Onion plants (Allium cepa L.) have a low competitive capacity against weeds, so these must be controlled from the beginning of the crop cycle. Plant communities respond differently to the management practices used in the fore crops (eg. tillage and fertilization). The objective was to evaluate the effect of different fore crops on the weed communities in direct seeding onion crops. During the 2015/16 season, an onion crop was implanted in the Lower Valley of the Rio Negro by direct seeding in plots with different fore crops: tomato, soybean, corn and carrot. The emergence of weeds was evaluated 15 and 45 days after sowing (DAS). The weeds on the ridge were collected in a 30 x 30 cm frame to determine the number and biomass for each species, and to calculate the richness and diversity. Ten weed species were observed in a cotyledonal state at 15 DAS, without differences between treatments. At 45 DAS, Lamium amplexicaule L., Xanthium spinosum L., Polygonum aviculare L., Picris echinoides L., Sonchusasper L. and Echinochloa crus-galli L. were the most frequent species. The greatest richness, density and diversity was observed after rotation with tomato. The differential response of the weeds to the fore crops would help design the rotations for more efficient weed control in an onion crop.

Asparagus is a non-traditional perennial vegetable crop for which evaluation of the performance of different genotypes is required. With the aim of determining the productivity of a set of all-male genotypes from Italy, a trial was planted on 22/11/06 using large (PG) and small (PCH) seedlings. The following characters were evaluated: total (PFT) and commercial (PFC) fresh production, total (NTT) and commercial (NTC) spear number, calibre distribution (J: Jumbo; XL: Extra-Large; L: Large; M: Medium; S: Small and A: Asparagina), defects (DE: opened bracts; P: plague damage; and OD: other defects). Thirty-two harvests were carried out between 1/9/14 and 14/11/14. Data were analysed by ANOVA-LSD (P≥0.05). No significant differences were found between the two seedling sizes. From the thirty-two harvests, a mean productivity of 14.5t.ha-1 was obtained, with a commercial prime quality productivity of 5.4 t.ha-1. A total of 553,241 spears were obtained, of which 252,420 were of commercial prime quality, with an average weight of 21 g per spear. Regarding seedling size, no significant differences were found. The Italian genotypes performed better than the control genotype from the USA, with Eros outstanding for PFT, and Ercole, Eros, Italo and H-668 for PFC. For spears produced, significant differences were observed between hybrids: for NTT, Zeno, Eros, Ercole and H-668 stood out, while for NTC, Ercole. Regarding calibre distribution, Italo, UC-157, H-668, Zeno and Eros stood out for J; Eros, Italo, Zeno and H-668 for XL; Eros, Italo, Ercole and H-668, UC-157 and Zeno for L; Ercole, Eros and H-668, and UC-157 for M; UC157 and Ercole for S; and UC-157 and Ercole for A. In conclusion, all male hybrids represent a valuable production alternative.

Viral diseases can affect the stability of common bean (Phaseolus vulgaris L.) production, therefore it was considered of interest to evaluate the behavior of different cultivars and promising lines obtained by the INTA breeding program against natural virus infection. Symptoms severity, incidence and relative concentration of Cucumber mosaic virus (CMV), Cowpea mild mottle virus (CpMMV), Alfalfa mosaic virus (AMV), Soybean mosaic virus (SMV) and geminiviruses were evaluated for 14 bean cultivars during three growing seasons. SMV and AMV were found in very low incidence during the three years. Differences in cultivar response were observed: L24 and L15 were tolerant to begomoviruses, while CR8, CR5, L22 (cranberry and white bean types) were susceptible. The most severe symptoms were found during the 2013 growing season, when a high incidence of begomovirus and CpMMV were observed. No differences between cultivars were found for CpMMV incidence, but a higher relative concentration of virus was detected in CR5, CR8 and L17. Although L15 was tolerant to geminiviruses, it was the most susceptible to CMV, a fact that must be taken into account because this virus is transmitted by seeds and might become a serious problem in bean production.

