ABSTRACT The objective of this study was to evaluate the effect of combinations of nitrogen, phosphorous and potassium doses on the production components of custard-apple irrigated with saline waters. The experiment was conducted in a greenhouse, using a Neossolo Regolítico (Entisol) of clay loam texture in Campina Grande-PB, Brazil. The treatments were distributed in a randomized block design, in a 2 × 8 factorial scheme, with three replicates, corresponding to two levels of electrical conductivity of water - ECw (0.8 and 3.0 dS m-1) and eight combinations of fertilization with nitrogen, phosphorus and potassium (100-100-100; 100-100-125; 100-125-100; 100-125-125; 125-100-100; 125-100-125; 125-125-100 and 125-125-125% of the recommendation, for the third year of cultivation). The combination of 100-100-100% corresponded to 100, 60 and 60 g of N, P2O5, K2O per plant per year, respectively. High concentrations of salts in the irrigation water reduced the number of fruits, fresh fruit mass, total number of seeds and mass of seeds of custard-apple. Plants achieved the best development when grown under 125-100-100, 125-125-125 and 100-100-100% combinations of N-P-K recommendation. Irrigation with ECw of 3.0 dS m-1 associated with the 100-125-125% combination of fertilization increased the average mass and height of the custard-apple fruits.

ABSTRACT Information of the variation for important morphological and physiological traits of okra is still limited. Molecular analysis is an important additional tool in germplasm characterization studies. The study aimed to evaluate the performance of the growth and yield of 20 pre-commercial okra accessions to identify molecular markers’ association with morphological traits. Nineteen morphological traits were measured with five qualitative and 14 quantitative descriptors. For analysis of genetic patterns Random Amplified Polymorphic DNA (RAPD) markers were used with nine primers and 24 usable bands. The genetic dissimilarity was evaluated based in morphological and genetic matrices. Also, graphical representation of genetic distances was obtained by UPGMA and Tocher’s optimization method. The morphological characterization of the accessions detected polymorphism for all evaluated traits. RAPD markers were efficient in detecting genetic variability among okra accessions. For the primers used in the experiment, only OPE10 did not amplify the DNA strand. The other eight primers produced a total of 35 bands, in which 25 were polymorphic and ten were monomorphic. The morphological traits and molecular markers identified wide genetic variability among the 20 okra accessions, indicating successful crosses in breeding programs and isolating some interesting materials. Morphological and molecular cluster analyses were complementary and helped in the genotype selection. Molecular analysis indicated some divergent accessions that were not found in morphological analysis, which could highlight some materials that have a desirable trait, that is difficult and highly costly to access in field experiments.

ABSTRACT The use of intercropping system allows crops to better utilize inputs supplied and the productive capacity of the area, which can be advantageous to the farmer. Thus, the aim of this study was to evaluate the production performance of eggplant and industrial tomato intercropped as a function of the date of eggplant transplantation compared with tomato transplantation, in two seasons. Ten dates of eggplant transplantation were evaluated (-30, -25, -20, -15, -10, -5, 0, + 5, +10 and +15 days compared with tomato transplantation), with the first season from February to September 2009 and the second from August 2009 to February 2010. The number of commercial fruits per plant, commercial yield per plant and commercial yield of eggplant and tomato were influenced by the date of transplanting of eggplant. Highest eggplant yields were obtained in the second season, due to the more favorable weather conditions for the development of this crop. Late eggplant transplants resulted in yield losses due to tomato interference. For tomatoes, the later the eggplant was transplanted, the higher the yield. Therefore, it is concluded that the species have a high degree of interference with each other and the variation in the time of eggplant transplantation influenced the production characters of both crops. In terms of production, the intercropping of these species may not be economically viable for the farmer due to negative influences on the growth, development and production of these crops.

