<i>In vitro</i> Characterisation of Endophytic Fungi Strains from Lantana camara Leaves Displaying Antifungal Activity Against Phytophthora colocasiae

Abstract

Colocasiae esculenta is an important tropical tuber crop susceptible to attack by many diseases. The most devastative among these is Taro leaf blight cause by the pathogen Phytophthora colocasiae. The pathogen can cause rapid complete defoliation and crop destruction and under some circumstances, the disease can attack harvested corms and cause heavy losses during storage. Endophytes constitute an important source of bioactive secondary metabolites and enzymes. Based on their phytochemical properties, they can be used as a source of antifungal agent for the treatment of some infectious diseases. In order to evaluate the impact of endophytes on plant defence, in vitro evaluation of the growth effect of endophytic fungi against P. colocasiae was conducted in dual culture, after isolating and screening endophytic fungi from L. camara leaves for their production of some extracellular enzymes (amylases, lipases, laccases, protease and cellulose) and some secondary metabolites (tannins, saponins, phenols, cardiac glycoside) using standard procedures. In-vitro culture techniques with Potato Dextrose Agar (PDA) as culture medium were used to isolate endophytes from L. camara leaf tissues. Isolate identification was done using macroscopic and microscopic characteristics. These isolates were then tested in vitro to evaluate their morphological growth effect against P. colocasiae via the dual culture. Five endophytic fungi were isolated from Lantana camara leaves and coded L1, L2, L3, L4 and L5. The L2, L3 and L5 strains were filamentous and showed coenocytic hyphae which bore some structures’ called conidiosphores identified as Cladosporium sp. L1 strain was filamentous fungi having clamp connections hyphae (bridge-like growth) above hyphal septa and brown sclerotia. L4 strain showed very tiny interwoven and tightly parked mycelia. As enzyme activities, all the strains were found to produce amylase and not protease. L1, L3 and L4 were able to synthesis laccase while L5 produced cellulose and lipase. For the secondary metabolites, all the strains were able to produced tannins and cardiac glycoside but they did not synthesis saponins. L1, L2 and L4 strains were able to produced phenol. In dual culture, the growth of the pathogen decreased the growth rate of the endophytes. L2 strain grew normally by forming an arc around P. colocasiae growth while L3 and L5 strains induced the pathogen to grow on the opposite side of P. colocasiae. Concerning L1 and L4 strains, there were no effect. Based on the antifungal activities against P colocasiae, these strains L2 and L3 could be used for biological control of taro life blight.