<i>Rhizoctonia solani</i> AG-3PT is the major pathogen associated with potato stem canker and black scurf in Jordan

Abstract

Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) is a global soil-borne pathogen that severely harms potato crops, leading to significant product losses. Black scurf and stem canker are two manifestations caused by this pathogen, with variable intensity based on the distinctive anastomosis group endemic to the region. During the growing season of 2017 (March and April), 57 different fungus isolates were collected from potato crops farmed in the Jordan Valley. The identity of all the isolates was confirmed by sequencing the internal transcribed spacer (ITS) of the ribosomal DNA gene, and the hyphal interactions were also performed with R. solani isolates. The sequences were deposited in GenBank, where accession numbers were obtained. 21 of the isolates were AG-3PT R. solani, with 98–99% identity to reference strains. Somatic compatibility was determined by hyphal interactions, which showed pairing compatibility among the isolates. Around 86.7% of the pairings were somatically incompatible, indicating a high level of genetic diversity among the isolates, while only 13.3% of the pairings were somatically compatible. Testing for pathogenicity revealed that AG-3PT affected the stems of solanaceous plants, including potatoes, and the roots of other plant species. Based on the findings of this study, R. solani AG-3PT was the primary pathogen associated with potato stem canker and black scurf diseases in Jordan. To our knowledge, this is the first report on this pathogen's isolation and identification in Jordan.

Keywords

• black scurf
• pathogenicity
• rhizoctonia solani
• stem canker
• thanatephorus cucumeris