In: Sydowia 74, (2022): 343-350; ISSN 0082-0598, DOI 10.12905/0380.sydowia74-2021-0343, Published online on February 08, 2022

Kalmusia variispora, a fungal pathogen newly associated with decline of walnut trees in Iran

Shima Bagherabadi & Doustmorad Zafari

Department of Plant Protection, Faculty of Agriculture, Bu-Ali Sina University, P.O. Box 65178–38695, Hamedan, Iran

e-mails: Zafari_d@yahoo.com; Bagherabadi90@yahoo.com

Bagherabadi S. & Zafari D. (2022): Kalmusia variispora, a fungal pathogen newly associated with decline of walnut trees in
Iran. – Sydowia 74: 343–350.
During a survey in 2016–2020, the symptoms of decline were observed on walnut trees in some of the provinces in Iran. The
most common symptoms were sudden wilting, yellowing of the leaves and necrotic lesions of woody tissues surrounding the Zeuzera
pyrina damage in the walnut orchards. In the cross-section of the stems, V-shaped necrosis and brown discolorations were
observed adjacent to larval galleries of Z. pyrina. Generally, the decline is considered a complex disease caused by interacting
abiotic and biotic agents. In order to identify the possible causative agent of V-shaped necrosis, sampling was conducted from
symptomatic trees in the main walnut-growing provinces of Iran. After isolation using the standard method on potato dextrose
agar (PDA) medium and purification, 67 fungal isolates were obtained from symptomatic tissues. The common occurrence of
similar fungal isolates in symptomatic tissues of walnut trees called into question the identity of this fungus. Assessment of morphological
and cultural characteristics along with analysis of ITS region sequences showed that these isolates were Kalmusia
variispora. The results of pathogenicity tests confirmed that K. variispora to be pathogenic on walnut trees. To our knowledge,
this study is the first to present insights into K. variispora associated with the decline of walnut trees in the world.

Keywords: Dendrothyrium variisporum, Juglans regia, walnut decline, Zeuzera pyrina.