IDENTIFICACIÓN DE CEPAS DE Fusarium oxysporum AISLADAS DE CHILE “SIETE CALDOS” (Capsicum frutescens L.) Y SU PATOGENICIDAD EN Capsicum chinense JACQ.]

<p><strong>Background. </strong>Chili pepper (<em>Capsicum</em> spp.) cultivation extends throughout Mexico, hosting a wide variety worldwide. However, crop health is reduced by the incidence of pathogenic microorganisms such as those of the <em>Fusarium</em> genus, which is one of the main agents causing vascular wilt and mortality of plant species. The use of molecular tools allows for rapid and reliable identification of organisms at the species level and help characterize the symptoms and pathogenicity they cause in hosts, which is important for field management and control. <strong>Objective. </strong>To identify at the molecular level fungal strains isolated from Siete Caldos chili (<em>C. frutescens</em>) using ITS and evaluate their pathogenicity in <em>C. frutescens</em> and <em>C. chinense</em>. <strong>Methodology. </strong>Strains of <em>Fusarium</em> from chile Siete Caldos plants (<em>C. frutescens</em> L.) were isolated and identified using traditional techniques (humid chamber and isolation in specific culture media) and molecular techniques (ITS1 and ITS4), and their pathogenicity in <em>C. chinense</em> Jacq. and <em>C. frutescens</em> was evaluated. <strong>Results. </strong>Seven strains were identified using taxonomic keys denoted as: <em>44hp</em>, <em>45ta</em>, <em>46ta</em>, <em>46hp</em>, <em>47hp</em>, <em>45hpssc</em> and <em>45hpmcsc</em>. From the amplified regions, the phylogenetic tree was obtained using the maximum-likelihood method based on the comparison of ITS sequences. The fungal isolates were identified and grouped, which corresponded to <em>F. oxysporum</em> strains reported in the NCBI database. The pathogenicity test showed the presence of symptoms in <em>C. frutescens</em>, with strain <em>45ta</em> being the most virulent (80 % incidence in inoculated plants). However, under the evaluation techniques used, <em>C. chinense</em> plants did not present wilting symptoms. <strong>Implications. </strong>The higher incidence of strain <em>45ta</em> in <em>C. frutescens</em> could be due to the affinity of <em>F. oxysporum</em> for its host (Siete Caldos chili), while the absence of symptoms in <em>C. chinense</em> could be due to an asymptomatic infection. <strong>Conclusions. </strong>The isolated strains showed no variability in their molecular identification, but not all showed the same infective capacity in the pathogenicity test. Therefore, it is necessary to perform tests with greater specificity to determine whether subspecies of the studied isolates exist.</p>