Key points are not available for this paper at this time.
Abstract Anthracnose, caused by Colletotrichum lindemuthianum, is the major disease of the common bean and causes serious economic losses. In the present study, we evaluated: (i) the antifungal activity of 26 essential oils (EOs) in the germination and mycelial growth of pathogen races 65 and 73, (ii) ultra structural changes of Cymbopogon citratus, Eugenia caryophyllata and Cymbopogon martini EOs in fungal conidia, (iii) the effect of these EOs on anthracnose control, applied before and after inoculation, and (iv) the effect of C. citratus EOs on the activity of defense enzymes on bean plants. Among the 26 EOs, C. citratus, C. martini, Cinnamomum sp., T. vulgaris, E. caryophyllata and M. recutita inhibited 95% conidial germination of fungal strains in concentrations lower than 0.1%. Mycelial growth was completely inhibited by C. citratus, E. caryophyllata and C. martini at 0.1% for 65 and 73 races. There was little mycelial growth in the fungicide treatment 4 DAI. Transmission electron microscopy (TEM) ultrastructure showed that C. citratus, C. martini and E. caryophyllata had direct antifungal action against C. lindemuthianum. These EOs caused serious ultrastructural damage to conidia, such as vacuolization, cytoplasm leakage and invagination of plasma membrane. Cymbopogon citratus and E. caryophyllata reduced anthracnose severity in both preventive and curative experiments. The activity of plant defense enzymes increased in the treatment with C. citratus. Essential oils show potential for the management of bean crop disease, especially anthracnose caused by C. lindemuthianum.
Hoyos et al. (Tue,) studied this question.