Abstract
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.
Highlights
Verticillium wilt, caused by V. dahliae or V. albo-atrum, is a major disease that engenders significant yield losses in potato production, valued at millions of dollars each year [1]
To mimic as much as possible what happens in nature, we first assessed the gene expression in V. dahliae in response to potato plant exudates; we investigated their expression during infection of potato detached leaves
The highly aggressive isolate (Vd1396-9) induced significantly more disease measured as total area under disease progress curves (AUDPC) of “percentage of infection” and “disease severity” than the weakly aggressive isolate (Vs06-07) or water control (Figure 1A,B)
Summary
Verticillium wilt, caused by V. dahliae or V. albo-atrum, is a major disease that engenders significant yield losses in potato production, valued at millions of dollars each year [1]. Referred to as potato early dying (PED), this disease can cause 5 to 12 metric tons of tuber yield loss per hectare, and result in up to 90% disease severity [1,2,3,4]. Previous research showed a correlation between the density of V. albo-atrum in the soil and severity of wilt symptoms under favorable conditions [5]. V. dahliae produces microsclerotia that can be released in the soil and remain viable for 10 to 15 years [4,6]. V. dahliae can enter the susceptible plants from the root tip, extend to cross the endodermis and penetrate the young xylem elements, reaching the vascular cylinder [9]. V. dahliae sporulates in the vascular tissue and moves following the sap stream, but may be trapped in pit cavities [8]
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