Relationship between Morphologic, Phenotypic and Pathogenic Characteristics in Macrophomina phaselina Isolates from Cucumber Plants

Abstract

During 2018 summer season, surveys were carried out in cucumber growing areas of Hatay province of Turkey. Roots and crowns of cucumber plants showing disease symptoms such as yellowing, wilting, root rot, damping-off and gumming were collected. A total of 25 Macrophomina phaseolina isolates were determined by morphologic characteristics on PDA medium. Colony sizes were measured after incubation for 3 days on PDA and colony diameters ranged from 45 to 81mm. A strong positive correlation was present between mycelial growth and disease severity (R=0,801). PDA medium amended with 120 mM potassium chlorate was used for phenotyping. Eight isolates were dense, 12 isolates feathery and 5 isolates were restricted. A high correlation was present between mycelial growth and disease severity (R=0.920). Sclerotia size of M. phaseolina isolates ranged from 19.1 to 29.9. In the pathogenicity test, cucumber seedlings were transplanted to plastic pots containing potting mixture of soil, perlite, peat (1:1:1) amended with 50g of M. phaseolina inoculum grown in cornmeal-sand mixture. Disease severity was measured with a 0-4 scale according to the symptoms on roots. Disease severity index was varied from 2 to 4 and virulence was significantly different (P<0.05) among isolates. Dense isolates were most virulent with the 3.75 mean disease scale followed by Feathery and Restricted phenotyped isolates with 3.17 and 2.27 respectively. According to the results of this study, a high correlation (R=0.92) was determined between chlorate phenotype and virulence in M. phaseolina isolates from cucumber plants in Turkey.