Short-day Onion Research Articles

Effect of Postharvest Chemical Treatments, Heat Curing, and Refrigerated Storage on Marketability of Short-day Onions

Vidalia onions (Allium cepa) are very susceptible to infection from pathogens and diseases compared with other types of onions. Botrytis neck rot (BNR) (Botrytis allii) is the most common and destructive storage disease, whereas sour skin (Pseudomonas cepacia) can cause significant bacterial losses, particularly, for late season cultivars. The objective of this study was to assess the effects of different fungicide and bactericide drenches on marketability of Vidalia onions using the cultivar Savannah Sweet grown, harvested, and graded for high-quality onions. Six different fungicide treatments were evaluated, including fludioxonil at two different rates, fluopyram and pyrimethanil in combination, and pyraclostrobin and boscalid in combination with a water-only and an untreated entry. In addition, four different bactericide treatments were evaluated, including copper hydroxide and copper sulfate pentahydrate with a water-only and untreated control. Treatments were applied by drenching the onion bags with 1 gal of solution at the desired concentration. Onions treated with fungicide were inoculated with the pathogen that causes BNR, whereas the bactericide treatments were inoculated with the pathogen that causes sour skin by placing a single inoculated bulb into each bag. Half of the bags were heat-cured for 48 hours and all of the onions were stored immediately under refrigerated conditions at 34 to 36 °F for 2 or 4 months. Bactericide treatments were not heat-cured the second year of the study. Onions were evaluated after 1 and 14 days of shelf life. For both years, all the fungicide applications were effective with more marketable onions compared with the controls. Fludioxonil, fluopyram/pyrimethanil, and boscalid/pyraclostrobin had the highest percentage of marketable onions compared with the water or untreated controls. Fluopyram/pyrimethanil and boscalid/pyraclostrobin fungicides had significantly higher percentage of marketable onions than the controls but were similar to the low rate of fludioxonil. Bactericide applications were not effective in reducing losses when compared with the controls.

Yield and nutritional quality of different short-day onion cultivars as affected by nitrogen application

Onion is one of the most important vegetable crops in the world, cultivated and consumed for its flavour-enhancing and medicinal properties; hence, comprehensive understanding of crop responses to N application is of immense importance. To determine the effects of different nitrogen (N) levels on yield, quality and mineral content of onion, four short-day onion cultivars (‘Mata Hari’ [red onion], ‘Mikado’ [brown onion], ‘Cristalina’ [white onion] and ‘Star 5516’ [brown onion]) were subjected to six different N levels (0, 30, 60, 90, 120 and 180 kg ha−1). Application of 180 kg N ha−1 significantly increased total yield (46.51 t ha−1), whereas no N application resulted in poor yield (15.35 t ha−1). ‘Star 5516’ produced the highest marketable and total yield compared with the other cultivars, and ‘Mata Hari’ had the lowest marketable yield, possibly due to higher bolting percentage. An increase in N application resulted in an elevation of N, magnesium, manganese, zinc and sulphur concentrations in bulbs. Bulbs of the red onion cultivar had higher N, phosphorus, calcium, sodium, iron, zinc and sulphur levels than those of the other cultivars, with a significantly higher percentage total soluble solids and sulphur concentration than the white and brown onion cultivars. The results of this study show that increasing N fertilisation up to 180 kg N ha−1 increases the concentration of certain minerals in bulbs, as well as marketable yield, with ‘Star 5516’ yielding highest and ‘Mata Hari’ showing the best quality.

