ABSTRACT. Most coffee (Coffea arabica) phytosanitary management techniques are performed using ground-based equipment, and remotely piloted aircraft are a recent alternative. Therefore, this study evaluates the effect of different application rates and hydraulic tips used for spreading phytosanitary products on coffee crops using a remotely piloted aircraft, assisted by artificial targets and dye tracing. The experiment was a 4 × 3 factorial randomized block design with four tips (XR 110-01, TT 110-01, AIXR 110-015, and TTJ60 110-02) and three application rates (8, 12, and 16 L ha-1). Hydrosensitive paper was used to analyze the droplet spectrum, and the Brilliant Blue tracer was used to detect spray deposition. The DJI Agras T20 remotely piloted aircraft was used to apply the phytosanitary product. Speed, flight height, and application range were maintained at 5.56 m s-1, 2 m, and 5 m, respectively. The flight direction was perpendicular to the crop planting lines. The application rate and hydraulic tip jointly controlled the accumulation of droplets on the target according to its position in the plant canopy. Therefore, remotely piloted aircraft can be used in coffee phytosanitary management, particularly to control targets that predominately occur in the upper third of the plant canopy.

ABSTRACT. Lettuce (Lactuca sativa L.) is the most consumed leafy vegetable in Brazil. It is cultivated using at least four distinct systems, the most common of which are conventional and hydroponic systems. These systems provide different cultivation conditions for plants, causing physiological changes that are important for commercial production, such as nutrient uptake and biomass accumulation. However, only a few studies have compared the physiological aspects of these two cultivation systems. The objective of this study was to evaluate the physiological behavior of ‘Rubinela’ lettuce plants grown in hydroponic and conventional pot systems, by comparing dry mass (DM) and fresh mass (FM) production, number of leaves (NF), stomatal density, and contents of chlorophyll, carotenoids, anthocyanin, sugars, and starch. Plants cultivated in hydroponic systems presented significant differences in chlorophyll content, producing more biomass than plants cultivated in conventional pot systems, probably because of better nutritional conditions, primarily with respect to macronutrients, provided by the nutrient solution of the hydroponic system. The lower water availability encountered by plants cultivated in conventional pot systems influenced the increased sugar and starch concentrations, as well as the anthocyanin content, which may be a strategy to mitigate the possible damage caused by hydric stress conditions.

ABSTRACT. Popcorn (Zea mays L. everta) is a specialty crop with a higher aggregate economic value than that of common maize. In Brazil, national literature is still incipient and contradictory in terms of plant population management and water requirements. Furthermore, the interaction between these factors has not been reported, despite the increasing cultivation of popcorn. The objective of this trial was to determine whether agricultural traits and popping expansion from hybrid IAC 125 could be affected by plant density and levels of irrigation water, in addition to determining the significance level of the interaction between both factors. We investigated five plant populations (40,000, 55,000, 70,000, 85,000, and 100,000 plants ha-1) and five different levels of water depth in 2014/2015 [574.86 (without supplementary irrigation), 609.86, 644.86, 679.86 (control), and 714.86 mm] and 2015/2016 [857.4 (without supplementary irrigation), 867.26, 886.60, 916.78 (control), and 959.81 mm] using a complete block design with split-plot, comprising a main plot (for plant populations) and subplot (for water depth), with six replicates for each set. We found increasing linear effects from grain yield under population density and levels of water depth, but this interaction was not significant. Moreover, the popping expansion for the main effects and the interaction between plant populations and water depth, were not significant.

