Root rot and damping-off of Aleppo pine seedlings caused by Pythium spp. in Algerian forest nurseries

Abstract

Aleppo pine (Pinus halepensis Miller) is a common forest tree in the Mediterranean Region. Production of Aleppo pine seedlings is hindered by damping off and root rot diseases in cooler conditions of north-western Algeria, which significantly reduces the seedling emergence. This work was carried out to evaluate the pathogenicity of different Pythium Pringsheim species on Aleppo pine seedlings. Seventeen isolates of Pythium spp. were isolated from diseased seedlings, identified to the species level based on DNA sequence from the internal transcribed spacer region and their identity was confirmed on morphological basis. The obtained isolates were pathologically characterized in Petri dish and pot assays. Germination was significantly inhibited by the different Pythium spp. isolates. The highest inhibition was observed with Pythium ultimum Trow in Petri dish and pot assays. The reduction in root growth differed significantly between different isolates. The maximum reduction in root growth (92.2%) was observed for P. ultimum in Petri dish assay. The various isolates of Pythium showed a significant influence on root length, shoot length and vigour index. The maximum disease incidence (89.7%) was caused by P. ultimum. Our results indicated that Pythium spp. is commonly found on diseased seedlings, in most containers and bare-root nurseries.