Endophytes from Wild Rubber Trees as Antagonists of the Pathogen <i>Corynespora cassiicola</i>

Abstract

The Corynespora leaf fall disease of rubber trees, caused by the necrotrophic fungus <i>Corynespora cassiicola,</i> is responsible for important yield losses in Asian and African plantations, whereas its impact is negligible in South America. The objective of this study was to identify potential antagonists of <i>C. cassiicola</i> among fungal endophytes (i.e., <i>Pestalotiopsis, Colletotrichum</i>, and <i>Trichoderma</i> spp.) isolated from wild and cultivated rubber trees distributed in the Peruvian Amazon. We first tested the endophytes in dual in vitro confrontation assays against a virulent <i>C. cassiicola</i> isolate (CCP) obtained from diseased rubber trees in the Philippines. All <i>Trichoderma</i> isolates overran the CCP colony, suggesting some antagonistic mechanism, while species from the other genera behaved as mutual antagonists. <i>Trichoderma</i> isolates were then tested through antibiosis assays for their capacity to produce growth-inhibiting molecules. One isolate (LA279), recovered as an endophyte from a wild <i>Hevea guianensis</i> specimen and identified as <i>Trichoderma koningiopsis</i>, showed significant antibiosis capacity. We demonstrated that LA279 was also able to endophytically colonize the cultivated rubber tree species (<i>H. brasiliensis</i>). Under controlled laboratory conditions, rubber plants were inoculated with three <i>Trichoderma</i> strains, including LA279, in combination with the pathogenic CCP. Results showed that 1 week preinoculation with the endophytes differentially reduced CCP mycelial development and symptoms. In conclusion, this study suggests that <i>T. koningiopsis</i> isolate LA279-and derivate compounds-could be a promising candidate for the biological control of the important rubber tree pathogen <i>C. cassiicola.</i>