Ano 2023

Vol. 70

No. 2

Enviromental temperature and age of seeds in tolerance to thermoinhibition in lettuce genotypes

Lactuca sativa L germination seed storage

Lettuce seeds usually show germination problems that can be related to dormancy and or thermoinhibition, as well as to the genotype constitution. The knowledge of the temperature at which the thermoinhibition process begins, as well as the influence of the age of the seed on its germination, is extremely important to establish more suitable parameters for the selection of higher genotypes in breeding programs. The objective of this work was to evaluate the seed germination of three lettuce cultivars according to the enviromental temperature and the age of the seeds. The cultivars Everglades (tolerant to thermoinhibition), Luisa (medium tolerant) and Verônica (sensitive) were used. Seeds of each cultivar were evaluated by the standard germination test, first count test, germination speed index and germination test of remaining seeds. The analyses were performed at four environmental temperatures and in seven storage periods after harvest. None of the cultivars showed primary dormancy. The tolerance to thermoinhibition showed by cultivars Everglades and Luisa and the sensitivity of cultivar Verônica were confirmed. The most suitable temperature for differentiating tolerant and sensitive thermoinhibition genotypes occurred from 30.5 ºC and 260 days after harvest.

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Biomass, yield and competitiveness of maize and bean crops in an association system

Zea mays Phaseolus vulgaris land equivalent ratio competitive ratio

Polycultures are of great importance in conventional agriculture in the tropical zone, where they are a sustainable source of food production. In this study, the biomass distribution, crop yield and competition were determined in the maize and bean association. The total dry biomass accumulation of maize plants of the monoculture Simijaca SM(o) was higher than that of beans of monocultures cultivars Iraca IB(o) and Hunza HB(o). In monoculture, cultivar Iraca obtained the highest bean yields reaching 2744.0 kg ha-1 in the municipality of Gama, whereas cultivar Simijaca had the highest yields with a value of 7766.7 kg ha-1. In the association, the best environment was the municipality of Simijaca for the SMxIB treatment, which showed a total yield of 9767.5 kg ha-1. The total land equivalent ratio (LERt) was higher than 3.65, showing the advantage of this association. Additionally, the competitive ratio (CR) of the crops showed the high competition effect between maize and the two bean cultivars. The study generated new knowledge about the genetic resources of maize and climbing beans grown at the same time and in the same place, in the search for sustainable and resilient production. 

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Production of edible flowers: irrigation and biotechnology

Viola × wittrockiana floriculture water deficit mycorrhizal fungi

Garden pansy is a versatile gardening plant – it produces beautiful colorful edible-flowers with high value in gourmet cuisine. The use of irrigation and biotechnology in garden pansy cultivation can provide gains in flower productivity and nutritional value. The goal of this study was to evaluate the growth and edible flower production in garden pansy plants, submitted to different levels of irrigation and mycorrhizal inoculation. The experiment was conducted in randomized blocks in the 2 x 5 factorial design, with the presence and absence of mycorrhizal inoculation in combination with 5 levels of irrigation with 6 replicates, in a greenhouse. There was no significant interaction between the factors mycorrhizal inoculation and irrigation levels by the F test. Under the tested conditions, the mycorrhizal inoculation was unable to provide significant changes in the growth, development and flowering of garden pansy plants. It was concluded that no symbiotic efficiency was pointed out between the mycorrhizal fungus used and garden pansy plants. The best growth and yield results for cultivating and producing edible flowers of garden pansy were obtained at the 100% replenishment level of water evaporation.

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Refrigerated storage of blackberry cultivar ‘BRS Cainguá’ harvested at different ripeness stages

Rubus spp. physicochemical small fruits postharvest flavor harvest point

Blackberries have a short post-harvest conservation period, making it necessary to optimize harvest and storage conditions. The objective of this study was to evaluate the impact of refrigerated storage and maturation stage on the physicochemical quality of ‘BRS Cainguá’ blackberries, produced in an organic system. Blackberries from an experimental orchard, were harvested at three ripeness stages (RS), with RS1 being fruits with 100% red skin; RS2 skin 50% red and 50% black; and EM3 100% black skin. The samples were stored in a cold chamber at 4±0.5ºC and 90-95% RH for 12 days. The evaluations were carried out after 0, 3, 6, 9 and 12 days of storage, for: weight loss (WL), soluble solids (SS), pH, titratable acidity (TA), ratio (SS/TA) and color parameters. Blackberries harvested in RS3 had the highest SS content, lowest TA and the highest SS/TA ratio and pH. During storage, TA and WL showed decreasing and increasing linear responses, respectively, regardless of the RS of the fruits. Harvesting based on the skin color of ‘BRS Cainguá’ blackberries influences the physicochemical quality and postharvest conservation. Fruits harvested with 100% black skin, have the best quality and are the most suitable for subsequent refrigerated storage.

