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

Abstract

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°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.