The center of origin and domestication of Piper nigrum L. are in high rainfall regions. But when grown in regions with irregular or insufficient rainfall, irrigation becomes essential. This study evaluated the impact of irrigation levels on the physiological and growth characteristics of black pepper plants, cv. Bragantina. It was carried out from April 2019 to May 2020, using automatic activation irrigation. We used emitters with different flow rates to apply water depths corresponding to 100, 81, 62, and 42% of the crop water requirement. The parameters evaluated comprised main stem length (MSL), stem diameter (SD), number of leaves (NL), leaf area (LA), chlorophyll contents, chlorophyll-a fluorescence, and some photosynthetic parameters. The treatments significantly influenced (p < 0.05, F-test) MSL and NL. Plants submitted to the control treatment showed MSL (65.8%) and NL (123%) greater than those irrigated with the smallest volume (p < 0.05, F-test). However, the treatments had no significant effect on SD. Moreover, chlorophyll b levels decreased by 26% and chlorophyll a/b ratio increased by 22% at 120 and 180 DAT, respectively. Some photosynthetic parameters such as FV/FM, ABS/RC, and DI0/RC were affected by water deficit at 120 DAT. Our results suggest the sensitivity of black peppers to water deficit and contribute to the proper management of this crop.

Black pepper is widely produced in Brazil, though there are few studies related to its water requirements and the effects of water deficit (WD) applied under tropical conditions. The growth, sensitivity to WD, and first-year productivity of irrigated plants from the Bragantina cultivar were evaluated, employing an irrigation system with automatic management. The plants were cultivated in plastic pots installed in the field for 391 days using emitters with different flow rates (2.2 [T1], 3.3 [T2], 4.3 [T3], and 5.3 L h–1 [T4 – control]). Fresh weight of the leaves, stems, and shoots, and dry weight of the leaves, stem, roots, and shoots as well as the total dry weight of the plant, were evaluated. Productivity was determined by evaluating the grains and spikes from a single harvest. Yield results and the actual versus maximum evapotranspiration rate for the entire growing season was used for calculating the Ky coefficient. Despite 1,346 mm of rainfall, the irrigation system was activated 165 times, distributing a mean volume of 19.0 (T1), 28.5 (T2), 37.1 (T3), and 45.8 L per plant (control). All traits were negatively affected by the WD, and the Ky values obtained (from 1.72 to 2.96) indicate the high sensitivity of black pepper to WD. In general, the spikes produced with at least 81 % of the crop water demand were larger and more numerous than those subjected to inferior treatments. WD occurring during the flowering stage severely hampers the size, weight, and quality of the spikes and grains of black pepper.

pGhERF105 and pGhNc-HARBI1 promoters are highly responsive to CBW infestation and exhibit strong activity in vegetative and reproductive tissues, increasing their potential application in GM crop plants for pest control. The main challenge to cotton (Gossypium hirsutum) crop productivity is the constant attack of several pests, including the cotton boll weevil (CBW, Anthonomus grandis), which uses cotton floral buds for feeding and egg-laying. The endophytic nature of the early developmental stages of CBW makes conventional pesticide-based control poorly efficient. Most biotechnological assets used for pest control are based on Bacillus thurigiensis insecticidal Cry toxins or the silencing of insect-pest essential genes using RNA-interference technology. However, suitable plant promoter sequences are required to efficiently drive insecticidal molecules to the target plant tissue. This study selected the Ethylene Responsive Factor 105 (GhERF105) and Harbinger transposase-derived nuclease (GhNc-HARBI1) genes based on available transcriptome-wide data from cotton plants infested by CBW larvae. The GhERF105 and GhNc-HARBI1 genes showed induction kinetics from 2 to 96 h under CBW’s infestation in cotton floral buds, uncovering the potential application of their promoters. Therefore, the promoter regions (1,500 base pairs) were assessed and characterized using Arabidopsis thaliana transgenic plants. The pGhERF105 and pGhNc-HARBI1 promoters showed strong activity in plant vegetative (leaves and roots) and reproductive (flowers and fruits) tissues, encompassing higher GUS transcriptional activity than the viral-constitutive Cauliflower Mosaic Virus 35S promoter (pCaMV35S). Notably, pGhERF105 and pGhNc-HARBI1 promoters demonstrated more efficiency in driving reporter genes in flowers than other previously characterized cotton flower-specific promoters. Overall, the present study provides a new set of cotton promoters suitable for biotechnological application in cotton plants for pest resistance.

