First report of Asian rust of soybean caused by Phakopsora pachyrhizi in Cuba

Abstract

In April 2009, a severe rust outbreak in soyabean developed at phenological stage R3 of the plants, leading to the complete defoliation of two 50-ha fields of soyabean cv. Conquista in Jovellanos, Matanzas province, Cuba. Initial symptoms in the field consisted of yellowing of the lower leaves of plants leading to defoliation and early maturation. Symptoms on the upper side of leaves consisted of yellow spots that turned brown then necrotic, surrounded by wide yellow areas. Uredinia developed on the undersides of the leaves. Anamorphic sori (Malupa-type) were amphigenous, circular, minute, pulverulent, whitish becoming pale cinnamon-brown, scattered or in groups on discoloured spots, sub-epidermal becoming erumpent, cone-like. The results of PCR analysis confirmed the presence of both P. pachyrhizi and P. meibomiae causing mixed infections within the same plant, although higher concentrations of DNA of P. pachyrhizi were noted. This is the first report of P. pachyrhizi infecting soyabean in Cuba and the confirmation by advanced diagnostic procedures of the presence of P. meibomiae.