FIRST REPORT OF CROWN ROT CAUSED BY RHIZOCTONIA SOLANI AG-4 HG-I ON ASPARAGUS OFFICINALIS IN TURKEY

Abstract

In 2011, crown rot symptoms were observed on the base, root and spears of asparagus plants in Balikesir province (north-eastern Turkey). Surface-disinfected tissues were placed on potato dextrose agar medium and incubated at 22±1°C. Rhizoctonia cultures were obtained and identified based on vegetative hyphae, nuclear staining, and anastomosis typing with known tester isolates of Rhizoctonia solani (Sneh et al., 1991). Positive anastomosis was observed with tester strain of AG-4. To confirm identity of the causal fungus, the complete ITS rDNA of a representative fungal isolate was amplified using primers ITS1 and ITS4 (White et al., 1990), and sequenced. The resulting sequence (GenBank accession No. JX437939) was compared with other sequences from database showing 97% identity with ITS sequences of strain AG-4 HG-I. To meet Koch’s postulates, inoculum was prepared by growing the fungus on sterilized wheat kernels and its pathogenicity was tested on 45-day-old asparagus seedlings inoculated by placing two colonized wheat kernels in contact with the base of each plant. After six weeks, plants were removed and assessed for disease symptoms. The fungus caused damping off of seedlings, brown-red lesions on roots and spears, and was consistently re-isolated from infected tissues. This pathogen was reported previously on asparagus seedlings in Japan (Sakaguchi et al., 1990). To our knowledge, this is the first report of crown rot on asparagus caused by Rhizoctonia solani AG-4 HG-I in Turkey.