Identificação de espécies biológicas no complexo Fusarium solani - FSSC

Abstract

The Fusarium solani species complex - FSSC (teleomorph Haematonectria) is an aggregate of several phylogenetic and biological species, which cause disease in a wide range of crop plants. The objective of this work was to evaluate the presence of biological species within a collection of 68 isolates belonging to the FSSC, obtained from different host plants and from soil in Brazil. The mating type was determined by PCR using specific primers, followed by evaluation of sexual compatibility through crossings of isolates belonging to opposite mating types on carrot agar. To check for homothalism, monosporic cultures were plated on SNA and maintained at about 25°C for spontaneous production of fertile perithecia. The presence of differential morphological markers amongst the isolates was also evaluated. Eleven isolates were found to be homothallic and showed morphological characters matching the descriptions of Haematonectria ipomoeae. It was possible to determine the mating type of 26 isolates, eight of MAT-1 and 18 of MAT-2. Fertile perithecia were produced in 17 crossings among different isolates from soybean and common bean. This heterothallic species was tentatively identified as Haematonectria haematococca. Isolates from others plants did not produce fertile crossings. The size of asci was a useful marker for distinguishing the two biological species, with H. haematococca producing bigger asci. Characters of the anamorph were variable and could not be used as morphological markers. The homothallic species seems to be an unspecific pathogen, occurring in different host plants, while the heterothallic species probably represents a pathogen of leguminosae. Identification of biological species will be complemented by phylogenetic analysis and pathogenicity tests.