Scale size was determined by scanning electron microscopy To tes

Scale size was determined by scanning electron microscopy. To test the hypothesis that scales were a haven for Fusarium, leaves were inoculated with conidia. Detached leaves were disinfected with 1.5% hypochlorite and rinsed with distilled water. Leaves were inoculated at about 2 cm from the leaf base, within the non-chlorophylled potion, with 100 μl of the fungal suspension (105 conidia ml−1) of F. guttiforme (E-203; NRRL25624). Fungus was derived from single conidia from the INCAPER Plant Pathology Laboratory, according to Ventura (1994). Leaves inoculated with sterile

distilled water were used as control. A paradermic section of 1 cm2 was obtained from the abaxial face 24 h post-inoculation (hpi). These portions were cut and suspended in saline (0.9%), selleck screening library vortexed, diluted in saline and plated on potato dextrose agar (PDA

– Oxoid Unipath Ltda, Basingstoke, Hampshire, UK) to determine the number of colony forming units (CFU/cm2) of F. guttiforme. To confirm the identity of the colonies, slides were prepared from representative colonies, stained with lactophenol–cotton blue (0.1%) and observed under light microscopy. To observe surface germination of conidia, leaves were disinfected and rinsed as above. The leaf surface learn more was injured by use of a histological pin and immediately inoculated with conidia (105 conidia ml−1). After 24 hpi, leaf samples were free-hand cut in transverse sections and the sections were stained for 1–2 min., using lactophenol–cotton blue

(0.1%) for analyses of fungal hyphae in the scales. Statistical analysis was performed using completely randomized blocks with 5 repetitions. Each repetition was the means of 3 different leaves. Means were compared using Tukey’s tests with significance set at P < 0.05. Previous observation under field conditions showed absence of any fusariosis symptoms on cv. Vitoria, whilst the cv. Smooth Cayenne presented intermediate severity of the disease and cv. Perola extreme severity of fusariosis symptoms (Ventura and Zambolim, 2002). The anatomy of the pineapple leaf has already been described for ‘Smooth Cayenne’ by Krauss (1949). Our observations of the cultivars Vitoria and Perola found identical structures in each case. Scales were found on the surface of the unstratified epidermis of the hypostomatic leaf (Fig. 1A). Scales are peltate formed by a stalk inserted in the epidermis with a disk form head of shield-like (scutiform) structure (Fig. 1B–E). In frontal view the young scales present a group of central isodiametic cells, surrounded by a series of elongated cells. All these aggregated cells form a symmetrical shield (Fig. 1B). In mature scales, cells in the central region become less evident, the shield increases in size and becomes more asymmetric (405 μm of length ± 72), with a region formed of elongated cells (Fig. 1C and D).

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