ABSTRACT. Invasive species threaten crops and ecosystems worldwide. Therefore, we sought to understand the relationship between the geographic distribution of species populations and the characteristics of seeds using new techniques such as seed image analysis, multivariate analysis, and machine learning. This study aimed to characterize Leucaena leucocephala (Lam.) de Wit. seeds from spatially dispersed populations using digital images and analyzed their implications for genetic studies. Seed size and shape descriptors were obtained using image analysis of the five populations. Several analyses were performed including descriptive statistics, principal components, Euclidean distance, Mantel correlation test, and supervised machine learning. This image analysis technique proved to be efficient in detecting biometric differences in L. leucocephala seeds from spatially dispersed populations. This method revealed that spatially dispersed L. leucocephala populations had different biometric seed patterns that can be used in studies of population genetic divergence. We observed that it is possible to identify the origin of the seeds from the biometric characters with 80.4% accuracy (Kappa statistic 0.755) when we applied the decision tree algorithm. Digital imaging analysis associated with machine learning is promising for discriminating forest tree populations, supporting management activities, and studying population genetic divergence. This technique contributes to the understanding of genotype-environment interactions and consequently identifies the ability of an invasive species to spread in a new area, making it possible to track and monitor the flow of seeds between populations and other sites.

ABSTRACT. Bahiagrass (Paspalum notatum Flügge) is an important forage in South America and the United States because of its high palatability, resistance to trampling and grazing, and tolerance to cold, but it exhibits low seed yield and poor seed quality. Previous studies reported improvements in forage production and nutritive value in hybrids and ecotypes; however, information about seed yield and quality in forage bahiagrass is limited. This study aimed to characterize the seed yield and quality of nine P. notatum intraspecific hybrids and three controls: P. notatum ecotypes V4 and Bagual and cultivar Pensacola. Inflorescence density, 1,000-seed weight, seed yield and germination rate decreased in year 2 influenced by weather conditions and ergot. Seed yield ranged from 139 (Pensacola) to 1,158 (Bagual) kg ha-1 among all entries, where Bagual, C18, and V4 produced more than 974 kg ha-1, which was approximately seven times more than Pensacola. Bagual, C18, V4, 336, C15, 225, and D3 showed germination rates greater than 83%. In conclusion, Bagual had the highest seed yield and germination rate, whereas hybrids C18 and 336 showed high seed yield, 1,000-seed weight, and germination rate in both years. Bagual, C18, and 336 should be used in future breeding programs to improve seed production traits. Our study revealed that selection for seed production traits can result in improvements in seed yield and quality in bahiagrass.

ABSTRACT. Management systems that include trees tend to provide higher amounts of plant biomass to the soil, contributing to the increase in carbon (C) and nitrogen (N) stocks. This study simulated C and N stocks and their compartments in a crop-livestock-forest integration system in the edafoclimatic conditions of the Maranhão Cerrado using the Century 4.5 model. The evaluated areas were native Cerrado vegetation (NV) and crop-livestock-forest integration (CLFI). The calibration process gradually modified the model parameters to better fit the simulated and observed soil C and N stocks. The best fit between the data was obtained after changes in the main parameters (DEC3(2), DEC4, and DEC5) that controlled the rate of decomposition of soil organic matter. C and N stocks increased by 14% and 15%, respectively, over 14 years after replacing NV with CLFI. The slow compartment of C presented greater sensitivity to changes in management, with an increase of 47% compared with that of NV. The active compartment increased by 31% and the passive compartment remained constant for over 14 years. Future scenarios, where pasture was maintained between the eucalyptus trees and the scenario that allowed the soybean, corn, and Brachiaria rotation between the trees, were more effective, accumulating approximately 37 Mg C ha-1. The continuous contribution of residues from the trees and pasture increased C and N stocks in the long-term in the slow fraction, where the total organic carbon increased from 32 to 36 Mg ha-1 when NV was replaced with CLFI. The model predicted the C and N stocks with accuracies ranging from 1 to 11% of the observed values.

