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The increase on the worldwide influx of solar ultraviolet radiation (UV-B) has inflicted a considerable challenge, due to its deleterious effects to live beings and pose a special threat to phyllosphere communities. However, UV-B influence on epiphytic yeasts associated with agricultural crops remains limited. Main aim of the present study was to determine the effect of ultraviolet-B radiation on the epiphytic yeast populations associated with strawberry under field conditions. Thus, strawberries (Fragaria x ananassa Duchesne cv. Oso Grande) were grown under three different treatments: a) environmental UV-B, b) enhanced UV-B and c) decreased UV-B; thereafter, their yeast epiphytic populations were analyzed by T-RFLP prior to yeast isolation, identification and in vitro test for the sensitivity against UV-B. Our results demonstrated that UV-B radiation did not significantly affect the strawberry epiphytic yeast populations. However, isolates directly exposed to radiation, generally revealed morphological abnormalities and a diminishing

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Leaf-cutter ants (Hymenoptera: Formicidae) have evolved as dominant herbivores on the American continent. These social insects remove the leaves of economically important plant species to maintain their colony’s food reserves, the symbiotic fungus Leucocoprinus gongylophorus, a basidiomycete. Such fungus can be used for applications of fungicide molecules from metabolites generated by symbiont bacteria (Xenorhabdus and Photorhabdus) from entomopathogenic nematodes (Steinernema and Heterorhabditis). Through isolation and multiplication in tryptic soy broth (TSB) medium of the bacteria Xenorhabdus szentirmaii isolated PAM 25, we conducted laboratorial tests using treatments with 10, 25, and 50% of the metabolites obtained in the sixth day of cultivation. The treatments were centrifuged and filtered to generate a supernatant, which was diluted in potato + dextrose + agar (PDA), to verify the consequences of exposure to the fungus L. gongylophorus in Petri dishes. To confirm metabolite efficiency, the control treatments in PDA only and mixed (PDA+TSB) media were conducted simultaneously for 14 days. We observed total inhibition of the symbiont fungus in both the 25 and 50% dilutions during the first days of the tests. Our results support that these metabolites have inhibitory effect on the development of symbiont fungus of leaf-cutter ants.

Dissertação apresentada para obtenção do título de Mestra em Ciências. Área de concentração: Microbiologia Agrícola Piracicaba 2016 Ana Gabriele Barbosa Casteliani Bacharel em Ciências Biológicas Estrutura e diversidade das comunidades bacterianas associadas à Triticum aestivum L. e potencial antagonista contra os fitopatógenos Pyricularia grisea e Fusarium graminearum