The experiment was conducted in the district of Minga Guazú, Paraguay (25º29'04''S, 54º45'52'' W). The study evaluated the effect of two types of organic fertilizer (cow and hen manure) applied in different doses to cabbage (Brássica oleracea L.). The general objective was to determine the yield, weight and diameter of the fruit or head of the cabbage. The design used was completely randomized blocks with 5 treatments; T1: control (without any fertilization); T2: 3 kg.m-2 hen manure; T3: 5 kg.m-2hen manure; T4: 3 kg.m-2cow manure; T5: 5 kg.m-2 cow manure; and with 4 replicates totaling 20 experimental units. The evaluated variables were fruit weight and diameter, and yield (kg) per hectare. The values obtained were subjected to analysis of variance, and for mean comparison, the Tukey test at 5% probability of error was used. There was an effect due to the treatments on the studied variables. The largest fruit diameter corresponded to the T3 treatment with 20.68 cm, while the highest fruit weights corresponded to the T3 treatments (890.25 g) and T2 (701.25g). The highest yields corresponded to treatments T3 (7.05 kg.m2), T2 (5.59 kg.m-2) and T4 (4.37 kg.m-2).

The volume of onion production in Paraguay does not supply the domestic demand causingthe import of the product mainly from Argentina. The local research on onion cultivation is scarce and hinders the improvement of the national production.The effects of transplanting dates on onion cultivars performance are not well known in the Paraguayan environments. Therefore, seedlings of 17 onion cultivars weretransplanted on three different dates, May 24, June 26 and August 6, 2012, respectivelyin order to evaluate the effects on yield and quality of the bulbs. The trial was carried out in the experimental field of the "Hernando Bertoni" Research Center, Paraguayan Institute of Agrarian Technology, Caacupé, Paraguay. The experimental design used was the split-plot with three replications. The mass, total and commercial yield of onion bulbs were evaluated. The data were subjected to the analysis of variance and the comparison of means performed by the Tukey test at 5% of probability. The obtained results indicate that delaying the transplant date reduces the yield and mass of bulbs. The cultivars that recorded the highest yields and mass of bulbs on the first date of transplant were Aurora, Primavera, Bella Dura, Victoria, BaiaPeriforme, Rainha and Red Creole. On the second transplant date, the Aurora, Cascata and Yellow Grano cultivars, and on the last transplant date, the Cascata cultivar obtained higher yields, respectively.

Squash, summer squash or zucchini, is grown in the green belts and major vegetable areas of the country. It is an alternative for the area of Villa Mercedes, due to the great demand of the local consumerswhich is satisfied by the neighbor provinces productions.Traditionally, Cucurbitaceaeare direct seeded at the beginning of cultivation, however the transplanting system in pots  has been increasingly used for the advantages it offers. The objective of the trial was to evaluate two techniques of starting cultivation (direct seeding and transplanting) and their effect on the performance of different genetic materials.The two implantation techniques combined with five materials of zucchini were considered as treatments: ItalianoAlargado, Italiano Redondo, ItalianoOvalado, Nutri-C INTA andVeronés INTA.The experimental design was a factorial of implantation techniques and cultivars as treatments, established in a completely randomized plot structure (2m2of four plants). The yields obtained were statistically analyzed through the InfoStat program. It was demonstrated that the best culture starting technique was by transplanting, regardless of the materials used. The material with the highest yield was Veronés INTA summer squash initiated through the pot technique and subsequent transplant with an average performance of 21.5 kilograms per plot. 

It was observed in the walnut nursery of Valle Viejo department - Catamarca, symptoms coinciding with those caused by Agrobacterium tumefaciens circumscribed to the area of ​​the graft. The transmission of the pathogen causing these gills can be by means of tools during the grafting work. The nurserymen disinfect the tools with sodium hypochlorite between 2 and 5%, with the difficulty of deteriorating the blades, leaving them blunt. The objective of the present work was to corroborate the presence of the pathogenic organism that causes the gills observed, and to test, in the laboratory, the effectiveness of different tool disinfectant products. The bacterium was isolated by planting small pieces of gills in two different culture media: Nutritive Agar (AN) and Agar extract of yeast dextrose calcium carbonate (YDC). The ability of four antiseptics to disinfect the graft blade was also evaluated: Sodium Hypochlorite, Glutaraldehyde, 70 ° Alcohol and Quaternary Ammonium, at different concentrations, for 10 and 30 s. Colonies corresponding to A. tumefaciens were isolated and the pathogenicity tests on tomato seedlings reproduced the symptoms. The re-isolations confirm A. tumefaciens as causal agent of the gills in the walnut seedlings examined. The glutaraldehyde at 2% has an efficiency of 100% when submerging 10 s the tool. The glutaraldehyde does not oxidize the tools and does not remove the edge, an advantage over the hypochlorite rejected by the operators because it deteriorates the tools and they must be replaced more frequently.

