Abstract
The Pink Disease is caused by Erythricium salmonicolor, which attacks broad hosts, such as citrus, coffee, rubber, Eucalyptus spp. and Acacia spp., infecting mainly branches. This disease became a serious problem in Brazil, reducing the citrus production up to 10%. However the genetic diversity and compatibility of the fungus E. salmonicolor from Brazilian citrus plants is not yet evaluated. Therefore, the aims of this study were to evaluate: i) the genetic variability of E. salmonicolor in the São Paulo and Minas Gerais States by the RAPD technique, and ii) the vegetative compatibility between these isolates. After RAPD analysis, six distinct groups were observed without correlation between the isolation site or host species. In the vegetative compatibility test, the contact of fungal hyphae between all evaluated crosses was observed, of which 84% presented hyphal fusion. Although the compatibility between strains was observed, no correlation between RAPD haplotypes and hyphal anastomosis was verified. These results show the importance of future studies on the sexual cycle of E. salmonicolor, since hyphal fusion, which precedes the formation of heterokaryons (sexual and parasexual reproduction) that could be responsible for the genetic variability in this species.
Highlights
Brazil is the largest citrus fruit producer in the world, dominating 80% of the international trade of concentrated orange juice, an activity that trades about US$ 4 billion per year
RAPD analysis was conducted with seven primers and only the well-defined and reproducible bands were considered
The obtained dendrogram (Figure 2) shows the genetic variability among isolates, clustering the strains in two major groups, whose genetic similarity is around 35%
Summary
Brazil is the largest citrus fruit producer in the world, dominating 80% of the international trade of concentrated orange juice, an activity that trades about US$ 4 billion per year. Brazilian citriculture has many phytossanitary problems, including more than 50 fungal diseases - among them, the Pink Disease, caused by fungus E. salmonicolor (Feichtenberger & Spósito, 2004). The symptoms include production of a salmon pink mycelium on branches and stems of the tree, causing twig and branch injuries, stem canker, and. Genetic variability of E. salmonicolor insolates eventually host plant death. Initial infections are characterized by a gum production and white mycelial growth on the surface of infected branches and stems. Host trees with severe infection present salmon color of the mycelium, crank and dry branches and fall of fruits, causing a decrease of plant growth, resulting in a reduction of citrus production (Gezahgne et al, 2003; Ploetz, 2003; Old et al, 2000)
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