Colonization process of olive tissues by Verticillium dahliae and its in planta interaction with the biocontrol root endophyte Pseudomonas fluorescens PICF7.
Bottom Line: Isolate VDAT-36I quickly colonized olive root surface, successfully invaded root cortex and vascular tissues via macro- and micro-breakages, and progressed to the aerial parts of the plant through xylem vessel cells.For the first time using this approach, the entire colonization process of a woody plant by V. dahliae is reported.Early and localized root surface and root endophytic colonization by P. fluorescens PICF7 is needed to impair full progress of verticillium wilt epidemics in olive.
Affiliation: Departamento de Mejora Genética, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Alameda del Obispo s/n, Apartado 4084, 14080 Córdoba, Spain.Show MeSH
Related in: MedlinePlus
Mentions: Detailed microscopic observations of ‘Arbequina’ olive tissues have been carried out. Weak autofluorescence from cell walls was always observed, but did not interfere with detection of the tagged pathogen (and bacteria, see below), even helping to image plant tissues and cells morphology and avoiding extra tissue staining. Likewise, no autofluorescent native microorganisms were detected on/in olive tissues at any time. VDAT‐36I conidia were readily detected on the root surface just 1 DAI, and at this time it was consistently observed that on average half of the conidia present in the microscopy samples were germinating (Fig. 2A). Nonetheless, a mixed population of non‐germinated conidia, germinating conidia, and hyphae of variable lengths was observed during the first 2 days of root sampling. Profuse VDAT‐36I colonization of the entire root surface was found at these sampling times, without differences among the meristematic, elongation and differentiation zones (Fig. 2B). However, colonization differences were observed among these zones by 3 DAI. Indeed, at this time, the differentiation and the elongation zones were more abundantly colonized by VDAT‐36I than was the meristematic zone. In the former zones, conidia had germinated profusely, producing elongating hyphae interspersed among root hairs (Fig. 2C). In fact, most of the conidia were germinated at 3 DAI, and a hank of hyphae was then observed wrapping the root surface. Although many hyphae grew in parallel to the longitudinal axis of the roots within the junctions of epidermal cells, others did not exhibit such a clear thigmotropic growth. Indeed, most of the samples from this time‐point showed a non‐specific growth pattern, resulting in a complicated network of hyphae covering the root epidermis (Fig. 2D).
Affiliation: Departamento de Mejora Genética, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Alameda del Obispo s/n, Apartado 4084, 14080 Córdoba, Spain.