White rot in heartwood of Melia azedarach (Meliaceae) specimens from urban trees of La Plata (Buenos Aires): causal agent and chemical-anatomical characterization of the attacked wood Pudrición blanca en duramen de ejemplares de Melia azedarach (Meliaceae) del arbolado urbano de La Plata (Buenos Aires): agente causal y caracterización químico-anatómica del leño atacado

MURACE, MÓNICA; LUNA, MARÍA L.; LUCENTINI, GUSTAVO; LAURA, MALY; PERELLÓ, ANALÍA; SAPARRAT, MARIO C.N.

Lilloa

Fundacion Miguel Lillo

Año: 2022 vol. 59 p. 387 - 407

0075-9481

The xylophagous fungi frequently attack specimens of urban trees, decomposing their wood. This negatively affects stability and resistance to breakdown, putting the population and their goods at risk. During a survey of the rot present in the trees of La Plata city, specimens of Melia azedarach (Meliaceae) with evidence of white rot in exposed heartwood were observed. The aim of this work was to identify the fungus responsible for this rot and to analyze the anatomical and chemical alterations it causes in the wood. Heartwood samples with evidence of white rot in intermediate and advanced stages attained from stem and branch, respectively, were used. Fungal isolates were obtained from wood sections cultured on malt agar with antibiotic and fungicide. The identification was based on the characteristics of the colonies and confirmed by molecular techniques. Anatomical studies were performed with stereoscopic, optical and scanning electron microscopes and the chemical analysis by using wet chemistry and Fourier transform infrared spectroscopy (FT-IR). Phlebia brevispora (Basidiomycota, Polyporales) was the only xylophagous species isolated from the material. The anatomical alterations recorded allowed the diagnosis of simultaneous white rot in the stem and the coexistence of simultaneous and selective white rot in branch. Through wet chemistry, relative increases in the content of lignin and lipophilic extracts were determined, and decreases in the percentage of hydrophilic extractables in the samples of both degradation stages (branch and stem); the decrease in cellulose content was only identified in branch. FT-IR revealed the attack on cellulose and lignin. Although there is previous information about the presence of P. brevispora in standing trees, the current finding constitutes the first record for Argentina, while the interaction P. brevispora - Melia azedarach is reported for the first time in this contribution.