Psidium myrtoides O. Berg fruit and leaves: physicochemical characteristics, antifungal activity and chemical composition of their essential oils in different seasons.

This paper aims to investigate, for the first time, physicochemical characteristics and antioxidant capacity of Psidium myrtoides ripe and unripe fruit. In addition, essential oil was extracted from fresh leaves (PM-EO) collected in dry and rainy seasons to investigate the influence of seasonality and, after that, to evaluate its antifungal activity on mycelial growth of Colletotrichum gloeosporioides. Both GC-FID and GC-MS analyses revealed that major components determined in PM-EO were ß-caryophyllene (20.0% and 32.9%) and limonene (10.4% and 19.8%) in rainy and dry seasons, respectively. High antioxidant capacity was displayed by unripe fruit (IC50 = 3.57 mg/mL) and ripe ones (IC50 = 3.68 mg/mL). Both showed high total phenolic and tannin contents. In sum, PM-EO showed satisfactory antifungal activity, since its inhibitory action on mycelial growth of C. gloeosporioides was above 70% in the dry season, while it exhibited weak activity in the rainy season.

Signaling defense responses of upland rice to avirulent and virulent strains of Magnaporthe oryzae.

Rice blast (Magnaporthe oryzae) can cause large losses in crop yields, especially in upland rice systems. Avirulent strains of M. oryzae can induce resistance to subsequent attacks by virulent strains in plants. This study aimed to investigate the defense responses in upland rice challenged with a virulent strain of M. oryzae after acclimation with an avirulent strain. The avirulent strain decreased rice blast severity in the challenged plants. Induced resistance was characterized by a hypersensitive response and early accumulation of phenolic compounds. Scanning electron microscopy showed that M. oryzae conidia germinate and form appressoria, but do not colonize leaf tissues. The activities of pathogenesis-related proteins, total phenolic compounds, and salicylic acid (SA) were affected by acclimation to the avirulent strain. The activities of ß-1,3-glucanase, phenylalanine ammonia-lyase, and peroxidase, as well as the SA levels explained most of the variability in the rice plant responses to M. oryzae. In addition, OsXa13, OsMAPKKK74, OsAOS2, OsACO7, and OsMAS1 expression was modulated depending on the virulence of the M. oryzae strains. This modulation in gene expression is critical for infection and some of these mechanisms are targeted by effectors, resulting in enhanced susceptibility and pathogen infection. These results have practical importance in plant-pathogen interaction studies to identify resistance-relevant mechanisms against M. oryzae in upland rice.

Wickerhamiella dianesei f.a., sp. nov. and Wickerhamiella kurtzmanii f.a., sp. nov., two yeast species isolated from plants and insects.

Six yeast strains representing two novel Wickerhamiella species were isolated from plants and insects collected in Costa Rica, Brazil, and French Guiana. They belong to a subclade containing Wickerhamiella domercqiae and Wickerhamiella bombiphila, and differ by approximately 12 % in the D1/D2 sequences of the large subunit rRNA gene from these species. The intergenic spacer (ITS) regions of the two novel species differ by around 19 and 27 %, respectively, from those of W. domercqiae. The novel species exhibit 5 % divergence in the D1/D2 sequences among them (around 4 % in the ITS). The names Wickerhamiella dianesei f.a., sp. nov. and Wickerhamiella kurtzmanii f.a., sp. nov. are proposed to accommodate these species, for which a sexual cycle has not been observed. Wickerhamiella dianesei was isolated from the stingless bee, Trigona fulviventris, collected in an Asteraceae flower in Costa Rica, and from leaves of Sabicea brasiliensis (Rubiaceae) and a flower of Byrsonima crassifolia (Malpighiaceae) in Brazil. Wickerhamiellsa kurtzmanii was isolated from a flower of Ipomoea batatoides (Convolvulaceae) in Costa Rica, the surface of a fruit of B. crassifolia in Brazil, and flowers in French Guiana. The type strains are Wickerhamiella dianesei UWOPS 00-107.1T (=CBS 14185=NRRL Y-63789; Mycobank number MB 827008) and Wickerhamiella kurtzmanii UWOPS 00-192.1T (=CBS 15383=NRRL Y-63979; MB 827011).