Development of a semiselective medium for detection of Mycosphaerella pinodes in soil, plant debris and seed

Abstract

Garden pea leaf blight, caused by Mycosphaerella pinodes, is a severe disease of peas worldwide. Detection of this pathogen from seed, plant debris and soil is difficult using non-selective agar media. This study was conducted to develop a semiselective medium for the isolation of this pathogen. Of the 14 carbon sources and 18 nitrogen sources tested, maltose and soluble starch were the most suitable carbon sources and casein was the most important nitrogen source for mycelial growth of three isolates of M. pinodes. Among 13 pesticides and two antibiotics tested, atrazine, mepronil, paraquat, propamocarb and TMTD showed no adverse effect on growth of M. pinodes. Based on these results, a starch–casein semiselective medium (designated as the SC-semiselective medium) was developed by amendment of 1 L Czapek–Dox agar with 30 g soluble starch, 2 g casein, 25 μg mL-1 propamocarb, 10 μg mL-1 benomyl, 50 μg mL-1 mepronil, 300 μg mL-1 atrazine, 100 μg mL-1 streptomycin sulfate and 200 μg mL-1 neomycin sulfate. This SC-semiselective medium was effective for detection of M. pinodes in artificially and naturally infested field soils, diseased seeds, leaves, and stems of peas. It should have potential for applications in research on biology, ecology and control of M. pinodes in peas.