Florogenesis and Female Gametophyte Development in <i>Allium cepa</i> L. cv. Krishnapuram

Florogenesis is one of the most complicated and interesting processes in the nature. This process involves developmental, physiological and molecular events leading to transformation from vegetative to reproductive phase for optimal seed production and the continuation of species. The basic knowledge about flowering processes, male and female sexual systems support basic and applied research and breeding programs. Most of the onion varieties from India are short day varieties, more diverse than other exotic germplasm and useful as a source of new alleles for supporting breeding programs. The present investigation was focused to study for the first time florogenesis process by scanning electron study for the first time florogenesis process by scanning electron microscopy (SEM) and development of female gametophytes by light microscopy in order to acquire basic knowledge useful for optimizing in vitro process to produce gynogenic haploid to support and speed breeding program in short-day onion Allium cepa L. cv. Krishnapuram (KP) or Bangalore Rose. This study revealed that shoot primordium differentiated into inflorescence meristem in the month of December, while seeds were planted in the field in the September. The individual florets are preceded by a variying number of floral initials. The female gametophyte developed from chalazal side megaspore. The embryo sac development is a bisporic Allium type showing short-lived antipodals. The histological study suggests that the use of big or preanthesis flower buds with embryo sac for production of gynogenic haploids to support breeding program in onion cv. Krishnapuram (KP). However further studies are needed for confirmation of this observation.

Mechanization Technologies on Short-day Onion Production with Mulching Cultivation

Mechanization Technologies on Short-day Onion Production with Mulching Cultivation

Molecular characterization of CMS lines in short-day white onions

Molecular characterization of CMS lines in short-day white onions

Fenologia e acumulação de nutrientes por cebola de dia curto em semeadura direta

This study aimed to characterize the phenology and nutrient uptake throughout the crop cycle of short-day onion established by direct seeding. The experimental design was in randomized blocks with four replications. The treatments were different evaluation times. The characteristics evaluated were number of leaves, transversal and longitudinal diameter of the bulb, dry mass and plant nutrient accumulation. At the harvest, the plants reached 39.0 g of dry mass. The sequence of nutrient accumulation (g plant-1) was K (0.80) > N (0.49) > Ca (0.26) > S (0.17) > P (0.09) > (0.05) and (mg plant-1) Fe (2.17) > Zn (1.42) > Mn (1.36) > Cu (1.06) > B (0.92). For a population of 320,000 plants ha-1 and yield of 78,9 t ha-1, the plants extracted at the end of the cycle, 256.2; 157.2; 83.6; 53.2; 29.1; 15.4 kg ha-1 of K, N, Ca, S, P and Mg, and 694.8; 455.7; 436.0; 339.3; 294.6; g ha-1of Fe, Zn, Mn, Cu, and B. The bulbs exported 38, 55, 38, 28, 42, 40, 41, 9, 20, 10 and 30% of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn.

Effects of Postharvest Curing, Ozone, Sulfur Dioxide, or Low Oxygen/High Carbon Dioxide Storage Atmospheres on Quality of Short-day Onions

Vidalia onions (Allium cepa) are a branded product of southeastern Georgia marketed under a federal marketing order. They are short-day, yellow onions with a Granex shape that are susceptible to a number of diseases postharvest, limiting the amount of time they can be marketed. Postharvest treatments and storage methods can help extend their marketability. Thus, the objective of this study was to evaluate these postharvest treatments and storage conditions on quality of three Vidalia onion varieties: ‘WI-129’, ‘Sapelo Sweet’, and ‘Caramelo’. All varieties were undercut, then either harvested immediately (zero cure), field cured (2 days), or forced-air heat cured (3 days at ≈37 °C) when judged mature. ‘WI-129’, ‘Sapelo Sweet’, and ‘Caramelo’ represent early, midseason, and late varieties, respectively. Bulbs were then sorted and stored in refrigerated storage [0–1 °C, 70% relative humidity (RH)], sulfur dioxide (SO2) (1000 mg·L−1 in 2010 and 5000 mg·L−1 in 2011, one time fumigation) followed by refrigeration, ozone (O3 (0.1–10 mg·L−1; continuous exposure, 0–1 °C, 70% RH), or controlled-atmosphere storage [3% oxygen (O2), 5% carbon dioxide (CO2), 0–1 °C, 70% RH]. After 2 and 4 months, bulbs were removed from storage, and evaluated after 1 and 14 days for quality and incidence of disorders. ‘Caramelo’ had the lowest percent marketable onions after curing in 2010, while ‘WI-128’ had the lowest percent marketable onions in 2011. There was a rain event immediately before harvesting ‘Caramelo’ that may have contributed to low marketability in 2010. Heat curing improved marketability for ‘Sapelo Sweet’ and ‘WI-129’ in 2010 compared with no curing. In 2011, heat curing resulted in more marketable onions for ‘Sapelo Sweet’ compared with no curing. Curing had no effect on ‘Caramelo’ in 2011 and field curing had the greatest percent marketable onions for ‘WI-129’ in 2011. In 2010, controlled-atmosphere storage had more marketable onions compared with SO2 for ‘Caramelo’ and was better than simple refrigeration or O3 with ‘WI-129’. In 2011 refrigeration, controlled-atmosphere storage, and O3 were all better than SO2 with ‘Caramelo’. ‘Sapelo Sweet’ and ‘WI-129’, on the other hand in 2011, had better storage with SO2 compared with other storage methods. Onions stored for 2 months had 32% and 17% more marketable onions after removal compared with 4 months of storage regardless of storage conditions for 2010 and 2011, respectively. Poststorage shelf life was reduced by about one-third, 14 days after removal from storage regardless of the storage conditions.

