Clara Beatriz Hoffmann-Campo

Are Chemical Compounds Important for Soybean Resistance to Anticarsia gemmatalis

The identification and quantification of flavonoids (rutin and genistin) present in extracts of soybean genotypes, and their effects on the biology and physiology of Anticarsia gemmatalis Hübner (Lep.: Noctuidae) were studied. Analysis of covariance and bicoordinate utilization plots were used to remove the effect of feeding time from pupal weight and consumption as well as to separate pre- and postingestive effects of treatment on A. gemmatalis growth. Genotypes PI 274454, PI 227687, and “IAC-100” extracts in general, caused higher mortality, negatively influenced initial larval and pupal weight, and elongated larval cycle. Larvae fed on the “IAC-100” extract diet ingested larger amounts of food per unit of time, but were less efficient in its conversion to biomass. Leaf extracts of PI 227687 had the largest concentration of rutin (quercitin 3-O-rhamnosylglucoside), followed by PI 274454, and “IAC-100”; PI 74454 also had the highest genistin (genistein 7-O-glucoside) content. The susceptible cultivar “BR-16” showed only a kaempferol-based flavonoid in its chemical profile, indicating that after successive crosses, secondary compounds responsible for plant defenses were eliminated. Genotypes PI 274454, PI 227687, and “IAC-100” showed accentuated resistance characteristics and were considered inadequate sources for the development of A. gemmatalis. Considering rutin and genistin concentration in these genotypes, it is suggested that flavonoids are important factors conferring resistance to A. gemmatalis.

Investigation of cytotoxic, apoptosis-inducing, genotoxic and protective effects of the flavonoid rutin in HTC hepatic cells

Rutin is a flavonoid with antioxidant, vasodilatory, anti-inflammatory and immune-stimulating activities. To study the toxicity of rutin and its protective effect, this work investigated the cytotoxic, apoptosis-inducing, genotoxic and protective effects of rutin in HTC cells. In the MTT assay, the highest concentration tested (810 μM) showed cytotoxicity after 72 h of treatment, where cell viability and cell proliferation was diminished. None of the concentrations of rutin tested induced apoptosis after 24h treatment. The highest concentration of rutin after 24h treatment induced DNA damage, shown in the comet assay, but did have a genotoxic effect in the micronucleus test. Rutin was tested against the pro-carcinogenic agent benzo(a)pyrene, at concentrations of 90, 270 and 810 μM, and was found to reduce induced DNA damage significantly. This protective effect of rutin against a pro-carcinogen, suggests an important biological activity for this compound, which can contribute to human health through the diet.

FLAVONOID INCREASE IN SOYBEAN AS A RESPONSE TO Nezara viridula INJURY AND ITS EFFECT ON INSECT-FEEDING PREFERENCE

The ability of the stink bug (Nezara viridula) to induce and/or increase production of chemical defenses, i.e., flavonoids, in immature seeds of five genotypes of soybean (BR-16, IAC-100, PI 227687, PI 229358, and PI 274454) was investigated under greenhouse and laboratory conditions. Samples from pods of each genotype damaged by stink bug were analyzed for flavonoid content with high performance liquid chromatography. A dual-choice test was conducted to evaluate the feeding preference of N. viridula comparing BR-16 pods treated with extracts of PI 227687 seeds (with and without stink-bug injury), with water-treated pods. Seeds of PI 227687 damaged by N. viridula presented the highest concentration (352 μg/g) of daidzin (4′-hydroxyisoflavone-7-glucoside). The same trend was observed with genistin (4′,5,7-trihydroxyisoflavone-7-glucoside): PI 227687 contained 142.4 μ g/g, PI 274454, 31.6 μg/g, and PI 229358, 38.9 μg/g. Seeds damaged by stink bugs had higher isoflavone contents (daidzin and genistin), compared to controls. However, after being damaged, PI 274454 and PI 229358 produced less genistin than the other genotypes and no differences in concentration between damaged and nondamaged plants of this genotypes were observed. The numbers of observations of the insect feeding and the numbers of stylet sheaths left in water-treated BR-16 pods were greater than in those treated with PI 227687 extracts. The insects fed for longer periods on BR-16 pods treated with extract of PI 227687 without injury compared to those that were treated with extract of PI 227687 previously injured by stink bugs. Extracts of PI 227687 pods (damaged or not) were deterrent to adults of N. viridula, and insect injury increased concentrations of daidzin and genistin in PI 227687 seeds. The deterrence seemed to be more pronounced after pods had suffered stink-bug injury.

