Estimation of reference evapotranspiration (ETo) is very relevant for water resource management. The Penman-Monteith (PM) equation was proposed by the Food and Agriculture Organization (FAO) as the standard method for estimation of ETo. However, this method requires various weather data, such as air temperature, wind speed, solar radiation and relative humidity, which are often unavailable. Thus, the objective of this study was to compare the performance of multivariate adaptive regression splines (MARS) and alternative equations, in their original and calibrated forms, to estimate daily ETo with limited weather data. Daily data from 2002 to 2016 from 8 Brazilian weather stations were used. ETo was estimated using empirical equations, PM equation with missing data and MARS. Four data availability scenarios were evaluated as follows: temperature only, temperature and solar radiation, temperature and relative humidity, and temperature and wind speed. The MARS models demonstrated superior performance in all scenarios. The models that used solar radiation showed the best performance, followed by those that used relative humidity and, finally, wind speed. The models based only on air temperature had the worst performance.

ABSTRACT. The aim of this study was to evaluate the physiological and biochemical changes related to desiccation tolerance loss in millet seeds. The studied points of the germination process were determined according to the seed imbibition curve of the millet hybrid ADRF6010: control (0h), 3h of imbibition, 1 and 3 mm radicle. The seeds were dried on silica gel for 72h at 20°C, followed by pre-humidification at 25°C for 24h. Seed physiological quality was evaluated by electrical conductivity and a germination test, and seed vigor was evaluated with a first germination count and a germination speed index. The experiment was performed in a completely randomized design, and means were compared by the Scott-Knott test at a 5% probability. The enzymatic systems of superoxide dismutase, catalase, peroxidase, and α-amylase, as well as the expression of heat-resistant proteins were evaluated. Enzymatic activity was quantified with the ImageJ® software. Millet seeds lost desiccation tolerance when the radicle reached 1 mm in length. According to enzymatic standards, peroxidase and α-amylase activity, as well as heat-resistant protein activity, were related to desiccation tolerance loss in millet seeds.

ABSTRACT. As the fourth largest importer of olive oil and the fifth largest importer of olives, Brazil is one of the largest importers of olive (Olea europaea L.) products in the world. In recent decades, the introduction and growth of olive cultivars with lower chilling requirements in the south and southeast regions of Brazil have made olive production viable in the country. However, there is a dearth of information about the management of olive crops in Brazil, especially in relation to studies about the nutritional needs of olive trees grown in subtropical regions, which may enable advances in the productivity of this fruit. The aim of this study was to evaluate the growth, dry matter production and nutritional status of the olive tree under the effect of nutrient omissions, as well as to establish visual diagnostic parameters of nutrient deficiencies. We used a completely randomized design with ten treatments and three replicates grown in the Hoagland-Arnon nutrient solution and solutions with individual omissions of N, P, K, Ca, Mg, S, B, Fe, and Zn. The treatments that most limited the growth of olive trees were the N, Ca, and B omission treatments.

ABSTRACT. Triazole fungicides have not been effective for managing the wheat blast disease in Brazil. A broad analysis across six geographical populations of Pyricularia graminis-tritici in central-southern Brazil indicated a high level of resistance to triazole fungicides. Since P. graminis-tritici is also associated with others poaceous species, here, we analyzed whether triazole-resistant isolates of the blast pathogen could be recovered from other poaceous hosts that are invasive of sprayed wheat fields. In addition to P. graminis-tritici (Pygt), we also evaluated the levels of sensitivity of three other grass-associated blast pathogens, which included P. grisea (Pg), P. pennisetigena (Pp), and P. urashimae (Pu). Resistance to the triazole fungicides tebuconazole and epoxiconazole was assessed phenotypically based on EC50 values and molecularly by analysis of the presence of mutations in the CYP51A gene, which encodes for the target enzyme 14-alpha-demethylase. We detected triazole-resistant Pyricularia spp. (Pg, Pp, Pu and Pygt) that is associated with Avena sativa, Cenchrus echinatus, Chloris distichophylla, Cynodon sp., Digitaria horizontalis, D. sanguinalis, Panicum maximum or Urochloa spp. The major outcome from our study was the evidence that invasive poaceous species from wheat fields could be an important source of triazole resistant fungal inoculum for the initial phases of the wheat blast epidemics.

Calcium chloride application on fruits maintains the firmness of fruits, decreases storage breakdown and rot, extends shelf-life, and increases vitamin C and calcium content. Blackberries have low post-harvest durability due to the intrinsic characteristics of their fruits, mainly the high respiratory rate and low firmness, which causes problems in the production chain of fresh fruits. The current study aimed to evaluate the effects of pre-harvest application of calcium chloride on the fruits of ‘Tupy’ blackberry (Rubus spp.). A randomized block design for a factorial scheme was used, i.e. calcium chloride concentrations (0, 1.5, 3, and 4.5%) and number of applications (1, 2, and 3). Multiple applications occurred between 5-day intervals. The results showed that the calcium content in the fruits increased with a single application of 2.2%, but a decrease in mass loss was observed with a 4.5% application. The results also indicated great firmness and ascorbic acid content of fruits of ‘Tupy’ blackberry, in addition to the significant increase in fruit size and mass. However, in general, the content of soluble solids, sugars, antioxidant activity and total polyphenols decreased.

