No abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama, transmits the bacteria Candidatus Liberibacter associated with huanglongbing (HLB), a devastating disease of the citrus industry. The use of genetically modified plants is an alternative to control this vector. Conversely, technology based on RNA interference (RNAi) for silencing specific genes of a target insect could be attempted. This work evaluated the knockdown effect of the target genes calreticulin (DcCRT), laccase (DcLAC), and Snf7 (DcSnf7) by RNAi through feeding D. citri in Murraya paniculata leaves after the uptake of an aqueous solution with dsRNA homologous to each vector target gene. Confocal microscopy revealed the uptake of the fluorescent-labeled dsRNA by detached leaves and the symplastic movement, allowing the ingestion by the feeding insect. A reduction in the survival rate was observed only 144 h after the beginning of feeding with dsRNA targeting DcSnf7; however, no reduction in transcript accumulation. The knockdown of the DcCRT and DcLAC genes was detected only 12 and 96 h after insect feeding, respectively. Additionally, a reduction in amino acid excretion from insects fed with dsRNA targets to DcCRT and DcLAC was observed 120 h after the beginning of feeding. However, the effects of the dsRNAs tested here appear to be minimal, both at the transcriptional and phenotype levels. For most concentrations and time points, no effects were observed. Therefore, the knockdown of genes DcCRT, DcLAC, and DcSnf7 do not appear to have the potential to control of D. citri through RNAi-mediated gene silencing.

Citrus species, including sweet oranges, grapefruits, pomelos, and lemons, are the most widely cultivated trees and consumed fruits worldwide. In citrus orchard management, the control of Huanglongbing (HLB) disease and its insect vector Diaphorina citri (Asian citrus psyllid, ACP) represents a major global challenge. Consumers have been increasingly pushing the citrus production chain toward a more sustainable system, including stringent measures to prevent the use of chemical pesticides. In recent years, biotechnological advances have offered safe and environmentally friendly alternatives for crop production. Technologies such as RNA interference (RNAi)-mediated gene silencing have emerged as innovative tools for agricultural pest management. Here, we provide an overview of RNAi as a promising approach for ACP control and discuss the associated challenges. Despite the availability of specific silencing sequences aimed at a target gene of the insect pest, the uptake of double-stranded RNA is limited in hemipteran insects. In this context, improved delivery methods, stability maintenance, and RNAi response are considered the factors contributing to the increased effectiveness of exogenous RNAi against hemipteran pests. These approaches can serve as potential tools for efficient ACP control.

The objective of this work was to verify if the introgression of the AtAREB1 gene in the 'LS93-0375' and 'BMX Desafio RR' elite soybean germplasms increases the tolerance of these plants to water deficit. The F4 progenies of these two elite cultivars and of the AtAREB1 transgenic line (BR16-AtAREB1) and its background ('BR16') were subjected to water deficit assays. The water deficit bioassays were performed in a greenhouse using the following six soybean lines: the genetically modified BR16-AtAREB1 and its background 'BR16'; 'LS93' and its F4 progeny, LS93-AtAREB1; and 'BMX Desafio RR' and its F4 progeny, Desafio-AtAREB1. A randomized complete block experimental design was carried out in a 6x2 factorial arrangement, with the six soybean genotypes and two water conditions – control (C) and water deficit (WD) treatments – with nine replicates. Soybean genotypes containing the AtAREB1 gene showed better physiological performances under drought stress and altered expressions of drought-responsive genes. The intogression of AtAREB1 in soybean increases the plant drought tolerance, regardless of the genetic background in which the gene was introduced.

Climate change and population size records threaten food security. Therefore, the call for a more sustainable and efficient crop production has never been more urgent. Traditional plant breeding was one of the first successful approaches to expand cultivation areas and crop yield. Later, biotechnological tools and their products, such as genetically modified organisms containing exogenous DNA, further broadened the limits of agricultural results, yet bringing huge financial, bureaucratic, and public rejection hurdles. In the 90s, scientific advances brought the opportunity to drive mutations using engineered nucleases, and since 2013 CRISPR-Cas has emerged as the most practical toolkit to edit genomes. One of the most striking possibilities is to generate edited and non-transgenic plants. In this review, we present the working mechanism behind CRISPR-induced mutations and pinpoint the latest techniques developed, as well as its myriad of applications in agriculture. The enhancing scope of CRISPR ranges from introducing traits of agronomic interest – such as herbicide resistance, resistance/tolerance to biotic and abiotic stresses, and quality and durability of products – to accelerating plant breeding processes, including haploid induction, generating male-sterile lines, fixating hybrid vigor, and overcoming self-incompatibility. We also discuss regulatory issues surrounding edited plants and derived products around the world, challenges that must be overcome, and future prospects to harness all the potential of this amazing tool to guarantee the new crop production revolution.

