Maíra Ferreira de Melo Rossi

The use of herbicides to control weeds in passion fruit orchards is a more accessible and lower-cost alternative. However, the lack of registered agrochemicals for the crop, combined with the scarcity of studies on their phytotoxic effects, makes this aspect one of the main obstacles to production. Thus, this study aimed to evaluate the tolerance of advanced sour passion fruit (Passiflora edulis Sims) seedlings to the application of different herbicides. The experimental design was randomized blocks, with seven treatments, four replications, and three plants per plot. The treatments consisted of a control (without herbicide application), sulfentrazone, diuron, S-metolachlor, ammonium glufosinate, imazethapyr, and terbuthylazine. It was observed that S-metolachlor caused the lowest levels of visual phytotoxicity, followed by imazethapyr and terbuthylazine, throughout the evaluation period. In contrast, ammonium glufosinate, sulfentrazone, and diuron caused greater phytotoxic effects, negatively affecting plant development. Overall, herbicide tolerance in sour passion fruit seedlings varies significantly depending on the active ingredient.

Citrus production is a significant agricultural activity in Brazil, the world's largest producer and exporter of orange juice. However, this production faces phytosanitary challenges, including postbloom fruit drop (PFD) caused by fungi of the genus Colletotrichum . The development of this disease is associated with climate conditions, such as temperature and leaf wetness duration (LWD). Citrus production in Brazil has recently migrated to regions with no records of greening disease (caused by Candidatus Liberibacter spp.), and these areas require assessments of the impacts of other diseases. Such assessments are essential to identify phytosanitary risks and implement effective management strategies to ensure sustainability and support the expansion of citrus production. The objective of this study was to conduct agroclimatic zoning for PFD using climate variables, such as mean temperature and LWD. The analysis covered the entire Brazilian territory, using data from 1989 to 2020, collected from the NASA/POWER platform. The areas were classified climatically as unfavourable, relatively favourable, or highly favourable. The results revealed that the North and Northeast regions are highly favourable for the development of the disease year-round, while the South, Southeast and Central-West regions present lower risk during the winter. The risk of disease occurrence in the main citrus-producing areas of the Southeast region is higher from January to March, and August to December. The analysis indicated that emerging citrus-producing areas exhibit higher climatic suitability from January to May. This study highlights the importance of management strategies, such as the use of fungicides and climate monitoring, to mitigate the impacts of PFD.

One of the main challenges in citrus nursery plant production under protected environments is the space required for plant growth due to the large volume of containers and substrates, along with nutritional management demands. Hydroponics emerges as a promising alternative, offering more precise nutrient supply, efficient water use, reduced space requirements, and better control of growth conditions. This study aimed to evaluate the production of ‘Ponkan’ mandarin nursery plants in conventional cultivation and hydroponics systems, using five rootstocks: ‘Swingle’ citrumelo, ‘Rangpur’ lime, ‘Limeira’ and ‘Rubidoux’ trifoliate, and ‘Índio’ citrandarin. Two experiments were conducted in randomized blocks with five treatments, four replicates, and 18 plants per plot. One hundred and 50 days after grafting, growth and physiological parameters were measured, including scion length,plant height, stem diameters, number of leaves, root length, root volume, dry mass, Dickson quality index, leaf traits, photosynthetic pigments, chlorophyll a-fluorescence, gas exchange, and water use efficiency. The joint analysis of experiments was performed, and the means were compared using the Tukey’s test. In the conventional system, plants were produced in 3.2 dm3 bags with commercial substrate, while in the hydroponic one they were produced in 280 cm3 tubes with vermiculite placed in pools supplied with nutrient solution. Higher growth of ‘Ponkan’ mandarin nursery plants was obtained in the conventional system with ‘Swingle’ citrumelo, ‘Rangpur’ lime, and ‘Índio’ citrandarin rootstocks. Photosynthetic parameters showed no significant differences between rootstocks and production systems, except for photochemical dissipation coefficient, which was higher in hydroponics for plants grafted onto ‘Swingle’ citrumelo and ‘Rangpur’.

Citriculture has worldwide importance, and monitoring the nutritional status of plants through leaf analysis is essential. Recently, proximal sensing has supported this process, although there is a lack of studies conducted specifically for citrus. The objective of this study was to evaluate the application of portable X-ray fluorescence spectrometry (pXRF) combined with machine learning algorithms to predict the nutrient content (B, Ca, Cu, Fe, K, Mg, Mn, P, S, and Zn) of citrus leaves, using inductively coupled plasma optical emission spectrometry (ICP-OES) results as a reference. Additionally, the study aimed to differentiate 15 citrus scion/rootstock combinations via pXRF results and investigate the effect of the sample condition (fresh or dried leaves) on the accuracy of pXRF predictions. The samples were analyzed with pXRF both fresh and after drying and grinding. Subsequently, the samples underwent acid digestion and analysis via ICP-OES. Predictions using dried leaves yielded better results (R² from 0.71 to 0.96) than those using fresh leaves (R² from 0.35 to 0.87) for all analyzed elements. Predictions of scion/rootstock combinations were also more accurate with dry leaves (Overall accuracy = 0.64, kappa index = 0.62). The pXRF accurately predicted nutrient contents in citrus leaves and differentiated leaves from 15 scion/rootstock combinations. This can significantly reduce costs and time in the nutritional assessment of citrus crops.