ABSTRACT In recent decades, soybean has been one of the most widely grown crops in Brazil. The soybean looper, Chrysodeixis includens (Walker, [1858]; Lepidoptera: Noctuidae), is one of the main defoliating pests of soybean that cause damage and affect the cost of production. The overall objective of the present study was to characterize the resistance of C. includens to diamide insecticides. To this end, the baseline susceptibility of C. includens to flubendiamide, chlorantraniliprole, and cyantraniliprole was characterized to estimate their concentrations for diagnostic monitoring of resistance in populations collected in commercial soybean crops in southern Brazil during the 2018/19 season. Under field conditions, evaluations were made of the residual activity of three diamide insecticides: chlorantraniliprole + lambda-cyhalothrin, teflubenzuron, methoxyfenozide, and bifenthrin for discrimination between flubendiamide-susceptible and resistant C. includens. Chrysodeixis includens was more tolerant to cyantraniliprole than to flubendiamide and chlorantraniliprole. The field populations had a higher survival rate than the susceptible population. The resistant population showed a resistance ratio to flubendiamide of 70.1-fold. Under field conditions, the residue of the study insecticides, except for bifenthrin, enabled discrimination between flubendiamide-susceptible and resistant C. includens. The data indicate the need to study the cross-resistance relationships between insecticides to improve the rotation recommendation. They also reinforce the importance of using other good management practices, e.g., the use of insecticides based on pest sampling and the choice of other control methods to prevent C. includens from becoming resistant to diamide insecticides.

ABSTRACT Plant breeding programs have been investing in the development of high commercial standard onions; thus, they depend on the genetic resources available for obtaining commercial hybrids. The objective of this study was to evaluate genetic parameters and diversity, and phenotypic and genotypic correlations of characters related to onion production. The experiment was conducted in Uberlândia, Minas Gerais, Brazil. Fifty-three onion strains were evaluated, and a randomized block design was used. The number of plant and bulb characteristics evaluated was 13. The statistical analyses were performed using Genes and R software. A genetic variability among the genotypes was found for most of the characters at 1% level of significance in the F test. The heritability of most characters presented moderate to high values (≥ 70%) and high CVg/CVe ratio (≥ 1). The UPGMA method separated the genotypes into 20 groups, while the Tocher method separated them into 19 groups. The groups that stood out were V, XIV, XV, XV, XVI, XVII, XVIII, XIX, and XX. The results of t-test showed six significant phenotypic correlations with low to moderate degree of association, and the genotypic correlations, in most cases, were higher than the phenotypic ones and showed the same sign. From the genetic parameters studied, the possibility of gains in the selection is high. The separation of groups of divergent genitors was possible due to the wide genetic variability for the studied characters. Moreover, the phenotypic and genotypic correlations showed that indirect selection is not feasible.

ABSTRACT The objective of this study was to evaluate the effect of different irrigation depths applied by drip system and nitrogen fertilization levels that promote higher yield and water use efficiency in onion (Allium cepa L.). The treatments consisted of five irrigation depths (50; 75; 100; 125; 150% of crop evapotranspiration), applied by drip system, combined with five nitrogen fertilization rates (0, 40, 80, 120 and 160 kg ha−1), in a 5 x 5 factorial scheme, in a randomized block experimental design, with four replicates. Irrigation depths estimated at 120.2% and 77.81% of crop evapotranspiration promoted higher yield and water use efficiency for total yield of onion bulbs, respectively. Nitrogen dose of 160 kg ha−1 promoted maximum total yield and water use efficiency.

ABSTRACT Intensification of the eutrophication process in surface water leads to an increase in the intensity and frequency of cyanobacterial blooms, compromising the availability of drinking water. Therefore, the aim of this study was to investigate the spatio-temporal dynamics of cyanobacteria and identify the most important nutrients for such dynamics in a semiarid artificial lake, the Orós reservoir, in north-eastern Brazil. Seventy-seven water samples were collected in 11 campaigns (six during the dry season and five during the rainy season) from seven points. The attributes under investigation were the Secchi transparency, turbidity, pH, apparent colour, electrical conductivity, total solids, total phosphorus, soluble orthophosphate content, total Kjeldahl nitrogen, ammonia content, nitrate content, and cyanobacteria dynamics, resulting in a total of 924 samples (number of campaigns × number of points × number of attributes). Principal component analysis and cluster analysis were used to investigate the significance and determinant attributes of the spatio-temporal dynamics of cyanobacteria. Of the 17 species of cyanobacteria identified, 10 accounted for 72.47% of the total accumulated variance. During the rainy season, four homogeneous groups of cyanobacteria formed, whereas during the dry season, only three groups formed. The greatest concentrations occurred during the dry season, notably for Aphanocapsa spp., Cylindrospermopsis sp., and Geitlerinema sp., which are potentially toxic and show a greater affinity to the physical attributes of water. Climate seasonality was decisive in the spatio-temporal dynamics of cyanobacteria, and high transparency values limited excessive proliferation of the dominant species.