ABSTRACT. Fig orchard expansion requires knowledge of the thermal requirements of genotypes available in different climatic regions. The budburst of fig cultivars was assessed by biological single-node cutting and exposure to artificial chilling. Cuttings from five cultivars were collected during two crop seasons, subsequently packaged in a horizontal position in a cold chamber (8 ± 0.5ºC), and artificially chilled for 0, 40, 80, 120, and 160h. Cuttings were preserved under controlled conditions (23 ± 1°C, RH 85%, and 16h photoperiod). The variables evaluated were the budding velocity, average time and final rate of sprouting, vigorous shoot rate, and average time to leaf opening. The single-node cutting test allowed the assessment of dormancy, which is influenced by the accumulation of chilling in each crop season. The average time and final budding rate varied depending on the temperature requirements for budding. The cultivars were classified on an increasing scale according to their chilling requirements as follows: Pingo de Mel < Roxo de Valinhos < Brown Turkey < White Genova < Troyano. The traditional cultivar in Brazil is Roxo de Valinhos, but all of the cultivars studied had the potential to diversify the fig orchards in this region.

ABSTRACT. Purslanes are frequently used in Brazil as potted plants and for landscaping because of their beautiful colored flowers. Despite their commercial importance, the genetic diversity within ornamental purslane remains largely unknown. Thus, a complete characterization of ornamental purslane resources is essential for its utilization since genetic variability is indispensable for the efficient development of new cultivars. This study aimed to evaluate genetic variability and recommend accessions to start a genetic breeding program for purslane (Portulaca umbraticola). Twenty purslane accessions were collected in public places in Areia City and Santa Rita City, Paraiba State, Brazil. The experiment was conducted in a greenhouse. An entirely randomized experimental design with 20 accessions and 5 replicates was utilized. Plants were evaluated for quantitative and qualitative traits. Data were submitted to analysis of variance and grouped by Scott-Knott’s criteria (p ≤ 0.05). The accessions were grouped using Tocher’s method based on the generalized Mahalanobis distance. Principal component analysis was also used to analyze the genetic divergence. There were significant differences (p ≤ 0.05) for all evaluated traits except for internode distance, plant height, and leaf length. The Scott-Knott criteria clustered the accessions into two groups for all traits except days to flowering (five groups). Tocher’s grouping based on Mahalanobis distance allowed the accessions to be separated into eight clusters. The genetic diversity observed in this study was supported by the consonance between the Tocher cluster method and the PC analyses. The traits that most contributed to genetic divergence among accessions were days to flowering (70.37%), flower length (6.10%), leaf width (3.89%), branch number (3.57%), and stem length (3.36%). Considering the criteria for use in outdoor spaces, wider plants with several large colored flowers, thicker stems, greener leaves, and earliness were interesting. Accessions 5, 7, 13, 14, 16, 18, and 20 should be selected as parents for further breeding programs. However, if the objective is to produce potted plants, dwarf plants with bigger leaves are desired, and accession 1 should be selected. This will create greater variability in segregating populations, which will increase the overall quality of ornamental use of this species. For those accessions with no reproductive verticils but with other excellent attributes, for example, high chlorophyll content breeding strategies, such as induced mutations or protoplast fusion, can be used.

ABSTRACT. Brazil has high soil loss rates due to its tropical and subtropical climate characteristics. In this sense, soil use and management practices may minimize such losses. In this study, experimental plots were monitored for eight years in southern Brazil during natural rainfall events. Treatments were as follows: I) bare soil under conventional tillage, II) barley-oat/ soybeans succession under conventional tillage, III) oat-lupine-vetch/ maize succession under conventional tillage, IV) barley-oat/ soybeans succession under no-tillage, and V) oat-lupine-vetch/ maize succession under no-tillage. Data on rainfall amount and erosivity indices (EI30, EI20, and EI10) were subjected to regression analyses, evaluating the effects of climatic variables on soil and water losses. We could also analyze crop species, conventional and no-tillage systems, and winter and summer seasons. The highest soil and water losses occurred in treatments under conventional tillage. In addition, soybeans treatments increased soil and water losses. Maize under no-tillage was the most efficient practice, as it had soil losses (3.4 times) and water losses (1.5 times) lower than soybeans under conventional tillage. Rainfall amounts and EI30 were better correlated with soil and water losses in conventional tillage treatments. However, EI10 could better explain the soil losses from the conservationist treatment.

