Black spot caused by Pseudocercospora opuntiae in cactus pear productive systems of Jalisco, Mexico

Black spot is an important fungal disease widely spread in different cactus pear production systems in Mexico. In Jalisco, the disease was detected in the 1990's; nowadays almost 100% of plantations are damaged by it. The objective of this paper was to study the morphological variability, pathogenicity and virulence of the causal agent in cactus pear production systems, for fruit and vegetable (nopalitos) crops, in Jalisco, Mexico. Pseudocercospora opuntiae was isolated and characterized morphologically and molecularly from cladodes collected in cactus pear production systems of Zapopan and Ojuelos showing advanced symptoms of the disease. Pseudocercospora opuntiae exhibited high growth rates and conidia development in malt extract at 2% in 16/8 h light/darkness at 26 degrees C. Pathogenicity and virulence were tested in healthy cladodes under field and greenhouse conditions, as well as on individual cladodes, in vitro young explants and Phaseolus vulgaris inoculated with the fungus. Pseudocercospora opuntiae was able to infect under all established conditions, the first symptoms appeared 120 days after inoculation. This is the first report of isolation, identification, morphological and molecular characterization, and pathogenicity of the causal agent of cactus pear black spot in Jalisco, Mexico.