Pitaya production has been expanding in several regions of Brazil despite the lack of technical information on plant management. To obtain good crop productivity, weed control is essential; however, the use of herbicides can cause phytotoxicity and reduce plant growth and production. Thus, the present work aimed to evaluate the tolerance of red (Selenicereus polyrhizus) and white (S. undatus) pitaya seedlings to different herbicides applied after emergence. Two experiments were installed, one with red pitaya and the another with white pitaya, on August 15, 2020 in the Fruit Production Sector of the Federal University of Lavras. Experiments were arranged in a randomized block design, with four and three replicates, respectively, eight treatments and three plants per plot in both experiments. Treatments consisted of control, fomesafen, ammonium glufosinate, glyphosate, clethodim, carfentrazone-ethyl, imazethapyr and chlorimuron. Visual phytotoxicity symptoms were evaluated at 7, 14, 21 and 28 days after herbicide application. At 30 and 60 days after application, percentage of necrosis, cladode length and number of new shoots were evaluated. Herbicide fomesafen caused greater damage to red pitaya seedlings and fomesafen and glyphosate caused greater damage to white pitaya seedlings. For both pitaya species, herbicide clethodim can be an alternative for controlling narrow-leaf weeds without causing visual damage to the growth and development of pitaya plants.

The economic exploration of pear in the subtropical areas is possible when using hybrid cultivars obtained by crossing European (Pyrus communis) and Asian cultivars (Pyrus pyrifolia). Genetic improvement programs in Brazil have launched some cultivars in recent decades. Pear requires cross-pollination to improve fruit set in commercial plantations. In the case of these hybrid pear trees, the combinations of pollen receptor and donor cultivars that are best for cultivation in subtropical regions are not known. The objective of this study was to select cultivars with the potential to be pollinators of pear trees in subtropical regions. Four cultivars that received pollen grains (mother plants) (‘Packham’s Triumph’, ‘Tenra’, ‘Triunfo’, and ‘Seleta’) and three donors (‘Cascatense’, ‘Primorosa’, and ‘Shinseiki’) were used. Stigmatic receptivity was observed in all cultivars during all stages of reproductive development. All cultivars had highly viable pollen grains. The cultivar ‘Seleta’ was the best recipient cultivar. The ‘Seleta’ × ‘Shinseiki’ cross showed the highest percentages of fruiting. The highest percentages of pistils with pollen tubes reaching the ovary were observed in the crosses ‘Triunfo’ × ‘Shinseiki’ and ‘Seleta’ × ‘Shinseiki’. The ‘Shinseiki’ pear is an option as a pollinator of crops in subtropical regions.

BACKGROUND: Brazilian citrus farming has been migrating to nontraditional citrus‐growing regions, which can be considered a challenge for citrus growers, as not all these areas are suitable for tangerine cultivation. Thus, the mapping of regions exhibiting favorable climatic conditions for Alternaria brown spot has become crucial in the selection of appropriate locations for the establishment of new orchards. This mapping enables the implementation of an avoidance strategy, which entails steering clear of areas where the disease is prevalent, aligning with fundamental principles of disease control.RESULTS: Thus, this study seeks to zone areas with high and low climatic favorability for the occurrence of Alternaria brown spot in tangerine trees in Brazil. Historical climate data series from the NASA‐POWER database were used for all municipalities in Brazil. Agrometeorological variables used to determine the development of Alternaria brown spot were average monthly air temperature (Tmean) and duration of leaf wetness period (LWD). Areas were considered unsuitable climatically when Tmean was 33 °C, relatively suitable when Tmean was between 13 °C and 33 °C and LWD 10%. The states of Paraná, Santa Catarina and Rio Grande do Sul showed greater thermal amplitude within months and throughout the year. The southern region of the country has harsher winters, with minimum temperatures below 15 °C, which is unfavorable for the disease incidence.CONCLUSION: The states with the greatest favorability for Alternaria brown spot were Paraná, Santa Catarina, and Rio Grande do Sul, mainly from May to September. Rio Grande do Sul was the state in this region that showed the greatest favorability, as a consequence of leaf wetness exceeding 10 h. The main tangerine‐producing regions in Brazil, including the southern part of Minas Gerais, the state of São Paulo and the metropolitan region of Porto Alegre, were mostly classified as relatively favorable areas for the occurrence of Alternaria brown spot. It is recommended that when establishing new tangerine orchards, regions with lower favorability for the occurrence of Alternaria brown spot, such as the North and Central‐West regions of Brazil, particularly the states of Amazonas, Pará and Mato Grosso, should be selected. © 2023 Society of Chemical Industry.