Cotton is the most important crop for fiber production worldwide. However, the cotton boll weevil (CBW) is an insect pest that causes significant economic losses in infested areas. Current control methods are costly, inefficient, and environmentally hazardous. Herein, we generated transgenic cotton lines expressing double-stranded RNA (dsRNA) molecules to trigger RNA interference-mediated gene silencing in CBW. Thus, we targeted three essential genes coding for chitin synthase 2, vitellogenin, and ecdysis-triggering hormone receptor. The stability of expressed dsRNAs was improved by designing a structured RNA based on a viroid genome architecture. We transformed cotton embryos by inserting a promoter-driven expression cassette that overexpressed the dsRNA into flower buds. The transgenic cotton plants were characterized, and positive PCR transformed events were detected with an average heritability of 80%. Expression of dsRNAs was confirmed in floral buds by RT-qPCR, and the T1 cotton plant generation was challenged with fertilized CBW females. After 30 days, data showed high mortality (around 70%) in oviposited yolks. In adult insects fed on transgenic lines, chitin synthase II and vitellogenin showed reduced expression in larvae and adults, respectively. Developmental delays and abnormalities were also observed in these individuals. Our data remark on the potential of transgenic cotton based on a viroid-structured dsRNA to control CBW.

Soil salinity has the potential to severely affect crop performance. To maintain cell functioning and improve salt tolerance, the maintenance of K+ homeostasis is crucial in several plant metabolism processes. Besides, potassium fertilization can efficiently alleviate the perilous effects of salinity. We characterized impacts in Setaria viridis exposed to NaCl and KCl to underlying photochemistry mechanisms, K+ and Na+ shoot contents, enzymatic activity, electrolytic leakage, and morphological responses focusing on non-stomatal limitation of photosynthesis. Plants were exposed to sodium chloride (NaCl; 0, 150 and 250 mM) and potassium chloride (KCl; 0, 5, 9 mM). The exposure to NaCl affected S. viridis leaves morphological and physiologically. Plants submitted to 150 mM showed reductions in performance indexes (PIabs and PItotal; JIP-test), and the presence of positive K- and L-bands. Plants exposed to 250 mM exhibited blockage in electron flow further than Q(A) within 48h and permanent photoinhibition at 96 h. The presence of 9 and 5 mM of KCl counteracted the effects of NaCl on plants submitted to 150 mM, concomitant with increases in K+ accumulation and cell turgidity conservation, causing positive effects in plant growth and metabolism. Neither KCl concentrations were effective in reducing NaCl-induced effects on plants exposed to 250 mM of NaCl. Our results support the conclusion that greater availability of K+ alleviates the harmful effects of salinity in S. viridis under moderate stress and that application of KCl as means of lightning saline stress has a concentration and a salt level limit that must be experimentally determined.

Drought-tolerant species, such as Setaria viridis, a C4 model plant, make physiological and biochemical adjustments water limitation and recover from the stress upon its release. We investigated S. viridis (A10.1 accession) responses to continuing osmotic stress. The osmotic stress was imposed using polyethylene glycol (PEG) 8000 (7.5%) for 10 days. Morphological traits and stomatal conductance were measured daily for the 10 days. On days 6 and 10, the following traits were measured separately for root and shoot: relative water content (RWC), osmotic potential (OP), electrolytic leakage (EL), and proline content. qPCR analysis was used to evaluate the expression of five selected genes in roots (SvLEA, SvDREB1C, SvPIP2-1, SvHSP20, and SvP5CS2), and chlorophyll a fluorescence was measured on three key days. The morphological data demonstrated a drastic reduction in shoot biomass as an effect of water deficit caused by the osmotic stress. Shoot biomass reduction could be associated with putative ABA-dependent signaling involved in SvDREB1C expression. Stomatal conductance and photosynthesis were severely affected up until day 6, however, stomatal conductance and some photosynthetic parameters such as FV/FM, ABS/RC, and DI0/RC showed total or slight recovery on day 10. Root EL decreased in treated plants suggesting an investment in membrane protection by osmoregulator expression such as dehydrin (SvLEA) and proline (SvP5CS2) genes. Our data suggest that S. viridis exhibited a partial recovery from an imposed and constant osmotic stress within 10 days.