Response of the parasitoid Telenomus podisi to induced volatiles from soybean damaged by stink bug herbivory and oviposition

Abstract Egg parasitoids have a short time frame in which their host eggs are suitable for parasitism, and in several systems these parasitoids respond to plant volatiles induced by oviposition on the plant (either in isolation or in combination with feeding damage) as a means of finding suitable hosts. It is known that the parasitoid of pentatomid eggs Telenomus podisi responds to damage done to soybeans by female Euschistus heros, its preferred host. In this study our aim was to determine the type of E. heros damage to soybean (herbivory, oviposition or a combination of both) necessary for attraction of T. podisi. In a Y-tube olfactometer the parasitoid has shown to respond to the undamaged plant over clean air and herbivory-damaged plants over undamaged plants. However, the parasitoids did not respond to the treatments where oviposition occurred, either in isolation or in combination with herbivory. Analysis of volatile blends revealed that herbivory plus oviposition damage to soybean induced a volatile blend different to those induced when herbivory or oviposition occurred separately. These results, along with other results from this system, suggest that T. podisi uses plant volatile cues associated with female E. heros damage in order to be present when E. heros lays its eggs, and thus ensure its resource is optimal for parasitism.

Detrimental effect of rutin on Anticarsia gemmatalis

O efeito de dieta contendo rutina (quercetina 3-O-rutinosideo) no comportamento e na nutricao do principal desfolhador da soja, Anticarsia gemmatalis Hubner (Lep.: Noctuidae) foi avaliado do terceiro instar ate a formacao da pupa. Rutina e um dos flavonois glicosidicos identificados em folhas da soja selvagem PI 227687. O peso das lagartas e o consumo decresceram com o aumento na concentracao de rutina na dieta. Houve interacao entre o tempo de alimentacao e a dieta no crescimento do inseto; lagartas alimentadas com dieta pura, cujo tempo de alimentacao prolongou-se, originaram pupas mais pesadas. O peso das pupas alimentadas com dieta contendo rutina permaneceu estavel, apesar do maior tempo de alimentacao. Rutina afetou negativamente o crescimento do inseto, nao somente pela inibicao alimentar, mas tambem em consequencia de eventos pos-ingestivos, ja que depois do ajuste do peso de pupa pelo consumo (covariavel), o efeito do tratamento permaneceu significativo. Assim, o efeito negativo de rutina em A. gemmatalis resulta de efeitos pre-ingestivos, indicados pela reducao no consumo, e pos-ingestivos, indicados por baixas conversoes do alimento ingerido em biomassa e assimilacao de alimentos.

Do different casein concentrations increase the adverse effect of rutin on the biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)?

The flavonoid rutin is recognized as playing an important role in the protection of plants against lepidopterans. Bioassays with this compound are generally carried out using artificial diets. Proteins of high energy value, such as casein, are important ingredients of insect artificial diets as a source of essential amino acids. However, such proteins can generally increase the allelochemical activity. Our objective was to evaluate the effects of rutin on larvae of the velvetbean caterpillar Anticarsia gemmatalis Hübner by incorporating this allelochemical into diets with different concentrations of casein. Three casein concentrations (0, 7 g, or 14 g) combined with none, 0.65%, or 1.30% of rutin were added to the rearing diet and offered to the larvae from hatching to pupation. Rutin negatively affected larval development, the amount of food consumed, and pupal weight of A. gemmatalis. These negative effects were clearly seen in insects fed on diets with 7 g of casein to which any concentration of rutin was added. The effects of rutin when added to the diets without casein were stronger than in diets containing a suitable amount of casein (14 g). The greater negative effects of rutin in diets containing suboptimal concentrations of casein indicate that casein can increase the effects of rutin only when the diets are nutritionally unsuitable for insect development.

Efeito do manejo de solo na população e nos danos de corós em soja

Foram realizados varios experimentos para avaliar o efeito de diferentes sistemas de manejo de solo na populacao de coros (Phyllophaga cuyabana Moser), e seus danos em soja, em areas de plantio direto e de preparo convencional do solo (preparo primario com arado de discos e uma gradagem niveladora). Varios implementos utilizados no preparo primario de solo, como arado de aivecas, arado de discos, escarificador e grade aradora tambem foram avaliados. A flutuacao populacional de coros e a intensidade de dano causado por eles foram similares nas areas de plantio direto e de preparo convencional. Os implementos de preparo primario do solo afetaram a populacao de coros diferentemente, dependendo da epoca em que o preparo de solo foi executado. A mortalidade larval pode ser atribuida mais a exposicao a fatores adversos logo apos o preparo, do que a mudancas nas condicoes do solo. A reducao na populacao de coros foi mais evidente nas parcelas preparadas com implementos mais pesados, como arado de aivecas. O manejo de solo pode ser um componente dentro do manejo de pragas do solo em soja, porem sua utilizacao nao pode ser generalizada.

