Harnessing Phytohormones: Advancing Plant Growth and Defence Strategies for Sustainable Agriculture.

Phytohormones, pivotal regulators of plant growth and development, are increasingly recognized for their multifaceted roles in enhancing crop resilience against environmental stresses. In this review, we provide a comprehensive synthesis of current research on utilizing phytohormones to enhance crop productivity and fortify their defence mechanisms. Initially, we introduce the significance of phytohormones in orchestrating plant growth, followed by their potential utilization in bolstering crop defences against diverse environmental stressors. Our focus then shifts to an in-depth exploration of phytohormones and their pivotal roles in mediating plant defence responses against biotic stressors, particularly insect pests. Furthermore, we highlight the potential impact of phytohormones on agricultural production while underscoring the existing research gaps and limitations hindering their widespread implementation in agricultural practices. Despite the accumulating body of research in this field, the integration of phytohormones into agriculture remains limited. To address this discrepancy, we propose a comprehensive framework for investigating the intricate interplay between phytohormones and sustainable agriculture. This framework advocates for the adoption of novel technologies and methodologies to facilitate the effective deployment of phytohormones in agricultural settings and also emphasizes the need to address existing research limitations through rigorous field studies. By outlining a roadmap for advancing the utilization of phytohormones in agriculture, this review aims to catalyse transformative changes in agricultural practices, fostering sustainability and resilience in agricultural settings.

Dietary antioxidants impact DDT resistance in Drosophila melanogaster.

Insects experience a diversity of subtoxic and/or toxic xenobiotics through exposure to pesticides and, in the case of herbivorous insects, through plant defensive compounds in their diets. Many insects are also concurrently exposed to antioxidants in their diets. The impact of dietary antioxidants on the toxicity of xenobiotics in insects is not well understood, in part due to the challenge of developing appropriate systems in which doses and exposure times (of both the antioxidants and the xenobiotics) can be controlled and outcomes can be easily measured. However, in Drosophila melanogaster, a well-established insect model system, both dietary factors and pesticide exposure can be easily controlled. Additionally, the mode of action and xenobiotic metabolism of dichlorodiphenyltrichloroethane (DDT), a highly persistent neurotoxic organochlorine insecticide that is detected widely in the environment, have been well studied in DDT-susceptible and -resistant strains. Using a glass-vial bioassay system with blue diet as the food source, seven compounds with known antioxidant effects (ascorbic acid, ß-carotene, glutathione, α-lipoic acid, melatonin, minocycline, and serotonin) were orally tested for their impact on DDT toxicity across three strains of D. melanogaster: one highly susceptible to DDT (Canton-S), one mildly susceptible (91-C), and one highly resistant (91-R). Three of the antioxidants (serotonin, ascorbic acid, and ß-carotene) significantly impacted the toxicity of DDT in one or more strains. Fly strain and gender, antioxidant type, and antioxidant dose all affected the relative toxicity of DDT. Our work demonstrates that dietary antioxidants can potentially alter the toxicity of a xenobiotic in an insect population.

Dietary antioxidant vitamin C influences the evolutionary path of insecticide resistance in Drosophila melanogaster.

Herbivorous insects encounter a variety of toxic environmental substances ranging from ingested plant defensive compounds to human-introduced insecticidal agents. Dietary antioxidants are known to reduce the negative physiological impacts of toxins in mammalian systems through amelioration of reactive oxygen-related cellular damage. The analogous impacts to insects caused by multigenerational exposure to pesticides and the effects on adaptive responses within insect populations, however, are currently unknown. To address these research gaps, we used Drosophila as a model system to explore adaptive phenotypic responses to acute dichlorodiphenyltrichloroethane (DDT) exposure in the presence of the dietary antioxidant vitamin C and to examine the structural genomic consequences of this exposure. DDT resistance increased significantly among four replicates exposed to a low concentration of DDT for 10 generations. In contrast, dietary intake of vitamin C significantly reduced DDT resistance after mutigenerational exposure to the same concentration of DDT. As to the genomic consequences, no significant differences were predicted in overall nucleotide substitution rates across the genome between any of the treatments. Despite this, replicates exposed to a low concentration of DDT without vitamin C showed the highest number of synonymous and non-synonymous variants (3196 in total), followed by the DDT plus vitamin C (1174 in total), and vitamin C alone (728 in total) treatments. This study demonstrates the potential role of diet (specifically, antioxidant intake) on adaptive genome responses, and thus on the evolution of pesticide resistance within insect populations.

The complete mitochondrial genome of Anoplocnemis curvipes F. (Coreinea, Coreidae, Heteroptera), a pest of fresh cowpea pods.

The complete 16,345-bp mitochondrial genome of the agriculturally destructive pod sucking pest, the giant coreid bug, Anoplocnemis curvipes (Hemiptera: Coreidae), was assembled from paired-end Illumina HiSeq 2500 reads. The A. curvipes mitochondrial genome consists of 13 protein coding genes (PCGs), 22 tRNAs, 2 rRNAs and a control region in the order and orientation typical among insects. PCG initiation codons (ATG, ATC, ATT and ATA) with termination codon (TAA) are used with the exception of TAG stop codons by Cytb and ND3. All tRNA genes fold into predicted cloverleaf secondary structures having requisite triplets on the anticodon loop, apart from tRNA-Ser1 (AGN) whose dihydrouridine (DHU) arm forms a simple loop. The phylogenetic analysis of hemipteran mitogenomes clusters to the family level and supports the monophyly of the five superfamilies in Pentatomomorpha of Hemiptera. The Coreoidea and Pyrrhocoroidea are sister groups, while Coreidae and Alydidae are sister groups to Rhopalidae. These analyses provide insight to mitogenomics and evolutionary relationships among pentatomoid insects.

Rearing the maize weevil, Sitophilus zeamais, on an artificial maize-cassava diet.

Dry artificial diet pellets prepared with maize, cassava chips, and amino acid supplements (lysine and methionine) were evaluated for mass culture of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), a highly polyphagous pest of many stored grains. Evaluation was done in the laboratory at temperature 26 ± 2 °C, 60-70% RH, 12:12 L:D photoperiod. The artificial diet was compounded from different proportions of maize (M) variety TZPB-SW-R, cassava (C) variety TMS-2110, and amino acid supplements, and was pelletized into 6 mm diameter pellets on which five pairs of one-day-old S. zeamais were bioassayed. The diet M(9)C(1) (90% M and 10% C) was the most suitable diet with comparatively shorter developmental period (34.8 days) and the highest F(1) emergence of progeny (145.4) compared to the control, M(10)C(0) (100% M and 0% C).