Métodos para preservação de urediniósporos de Puccinia Kuehnii

Fabiana Tibolla

Among the diseases of the culture of sugarcane in Brazil stands out the rusts. Currently, the most worrying is the orange rust due their potential for harm. The objectives were to test the feasibility periods of uredinósporos, preservation methods and influence of aqueous extracts in the in vitro germination urediniospores of Puccinia kuehnii.The work was divided in two experiments (E1 and E2), and this in two bioassays (B1 and B2). In E1 was assessed the viability of urediniospores as a function of time (days) after collection of the leaves, and influence of aqueous extracts of leaves of sugarcane in the in vitro germination of urediniospores of P. kuehnii. It was used orange rust urediniospores from the varieties SP89 1115 and RB 72 454. E2 was accomplished making the extraction of urediniospores of P. Kuehnii with the aid of vacuum bomb. These were placed in microcentrifuge tubes, and subjected to different methods for the preservation of urediniospores. The experimental design was a factorial arrangement. The evaluations of both experiments were made after prepare urediniospores suspensions in distilled water. Aliquots of 0.1 mL were transferred to Petri dishes containing agar-water (15 g L-1). It was evaluated the germination of 200 urediniospores per plate. The results of E1 at B1 demonstrated that the percentage of germination of urediniospores extracted from the variety RB72 454 started in 93.1% on the day of collection and decreased to 32.4% at 16 days, while for variety SP89 1115 was 26.4% to 24.8%, respectively. In B2 the percentage of germination of urediniospores, which received aqueous suspension of the resistant variety, were significantly (p <0.05) lower than those who received the aqueous suspension of the susceptible variety. In E2, were B1 received a silica gel granule, unlike B2, the results showed that the viability decreased function of time, the best treatments reached 27.6% and 6.6% at 30 days, and 12.0% and 1.9% at 60 days for B1 and B2, respectively. At 30 days, the best methods of preservation in B1, was dehydration in silica gel, followed by storage at 20ºC. At 180 days, the dehydration methods in silica gel followed by storage at -80°C was the only who presented viable urediniospores (1.2%). In B2, for periods longer than 30 days, the best preservation method was dehydration, stored at 5°C, out rehydration. These methods showed better germination percentage at 120 days (0.4%). The inclusion of silica gel granules in microcentrifuge tube, increased for 23.6 percentage points the preservation of urediniospores in 30 days of storage and allowed recovery at 180 days.

Métodos para preservação de urediniósporos de Puccinia Kuehnii

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