Consumption of leafy vegetables is beneficial, however, the ingestion of contaminated food may cause diseases. The objective of this study was to obtain data on microbiological quality of leafy vegetables produced in the Fronteira Oeste region of Rio Grande do Sul. Samples of lettuce, cabbage leaf, arugula and a mixture of parsley and chive were collected, with quantification of total and thermotolerant coliforms by most probable number method and detection of Salmonella sp. using Petrifilm™ Salmonella Express System. A questionnaire was applied to understand the cultivation system of leafy vegetables used in the region: local, type of fertilizer, water source and surroundings.  Results showed high counts of coliforms ranging from 2.21 to 3.38 MNP/g for total coliforms and from 0.60 to 3.38 log MPN/g for thermotolerant coliforms, and 47% (n=16) of prevalence for Salmonella sp. In addition, 100% (n=8) of arugula, 85.7% (n=6) of parsley and chive, 75% (n=6) of cabbage leaf, and 60% (n=6) of lettuce samples were classified as improper for consumption, mainly in the municipalities of São Borja and Alegrete. The use of fertilizer considered organic and untreated water for irrigation and the presence of animals close to the production could be some of the factors involved in this type of contamination. Microbial contamination indicated unsatisfactory hygienic-sanitary quality, which emphasizes the need of good agricultural practices and good handling practices for leafy vegetables in order to reduce health risks to consumers.

The demand for efficient methods that assist in the identification and knowledge of the weed population by means of frequency identification and the prevailing species, are extremely important, since the characteristic of the population is  the type of management to be adopted, how and when. Thus, the scientific understanding of this vegetation will contribute to the knowledge of regional weed flora and the environment in which it is found. The aim of this study was to carry out a phytosociological study of weeds in fields planted with lettuce in an organic system, in order to verify the occurrence of changes of species according to the management adopted, as well as the effect of the presence and absence of mulching. Different organic and conventional fertilization applied in lettuce cultivation interfere with the dynamics of weeds present in the areas, and the degree of diversity and similarity of species is higher in areas with and without mulching. The most important species according to management conditions in work area I (with mulching) was Galinsoga parviflora and Gnaphalium spicatum in area II according to the management  conditions of the work.

In tomato (Solanum lycopersicum L.), pepper (Capsicum annuum L.) and eggplant (Solanum melongena L.) crops, there is a continuous introduction of hybrids, and it is of interest to study their adaptation to local growing conditions. The aim of this work was to characterize tomato, pepper and eggplant hybrids, according to thermal time and days from transplant required to reach flowering and fruiting between the first and fourth bunch. Crops were grown under a greenhouse located in La Plata, Buenos Aires, Argentina (34° 58´S, 57° 54´W). Tomato hybrids: Elpida and Griffy (Enza Zaden®), bell pepper hybrids: Almuden and Platero (Syngenta®) and eggplant hybrids: Barcelona (Fito®) and Monarca (Rijk Zwaan®) were planted on 08/14/2011. Air temperature and date of first flowering and fruiting from first to fourth bunches were registered. Days between transplant and start of phases and thermal time with a base temperature of 10 ºC for tomato and bell pepper and 11 ºC for eggplant were calculated. Statistical design was a randomized complete block with 4 replications. Number of days data were subjected to the non-parametric Friedman test and thermal time to analysis of variance (p<0.05). No statistical differences between hybrids were observed to reach first flowering or fruiting from first to fourth bunch, considering that under these trial conditions, the selection of these genetic materials for production can be done by different criteria than bioclimatic response.