Histopathology of the resistance to Colletotrichum gloeosporioides of wild strawberries and species related to commercial strawberry

Abstract

Three species of wild strawberries, as well as three related species, were tested against virulent isolate of Colletotrichum gloeosporioides. The purpose of this study was to assess genetic resources exhibiting resistance to anthracnose. The results of inoculation experiments showed that the species Fragaria vesca, Fragaria virginiana and Fragaria chiloensis were susceptible to fungi; whereas species Duchesnea indica, Duchesnea chrysantha and Potentilla tucumanensis showed higher levels of resistance. A histopathological study revealed a different response between susceptible and tolerant species. A significant thickening of the cell wall in epidermal cells, changes of stomata and mesophyll cells, the presence of idioblastic cells with unknown content and the accumulation of large starch grains in atypical tissues, namely, stomata and parenchyma cells, were observed in species of the genus Duchesnea. However, no morphological alteration was observed in Fragaria species or in P. tucumanensis, which did not show any apparent interaction with the isolate of C. gloeosporioides. Oxidative burst was evaluated in leaf tissues with the fluorescent probe DCFH-DA (2,7-Dichlorofluorescein diacetate) in susceptible and tolerant genotypes. Results showed that tolerant species present a noticeable accumulation of H2O2 whereas susceptible species did not. These results have led us to the conclusion that the changes observed were correlated with the resistance to disease.