New insights into scabby canker of Opuntia ficus-indica, caused by Neofusicoccum batangarum

Abstract

This study characterizes a fungal disease of cactus pear (Opuntia ficus-indica, Cactaceae), reported from the minor islands of Sicily. The disease, originally named ‘gummy canker’, was first reported in 1973 from Linosa, a small island of the Pelagian archipelago, south of Sicily. The causal agent was identified as Dothiorella ribis (currently Neofusicoccum ribis, Botryosphaeriaceae). In a recent survey the disease has been found to be widespread in minor islands around Sicily, including Lampedusa, Linosa, Favignana and Ustica. The causal agent was identified in Botryosphaeriaceae as Neofusicoccum batangarum on the basis of the phylogenetic analysis of the DNA sequences from ITS, tef1 and tub2 sequences, and the disease was renamed ‘scabby canker’, which describes the typical symptoms on cactus pear cladodes. In artificial inoculations, N. batangarum induced symptoms on cactus pear cladodes identical to those observed in naturally infected plants. The fungus also induced cankers on artificially wound-inoculated stems of several common Mediterranean plants including Aleppo pine (Pinus halepensis), almond (Prunus dulcis), sweet orange (Citrus × sinensis), citrange (Citrus sinensis × Poncirus trifoliata) and holm oak (Quercus ilex), indicating that the pathogen has a wide potential host range. Isolates of N. batangarum from cactus pear from several small islands around Sicily were genetically uniform, as inferred from microsatellite primed (MSP)-PCR electrophoretic profiles, suggesting the pathogen populations in these islands have a common origin. A preliminary report of the identity of the causal agent of this disease has been published as the first record of N. batangarum in Europe and on cactus pear worldwide.

Keywords

• Botryosphaeriaceae
• cactus pear
• phylogenetic analysis
• marker genes
• host range