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Commercial productivity and quality of pitaya as a function of number of fruits per cladode

Selenicereus undatus Hylocereus polyrhizus fruit size commercial yield

Increasing orchard productivity is among the main objectives of pitaya producers. However, the commercial productivity may reduce due to reduction of fruit size as a function of the high amount per plant. This study evaluated the influence of the number of fruit per cladode in commercial productivity and in quality of fruits of two pitaya species at different harvest times. The experiment was carried out in a six-year-old orchard formed by the species Selenicereus undatus and Hylocereus polyrhizus. At each flowering time, the number of fruits set per cladode was counted and plants with two, four, five and six fruits per cladode were selected, and surplus fruits removed. The evaluations followed a split plot design over time, with the main plot as the number of fruit per cladode and the subplot as the harvest seasons: December, February and March, with four replicates and one plant per plot. Plants grown with two fruits per cladode presented the highest percentage of fruits with commercial size and commercial productivity. Both species showed fruits with commercial size in the first harvest of the cycle (December). S. undatus fruits classified as Class I and H. polyrhizus fruits classified as Extra and Class I showed the best quality. 

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Germination response of palm seeds on a two-way thermogradient plate

Arecaceae cardinal temperatures Carpentaria acuminata palm propagation Phoenix canariensis temperature sensitivity

Palm trees are propagated almost exclusively by seeds and each species germinates under a certain temperature range. In this sense, the two-way thermogradient plate may be used to determine temperature limits for germination and seed response to temperature. The objective was to define the alternating temperature regime promoting higher and faster seed germination of Carpentaria acuminata and Phoenix canariensis palms using a two-way thermogradient plate. This equipment allowed 64 combinations of alternating and constant temperatures, ranging from 6.97 to 36.42 ºC for C. acuminata, and 7.96 to 35.94 ºC for P. canariensis. Seeds were sown in Petri dishes (25 x 9 cm) containing 1% water agar. Linear regressions were estimated to determine cardinal temperatures. After 50 days, non-germinated seeds were transferred from the two-way thermogradient plate to a germination chamber at 30 °C. The temperature regime promoting highest seed germination percentage of C. acuminata was 30.45/33.00 °C (day/night), with minimum, optimum, and maximum temperatures of 9.13, 28.53, and 36.33 °C, respectively. For seed germination of P. canariensis, the most appropriate temperature regime was 29.77/17.93 °C (day/night), with minimum, optimum, and maximum temperatures of 9.53, 28.03, and 35.43 °C, respectively.

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Use of grass and leguminous species as winter mulching in organic no tillage system of lettuce crop

Avena strigosa Lupinus albus organic farming

The no-tillage system for vegetables is an environmentally and economically suitable alternative, particularly for organic crops. However, further studies are needed using other plant species and under different growing conditions. This research aimed to evaluate the influence of different winter soil covers on lettuce development and yield under no-tillage system in an organic cultivation area. The experiment was arranged in a randomized block design with five treatments and six replications. The treatments used were three soil covers in the organic no-tillage system and two systems without cover crops and with soil tillage, one organic and the other conventional. The grass Avena strigosa (L.), the leguminous Lupinus albus (L.), and the intercropping of both species were used. The number of leaves per plant, stem length and diameter, head diameter, fresh and dry weight of plants, fresh weight of leaves and stem and Soil Plant Analysis Development (SPAD) index were evaluated. The use of leguminous straw is recommended for winter cultivation of lettuce in an organic no-tillage system. Black oat straw, single or intercropped, impaired the development and productivity of lettuce in the organic no-tillage system in winter cultivation.