Biological characteristics of Anticarsia gemmatalis (Lepidoptera: Noctuidae) for three consecutive generations under different temperatures: understanding the possible impact of global warming on a soybean pest.

Climate changes can affect the distribution and intensity of insect infestations through direct effects on their life cycles. Experiments were carried out during three consecutive generations to evaluate the effect of different temperatures (25°C, 28°C, 31°C, 34°C and 37±1°C) on biological traits of the velvetbean caterpillar Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae). The insects were fed on artificial diet and reared in environmental chambers set at 14 h photophase. The developmental cycle slowed with the increase in the temperature, within the 25°C to 34°C range. Male and female longevities were reduced with an increase in temperature from 25°C to 28°C. Egg viability was highest at 25°C, and the sex ratio was not influenced by temperature, in the three generations. There was no interactive effect between development time and temperature on pupal weight. The results suggested that the increase in the temperature negatively impacted A. gemmatalis development inside the studied temperature range, indicating a possible future reduction of its occurrence on soybean crops, as a consequence of global warming, mainly considering its impact on tropical countries where this plant is cropped. A. gemmatalis was not able to adapt to higher temperatures in a three-generation interval for the studied temperature range. However, a gradual increase and a longer adaptation period may favor insect selection and consequently adaptation, and must be considered in future studies in this area. Moreover, it is important to consider that global warming might turn cold areas more suitable to A. gemmatalis outbreaks. Therefore, more than a future reduction of A. gemmatalis occurrence due to global warming, we might expect changes regarding its area of occurrence on a global perspective.

Baculovirus-resistant Anticarsia gemmatalis responds differently to dietary rutin

The velvetbean caterpillar, Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae), the major soybean [Glycine max (L.) Merrill (Fabaceae)] defoliator pest in Brazil can be controlled by a specific and virulent nuclear polyhedrosis virus (AgMNPV). Flavonoids such as rutin (quercetin 3‐O‐rhamnosylglucoside) were identified in soybean; it is known that this compound plays an important role in plant defense against lepidopteran pests. Studies were carried out to evaluate the biological and physiological activity of rutin (0.65 and 1.30%) on populations of A. gemmatalis resistant and susceptible to AgMNPV. Larvae from the resistant population were more negatively influenced by rutin, in comparison to larvae of the susceptible population, even with the addition of the lowest level of the flavonoid (0.65%) to the insect diet. The highest mortality (98%) was observed in the resistant population, when larvae fed on the diet containing 1.30% of rutin. Elongation of the feeding time, smaller initial larval weight, and pupal weight was observed on the virus‐resistant and ‐susceptible populations after adding 0.65 and 1.30% rutin to the diet. Larvae of the resistant population to AgMNPV fed on diet plus rutin 0.65% were also less efficient in the conversion of ingested and digested food into biomass.

Feeding and oviposition preference of Phyllophaga cuyabana (Moser) (Coleoptera: Melolonthidae) on several crops

Laboratory and greenhouse experiments were carried out to study food and oviposition preference by Phyllophaga cuyabana (Moser) on different plant species as Cajanus cajan L. (pigeon pea), Crotalaria juncea L. (sun hemp), Crotalaria spectabilis Roth (showy crotalaria), Crotalaria ochroleuca G. Don (slenderleaf rattlebox), Glycine max [L.] Merrill (soybean), Gossypium hirsutum L. (cotton), Helianthus annuus L. (sunflower), Stizolobium aterrimum [Mucuna aterrima] Piper Tracey (velvetbean) and Zea mays L. (mayze). In no-choice experiments, the number of eggs layed in sunflower, C. juncea and soybean was larger compared to cotton. Despite the fact that the adults did not discriminate among plants, in dual-choice test, the proportion of eggs layed and leaf consumption by P. cuyabana adults in soybean were significantly higher than in C. spectabilis. The larval distribution in the soil was at random in multiple-choice, without any trend of preference, but in dual-choice, when soybean was the control, larvae always preferred to feed on its roots. P. cuyabana adults had preference for more suitable hosts and that could stand their offspring survival. This behaviour can be usefully exploited in an integrated management program for this pest.