<p class="p1"> </p><p class="p2"><span class="s1"> </span>El objetivo de este trabajo fue identificar aislamientos patogénicos de <em>Fusarium </em>en frutos de pitahaya amarilla afectados por pudrición basal. La caracterización molecular se realizó en diecisiete aislamientos asociados con la enfermedad, colectados en zonas productoras de pitahaya amarilla de los departamentos del Valle del Cauca, Risaralda, Boyacá y Cundinamarca, en Colombia. Se usó PCR con los cebadores ITS1 – ITS4 y TEF1α. Las secuencias de los productos de PCR se compararon con las registradas en el Cento Nacional de Información Biotecnológica (NCBI, por sus siglas en inglés), y se alinearon usando Clustal W2, se construyeron las relaciones filogenéticas con el programa MEGA 6 con el coeficiente de máxima verosimilitud. Los resultados de secuenciación para los marcadores mostraron que los aislamientos patogénicos correspondieron a <em>F. oxysporum</em>. El concepto filogenético confirmó que la pudrición basal de la pitahaya amarilla fue causada por <em>F. oxysporum</em>. Se identificó además una especie de <em>Fusarium </em>no reportada en el GenBank.</p>

Achira (Canna edulis Ker.) is a cultivated species for handcrafted food products and starch production. In Colombia is estimated an achira cultivated area of 800 ha; in the department of Nariño there has been a disturbance of viral etiology, known by farmers as Streak Virus, due to its symptoms in the leaves, but without previous records in the area. The disease causes losses in performance, although they have not been established precisely. In order to clarify the nature of this pathology and the identity of the pathogen associated with the problem, an investigation was carried out at the University of Nariño, by means of molecular tests of PCR and RT-PCR, sequencing, serology and electron microscopy, of foliar samples collected in the producing areas. The most outstanding symptoms in affected tissues were yellow mosaic, mottled, chlorotic streak and ribs discoloration, among others. There were no cytoplasmic inclusions similar to those produced by Potyvirus, nor viral particles were observed, nor serology positive results, but it was possible to achieve the amplification of a cDNA fragment, with specific primers for Potyvirus and 98% of homology of the sequences with Sugarcane mosaic virus. This is the first SCMV report in achira in Nariño, Colombia.

In Colombia, vascular rotting of passion fruit (P. ligularis) caused by the fungus Fusarium is considered the most important pathological problem in the cultivation of this fruit. Plants affected by the pathogen wilt and die, causing considerable yield losses and increased production costs. The objective of this work was to determine the genetic variability of the Fusarium species associated with this disease. For this, 50 samples were collected from producing farms in three municipalities of the department of Nariño. A total of 35 isolates were characterized morphologically and molecularly. The morphological identification was carried out using taxonomic keys. Molecular characterization was performed by PCR with primers ITS1 – ITS4 and TEF1α. The PCR products were sent to Macrogen (Korea) for sequencing. Sequencing results indicated that Fusarium oxysporum f.sp. passiflorae is associated as a causal agent of the disease. In addition, the presence of Ilyonectria robusta was determined, which, has not been reported before in passion fruit plants. The phylogenetic analysis allowed determine that there was little variability among the isolates evaluated; no grouping was observed associated to the geographical origin of the samples. The morphological characters corroborated the species information obtained from the molecular analysis.

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