Kretzschmaria zonata (Lév.) P.M.D. Martin, causal agent of root and neck rot in teak

Abstract

In commercial forest plantations in Campeche, Mexico, the root rot of the teak tree (Tectona grandis Lamiaceae) is a disease causing severe mortality in trees aged 4 to 8 years. This paper determines the causal agent of basal root and neck rot in teak. Symptoms were characterized from field collection, and young stromata from symptomatic trees and affected teak trees were collected. It was observed that infected trees reduce their growth and foliage, which has a yellowish green hue, and show root and neck rot. At the stem base a callous tissue (skirt) is formed, underneath which is a dark brown stroma with a black carbonaceous aspect. Kretzschmaria zonata was identified growing on the bark and forming stromatic plates as the causal agent of this rot. Its anamorph, belonging to the Geniculosporium genus, was isolated in a Potato Dextrose Agar culture medium (PDA). Geniculosporium grew radially in PDA at 25 ± 2 °C, changing its color from white to yellow-green in 15 days and staining the medium culture with a dark green hue. Hyaline conidiophores, hyaline and single-celled conidia from 4-5 (7) x 2-3 μm were registered.