Clomazone and saflufenacil are herbicides extensively used worldwide to weed control. We studied the effects of these two herbicides on morphoanatomical parameters of Setaria viridis. Plants were sprayed with four concentrations of each herbicide (clomazone: 500, 1000, 1500 and 2000 g of active ingredient (ai) ha(-1) and saflufenacil: 49, 98, 147 and 196 g ai ha(-1)) besides control (without spraying) 20 days after transplantation. The experimental design was completely randomized with five replicates per treatment. Pigment content, visible injuries, morphological and ultrastructural changes were evaluated. No signs of tolerance to either of the tested herbicides were observed. Clomazone caused a decrease in photosynthetic pigment content over time, mostly in young leaves, leading to an "albino" like appearance. There was a reduction in the number of grana in the chloroplasts of mesophyll cells (MC) in necrotic areas. Saflufenacil reduced chlorophyll content, impairing energy absorption in the antenna complex. Injuries to foliar tissues, such as necrosis and depigmentation, were visible as early as 24 h after herbicide application. Bundle sheath chloroplasts (BSC) and MC were completely deformed. The data support the use of S. viridis as a model plant for studies on herbicide effects in C-4 monocots. (c) 2020 SAAB. Published by Elsevier B.V. All rights reserved.

ABSTRACT: Seedling production is an important step in the lettuce production system. However, there is a tendency to apply excessive irrigation at this stage. The aim of this study was to test the use of the Simplified Irrigation Controller (SIC) under two conditions: first, with the sensor installed in the substrate (measuring the soil water tension) and second, in the atmosphere (“atmospheric” - responding to vapor demand in the atmosphere) to control the irrigation of lettuce seedlings. The performance of the SIC was evaluated by monitoring plant traits. The lettuce seeds of the Regina cultivar were sown in styrofoam trays with commercial organic substrate. Both experiments were conducted under greenhouse conditions and evaluated under different SIC activation tensions. Shoot fresh weight and dry weight, height, number of leaves, leaf length, leaf area, water use efficiency (WUE) (ratio between the dry mass of plant produced by the volume of water applied), chlorophyll content, stomatal conductance and chlorophyll a fluorescence were assessed. In the experiment with the substrate sensor, the tension of 11.5 kPa caused death in 94 % of the seedlings and was disregarded in the statistical analysis. All biometric and physiological traits evaluated decreased as the SIC tensions increased. Thus, tensions of 4.0 (substrate sensor) and 3.5 kPa (atmospheric sensor) showed greater potential for producing vigorous seedlings, with WUE average values of 1.86 and 1.37 g L−1, respectively. Cultivation of lettuce seedlings proved viable under both conditions when the SIC was used, with the emergence of a number of practical advantages of the atmospheric sensor over the substrate one.

ABSTRACT: Concerns with water crisis involve all sectors of society and irrigated agriculture remains the main water consumer. This study evaluated an agricultural production system for lettuce cultivation in greenhouse, “organic potponics”, to economize water and manure use, using a Simplified Irrigation Controller (SIC), based on soil matric potential monitoring. Five irrigation volumes were evaluated in pots with 4.8 L, fertilized with 200 g of vermicompost. One of the volumes was controlled with the SIC. The other volumes represented 130, 80, 60 and 33 % of that controlled by the SIC and all treatments received water at the same time. Shoot fresh weight, head diameter and stomatal conductance (gs) increased linearly with irrigation volumes. For shoot dry weight, number of leaves and water use efficiency (WUE), the regression was quadratic with maximum values at 126, 114 and 83 %, respectively. Leaf relative water content did not show variation among treatments and changes in some fluorescence parameters (Reo/RC, Sm, N and φR0) were much more remarkable to drought compared with the FV/ FM ratio, one of the most commonly used stress indicators. The data indicated a tradeoff between WUE and plant growth thus the economic values of water and lettuce should be taken into account to indicate the best SIC irrigation volume. Organic potponics is promising and should be further improved to save on water, labor and fertilizer use.

Two experiments were performed to evaluate the effect of ash (40, 80, and 120 g per plant), castor cake (140 and 280 g per plant) and water depth (135, 165, 191, and 213 mm) on the growth and production of organic tomato cultivated in pots in a greenhouse. The experimental design was randomized blocks, and the irrigation was managed using an automatic irrigation device. The following variables were evaluated: plant heights, numbers of leaves, bunches, flowers and fruits, total mass of fruits, mass of marketable fruits, mass of fruits with blossom-end rot, total diameter of fruits, and diameter of marketable fruits. Most of the growth variables showed gains with the application of 140 g of ash and 280 g of cake. The dose of 280 g of castor cake was responsible for the greatest mass of marketable fruits (1.78 kg per plant), regardless of the ash dose. The water deficit reduced values of most of the variables of growth and production. The irrigation depth of 213 mm was responsible for the greatest mass of marketable fruits (4.04 kg per plant). The highest water use efficiencies, 37.00 and 37.93 kg m(-3), were observed at irrigation depths of 191 and 213 mm, respectively.