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Sowing date and maturity group in soybean grown in lowlands

Glycine max L. crops system water regime

It is projected an increase of about 30% in the world population by 2050 and a food demand increase by 60%, mainly vegetable proteins. Due to this, soybean is being introduced in new production systems, such as in rotation with irrigated rice in lowlands. Irrigated and non-irrigated experiments were conducted in order to determine the influence of irrigation on maturity groups, on yield components and yield in lowlands. Five soybean cultivars with maturity groups (MG) ranging from 4.8 to 7.8 were used, representing the cultivars sowing in southern Brazil, and three sowings were performed (October, November and January). A decrease in the number of pods m-2 was observed with the delay in the sowing date in both water regimes and MG, except MG 4.8 and 5.5, which had a higher number of pods m-2 when irrigated and sown in November. The leaf area index (LAI) was higher under the irrigated condition, for all MGs and sowing dates. The interaction between the yield components can be maximized by the combination of supplemental irrigation, anticipation of sowing date and the choice for cultivars with MG from 6.2 to 6.8 for lowland environments

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Agronomic performance and productivity of Arabica coffee intercropped with timber species

Acrocarpus fraxinifolius Coffea arabica Khayana ivorensis Tectona grandis agroforestry system

The insertion of the tree component in coffee production is a strategy from an economic and environmental perspective. Thus, the objective of this study was to evaluate the temporal influence on the agronomic and productive performance of the coffee crop under the interference of different tree species as a function of spacing. The experiment was set in the municipality of Santo Antônio de Amparo-MG, in 2012, and conducted in a randomized block design with four replications. The treatments were: cultivar ‘Catuai Vermelho IAC 99’ in monoculture (3.40 m x 0.65 m) and intercropped with African mahogany, teak and pink cedar, in two spacings (9 x 13.6 m and 18 x 13.6 m), in coffee rows. Three coffee rows were fixed between rows, totaling 13.6 m. The following variables were evaluated: height (m), stem diameter (cm), crown diameter (m), productivity (bags ha-1) and yield (l/sc) for coffee. From the evaluations, there is a significant effect of height, productivity and yield for the coffee crop. The system intercropped with tree species did not influence coffee productivity and yield until the 3rd harvest and, for the 5th harvest, intercropping with mahogany favored productivity, although the accumulated productivity did not show any treatment effect.

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Combining performance and estimated genetic diversity among soybean parents and F1 populations

Glycine max diallel general capacity specific capacity UPGMA

Studies about the combining ability and genetic diversity can provide information on the genetic resources contained in the working collection of germplasm. The objective of this study was to estimate the combining ability of ten soybean parents and their hybrids in the F1 generation using diallel analysis and genetic diversity analysis to evaluate the dissimilarity between parents and crosses. The experiment was carried out in a greenhouse, in a completely randomized design with five replications, during the 2019/2020 crop season, in the municipality of Rio Verde, State of Goiás, Brazil. Agronomic and physiological variables were evaluated. Data were subjected to analysis of variance. Diallel analysis was performed using the Griffing method 2. Analysis of genetic diversity was performed with the Mahalanobis generalized distance and the hierarchical average linkage clustering. Additive gene effects were predominant in the control of all variables analyzed in the F1 generation. The parents SYN 1163 RR and CG 7370 RR showed good complementarity for the variable grain yield. The thirty-five genotypes were separated into six groups, and the variable weight of one hundred seeds had the greatest contribution to genetic diversity.

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Agronomic traits of white oat treated with the growth regulator trinexapac-ethyl

Avena sativa L. growth regulator productivity yield components

The growth and yield performance of white oat cultivars may vary in response to doses of trinexapac-ethyl (TE) growth regulator. The objective of the work was to evaluate the lodging and productive performance of white oat cultivars under different doses of trinexapac-ethyl growth regulator. The experiments were carried out in a randomized complete block design with four replications, in a 4 x 2 factorial scheme, with four doses of trinexapac-ethyl (0, 50, 100 and 150 g ha-1) applied in the phenological stage between the 1st visible stalk node and the 2nd perceptible node in two white oat cultivars (URS Altiva and URS Corona). The following were evaluated: plant height, panicle length, panicles per m2 , spikelets per panicle, grains per spikelet, number of grains per panicle, thousand grain weight, plant lodging and grain yield. The application of trinexapac-ethyl at doses 100 and 150 g ha-1 reduces plant height and panicle components: length, number of spikelets and grains per panicle of the two cultivars. TE doses above 100 g ha-1 provide a significant reduction in lodging with an increase in the number of panicles per m2 and in grain yield for the two white oat cultivars. Keywords: Avena sativa L.; growth regulator; productivity; yield components.

