Disease prevalence, incidence, morphological and molecular characterisation of Lasiodiplodia pseudotheobromae causing collar rot disease on peanut plants in Turkey

Peanut (Arachis hypogaea L.) holds significant commercial and dietary importance as a major source of edible oil and protein in Turkey. Stem, collar or root rot, caused by several fungal disease agent, are serious soil-borne diseases of peanut. Accurate and precise identification of the disease agent provides fundamental and precise information for integrated plant management. During the period from June to September 2021, symptoms consistent with collar rot disease, including dark-brown stem rot, chlorotic leaves, wilting, and eventual whole plant death, were observed on peanut plants cultivated in the different districts of Osmaniye Province of Turkey. The disease incidence ranged from 8.0 to 45.0% in the inspected fields with an average of 3.4% overall. Twenty-four single-spore representative isolates were obtained from surface-disinfected symptomatic tissues. Morphological characteristics of fungal mycelium, conidial and pycnidial structures on potato sucrose agar (PSA) and water agar (WA) closely resembled those described for Lasiodiplodia spp. All isolates caused typical collar rot symptoms upon artificial inoculation of peanut seedlings. Morphological identification of Lasiodiplodia spp. isolates was corroborated by MALDI-TOF and molecular analyses utilizing sequences from the internal transcribed spacer (ITS), β-tubulin 2 (tub2) and translation elongation factor-1 alpha (TEF1-α) loci. Phylogenetic analysis confirmed that the representative fungal isolates (MKUBK-B1 and MKUBK-K22) belong to Lasiodiplodia pseudotheobromae. To the best of our knowledge, this is the first report of L. pseudotheobromae infecting peanut plants in Turkey. This work is expected to contribute to previously limited knowledge regarding the host range, incidence and prevalence of L. pseudotheobromae as a soilborne pathogen of peanuts. Due to the potential destructiveness and broad host range of this pathogen, it is essential to develop new strategies to establish more reliable, environmentally sustainable, and cost-effective management approaches for this disease.