ABSTRACT In semiarid regions with greater climatic variability, including prolonged droughts and delayed rainy seasons, supplemental irrigation is critical to ensuring yields of forage cactus pear. The objective was to evaluate root distribution and nutrient concentration and accumulation in ‘Gigante’ forage cactus pear subjected to different irrigation regimes. Seven irrigation regimes were tested: no irrigation (rainfed); five liters of medium-salinity water, with an electrical conductivity (EC) of 0.75 dS m−1, applied per linear meter every 15 days; 7% reference evapotranspiration (ETo) with a 15-d irrigation interval (II); 15% ETo with a 7-d II; 33% ETo with a 3-d II; 50% ETo with a 2-d II; and 100% ETo, irrigated daily - high-salinity water, EC of 3.6 dS m−1, was used in the last five treatments. The treatments were laid out in a randomized block design with four replicates. Roots developed best in plants irrigated at 50% ETo with a 7-d II. Applying high-salinity water at 15% ETo with a 7-d irrigation interval promotes higher concentrations of P, Ca, Mg and S in cladodes of cactus pear. Applying high-salinity water at 33% ETo with a 3-d II promotes higher uptake/accumulation of P, Ca, Mg, S and Zn in cladodes of ‘Gigante’ forage cactus pear.

ABSTRACT Arrowroot (Maranta arundinaceae), a traditional plant used to extract medicinal starch that is gluten-free and of excellent nutritional quality, is understudied for its growth and development in the organic crop system. The objective of this study was to evaluate the growth and photoassimilate partitioning in plants of two cultivars, Comum and Seta arrowroot. The design was performed in random blocks with four repetitions. At 57 days after planting (DAP), the plants were collected at regular intervals of 25 days throughout the crop cycle, and the dry mass was determined. Growth analysis was performed using the primary data. The cultivars Comum and Seta show maximum absolute growth rates of 10.51 and 12.42 g plant−1 day−1 and the maximum leaf area index (LAI) of 18.74 and 14.62, as recorded for 216 and 205 DAP, respectively. The higher absolute growth rate and higher growth of arrowroot plants in a shorter time indicate greater precocity of cultivar Seta compared to Comum. The photoassimilate partitioning is balanced between the aerial parts and rhizomes at the end of the cycle. Both cultivars can be recommended for the organic crop system in the Zona da Mata region of Minas Gerais.

ABSTRACT Macrophomina (Botryosphaeriaceae) is one of the main genera of soilborne phytopathogenic fungi, which causes root and seed rot in more than 800 host plants worldwide. Recent phylogenetic studies identified the species M. phaseolina and M. pseudophaseolina in Trianthema portulacastrum and Boerhavia diffusa in melon and watermelon production areas in northeastern Brazil. Therefore, the objective of this study was: i) to verify the effect of temperature and salinity on the mycelial growth of M. phaseolina, M. pseudophaseolina and M. euphorbiicola, ii) to assess their pathogenicity on melon and watermelon seedlings, and iii) to determine their sensitivity to the fungicide carbendazim. The optimal temperature for mycelial growth rate (MGR) for Macrophomina spp. ranged from 27.18 ºC (CMM4771 – M. pseudophaseolina) to 31.80 ºC (CMM4763 – M. phaseolina). For the effect of salinity on mycelial growth of Macrophomina isolates, the EC50 ranged from 103.76 (CMM4868 – M. euphorbiicola) to 315.25 mM (CMM4801 – M. pseudophaseolina). The pathogenicity test demonstrated that M. phaseolina, M. pseudophaseolina and M. euphorbiicola are pathogenic on melon with M. phaseolina exhibiting a higher level of virulence. Macrophomina euphorbiicola isolates did not cause disease in watermelon. The most sensitive isolates to the fungicide carbendazim were CMM4868, CMM4867 (M. euphorbiicola) and CMM1531 (M. phaseolina) with EC50 of 0.003, 0.012 and 0.012 mg.L-1 a.i., respectively. All Macrophomina spp. used in these experiments were pathogenic to the tested melon and watermelon cultivars with the exception of the M. euphorbiicola isolate that did not cause damage to watermelon.