Colletotrichum theobromicola assigned as the causal agent of anthracnose in feijoa (Acca sellowiana)

Abstract

Feijoa (Acca sellowiana), a native fruit tree of Brazil and Uruguay, has both a unique aroma and flavour. This species is widely cultivated in Colombia, New Zealand, and, to a lesser extent, in Georgia and Ukraine, amongst other countries. In its centre of diversity, Brazil and Uruguay, the cultivated area is increasing yearly. However, the occurrence of typical symptoms of anthracnose in feijoa plants has made fruit production difficult, or unfeasible, without the use of pesticides. Yet, little is known about the causal agent of anthracnose symptoms in feijoa fruit. Thus, this work aimed to analyse morphological and pathogenic characteristics of diseased fruit by using a multi-gene phylogenetic analysis based on DNA sequencing of six loci of 40 isolates in feijoa fruits collected in southern Brazil. Morphological data showed that mycelial radial growth rate ranged from 7.5 to 10.2 mm/day; length of conidia (L) ranged from 13.8 to 19.4 μm; width (W) ranged from 4.0 to 5.6 μm; and L/W ratio ranged from 2.5 to 4.2 μm. The size of appressoria ranged from 7.2 to 10.8 μm in length; 5.4 to 8.0 μm in width, and 1.1 to 1.5 μm for L/W. Isolates produced cylindrical or fusiform conidia and appressoria globules, nailed and irregular. Multigene phylogenetic analyses revealed the presence of anthracnose symptoms in both orchard-grown and natural populations of feijoa caused by Colletotrichum theobromicola assigned to the Gloeosporioides complex. All tested isolates showed that anthracnose symptoms caused pathogenicity in inoculated feijoa fruits. These results, together with data on lifestyle of the isolates, will lead to improved management and handling of commercial feijoa orchards.