First Report of Fusarium redolens as a Causal Agent of Aleppo Pine Damping-Off in Algeria

Aleppo pine (Pinus halepensis Mill.) is a common native coniferous tree in the natural forests of the Mediterranean region. In 2008 and 2009, a survey of Aleppo pine seedling diseases was performed in three forest nurseries from Relizane, Sidi Bel Abbes, and Tlemcen departments in northwestern Algeria. Aleppo pine seedlings showed symptoms of pre- and post-emergence damping-off, resulting in severe crop losses. The problem was widespread with a disease incidence of 64 to 77%. Fusarium redolens Wollenw. was isolated from Relizane and Sidi Bel Abbes forest nurseries. Disinfested root and root collar segments, approximately 5 mm in length, were cultured on potato dextrose agar (PDA) and incubated at 25°C. Morphological identification was done according to Fusarium keys (2). PDA colonies consisted of flat mycelium with sparse white aerial hyphae. Macroconidia with three to five septa, 24 to 43.8 μm long, widest upper third, hooked apical cell, and foot shaped basal cell were observed. Microconidia with zero to one septa, 6.8 to 10.4 μm long, oval to cylindrical, and produced on monophialides were also observed. Chlamydospores were produced abundantly in terminal and intercalary chains, in 3- to 4-week-old cultures. To confirm the identity of the fungus, the internal transcribed spacer (ITS) of F5RS3, F91SR, F55RS1, F8RS3, and F09SS1 isolates of F. redolens were amplified and sequenced using ITS 1 and ITS 4 primers (3). GenBank Accession Nos. are JX051323 to 26, and JX114783, respectively. Those sequences bore 99% (JF311916) and 100% (U34565) similarity with sequences of F. redolens in GenBank. A Fusarium pathogenicity assay was used to complete Koch's postulates. Inoculum was produced by adding a 5 mm diam. agar disc from a 7-day-old CMA petri dish culture to a previously sterilized 500 ml flask (237.5 g of sand, 12.5 g of cornmeal, and 80 ml of deionized H₂O). Isolates were allowed to colonize the medium for 9 days, and flasks were shaken every day. The inoculum was mixed with sterile soil at a rate of 3:1 (v:v). Infested soil was then transferred to 500 ml pots, and 10 Aleppo pine seeds were planted. A completely randomized design was used with three replicates. After 1 month, all tested isolates caused typical damping-off symptoms on seedlings. The percentage of the inoculated plants that became infected was 53 to 91%. To our knowledge, this is the first report of F. redolens being pathogenic on Aleppo pine in northwestern Algeria and throughout the world. In Algeria, F. redolens has been reported on tomato (Solanum lycopersicum L.) (1), suggesting that it is adapted to the conditions of this area and could become a major threat to regional plant production. The annual economic impact of this disease was estimated at approximately US$50,000 per forest nursery. References: (1) N. Hamini-Kadar et al. New Dis. Rep. 22:3, 2010. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, Iowa, 2006. (3) T. J. White et al. Pages 315-322 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.