Fusarium Solani causing lemon verbena root rot in Iran

Abstract

Lemon verbena (Lippia citriodora) is a medicinal plant whose use and growing surface is increasing in Iran (Malekirad et al., 2011). Leaf chlorosis and necrosis associated with root rot symptoms were observed in the course of surveys in lemon verbena farms of Kerman province (southeast Iran) in November 2012. More than 45% of 140 randomly examined plants were symptomatic. Infected root tissues were surface-sterilized, cultured onto PDA and incubated at 25°C for a week. Cream-colored colonies developed, with thin-walled, hyaline, ovoid, 1-2 celled microconidia (7.1-15.6×2.1-4.7 μm). Macroconidia (30-62×4.1-5.8 μm) were 3-5 septate, thick walled, hyaline and slightly curved. Chlamydospores were rounded, thick-walled, single, double or several in chains. Based on the morphological features, the iso- lated fungi were identified as Fusarium solani (Leslie and Summerell, 2006). Pathogenicity of the isolates was confirmed by inoculation of healthy roots. Amplification of the internal transcribed spacer (ITS) region of rDNA of a representative isolate using the universal pri- mers ITS1F and ITS4 resulted in a 531 bp product (GenBank accession No. KM229706) which showed 99% similarity with comparable F. solani sequences and clustered with other F. solani isolates in phylogenetic analysis. A preliminary report on the isolation and morpho- logical identification of F. solani from lemon verbena in Fars province (south of Iran) was previously published (Bagheri et al., 2014). This study confirms the presence and pathogenic- ity of F. solani in a wider range in lemon verbena farms in southern Iran and to our knowledge is the first molecularly-supported report of this fungal pathogen on lemon verbena in the world.