Gene Expression of Putative Pathogenicity-Related Genes in Verticillium dahliae in Response to Elicitation with Potato Extracts and during Infection Using Quantitative Real-Time PCR.

Quantitative real-time PCR was used to monitor the expression of 15 Verticillium dahliae's genes, putatively involved in pathogenicity, highly (HAV) and weakly aggressive (WAV) V. dahliae isolates after either (i) elicitation with potato leaf, stem, or root extracts, or (ii) inoculation of potato detached petioles. These genes, i.e., coding for Ras-GAP-like protein, serine/threonine protein kinase, Ubiquitin-conjugating enzyme variant-MMS2, NADH-ubiquinone oxidoreductase, Thioredoxin, Pyruvate dehydrogenase E1 VdPDHB, myo-inositol 2-dehydrogenase, and HAD-superfamily hydrolase, showed differential upregulation in the HAV versus WAV isolate in response to plant extracts or after inoculation of potato leaf petioles. This suggests their potential involvement in the observed differential aggressiveness between isolates. However, other genes like glucan endo-1,3-alpha-glucosidase and nuc-1 negative regulatory protein VdPREG showed higher activity in the WAV than in the HAV in response to potato extracts and/or during infection. This, in contrast, may suggest a role in their lower aggressiveness. These findings, along with future functional analysis of selected genes, will contribute to improving our understanding of V. dahliae's pathogenesis. For example, expression of VdPREG negatively regulates phosphorus-acquisition enzymes, which may indicate a lower phosphorus acquisition activity in the WAV. Therefore, integrating the knowledge about the activity of both genes enhancing pathogenicity and those restraining it will provide a guild line for further functional characterization of the most critical genes, thus driving new ideas towards better Verticillium wilt management.

Pre-treatment of soybean plants with calcium stimulates ROS responses and mitigates infection by Sclerotinia sclerotiorum.

Considering the high incidence of white mold caused by Sclerotinia sclerotiorum in a variety of field crops and vegetables, different control strategies are needed to keep the disease under economical threshold. This study assessed the effect of foliar application of a calcium formulation on disease symptoms, oxalic acid production, and on the oxidative stress metabolism in soybean plants inoculated with each of two isolates of the pathogen that have contrasting aggressiveness (HA, highly-aggressive versus WA, weakly-aggressive). Changes in reactive oxygen species (ROS) levels in soybean plants inoculated with S. sclerotiorum isolates were assessed at 6, 24, 48 and 72 h post inoculation (hpi). Generation of ROS including hydrogen peroxide (H2O2), anion superoxide (O2-) and hydroxyl radical (OH) was evaluated. Inoculation with the WA isolate resulted in more ROS accumulation compared to the HA isolate. Pre-treatment with the calcium formulation restored ROS production in plants inoculated with the HA isolate. We also noted a marked decrease in oxalic acid content in the leaves inoculated with the HA isolate in presence of calcium, which coincided with an increase in plant ROS production. The expression patterns of genes involved in ROS detoxification in response to the calcium treatments and/or inoculation with S. Sclerotiorum isolates were monitored by RT-qPCR. All of the tested genes showed a higher expression in response to inoculation with the WA isolate. The expression of most genes tested peaked at 6 hpi, which preceded ROS accumulation in the soybean leaves. Overall, these data suggest that foliar application of calcium contributes to a decrease in oxalic acid production and disease, arguably via modulation of the ROS metabolism.