Isolation and identification of pathogens causing stem rot of the fig tree (Ficus carica)

Abstract

In Mexico, the intensive production system of fig (Ficus carica) var. “Nezahualcoyotl” requires densities of 12,500 plants ha-1 for yields greater than 100 t ha-1. The asexual propagation of the fig through cuttlings in the nursery is not exempt from diseases. The objective of this investigation was to identify the causal agents of the rot of cuttings of the variety “Nezahualcoyotl” and to generate the corresponding severity scale. The pathogenicity of the isolates was corroborated through Koch’s postulates. The sequencing of the ITS1-ITS4 regions indicated that the isolates were highly related to Fusarium solani, Alternaria alternata and Pythium ultimum. A severity scale with five levels of damage induced by F. solani and A. alternata and three by P. ultimum is reported for the first time. Inoculation separately with F. solani and A. alternata promoted 100% cortex damage between 21-25 days after inoculation (DAI). The coinoculation of the three pathogens induced earlier (between 11-13 DAI) necrosis of the epidermis (85%) and the cortex (80%). The severity scale will be a valuable help in the quantification and monitoring of the rot of the fig tree stem.