Algumas plantas podem produzir compostos secundários com potencial benéfico no manejo agrícola, como alternativa à utilização no tratamento de sementes, porém, podem apresentar algum tipo de alelopatia inibitória ao desenvolvimento de determinadas culturas de interesse. Logo, o objetivo deste trabalho foi avaliar efeitos alelopáticos do extrato aquoso de manjericão (Ocimum basilicum L.) e babosa (Aloe vera L.) em concentrações na germinação e desenvolvimento inicial de sementes de rúcula (Eruca sativa L.). A concentração para o extrato aquoso foi de 20% (peso/volume) e a partir desta, foram obtidas as demais concentrações. Os tratamentos utilizados foram as concentrações de 25, 50, 75 e 100% dos extratos de babosa e manjericão extraídos pelo método a frio de turbólise, e testemunha com água autoclavada.Os efeitos dos extratos foram avaliados quanto as variáveis: índice de velocidade de germinação, porcentagem de germinação, comprimento de radícula e parte aérea. O experimento foi conduzido em delineamento inteiramente casualizado, com 6 repetições, sendo a unidade experimental composta por uma caixa gerbox com 50 sementes de rúcula. As doses de manjericão e babosa foram testadas em experimentos distintos. Os extratos de manjericão e de babosa apresentam substâncias que favorecem o desenvolvimento da parte aérea, influenciaram negativamente no desenvolvimento da radícula, porém, não apresentaram efeito alelopático na germinação final e velocidade de germinação de sementes de rúcula.
The aim of this work was to evaluate the effect of the essential oils of Syzygium aromaticum, Cymbopogon citratus, Eucalyptus citriodora and Rosmarinus officinalis on the mycelial development of the fungus Colletotrichum sp. in fragments of Feijoa sellowiana fruits. The essential oils were incorporated in the PDA (Potato-Dextrose-Agar) medium in the concentrations of 250, 500 and 1000 ppm, 0 ppm (PDA only) (negative control), and fungicide fluazinam 1% (positive control). The area under the mycelial growth curve (AUMGC) and percent inhibition of mycelial growth (PIMG) were calculated. In the second evaluation, fruits fragments bordering the disease symptom were immersed in essential oils aqueous solution of S. aromaticum, C. citratus, and E. citriodora, at the concentration of 5000 ppm, 0 ppm (water only - negative control) and fluazinam 1% (positive control). The immersion times in the treatments were: 2, 4, 8, 12 and 24 hours, with subsequent incubation in Agar-Agar medium at 25°C. This evaluation was performed daily for 15 days, observing the moment of fungal germination through the emission of the mycelium. It was verified from the obtained results that all treatments reduced the fungal growth, and the essential oils of C. citratus and S. aromaticum totally inhibited its growth from the dose 500 and 1000 ppm, respectively. Regarding the test on fruit fragments, the essential oil of S. aromaticum at the immersion times of 12 and 24 hours was effective in inhibiting the fungus until the 15th day of evaluation.
La inducción de resistencia (IR) en plantas por productos naturales ha sido objeto de varios estudios, siendo estas activadas por moléculas elicitoras de origen biótica o abiótica. Los elicitores activan mecanismos de resistencia como las proteínas relacionadas a patogénesis (PRP’s), que actúan en la protección de plantas impidiendo el desarrollo del patógeno. El presente estudio tiene como objetivo verificar la activación de PRP’s (peroxidasa, catalasa, polifenoloxidasa e βglucanasa) en plantas de maíz pira (Zea mays) tratadas con diferentes concentraciones (0%, 0.5%, 1%, 1.5%, 3% y 5%) del biofertilizante comercial Microgeo®. Analizando las enzimas PRP’s se observó que el Microgeo® activó e incrementó la actividad de estas enzimas y que está inducción está más relacionada al tiempo de activación, pero no a la concentración utilizada.
In vitro inhibitory capacity of Lentinula edodes and Agaricus blazei extracts on Xanthomonas axonopodis pv. passiflorae and their capacity to induce resistance in passion fruit in a greenhouse are evaluated. Aqueous crude extracts (CEs) were prepared by hydrating the basidiocarp dry powder with distilled water for 24h, at 4 ºC. CEs were added in test tubes at concentrations 10, 20, 30 and 40%, whilst control contained water only. Bacterial suspension (1 mL) was added to each tube (108 cfu.mL-1) and incubated in the dark at 28 °C for 24h. The bacterial suspension was measured by a spectrophotometer at 550 nm. Passion fruit cultivars IAC-275 and Epagri Oval Grande were sown on two substrates in a greenhouse: substrate 1 (SB) - horizon B soil; substrate 2 (SBC) - 40% soil from horizon B + 40% organic compost + 20% roughage (rice husk). A. blazei aqueous crude extract (ACE) treatments were applied at 20% and 40%; L. edodes ACE 20% and 40%; biofertilizer Agromos® 1% and control (without treatment) were started when the plants were in the 4-6 leaf stage. Sprays were done weekly, totaling four applications. Seven days after the first application and seven days after the last spraying, leaves were collected to evaluate chitinase, peroxidase and β-1,3-glucanase activity seven days. In vitro aqueous mushroom extracts inhibited the CFU of X. axonopodis pv. passiflorae and increase in the activity of peroxidase and β-1,3-glucanase was observed in passion fruit plants in the greenhouse.
This study aimed to investigate the potential of rhizobacteria isolated from tomato plants to control Sclerotinia sclerotiorum and induce the activity of pathogenesis-related enzymes in Micro-Tom tomato plants. Three rhizobacterial isolates were evaluated to determine the most efficient antagonist agent, which was later identified by gene sequencing as Bacillus amyloliquefaciens PKM16. The antagonistic effects of B. amyloliquefaciens against S. sclerotiorum were assessed in vivo and in vitro using live and autoclaved cultures at concentrations of 0% (control), 20%, 30%, and 40% (v/v). The residual effects of four treatments (20% live culture, 20% autoclaved culture, a Bacillus subtilis-based commercial product, and autoclaved distilled water) on tomato plants inoculated with S. sclerotiorum were determined. The same treatments were also used to assess the myceliogenic germination of sclerotia and induction of plant defense enzymes (peroxidase, catalase, polyphenol oxidase, phenylalanine ammonia-lyase, and β-1,3-glucanase) in tomato plants. The live culture had a residual effect for 4 days and inhibited sclerotial germination by approximately 30%. Furthermore, live and autoclaved bacterial growth cultures stimulated enzyme activity. Therefore, B. amyloliquefaciens PKM16 was antagonistic to S. sclerotiorum, effectively inhibiting mycelial growth and activating defense mechanisms in Micro-Tom tomato plants.
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