Central International Journal of Plant Biology & Research Bringing Excellence in Open Access Research Article *Corresponding author Wellington G. Campos, Departament of Bio systems Engineering, Federal University of São João del Rei, Drought Stress affects Brazil, E-mail: Submitted: 30 May 2017 Accepted: 06 June 2017 Constitutive but not Herbivore- Published: 08 June 2017 ISSN: 2333-6668 Induced Glucosinolates in Copyright © 2017 Campos et al. Collard OPEN ACCESS Keywords 1 1 Janete Oliveira S. Valim , Natália C. Teixeira , Maria Goreti A. • Brassica oleracea Oliveira2,3, and Wellington G. Campos1,3* • Brevicorynebrassicae • Plant defense 1 Departament of Bio systems Engineering, Federal University of São João del Rei, • Plutellaxylostella Brazil • Water stress 2Department of Biochemistry and Molecular Biology, Federal University of Viçosa, Brazil 3National Institute of Science and Technology in Pest-Plant Interactions, Brazil Abstract The presence of glucosinolates (GLS) in Brassicaceaeis thought to be the first line of plant defense against a variety of insects and pathogens. Influence of drought stress on constitutive GLS has been documented; however, its effect on herbivory-induced GLS is poorly known, especially with respect to different feeding guilds of insects. Collard (Brassica oleracea L. cv. acephala) plants were grown in well-watered, slightly water-stressed and severely water-stressed conditions. Then, the plants were subjected to infestations by two host-specific herbivores, the leaf-chewingPlutellaxylostella L. (Lepidoptera: Plutellidae) or the phloem-feeding Brevicorynebrassicae L. (Hemiptera: Aphididae). Concentration of total leaf GLS decreased in severely drought-stressed plants; however, in no water regime collards had their total GLS increased due to damage by both specialist insects. Thus, we did not found evidence for total GLS induction by insect damage, irrespective of insect feeding guild or level of plant water-stress. Naturally occurring droughts or deliberate submission of collard crops to water limitation may not affect herbivore-induced GLS, but constitutive resistance against insect attack may be reduced. INTRODUCTION The presence of glucosinolates (GLS) in Brassicaceae and Induced responses are changes in plant chemistry and defense against a variety of invading organisms [11]. Even though structure following damage or stress. These traits may negatively related plant families [10] is thought to serve as a first line of abiotic and biotic factors [12]. Brassicaceous plants usually face when herbivores are present (induced defense) [1]. Thus, in damageGLS are by constitutive multiple insect defenses, herbivore their species, levels whichare influenced in most cases by affect herbivores (induced resistance) and benefit the plant addition to defense mechanisms that function independently of belong to different feeding guilds and different degrees of feeding damage (constitutive defenses), plants can be protected against specialization [13]. Thus, such plants may adjust their defense herbivores by defenses previously induced by biotic and abiotic strategies in response to herbivore feeding mode. In fact, studies stresses. Many of such stress conditions operate simultaneously, have shown that induced responses and GLS accumulation by in a way that the response of plants to combinations of two or more conditions cannot be directly extrapolated from the response to each of the different stresses applied individually [2]. some plants depend on the herbivore species and on the insect- Among the abiotic stresses, drought affects plants at various herbivore,feeding guild but [14-16]. induced It responseshas been suggested depend mainly that plant on insect responses taxa levels of their organization [3]. However, knowledge remains (i.e.,are notaphid influenced vs. lepidopteran by the species),degree oflikely specialization due to their ofdifferent insect feeding modes [14]. in plant resistance or plant defense compounds [4,5]. On the L. scant on the specific expression of drought-mediated changes Plutellaxylostella other hand, biotic stress caused by herbivores can induce, (Lepidoptera: Plutellidae) and the phloem feeding cabbage aphid besides slower changes in morphological traits, rapid increases BrevicorynebrassicaeThe leaf-chewing diamond L. (Hemiptera: back moth Aphididae) (DBM) are among the major insect pests that attack brassicaceous plants worldwide. secondary metabolites [6,7]. Induction of secondary metabolites in concentrations of anti-nutritional enzymes and proteins, and by biotic stresses is well documented, but less information is individually led to a decreased level of total GLS in collard available on how drought and other abiotic conditions affect BrassicaoleraceaBoth of