Characterization of Pathogenic and Nonpathogenic <i>Fusarium oxysporum</i> Isolates Associated with Commercial Tomato Crops in the Andean Region of Colombia

• Main Authors: Sandra L. Carmona, Diana Burbano-David, Magda R. Gómez, Walter Lopez, Nelson Ceballos, Jairo Castaño-Zapata, Jaime Simbaqueba, Mauricio Soto-Suárez
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Pathogens
• Subjects: <i>fusarium</i> wilt; physiological races; <i>six</i> genes; virulence; <i>forma specialis</i>; <i>solanaceae</i>
• Online Access: https://www.mdpi.com/2076-0817/9/1/70

In Colombia, tomato production under protected conditions represents an important economic contribution to the agricultural sector. <i>Fusarium</i> wilt diseases, caused by pathogenic <i>formae speciales</i> of the soil-borne fungus <i>Fusarium oxysporum</i> Schltdl., cause significant yield losses in tomatoes throughout the world. Investigation of the <i>F. oxysporum</i>&#8722;tomato pathosystem in Colombia is required to develop appropriate alternative disease management. In this study, 120 fungal isolates were obtained from four different departments in the Central Andean Region in Colombia from tomato crops with symptoms of wilt disease. A molecular characterization of the fungal isolates was performed using the <i>SIX1</i>, <i>SIX3</i>, and <i>SIX4</i> effector genes of <i>Fusarium oxysporum</i> f. sp. <i>lycopersici</i> W.C. Snyder &amp; H.N. Hansen (<i>Fol</i>). Additionally, we developed a new specific marker to distinguish between <i>Fusarium oxysporum</i> f. sp. <i>radicis-lycopersici</i> Jarvis &amp; Shoemaker (<i>Forl</i>) and <i>Fol</i> isolates. Furthermore, a phylogenetic analysis using the <i>Translation Elongation Factor 1-alpha</i> (<i>EF1a</i>) gene was performed with the collected isolates. Two isolates (named <i>Fol</i>59 and <i>Fol</i>-UDC10) were identified as <i>Fol</i> race 2, four isolates were identified as <i>Forl</i>, six isolates were identified as <i>F. solani</i>, and most of the isolates were grouped within the <i>F. oxysporum</i> species complex. The phylogenetic tree of <i>EF1a</i> showed that most of the isolates could potentially correspond to nonpathogenic strains of <i>F. oxysporum</i>. Additional pathogenicity assays carried out with <i>Fol</i>59 and <i>Fol-</i>UDC10 confirmed that both isolates were highly virulent strains. This study represents a contribution to the understanding of the local interaction between tomatoes and <i>F. oxysporum</i> in Colombia.