Neocosmospora spp. associated with dry root rot of citrus in South Africa. Neocosmospora spp. associated with dry root rot of citrus in South Africa

Citrus is one of the most important fruit crops cultivated in South Africa. Internationally, citrus dry root rot is a common disease among major citrus production areas. Several abiotic and biotic factors are involved in disease development, in which Neocosmospora species are considered important biotic agents. The diversity of Neocosmospora species associated with dry root rot symptoms of Citrus trees cultivated in South Africa was evaluated using morphological and molecular analyses. A multi-locus analysis based on fragments of seven loci was conducted: ATP citrate lyase (acl1), calmodulin (cal), internal transcribed spacer region of the rRNA (ITS), large subunit of the rRNA (LSU), RNA polymerase largest subunit (rpb1), RNA polymerase second largest subunit (rpb2), and translation elongation factor 1-alpha (tef1). A total of 62 strains representing 11 Neocosmospora species were isolated from crowns, trunks and roots of trees affected by dry root rot, as well as from soils sampled in affected citrus orchards. Of the known species, the most commonly isolated taxa were N. citricola, N. ferruginea and N. solani, while rarely encountered taxa included N. brevis, N. crassa, N. hypothenemi and N. noneumartii.