them are L.highly cv. acephala host-specific(Brassicaoleracea [13]. Drought L) stress [5], while applied GLS induced plant responses to herbivory [8,9]. Cite this article: Janete Oliveira SV, Teixeira NC, Maria Goreti AO, Campos WG (2017) Drought Stress affects Constitutive but not Herbivore-Induced Gluco- sinolates in Collard. Int J Plant Biol Res 5(3): 1069. Campos et al. (2017) Email: Central Bringing Excellence in Open Access induction by herbivore damage has been documented in many other plants [17]. However, few studies have investigated the interaction of drought stress with herbivory in inducing changes analysistreatment of (nGLS = on4 x the 8 x same 3). The day groups that the were treatment as follows: groups (1) received Control day-zero: undamaged plants, whose leaves were harvested for of insects. We addressed this issue using collards and herbivores, were harvested for analysis of GLS in the seventh day after the of GLS [18-20], especially with respect to differentB. feedingbrassicae guilds. We insects; (2) Control day-seven: undamaged plants, whose leaves assessed whether drought stress decreases both, constitutive the leaf-chewing DBM and the phloem-feeding treatment groups received insects; (3) DBM damaged: plants damaged by DBM, whose leaves were harvested for analysis of alsoand testedherbivore-induced whether caterpillars GLS. induceConsidering greater that production leaf-chewing of GLS B.GLS brassicae in the seventh, whose day leaves after were they receivedharvested 20 for third-instar analysis oflarvae GLS thanherbivores aphids. perceptibly cause leaf-damage of a greater extent, we inper the plant; seventh and (4)day Cabbage after they aphid received damaged: 20 plantsnymphs damaged per plant. by MATERIAL AND METHODS Each plant, including control groups, was caged individually in a bag of transparent organza. We established seven days of B. oleracea cv. acephala, hybrid Georgia with glossy plant exposure to insects because earlier studies have indicated and dark green leaves, were grown in a greenhouse (9 m x 25 systemic increase in GLS levels as quickly as four days after m) Collard,covered with transparent water proof plastic and laterally days period for GLS induction [16,18]. The cabbage aphid for the experimentherbivore infestation was collected [6]. fromOther commercial authors have B. oleraceaalso used crops, a seven- and coated with anti-aphid netting. The collards were grown in 10 L soil, without organic matter and humus addition. Firstly, soil . fertilityplastic pots, was whichanalyzed were and filled improvements with standardized in nutrients homogeneous were carried out at the beginning and during plant growth. We used it was reared in a greenhouse on potted-collards The DBM was a standard fertilization recommended for growing potted plants. ofobtained cabbage from (B. oleraceaea breedingcv. stockcapitata that) wasbefore kept the for trial ≈14 period. generations Macronutrients (N, P, K and Mg) were added via NPK fertilizer in a climate-controlled room, where they fed on detached leaves 4:14:8, urea, potassium chloride and magnesium sulfate. We harvested all the leaves (assuming systemic effect) from the eight plants of each water treatment per group of damage (n = sulfate, manganese chloride and ammonium molybdate. Physical 8 x 3 x 4), to determine systemic changes in GLS. The leaves were soilMicronutrients analysis indicated (B, Cu, Mnsandy and texture. Mo) by means of boric acid, copper frozen and ground to a powder in liquid nitrogen and maintained followed Jezeket al. [22], and Gallaher et al. [23], with protocol were grown in a greenhouse in 10 L plastic pots, which were at -20ºC [21] for further analysis. The determination of total GLS Collard, hybrid Georgia with glossy and dark green leaves, details in Valim et al. [5], The analytical method is based on alkalin matter and humus addition. Firstly, soil fertility was analyzed and improvementsfilled with standardized in nutrients homogeneouswere carried out soil, at thewithout beginning organic and ferricyanideet al., hydrolysis can be of assessed GLS to spectrophotometrically yield 1-thioglucose. Ferricyanide and used to during plant growth. We used a standard fertilization for growing determineoxidizes 1-thioglucose total GLS content and [22]. the loss of the chromogenic potted plants [5]. Physical soil analysis indicated sandy texture. Statistical analyzes were performed using the Graph The amount of water delivery required to achieve different water conditions (treatments) in the soil for 10 L pots followed homogeneityPad Prism 5.0 of software,variances Prismwas assessed Graph Inc.,by the San Bartlett’s Diego. Datatest. normality was verified using the Kolmogorov-Smirnov test, and Valim et al. [5], (I) Well-watered: