Keilor da Rosa Dorneles

CONTROLE IN VITRO DE Bipolaris oryzae (Breda de Haan) COM EXTRATO DE Curcuma longa (Linnaeus) E SUA INTERFERÊNCIA NA FISIOLOGIA DAS SEMENTES DE ARROZ

This study was conducted to evaluate the use of Curcuma longa (Linnaeus) extract in the in vitro control of Bipolaris oryzae (Breda de Haan) and to characterize the effect of this extract on rice seed germination. A completely randomized arranged in a factorial experimental design was used: three isolates of B. oryzae from rice seed from different rice-growing regions of Rio Grande do Sul (Fronteira Oeste, Campanha, and Sul) were tested with three concentrations (20, 40, and 80 mg/mL) of C. longa plus a control treatment (0 mg/mL). Each reaction was repeated in quadruplicate. The effect of the extract upon the disease development was evaluated based on mycelial growth (PMG) and spore production; rice seed germination was evaluated using a germination test (Germitest®). The PMG results demonstrate that the treatments were effective in reducing PMG, with a stronger response observed as the concentration of the extract increased. An average inhibition of 84% of sporulation was observed for the tested strains compared with the control treatment. There were, however, no significant differences in terms of seed germination test with the different C. longa concentrations. Therefore, treatment of rice seeds with C. longa extract does not affect seed germination but positively inhibits mycelial growth and sporulation, affecting the in vitro sporulation of the different isolates of B. oryzae.

First report of powdery mildew caused by Erysiphe quercicola on Cinnamomum camphora in Brazil

The camphor tree (Cinnamomum camphora (L.) J.) (Lauraceae) is used for industrial and pharmaceutical purposes, and also an evergreen shade tree (Singh and Jawaid, 2012). In 2016, intense defoliation and reduced seedling development was observed in camphor plants showing signs of powdery mildew in the municipality of Capao do Leao, Rio Grande do Sul, Brazil. White to gray rounded irregular patches, consisting of conidia and mycelia of the fungus were observed primarily on the adaxial surface of the leaves of camphor seedlings. When the disease was severe, the entire leaf surface was colonized by the pathogen, resulting in leaf necrosis and defoliation. For Kochs postulates, five healthy seedlings were inoculated on their adaxial surface using an eyelash brush to place conidia on the leaf surface (10 to 15 conidia cm-2). Five non-inoculated seedlings served as controls. Inoculated and non-inoculated seedlings were kept in a greenhouse, but in a separate compartment, with relative humidity around 80% and te...

First report of powdery mildew caused by Podosphaera xanthii on Lagenaria siceraria in Brazil

The bottle gourd (Lagenaria siceraria Mol.) is a plant in the Cucurbitaceae that is grown for its fruit which can either be harvested immature for consuming as a vegetable, or mature, dried and used for handcrafts as well as pipes and bottles. Powdery mildew on bottle gourd was observed on plants under field condition on three farms in the city of Capao do Leao (Rio Grande do Sul State – Brazil) during the spring/summer of 2016/2017. In the three areas, all bottle gourd plants were affected by powdery mildew, and foliar disease severity reached up to 50%. Powdery mildew symptoms characterized by circular white colonies on both leaf surfaces and on petioles were easily observed by the abundant production of mycelia, conidiophores, and conidia. On the oldest leaves, colonies coalesced, often covering the entire leaf surface causing chlorosis and eventual death. Mycelia was superficial with nipple-shaped to almost absent apressoria and producing erect conidiophores with three to six immature conidia produced...

ALLELOPATHIC EFFECTS OF MEDICINAL PLANTS EXTRACTS IN THE GERMINATION AND IN THE EARLY GROWTH OF MELON (CUCUMIS MELO L.)

The work aimed to analyze the allelopathic activity of aqueous extracts of leaves of Plectranthus barbatus, Rosmarinus officinalis, Ocimum basilicum, and Origanum majorana in germination and in the growth of melon. The extracts were obtained from the leaves of the plants at concentrations of 2 and 8%. The influence of the extracts on seed germination of melon was analyzed in the moistened paper with the extracts. The evaluation consisted of germination percentage, germination velocity index, length of plant and root. To analyze the influence of the extracts on growth, seeds were pre-germinated and transferred to filter paper moistened with extracts. The evaluation included the length of plant and root and fresh weight of seedlings. The results showed that the concentration of plant extracts influence the germination velocity index, length of plant and root, but the extracts did not interfere in the germination of melon.

Influence of secondary metabolites of Trichoderma spp. development of fungi transmitted by seeds and germination of rice

Rice seeds are degraded by a wide diversity of pathogens that affect the vigor and the germination. The fungus Trichoderma spp. has been used to treat seeds ...