External and Internal Root Colonization of Maize by TwoPseudomonas Strains: Enumeration by Enzyme-Linked...

Maize root colonization by two fluorescentPseudomonas strains M.3.1. and TR335, isolated respectively frommaize and tomato roots, were studied in hydroponic conditions. Each bacteriumwas inoculated separately, and three different colonization areas werestudied: nutrient solution, rhizoplane, and endorhizosphere. The twoPseudomonas strains established large rhizosphere populations, andrhizoplane colonization of the entire root system was similar for bothstrains. However, strain M.3.1. colonized the endorhizosphere moreefficiently than strain TR335. Seminal root cuttings from the tip to the seedallowed the assessment of colonization of three different root areas (i.e.,root cap and elongation area, root-hair zone, and mature zone). Rhizoplanecolonizations of all these three areas by M.3.1. were significantly the same,whereas strain TR335 colonized the rhizoplane of the root cap and elongationarea more actively than the root-hair zone and mature zone. Population sizeof the strain M.3.1. in the internal tissue of these areas was greater thanthat of strain TR335. Co-inoculations of the two strains indicated astimulation of the population size of strain M.3.1. regardless of root areastudied, whereas population size of strain TR335 remained unchanged. Theseresults demonstrated that external and internal maize root tissues werecolonized to a greater extent by a strain isolated from a maize rhizospherethan by one isolated from another rhizosphere.