ABSTRACT. Citrus tristeza virus (CTV) can be transmitted by several aphid species in a semi-persistent mode, with Toxoptera citricida being the most efficient vector. In Brazil, mild CTV isolates are used for pre-immunization of citrus trees against severe isolates. We aimed to determine the capacity and efficiency of T. citricida in separating the viral complex into haplotypes from three well-characterized CTV isolates (PIAC, CS1, and Forte Rolândia). Single-aphid transmission assays were conducted to determine CTV transmission efficiency. The results showed that T. citricida transmitted only haplotypes from the PIAC and CS1 isolates, with efficiencies of 8 and 4%, respectively. Both isolates caused mild CTV symptoms in Brazil. However, isolate Forte Rolândia, which causes severe symptoms in citrus trees, was not transmitted by T. citricida. The detection of CTV haplotypes from PIAC and CS1 isolates in sweet orange (Citrus sinensis) plants after a single aphid transmission occurred at different time points. The first haplotype observed was from PIAC 150 days after citrus was challenged by a single aphid, followed by CS1 at day 210 after transmission. In addition, differences in the single-strand conformation polymorphism patterns between the CTV isolates and CTV haplotypes were determined, suggesting that an aphid can acquire and transmit only one CTV haplotype to citrus plants during phloem feeding. The study of the mechanism of transmission by the vector can increase our knowledge of the interactions among hosts, vectors, and pathogens, which are often neglected.

ABSTRACT. Conservation practices such as no-tillage are necessary to maintain, and/or improve agricultural soil quality. However, straw formation and maintenance in tropical regions is a limiting factor to adopting this system. In this sense, this research aimed to study the effect of cover crops on straw formation, soil quality indicators, and cowpea yield under no-tillage in the Amazon savanna. Two experiments were carried out in consecutive years, on a Latossolo Amarelo. The treatments consisted of the straw of cover crops in a single (S) and intercrop (I) system, as follows: Urochloa brizantha (UBS), Pennisetum glaucum (PGS), Crotalaria juncea (CJS), Canavalia ensiformis (CES), Mucuna aterrima (MAS), U. brizantha and C. juncea (UBCJI), U. brizantha and C. ensiformis (UBCEI), P. glaucum and C. juncea (PGCJI), P. glaucum and C. ensiformis (PGCEI), and spontaneous vegetation (SV). Cowpea was cultivated after desiccation of the cover crops. Most of the straw favored soil particle aggregation, except for C. juncea and SV, which negatively influenced this variable. Basal soil respiration, organic carbon content, potassium, base saturation, geometric mean diameter, macroaggregates, and macroporosity at layer of 0-0.10 m were the most sensitive indicators for improving soil quality in a savanna environment. UBS, UBCJI, and UBCEI were superior to the other treatments in improving soil quality. Almost all treatments increased cowpea yield by up to 29%, except for CJS and SV.

ABSTRACT. Combinations between crop intercropping and forage production in a no-tillage system are not well established for environments under low water retention and soil fertility conditions. Our study aimed to evaluate the potential interactions between soybean-grass intercropping with residual nitrogen in a no-tillage system. The experimental design was a randomized block with four replications in a subdivided plot scheme. The main plots in the summer season were: 1) soybean monoculture; 2) soybean - Aruana Guinea grass (Megathyrsus maximus cv. Aruana) intercropping, and 3) soybean - Congo grass (Urochloa ruziziensis cv. Comum) intercropping. The subplots were the nitrogen rates of 0, 50, 100, and 150 kg ha-1, applied as side-dressing in maize and grasses during the autumn-winter season. Here, the results of the summer seasons are shown. To do so, the parameters evaluated were soybean agronomic traits, dry biomass production, and macronutrient concentrations of plants intercropped. The main effects and interactions were studied. Our findings showed that soybean-Aruana Guinea grass intercropping is an alternative to no-tillage system implementation. Moreover, residual nitrogen from the autumn-winter season directly interfered with the dry biomass production of grasses intercropped with soybeans in the summer season. In short, the systems studied seem suitable for implementing a no-tillage system, which aims to neutralize degraded pastures and produce forage for ensilage. Despite the changes in macronutrient concentrations within the intercropping system and residual nitrogen, and among intercropped crops over the years, Congo grass intercropped with soybeans in the summer season showed great capacity for phosphorus, potassium, and magnesium cycling.

