Cultural, Morphological and Molecular Diversity Among Stemphylium lycopersici Isolates Causing Tomato Gray Leaf Spot in Argentina

FRANCO, E.; VERA BAHIMA, J.; RONCO, L.; SAPARRAT, M; BALATTI, P. A.

Congreso; APS Annual Meeting; 2015

Cultural, Morphological and Molecular Diversity Among Stemphylium lycopersici Isolates Causing Tomato Gray Leaf Spot in Argentina   Mario E. E. Franco1, José Vera Bahima1, Blanca L. Ronco1, Mario C. N. Saparrat2 & Pedro Alberto Balatti1. 1. Centro de Investigaciones de Fitopatología, Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata. La Plata, Buenos Aires, Argentina. 2. Instituto Carlos Spegazzini, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata. La Plata, Buenos Aires, Argentina.   Twenty eight Stemphylium lycopersici strains were isolated from a similar number of tomato plants growing in several regions of Argentina with typical symptoms of gray leaf spot disease between 2010 and 2013. Cultural and morphological characteristics were studied on both homemade and commercial Potato Dextrose Agar (PDA) after culturing them for 7 days at 25 °C in the dark. Features such as growth rate, colony color, elevation, margin, zonation, media pigmentation and sporulation were examined. Furthermore, fifty mature conidia from each isolate were measured at x100 magnification and their morphology was assessed. Also variability was analyzed by using six inter-simple sequence repeat markers (ISSR-PCR). High levels of variability were observed at cultural and morphological characteristics. Using genomic fingerprints isolates were clustered at similarity coefficient values between 0.83 and 1.00 and no relationship was found between phenotypic and genotypic characters as well as the place of origin. The high rate of cultural and morphological variability as well as their sensitivity to environmental conditions, suggesting that the cultural conditions for diagnostic purposes must be carefully standardized, which should be accompanied by markers developed based on conserved gene sequences.