The recent exploration of autonomous robotics tasks in agro-industry has permitted the integration of theories of artificial vision and mobile robotics with tasks in precision agriculture. Artificial vision allows for the classification of weeds and crops from images of plantations. With 3D-image processing systems, the location of the weeds is determined, and then the movement of the tool responsible for eradication is proposed. This article presents the solution for finding weeds within a crop field using classifiers and the integration of a 3D-vision system that builds a point cloud featuring the plants to safeguard, the weeds and the free space using Zed technology. With this information, search techniques such as A* (A star) and RRT (Rapidly exploring Random Tree) are used to determine the trajectory that the weed-removal tool must follow. The last feature is an integral part of an XYZ-positioning system, and this is part of a mobile robot dedicated to precision agriculture tasks.

In most cases, in genetic breeding of Arabica coffee, plot size is defined in an empirical manner. It is often based only on the experience of the breeders and the availability of resources, potentially leading to a reduction in precision. Therefore, the aim of this study was to estimate the size of the experimental plot for evaluation of coffee yield. We evaluated two experiments for validation of cultivars with 12 treatments set up in a randomized complete block design with three replicates and plots composed of 50 plants. Each plant was considered as a basic unit. Estimates of ideal plot size were made by maximum curvature of the coefficient of variation, linear-plateau segmented model and by the resampling methods. We discussed the variations in the parameter estimates for different plot sizes. Divergence was seen among the plot sizes estimated by the different methodologies. Increasing the number of plants per plot led to a higher experimental precision to the point that the increase was no longer significant. The plot size recommended for evaluating coffee production is from seven to 19 plants.

The aim of this study was to verify the resistance of tomato genotypes (crossed with Solanum galapagense) to the green peach aphid, Myzus persicae, and the association of this resistance with glandular trichomes. Leaf trichomes were quantified for seven F2 genotypes of the BPX-486 population derived from crossing S. lycopersicum ‘TOM-684’ and S. galapagense accession ‘LA-1401’, for the commercial controls ‘TOM-584’ and ‘Santa Clara’, and for the accession ‘LA-1401’. After this evaluation, the genotypes were subjected to two nonpreference resistance tests of the green peach aphid in the laboratory, one with choice and the other without choice. Five genotypes (BPX-486-17, BPX-486-62, BPX-486-10, BPX-486-46, and BPX-486-08) and the accession LA-1401 exhibited a high density of type IV glandular trichomes and a lower mean number of nymphs and adults of M. persicae than two genotypes (BPX-486-313 and BPX-486-383) and the controls with a low density of glandular trichomes, in all the evaluations of both tests. Significant negative correlations between the density of type IV glandular trichomes of the tomato genotypes and the preference of M. persicae were found, which confirms the association between this type of glandular trichome and resistance to M. persicae in tomato genotypes.

Plants are often exposed to abiotic stresses such as salinity, which represents a barrier to the cultivation of agricultural species mainly in arid and semi-arid regions. This study evaluated the development of four saccharine sorghum genotypes for tolerance to different salinity levels under greenhouse conditions. The experimental design was a randomized complete block arranged in a 5 × 4 factorial scheme, which corresponded to five levels of irrigation water salinity [electrical conductivities of 0.5 (control), 2.5, 5.0, 7.5, and 10.0 dS m-1] and four saccharine sorghum genotypes (CSF 11, CSF 15, P 76 and P 298), with five replicates. The plants were evaluated for dry mass production, leaf area, height, stalk diameter, leaf gas exchange and relative chlorophyll content. The growth and leaf gas exchange measurements of the saccharine sorghum plants were significantly affected by salinity stress. Among the genotypes, CSF 11 and CSF 15 exhibited smaller reductions in growth, whereas P 298 showed the greatest reduction. These findings show that genotype CSF 11 can be classified as the most tolerant to salt stress, and genotype P 298 is the most sensitive.

The productive capacity of soybeans is associated with the adaptation of the culture to the cultivation environment. Factors such as a high number of pods, the weight of a thousand grains, and grain number are essential factors in determining cultivars of high productive potential. The launching of new varieties associated with new technologies makes it necessary to know the performance of these varieties in different growing environments. This study aimed to analyze the agronomic performance of transgenic soybean cultivars under Cerrado conditions. The experimental design used completely randomized blocks; six of the twelve cultivars used RR1 technology and the remaining six used RR2BT. The cultivars were grown in five distinct locations in the southwest region of Goiás. The results demonstrated no increments in the grain yield of the RR1 or RR2BT technologies and the precocity of the cultivars also did not favor an increase in grain yield. The localities of Jataí and Rio Verde did not influence the cultivar cycle.