The objective of this study was to investigate the effects of the application of indole-3-butyric acid (IBA) at concentrations of 0, 30, 60, and 90 mg·L−1, for 24 hours, on rooting of softwood and semihardwood cuttings of tea (Camellia sinensis var. sinensis ‘Yabukita’ and C. sinensis var. assamica ‘IAC-259’) collected in winter and summer. In the summer, IBA increased root percentage of softwood cuttings from ‘Yabukita’ compared with the control. However, the rooting of semihardwood cuttings was unaffected by this growth regulator. In winter, application of 90 mg·L−1 IBA increased the rooting regardless of the type of ‘Yabukita’ cuttings. In addition, in ‘IAC-259’, there was an increase in dry weight, number of roots (NOR), and rooting percentage of softwood cuttings collected in summer with application of 90 mg·L−1 IBA compared with control. In contrast, during the same period of the year, the semihardwood cuttings of ‘IAC-259’ were unaffected by the IBA. In winter, the percentage of cutting survival, rooting, the number, and length of roots were unaffected by IBA in ‘IAC-259’. Overall, we would recommend the use of exogenous IBA for rooting of cuttings collected in the summer or winter.

Fertilizer management is an essential step in the production process, as it allows the plant to use its productive capacity to the fullest extent possible. Researchers have tested maximum nutrient use with reduced losses to the environment aiming to increase productivity with fewer environmental impacts. This study compared the effects of controlled-release fertilizers (CRFs) with water-soluble fertilizer (WSF) and clear water (control) on the growth and nutrient uptake of croton (Codiaeum variegatum L.) and nitrogen leaching. The experiment was conducted with three replications and six treatments: two rates (1.5 g and 3.0 g per liter of substrate) of two CRFs [Osmocote Plus (15% N, 3.93% P, and 9.96% K) and Basacote (15% N, 3.49% P, and 9.96% K)], WSF, and clean water as control. All CRFs were applied before planting and WSF was supplied as nutrient solution through automated moisture sensor activated irrigation system. Plant growth (number of leaves, leaf area, stem height, root volume, and shoot and root dry weights) and total nutrient contents in the leaf tissue were evaluated every 30 days. Electrical conductivity (EC), pH, nitrate, ammonium, and total nitrogen contents were measured in the leached solution. Indeed, results showed that CRFs at a low rate provided similar development and quality of croton plants compared with WSF. Plant growth indicators were similar until 90 days after transplanting (DAT). After that, at 150 DAT, the highest values to number of leaves and leaf area occurred with WSF and with the lowest CRF rate as compared with the other treatments and control. The highest root volume was found with the WSF, which resulted in larger roots compared with the other treatments. These results showed WSF can be replaced by CRFs at low rates on croton growth. Moreover, according to the visual scale, the best treatments were WSF and Basacote at the low rate, where plants were bright, with multicolored leaves with prominent orange shades. However, CRFs maintained pH and EC within the recommended range for the growth of croton and reduced the nitrogen leaching from the pots.

Core Ideas Polymer‐coated urea reduced N leaching as compared with conventional urea. Climatic conditions during the lantana growth affected the N uptake and N‐use efficiency. These results can be used for water and fertilizer management for ornamental plants. This study can be used to minimize environmental impact caused by N leaching. Lantana (Lantana camara L.) is a popular ornamental plant in seaside communities and an annual plant in hanging baskets. This species cultivated as an annual plant in containers needs to receive fertilizers. The nutrient management in containers can be made using conventional or controlled release fertilizers. The effects of ratios among conventional urea (CU) and polymer‐coated urea (PCU), and irrigation water rates applied by evapotranspiration (ET)‐based irrigation were studied on dry weight of biomass and N uptake of lantana, N leaching, water‐use efficiency (WUE), and N‐use efficiency (NUE). Six ratios between CU and PCU (expressed in percentages) and two irrigation rates were evaluated: 0:100, 25:75, 50:50, 75:25, 100:0, and 0:0 of CU/PCU; and water volume applied by 150% of reference evapotranspiration (ETo) and 200% of ETo‐based irrigation. Two trials were conducted with environmental conditions varying between them. With greater temperatures, the cumulative number of inflorescences increased with 100% of PCU as compared with 100% of CU applied in the trial. Polymer‐coated urea (100%) as compared with CU (100%) also reduced N leaching by 64.5 and 61.5% in the first and second trial, respectively. High water volume applied (200% of ETo) increased the dry weight of biomass, N uptake, and NUE. Water volume applied by 150% of ETo‐based irrigation resulted in a reduction of 53.5 and 58.5% of N leaching in the first and second trial, respectively. The response of WUE to ratios among CU and PCU and irrigation rates was not consistent, and was influenced by climatic conditions since WUE increased 26.6% in the second trial characterized for lower temperatures.