Antioxidants of 15 onions with white, yellow, and red colors and their relationship with pungency, anthocyanin, and quercetin

We have investigated the antioxidant activity (AOA) of 15 short-day onions with white, yellow, or red colors and elucidated the relationships between pungency, anthocyanins, quercetin, and the AOA levels. There were substantial variations in both the pungency and total soluble solid content, which showed varying responses by bulb colors. The AOA in white or red onions tended to have low and high levels, respectively. However, there were many exceptions. The AOA levels assessed by the Folin–Ciocalteu (F–C) assay ranged between 440 and 785 μg/mL. The AOA levels based on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were between 19.1 and 79.8 μg/mL and displayed 10- to 20-fold differences. There was no correlation between the pungency and the AOA levels. The F–C assay showed no or low correlation with anthocyanin (r2 = 0.07) and quercetin (r2 = 0.59) contents, respectively. The DPPH assay showed correlations with anthocyanin (r2 = 0.65) and quercetin (r2 = 0.76) contents. Therefore, the onions with higher levels of anthocyanin and quercetin would have still higher AOA levels. Samples with alliinase action showed higher AOA levels than the samples without enzyme action. Onion juice without anthocyanin and flavonoids still contained considerable AOA levels. The methanol extract and fresh onion juices showed similar AOA levels by the F–C assay.

Response of short-day onion cultivar Pusa Red to planting dates and sulphur fertilisation

An experiment was carried out on the planting dates and forms of sulphur on chemical traits of ‘Pusa Red’ cultivar of onion (Allium cepa L.) during rabi season of 2012-13 at three different dates, viz., 15th November 2012, 15th December 2012 and 15th January 2013 and three doses of elemental sulphur and gypsum each 20, 40 and 60 kg/ha at Horticultural Research Farm of the Department of Applied Plant Science, School for Boiscience and Biotechnology, Babasaheb Bhimrao Ambedkar University, Lucknow (U.P.). The experiment was laid out in factorial Randomized Block Design with three replications. The data clearly revealed that higher TSS, ascorbic acid content in bulb were recorded in early planting (15th November with 60 kg/ha and 40 kg/ha), respectively and significantly higher reducing sugar, non-reducing sugar and total sugars were obtained with early planting, i.e., 15th November with 20 kg/ha of elemental sulphur, while higher content of pyruvic acid was found in late planting (15th January with 60 kg/h of elemental sulphur) of the crop.

