Volatile Organic Compounds from Cassava Plants Confer Resistance to the Whitefly Aleurothrixus aepim (Goeldi, 1886).

Cassava is an essential tuber crop used to produce food, feed, and beverages. Whitefly pests, including Aleurothrixus aepim (Goeldi, 1886) (Hemiptera: Aleyrodidae), significantly affect cassava-based agroecosystems. Plant odours have been described as potential pest management tools, and the cassava clone M Ecuador 72 has been used by breeders as an essential source of resistance. In this study, we analysed and compared the volatile compounds released by this resistant clone and a susceptible genotype, BRS Jari. Constitutive odours were collected from young plants and analysed using gas chromatography-mass spectrometry combined with chemometric tools. The resistant genotype released numerous compounds with previously described biological activity and substantial amounts of the monoterpene (E)-ß-ocimene. Whiteflies showed non-preferential behaviour when exposed to volatiles from the resistant genotype but not the susceptible genotype. Furthermore, pure ocimene caused non-preferential behaviour in whiteflies, indicating a role for this compound in repellence. This report provides an example of the intraspecific variation in odour emissions from cassava plants alongside information on odorants that repel whiteflies; these data can be used to devise whitefly management strategies. A better understanding of the genetic variability in cassava odour constituents and emissions under field conditions may accelerate the development of more resistant cassava varieties.

Morphology and distribution of antennal sensilla of Automeris liberia (Lepidoptera: Saturniidae).

The lepidopteran species Automeris liberia from the Saturniidae family is a polyphagous insect responsible for defoliating plants, such as the oil palm (Elaeis guineensis Jaquim). The antennae of insects play an important role in survival in various environments. Antennae are the main olfactory and sensory organs of insects and have different sensilla to detect chemical cues, movement, humidity and temperature. The olfactory structures present in the antennae are responsible for certain insect behavior, which is influenced by chemical communication. The morphology, distribution and location of the sensilla in the antennae of male and female A. liberia were investigated by scanning electron microscopy to understand the olfactory mechanisms relevant to insect-insect communication and insect-plant communication, among others. The results showed that the flagellum, scape and pedicel length and the number of antennomeres differed between the sexes and demonstrating the existence of sexual dimorphism in the antennae males (bipectinate) and females (filiform). According to the morphological data, seven types of sensilla were identified along the surface of the antennae, classified as trichodea, chaetica, basiconica, coeloconica, squamiformia, styloconica and Böhm's bristles. Among the sensilla chaetica, basiconica and Böhm's bristles, two subtypes based on length were identified in both sexes. The sensilla trichodea exhibited dimorphism since three subtypes were observed in males, while in females, only one subtype was observed, according to the length of the sensilla. Sensilla trichodea subtypes I and II were specific to males, while subtype III was observed in both sexes. These types of sensilla are involved in the recognition of pheromone molecules. Therefore, morphological study of the localization of the sensilla in the antennae will provide useful and relevant results for electrophysiological studies and behavioral tests. This information can help to understand the chemical communication of insects and helps in research directed strategies for pest control.

Cocos nucifera Linn. (Palmae) husk fiber ethanolic extract: antioxidant capacity and electrochemical investigation.

The present study aims to determine the antioxidant capacity of the ethanolic extracts of husk fiber of four coconut (Cocos nucifera L.) varieties (yellow dwarf, green dwarf, giant and hybrid) and to evaluate the electrochemical behavior of these extracts on a glassy carbon electrode and on a modified glassy carbon electrode. The highest values of total phenolic content were obtained for the hybrid (531 ± 24 mg GAE g(-1) dry extract) and yellow dwarf (501 ± 29 mg GAE g(-1) dry extract) varieties and the lowest was for the green dwarf variety with 58 ± 9 mg GAE g(-1) dry extract. The ability of the extracts to scavenge DPPH˙ radicals was in the order of giant > yellow dwarf > hybrid > green dwarf and the IC50 values varied from 8.6 to 55.9 µg mL(-1). All varieties showed reducing potential by the use of FRAP and CUPRAC methods, with the lowest performance obtained for the green dwarf variety. Additionally, through the use of mimetic biomembranes, ethanolic extracts of coconut husk were shown to protect lipids against oxidative damage independent of the variety. The main antioxidants identified in the extract of yellow dwarf variety by UPLC-MS were quercetin and catechin. Cyclic voltammetric studies of the ethanolic extracts on glassy carbon electrode confirmed the presence of easily oxidized compounds, and the high antioxidant capacity of the varieties. This capacity was expressed as mg quercetin equivalents g(-1) dry extract and ranged from 25.9 up to 53.5 mg QE g(-1). A poly-xanthurenic acid (poly-Xa)/multi-walled carbon nanotube (MWCNT) / glassy carbon modified electrode (poly-Xa/MWCNT/GCE) was used for this purpose. Our findings suggest that these extracts are potentially important antioxidant supplements for the everyday human diet, pharmaceutical and cosmetic industries, thereby aggregating value to the enormous amount of waste from the coconut industry, mostly used for burning purposes.