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Antifungal activity against Alternaria solani and control of early blight in tomato by essential oil of citronella

Cymbopogon nardus enzymatic activity  medicinal plant resistance induction

An alternative to the agrochemicals is the use of essential oils that can act in plant defense against phytopathogens. The objective of work was to evaluate the antifungal activity, the early blight control, and the enzymatic defense in tomato treated with citronella essential oil. Mycelial disks of the pathogen were added in Petri dishes, with treatments 0, 500, 1000, 1500, 2000 and 2500 μL L-1 of essential oil and a control treatment with fungicide, thus evaluated mycelial growth and sporulation. The treatments were applied in the second pair of leaves of plants (treated) and after 72 hours the pathogen was inoculated on the second pair (treated) and also on the third pair leaves (untreated). The severity was expressed through the area under the disease progress curve (AUDPC). The enzymatic activity of peroxidase, polyphenoloxidase, and phenylalanine ammonia-lyase were evaluated. The essential oil reduced the mycelial growth and sporulation of the pathogen. The AUDPC was reduced up to 38.14% in the treated leaves and 51.32% in the untreated, and increases in the activities of enzymes were found. The essential oil of citronella could be an alternative in the control of tomato early blight by antimicrobial activity and/or resistance induction local and systemically.

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Production of oil palm under phosphorus, potassium and magnesium fertilization

Elaeis guineensis Jacq. Amazon oilseed fertilizers

Oil palm production is strategic in the Amazon with high productive potential, but information on its fertilization is still relatively scarce for the region. The objective of this work was to evaluate the effects of phosphorus, potassium and magnesium fertilizations on oil palm production in different years in the state of Pará, Brazil. The study was conducted in Tailândia, Northeastern of Pará, Eastern Amazon, Brazil. A randomized block design was used in a 4 x 2 x 3 x 2 factorial scheme, with four levels of phosphorus, two sources of phosphorus, three levels of potassium and two levels of magnesium. Oil palm production responded positively to the increase in phosphorus levels, and until the eighth year of age of the plants, there was greater production when triple superphosphate was applied. From the ninth year onwards, fertilization with phosphine provided a production equal to the supply of phosphorus with triple superphosphate. The application of potassium chloride increased the number, weight and production of the bunches from the sixth year. The supply of magnesium sulfate increased the average weight of the bunches. Thus, phosphorus, potassium and magnesium fertilizations become essential to increase oil palm production in the Northeast of Pará.

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Diagrammatic scale for evaluation of Bremia lactucae sporulation in lettuce seedlings

disease severity downy mildew Lactuca sativa rating scale

In disease assessment, the use of diagrammatic scales provides a standard reference point for comparison. There is still no precise and accurate scale for the evaluation of sporulation intensity of downy mildew in lettuce seedlings. The objective of this study was to propose a diagrammatic scale for the evaluation of downy mildew severity in lettuce seedlings. Thirty lettuce seedlings with different sporulation intensities were used to develop the proposed diagrammatic scale. Solaris lettuce cultivar was sown, and fifteen days after sowing, inoculations occurred using distilled water, the pathogen sporangia, and Tween 20. The monitoring of disease development was performed daily.When the first sporulation appeared on the cotyledonaryleaves,the proposed scale was verified to meet the minimum and maximum levels of disease severity. Two evaluators verified the accuracy, precision and performed the estimation of the sporulation and reproducibility using a scale. The images obtained are important in the standardization of a scale to identify resistant, tolerant and susceptible plants to downy mildew. Furthermore, it allows validating a diagrammatic scale of sporulation intensity of B. lactucae in lettuce seedlings. Thus, it is the diagrammatic scale developed in the work will guide future research to accelerate the detection of mildew severity in lettuce seedlings.

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Plant extracts in the control of plant pathogens seeds and fusariosis in okra

Abelmoschus esculentus Fusarium oxysporum f. sp. Vasinfectum Alternative control Seed treatment

The objective of this study was to assess seed health and the effect of plant extracts on Fusarium oxysporum f. sp. vasinfectum mycelial growth and sporulation, plant pathogen reduction in seeds and fusariosis control in okra seedlings. Health was assessed by the Blotter Test, after immersing the seeds in natural extracts and plating. To verify the mycelial growth of the plant pathogen, the extracts were incorporated in PDA culture medium and the pathogen was added and assessed, including the spore count. In the greenhouse, the seeds were immersed in the extracts, sown and at 15 days they were sprayed with extracts, at 21 days inoculated with the pathogen and disease severity on the seedlings was assessed 7 days later. There were higher incidences of Fusarium sp. and Rhizopus stolonifer in the seeds of the cultivars Valença and Santa Cruz 47. The extracts that resulted in lower pathogen incidence was basil, in cv. Valença and cinnamon and neem, in cv. Santa Cruz 47. The neem treatment presented the best inhibition percentage and the lowest sporulation mean in mycelial growth of the pathogen. Neem presented higher disease incidence control in the seedlings of cv. Valença and basil on the seedlings of cv. Santa Cruz 47. 

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