First report of Puccinia psidii (myrtle rust) on Syzygium jambos in Venezuela

Puccinia psidii has a wide host range, being reported from more than 38 genera and 165 species, spanning 11 tribes, in the Myrtaceae (Roux et al., 2015). The pathogen was first described by Winter in 1884 on Psidium guajava (guava) in Brazil. In 1912, it was observed on Eucalyptus citriodora but was not formally described from this host until 1944 (Coutinho et al., 1998). Puccinia psidii is native to South and Central America but is now known from many other locations, including Africa, Asia, Australia, North America (including Hawaii, Puerto Rico) and the Caribbean (Cuba, Jamaica, Trinidad) (Roux et al., 2015).

In Venezuela, rust infection was found in ornamental plantings of Syzygium jambos (rose apple) around the city of Merida (altitude 1300-1700 m) and on route to the Culata Paramo mountain range (up to an altitude of approximately 2700 m). The infection on immature leaves and shoots resulted in shoot death and the damage was more severe in the rainy season (Fig. 1). The initial symptoms appeared as small purple flecks and leaf spots on young leaves and brown spots on older leaves, often with a faint chlorotic halo (Fig. 2). In case of severe infections, spots enlarged and coalesced, often causing distortion or crinkling of leaves (Fig. 3). These later developed the characteristic bright yellow pustules, mostly on the lower leaf surface (Fig. 4A). Infection also occured on young twigs (Fig. 4B). Echinulate urediniospores (Figs. 5A, 5B) were unicellular, pyriform to spherical or oval, 16 to 23 x 17 to 22 μm, with a truncate base (Fig. 5C). The symptoms observed and morphology of the fungus was consistent with P. psidii. To confirm the identification, the 28S sequence was amplified from two of the isolates using the protocols described in Aime (2006) and compared via a BLAST search to the GenBank database where they shared 100% sequence identity with all 12 sequences of P. psidii currently available in the database. Voucher specimens were deposited in the Arthur Fungarium, Purdue University (PUR N15011–N15015) and sequence data in GenBank (GenBank Accession Nos. KX869864–KX869865).

Puccinia psidii has been reported previously in Venezuela on Eucalyptus spp., Myrcia caracasana and Psidiopsis moritzianum (Chardon & Toro, 1934; Grgurinovic et al., 2006). The fungus has been observed on Syzygium jambos in Australia, Brazil, China, Colombia, Costa Rica, Panama, Uruguay and the USA (Farr & Rossman, 2016). To date, no P. psidii infections have been observed on Eucalyptus species in the Cordillera Los Andes mountains or in the eucalypt plantations in the West Centre and Eastern Venezuela. To our knowledge, this is the first report of P. psidii on Syzygium jambos in Venezuela.