ABSTRACT The search for bioherbicides has been encouraged, and plants used in food or with bioactivity have been studied. Therefore, this article aimed to investigate the bioherbicidal potential of essential oils from Psidium cauliflorum and P. acidum through a plant toxicity bioassay using Lactuca sativa and Sorghum bicolor. The seeds were treated with essential oils of both species, along with control groups treated with distilled water, dichloromethane, and glyphosate. Germination percentage (GP), germination speed index (GSI), root growth (RG), shoot length (SL), mitotic index (MI), chromosomal alterations (CA), and nuclear alterations (NA) were evaluated. The major compound of the essential oil of P. cauliflorum was α-pinene, and of P. acidum were trans-caryophyllene, β-elemene, germacrene A, and α-copaene. The essential oils from both species exhibited phytotoxic effects. P. acidum oil inhibited sorghum RG and lettuce SL, while P. cauliflorum oil reduced GP, GSI, RG, and SL in both plants, indicating higher phytotoxicity than P. acidum and non-selective behavior. Cytotoxic investigations showed that both oils inhibited the MI. CA analysis revealed that P. cauliflorum oil exhibited aneugenic and clastogenic action mechanisms. The results demonstrate the bioherbicidal potential of P. cauliflorum essential oil, in addition to being non-selective and displaying a similar inhibition rate to glyphosate.

Abstract We investigated whether essential oil and aqueous and ethanolic extracts from M. vittoriana leaves have phytotoxic effects on the germination and initial development, and cytogenotoxic effects on the cell cycle, of model plants. The essential oil and extracts of M. vittoriana were characterized and used as treatments in phytotoxicity and cytotoxicity tests. The results indicated a reduction in germinative parameters and plant growth, with the higher concentrations of extracts and essential oil having the most evident effects. The cell cycle was also affected with a reduction of the mitotic index and the presence of chromosomal and nuclear alterations. All treatments showed clastogenic and aneugenic modes of action. The results can be associated with the synergistic effects of metabolites found in the extracts and essential oil, mainly the presence of the sesquiterpene germacrene D in the essential oil and of catechins, saponins, and tannins in the extracts. These substances inhibit plant germination and growth, confirming the phytotoxic effects of M. vittoriana in plant models, which should now be tested under field conditions.

RESUMEN El presente estudio analizó la toxicidad por contacto residual y el efecto repelente de los aceites esenciales de Rosmarinus officinalis, Mentha piperita, Melaleuca alternifolia y Commiphora myrrha y sus mezclas en hembras adultas de Tetranychus urticae en laboratorio y cultivo protegido. El aceite esencial de C. myrrha exhibió una Cl50 de 0.55 ml L-1 y las mezclas R. officinalis + M. piperita + M. alternifolia + C. myrrha, C. myrrha + M. piperita, y C. myrrha + M. alternifolia presentaron 68%, 60%, y 36% de mortalidad, respectivamente. Los aceites esenciales de C. myrrha y M. alternifolia mostraron 95 y 70% de repelencia, respectivamente. Las mezclas de C. myrrha + M. alternifolia, C. mirrha + M. piperita y C. myrrha + R. officinalis proporcionaron repelencia de 85, 74 y 73%, respectivamente. La toxicidad por contacto residual del aceite esencial de C. myrrha en cultivo protegido presentó una mortalidad del 93%, mientras que el acaricida fenpiroximato presentó un 80%. Los componentes de los aceites esenciales fueron: eucaliptol (49.66%), M. piperita mentol (48.53%), M. alternifolia terpinen-4-ol (48.93%), y C. myrrha bencil benzoato (97.71%). El aceite esencial de C. myrrha y las mezclas R. officinalis + M. piperita + M. alternifolia + C. myrrha y C. myrrha + M. piperita mostraron una mortalidad significativa. Sin embargo, se necesitan más estudios para evaluar la relación costo/beneficio y los efectos en organismos no objetivo.

ABSTRACT This study analyzed the toxicity by residual contact and the repellency effect of the essential oils of Rosmarinus officinalis, Mentha piperita, Melaleuca alternifolia, and Commiphora myr-rha and their mixtures on adult females of Tetranychus urticae in laboratory and protected cultivation. The essential oil of C. myrrha exhibited a LC50 of 0.55 ml L-1, and the mixtures R. officinalis + M. piperita + M. alternifolia + C. myrrha, C. myrrha + M. piperita, and C. myrrha + M. alternifolia showed 68%, 60%, and 36% mortality, respectively. The essential oils of C. myrrha and M. alternifolia showed 95 and 70% of repellency, respectively. Mixtures of C. myrrha + M. alternifolia, C. myrrha + M. piperita, and C. myrrha + R. officinalis provided repellency of 85, 74 and 73%, respectively. Toxicity by residual contact of the essential oil of C. myrrha in protected cultivation exhibited 93% mortality, while the acaricide fenpyroximate showed 80%. The constituents of essential oils were eucalyptol (49.66%), M. piperita menthol (48.53%), M. alternifolia terpinen-4-ol (48.93%), and C. myrrha benzyl benzoate (97.71%). The essential oil of C. myrrha and the mixtures R. officinalis + M. piperita + M. alternifolia + C. myrrha and C. myrrha + M. piperita showed significant mortality. However, further studies are needed to assess the cost/benefit ratio and the effects on non-target organisms.

RESUMO Atualmente o ora-pro-nobis é apontando como cultura de potencial agrícola, porém com poucas informações sobre seu manejo agronômico. Uma das informações a ser buscada é quanto aos prejuízos que o convívio com plantas daninhas causa. Objetivou-se com este trabalho estudar o crescimento e desenvolvimento inicial do ora-pro-nobis em convivência com plantas daninhas. O delineamento experimental utilizado foi inteiramente casualizado, com cinco tratamento, ora-pro-nobis em convivência com caruru (Amaranthus viridis), picão preto (Bidens pilosa), trapoeraba (Commelina benghalensis) e tiririca (Cyperus rotundus) e a testemunha ausente de plantas daninhas, com seis repetições. A convivência com as plantas daninhas diminuiu o crescimento e desenvolvimento do ora-pro-nobis assim como a produção de folhas em até 40% e 23% do teor de proteínas, respectivamente. Porém, novos trabalhos devem ser realizados em ambientes de plantio a céu aberto, bem como a utilização de técnicas diferenciadas para a produção de mudas e seu transplante para as condições reais de campo.

ABSTRACT The Barbados gooseberry crop has agricultural potential, but little information is available regarding cropping practices. More information on weed interference in Barbados gooseberry will support growers to take weed management decisions. The objective of this work was to study initial growth and development of Barbados gooseberry under the interference of weeds. The experiment was conducted in a completely randomized design, with five treatments, composed of Barbados gooseberry in competition with four weed species: slender amaranth (Amaranthus viridis), hairy beggarticks (Bidens pilosa), Benghal dayflower (Commelina benghalensis), purple nutsedge (Cyperus rotundus), and a weed-free control, with six replicates. Weed competition led to a decrease in growth and development of Barbados gooseberry reflected in a reduction of up to 40% in yield and 23% in protein content. Additional work must be conducted evaluating these findings under field conditions, using different seedling production and planting techniques potentially affecting these results.