Kimiyo Shimomura Haida

Efeito de extratos aquosos vegetais sobre a lagarta-do-cartucho

Spodoptera frugiperda, conhecida como lagarta-do-cartucho, e considerada uma das principais pragas do milho. Como medida alternativa aos agroquimicos, o uso de plantas inseticidas, alem de preservar o ambiente, reduz os custos de producao e torna-se uma pratica adequada para a agricultura sustentavel. Desta forma, o objetivo deste trabalho foi verificar a acao inseticida de extratos aquosos de folhas de eucalipto (Eucaplyptus robusta), guaco (Mikania laevigata)e folhas e frutos de pimenta (Capsicum baccatum). Os extratos a 10% foram incorporados em dieta artificial de Spodoptera frugiperda, mantidas em condicoes de laboratorio (26 ± 2°C, umidade relativa de 60 ± 5% e fotofase de 16 horas). Foram utilizados 5 tratamentos com 4 repeticoes cada, sendo 15 lagartas por repeticao. Avaliaram-se a duracao da fase larval, mortalidade diaria, peso das lagartas ao 10o dia e das pupas apos 24 horas e quantidade de machos e femeas. Observou-se que os extratos de E. robustae folhas de C. baccatum resultaram em maior mortalidade e menor peso na fase larval, sendo promissores para testes em campo no controle dessa praga.

Getting ready for battle: do cabbage seeds treated with jasmonic acid and chitosan affect chewing and sap-feeding insects?

Induced defence allows plants to manage energy reserves more efficiently by synthesizing defence compounds only when needed. A risk of induced defence is that when plants are challenged by herbivores, they may suffer considerable damage before the defence is mounted. Priming can cause a state of readiness for the induction of the defence response, leading to a reduction in the damage received in an energy‐efficient and less costly manner. Our objective was to verify whether seed coating with jasmonic acid (JA) and chitosan (CH) could prime plants against chewing and sap‐feeding herbivores by affecting their herbivory of treated plants. We used Brassica oleracea L. var. capitata cv. Derby Day (Brassicaceae) seeds treated with JA and CH, second‐instar Plutella xylostella L. (Lepidoptera: Plutellidae), and newborn nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae). We evaluated life‐history, performance, and fecundity traits of the insects. Neither JA nor CH affected B. oleracea leaf area. Both JA and CH affected P. xylostella. JA reduced the mean relative growth rate of P. xylostella and led to 84% pre‐imaginal mortality, whereas CH reduced oviposition. JA reduced significantly the intrinsic rate of increase in M. persicae, whereas CH did not differ from the control. Therefore, JA and CH seed coating lead to long‐term defence priming in B. oleracea against chewing and sap‐feeding insects.

Compostos Fenólicos e Atividade Antioxidante de Goiaba (Psidium guajava L.) Fresca e Congelada

The fruit of Psidium guajava L. (Myrtaceae) has a high market acceptance in both in natura consumption as in processed form, due to its nutritional, sensory and biofunctionals properties. On the other hand, it shows a very short life spam, leading to the production of frozen pulps. The objective of this study was to evaluate the antioxidant capacity and content of phenolic compounds present in the guava fruit (Psidium guajava L.) green, ripe, frozen for 30 to 60 days. The fruits were purchased in a grocery in the 1st stage of maturation, after stored at room temperature for 5 days (ripe) and taken to freezing for 30 to 60 days. The content of total phenols was determined by Folin-Ciocalteau method. The antioxidant activity of the extracts was analyzed by the sequestration of radical DPPH method. The content of phenolic compounds ranged from 40.10 to 112,49 mg EAG.100g-1, respectively to mature and 30 days frozen guava. The ability to inhibit oxidative free radicals ranged from 46.53% for 30 days frozen to 98.84% for ripe guava. All phenolic compounds and extracts showed good antioxidant activity. Consumption of guava should be encouraged by their functional property.