Isolation and characterization of fungal pathogens causing date palm black scorch and false smut in Qatar

Abstract

Isolation and characterization of fungal pathogens causing date palm black scorch and false smut in Qatar Fatima A. Al-Naemi1, Resna K. Nishad1, Talaat A. Ahmed1 and Osman Radwan2 1Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar 2Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, IL, USA The ability of date palm (Phoenix dactylifera L.) to grow in hot and dry regions of the world makes it an important subsistence crop in most arid areas. Nevertheless, the conditions for date palm growth and production are optimal for some fungal diseases that cause significant yield loss. In Qatar, fungal diseases affecting the productivity of dates are black scorch, which is caused by necrotrophic fungal pathogen, Thielaviopsis punctulata and false smut, which is caused by biotrophic fungal pathogen, Graphiola phoenecis. This study aims to ultimately reduce the yield loss attributing to palm diseases by increasing our knowledge about pathogen, host, host-pathogen interactions and the factors that alter disease severity. In order to isolate and identify these two fungal pathogens, infected date palm samples were collected from 8 agricultural farms located in northern and southern Qatar and the fungal pathogens were isolated. Microscopic examination and physiological characterization revealed that T. punctulata (anamorph of Ceratocystic radicicola) is the causal fungal pathogen of black scorch disease. Although previous reports have showed that the closer species, Thielaviopsis paradoxa, as the causal agent of this diseases; this is the first report from Qatar demonstrated the involvement of T. Punctulata in black scorch disease. To examine the pathogenicity of this fungal pathogen, date palm healthy tissues, were infected by the pathogen and typical disease symptoms manifested within two weeks. On the other hand, characterization of the false smut disease showed yeast-like fungal colony reflecting the hallmark of Graphiola phoenecis. Molecular characterization of the isolated fungal pathogens is being performed by using sequences from the ribosomal region spanning internal transcribed spacers region 1 and 4 (ITS1 and ITS4). Additionally, real-time RT-PCR is being conducted to early identify the most important pathogens of date palm. Information from this study will help scientists to design effective strategies in controlling date palm diseases. Keywords: date palm, black scorch, false smut, Thielaviopsis punctulata, Graphiola phoenecis