Deciphering the transcriptomic response of Ilyonectria robusta in relation to ginsenoside Rg1 treatment and the development of ginseng rusty root rot.

Rusty root rot is a severe disease in ginseng (Panax ginseng C. A. Mey) production caused by Ilyonectria robusta. The severity of the disease may be related to the residual ginsenosides in soil. In order to elucidate the response mechanism between Rg1 treatment and the occurrence of ginseng rust, we performed growth, reproduction and transcriptome analysis on treated Rg1. The results showed that Rg1 significantly promoted the mycelial growth and sporulation compared with the control, and aggravated the disease symptoms of Panax ginseng. A total of 6708 transcripts out of 213 131 annotated genes identified from global transcriptomic analysis were differentially expressed in Ilyonectria robusta grown during the Rg1 treatment. These genes were found to be related to the carbon-nitrogen metabolism, transport and assimilation. Many of these genes were also associated with pathogenicity based on the Phi-base database. Several transcription factors were related to specific biological processes, such as nitrogen utilization. The current results revealed that Rg1 played a major role in the development of rusty root rot by promoting fungal cell growth and affected the expression of genes required for pathogenesis. Rg1 could aggravate the invasion of Ilyonectria robusta on ginseng root, which preliminarily revealed the reason for the aggravation of rusty root rot in ginseng soil-borne.