ABSTRACT. This work aimed to estimate the genetic diversity in accessions of Opuntia ficus-indica collected in 13 regions of the semiarid region of Bahia. A total of 65 accessions were evaluated in a randomized complete block design, with three replications, at the Rio Seco experimental station belonging to the State University of Feira de Santana, Amélia Rodrigues-BA. Characterization of the accessions was made through the evaluation of 17 descriptors, namely 11 agronomic and six bromatological. The average Euclidean distance was used to estimate the genetic diversity among accessions. The shortest distances were obtained for accessions from the same collection site while the largest were observed in accessions 54 and 62 (10.32 DE) and 63 and 3 (10.22 DE). The analysis of canonical variables indicated cladodes total number (CTN), plant width (PW), CL, plant height (PH), ether extract (EE), and dry weight (DW) for discard as they presented the lowest contribution of the data set variation. Principal component analysis and K-means method were used to establish the clusters, and the formation of four groups was indicated. The first two principal components captured 52.5% of the total variation present in accessions. The descriptors with the greatest contribution to the variation observed in O. ficus-indica were total cladode photosynthetic area (TCPA), cladode area (CA), and cladodes width (CW). There is divergence between cactus forage accessions collected in the semiarid region of Bahia. This information will allow the use of these materials for the formation of segregating populations in the genetic improvement program of the State University of Feira de Santana. The accessions of groups III and IV should be explored by the forage cactus breeding program, as they presented greater productive potential.

ABSTRACT. Climate change and the expansion of agricultural lands to low-fertility soils have prompted studies on the effects of water and nutritional stress on nutrient uptake and use. This study aimed to evaluate the efficiency of absorption, translocation, and use of N in coffee cultivars under water stress (WS) and different N doses. The experiment was performed hydroponically and arranged in a 4 × 2 × 4 factorial randomized block design with three replications. These factors consisted of four coffee varieties, two N doses, and four levels of WS. At the end of the experiment, the dry matter production, N concentration, and N accumulation of plants, as well as nutritional efficiency indices were evaluated. The data were subjected to analysis of variance and regression. The results showed that in plants previously well-supplied with N, N stress induces greater allocation of dry matter in roots, mitigating the effects of subsequent water deficits on shoot dry matter production. Young Mundo Novo plants subjected to N stress followed by increasing water stress maintained a high utilization efficiency (UE). Young Acauã plants well-supplied with N, maintained their N utilization efficiency up to -1.6 MPa of water stress; however, when they were N starved, they underwent a drastic reduction in UE at potentials below -0.22 MPa.

ABSTRACT. Determining the number of replicates required to produce statistically testable results based on previously conducted tests is important to minimize labor costs via the use of existing information. The objective of this work was to determine the number of repetitions necessary to evaluate the characters of productivity and soluble solids in hybrids of two types of Inodorus melons. The study consisted of 20 experiments: 12 evaluated 10 hybrids of honeydew melons and 8 evaluated 13 hybrids of yellow melons. The experimental design consisted of randomized blocks with three replicates. Analysis of variance was performed to estimate the repeatability and genotypic determination coefficients. Variability in accurately predicting the genotype was observed for different number of repetitions between the evaluated characters and melon types. In the yellow melon, experiments with three repetitions allowed the accurate identification of superior genotypes with 81.1 and 61.9% certainty for productivity and soluble solids, respectively. In the honeydew melon, 62.4 and 71.2% accuracy was obtained for productivity and soluble solids, respectively.