenic fungi, and salt/alkaline tolerance. This multifunctional bacterium has great potential for enhancing soil fertility and plant security in agricultural ecosystem. The genome size of B. subtilis A-5 was 4,190,775 bp, containing 1 Chr and 2 plasmids (pA and pB) with 43.37% guanine-cytosine content and 4605 coding sequences. The γ-PGA synthase gene cluster was predicted to consist of pgsBCA and factor (pgsE). The γ-PGA-degrading enzymes were mainly pgdS, GGT, and cwlO. Nine gene clusters producing secondary metabolite substances, namely, four unknown function gene clusters and five antibiotic synthesis gene clusters (surfactin, fengycin, bacillibactin, subtilosin_A, and bacilysin), were predicted in the genome of B. subtilis A-5 using antiSMASH. In addition, B. subtilis A-5 contained genes related to carbohydrate and protein decomposition, proline synthesis, pyruvate kinase, and stress-resistant proteins. This affords significant insights into the survival and application of B. subtilis A-5 in adverse agricultural environmental conditions.

In August 2022, melon (Cucumis melo), cucumber (Cucumis sativus) and luffa (Luffa aegyptiaca) plants showed virus-like symptoms characteristic of geminiviruses (yellowish green, mosaic patterns and...

Phytopathogenic Sclerotinia minor Jagger causes lettuce drop, a destructive soil-borne disease. As potential biocontrol agents for this disease, 2 of 31 bacterial strains isolated from soil samples from fields containing S. minor Jagger were identified using in vitro antagonistic assays against S. minor Jagger. Bioactivity experiments showed that Bac20 had higher inhibitory activity against S. minor Jagger than Bac45. Based on 16S rRNA sequences and phylogenetic analysis of a combination of sequences from gyrA, rpoB, purH, polC, and groEL, Bac20 and Bac45 were identified as Bacillus velezensis and Bacillus subtilis, respectively. Lipopeptide compounds produced by each strain were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI–TOF MS) analysis. Both strains produced three types of lipopeptides, namely surfactins, iturins, and fengycins, whereas Bac20 showed the strongest intensity in its production of iturins, more than that of Bac45. Bac20 inhibited oxalic acid formation in early-stage lettuce leaves infected with S. minor Jagger, delaying pathogen infestation. Greenhouse experiments for controlling lettuce drop demonstrated that inoculation with Bac20 controlled lettuce drop by 71.7%. In conclusion, this study revealed that B. velezensis Bac20 has high potential for use as a biocontrol agent for controlling the lettuce drop caused by S. minor Jagger.

Muskmelon (Cucumis melo L.) is one of the most widely cultivated and economically important fruit crops in the world. In January 2023, muskmelon leaves of cultivar 'Sheng Gu' were observed with irregularly shaped spots in four nurseries in Wanxiang Village, Pudong District of Shanghai, China. Initial symptoms were irregular soaking on the leaves, which progressed to rotting and necrotic spots. The disease incidence of melon seedlings in different nurseries ranged from 10 to 25%. To isolate and identify the causal agent, the small pieces of lesion tissues (5×5 mm) from symptomatic leaves were sterilized in 75% ethanol for 30 s and rinsed three times with sterile water. Following that, tissues were crushed with sterile glass rod in a sterile 2.0 mL centrifuge tube containing 100 μl of sterile water. The suspension was serially diluted before being spread on Luria-Bertani (LB) medium. After 48 h of incubation at 28°C, the cream-colored bacterial colonies from the 10-4 dilution were tiny and purified by streaking on new LB plates. To confirm the species identity of the bacterial isolates, genomic DNA was extracted from four independent representative colonies from different diseased plants, and several conserved genes were amplified and sequenced, including the 16S rRNA gene with primers 27F/1492R, gyrB gene with primers gyrBFor2/gyrBRev2, and rpoD gene with primers rpoDFor2/rpoDRev2 (Lelliot et al. 1966; Murillo et al. 2011). The results showed that the four colonies were identical. Using BLAST analysis in GenBank, the 16S rDNA (accession no. OQ659765, 1,402 bp), the gyrB (accession no. OQ708618, 911 bp), and rpoD sequences (accession no. OQ708619, 798 bp) showed 99.86-100% homology with 99-100% coveage as the corresponding gene sequences in the P. syringae pv. syringae strain HS191 (accession no. CP006256.1). The bacterial isolate was designated as P. syringae pv. syringae strain PDTG. Phylogenetic tree analysis of 16S rDNA, gyrB and rpoD genes further verified that the bacteria isolate was in close proximity to P. syringae pv. syringae. Additionally, all four isolates were detected in PCR with P. syringae pv. syringae specific primers, PsyF/ PsyR (Borschinger et al. 2016; Guilbaud et al. 2016). Ten two weeks old healthy 'Sheng Gu' muskmelon seedlings were inoculated by spraying with a bacterial suspension of 108 CFU/ml, and ten additional healthy plants treated with sterilized water served as the control. The inoculated plants were maintained at 25°C and 75% relative humidity for 7 days in artificial climate room. Water-soaked rot, similar as those seen in the nurseries, appeared on leaves 7 days after inoculation (dai), while the leaves of control plants remained healthy. The bacteria were re-isolated from rot of inoculated leaves and confirmed as the original pathogen by PCR with the PsyF/ PsyR primers and the 16S rRNA gene sequences. To our knowledge, this is the first report of P. syringae pv. syringae causing bacterial leaf spot on muskmelon in China, and this report expands the host range of P. syringae pv. syringae.