Five-Year Evaluation of Short-Day Onion Varieties

Short-day onion (Alliium cepa L.) production is important in many regions with mild winters. Onions are particularly important in southeastern Georgia, where Vidalia onions are produced. These onions represent the vegetable with the greatest farm gate value in the state and variety trials are an important part of University of Georgia research for this industry. Short-day onion variety trials were conducted in southeastern Georgia from 2004 to 2008. Data collected and evaluated included total yield, graded yield, harvest date, number of seed stems, number of doubles, number of onion centers, bulb shape, disease incidence, bulb pungency, and storability in controlled-atmosphere (CA) storage. Not all data were collected in all years. There were between 35 and 68 entries in the trials. Sixteen varieties appeared in all 5 years. Total yields were from ˜23,000 to ˜72,000 kg•ha−1. Marketable yields ranged from 23% to 99% of total yield depending on variety and year. Average marketable yield for the 5 years ranged from 61% to 82%, with the 2006–2007 season having the best average marketable yield. In general, later maturing varieties had lower marketable yields because of bacterial diseases such as sour skin, caused by Burkholderia cepacia Palleroni & Holmes 1981 ex Burhkolder 1950, that developed as temperature increased. Seed stems (flowering) and doubled bulbs differed over years. Both are believed to occur because of a combination of environmental and varietal effects. Average percentage marketable onions, after removal from CA storage, ranged from 48% to 82% depending on year. Botrytis neck rot, caused by Botrytis allii (Munn) Yohalem, was the primary disease affecting marketability post-CA. Onions held for 2 weeks after removal from CA storage under ambient conditions could see a reduction in average marketable onions from 17% to 33% depending on year.

Variation in gynogenic potential for haploid induction in Indian shortday onions

Gynogenic haploid induction was tried in 14 Indian shortday onion varieties. Variation in gynogenic potential was observed (0.9 to 4.5 per cent) between genotypes. The highest frequency of gynogenic plants was in Bhima Shubhra (4.5%) and the lowest in Bhima Shweta (0.9%). Accumulation of mutant alleles likely contributed to the low gynogenic frequency. Time to embryo sprouting varied between 40 to 98 days after inoculation. Highest range in time of sprouting was observed in Bhima Shubhra, from 51 to 98 days. Non-haploid regenerants were also observed among gynogenic plants and their gynogenic origin was confirmed by SSR markers. Parents with good gynogenic potential can be utilized for introgression breeding in onion where a reduction in the breeding cycle is beneficial.

Changes in Flavor Precursors, Pungency, and Sugar Content in Short‐Day Onion Bulbs during 5‐Month Storage at Various Temperatures or in Controlled Atmosphere

Short-day onion bulbs (cv. TG 1015Y) were stored in 1% O(2,) 99% N(2) air at 5 °C (controlled atmosphere [CA]), or in ambient air at 5, 24, or 30 °C, for 5 mo. Changes in flavor precursors, pungency, and sugar content were investigated. After 5 mo of storage, 1-propenyl-L-cysteine sulfoxide concentrations increased continuously at 5 °C, gradually decreased in CA, slightly increased for 3 mo, and returned to initial levels at 24 °C and decreased below initial levels at 34 °C. Methyl-L-cysteine sulfoxide concentrations remained unchanged in all storage conditions. Onion pungency levels significantly increased at 5 °C, and decreased at 30 °C. Storage in CA and at 24 °C resulted in some fluctuations in pungency but the levels remained similar to initial levels. The calculated pyruvic acid concentrations were approximately 1.0 μmole/mL higher than the measured concentrations, and showed an increase at 5 °C and a slight reduction at 30 °C, consistent with the pungency results. Storage at 5 °C and in CA resulted in slight increases in fructose and glucose concentrations for 3 to 4 mo with subsequent rapid decreases, while sucrose concentrations remained unchanged. However, at 24 and 30 °C, fructose and glucose concentrations continuously decreased, accompanied by a continuous increase in sucrose concentrations. Storage in CA maintained the quality of onions best, as evidenced by the smallest changes in flavor precursors, pungency, and sugar concentrations, while storage at 5 °C resulted in increased pungency. Storage at 24 and 30 °C was tested for the purpose of comparison only; these temperatures are not recommended for commercial storage.

Crop Coefficient-based Deficit Irrigation and Planting Density for Onion: Growth, Yield, and Bulb Quality

Agricultural communities in the semiarid regions of the world are constantly being affected by water scarcity, increased regulations restricting water use, strong competition for irrigation water with the urban sector, and severe drought periods. Conversely, the consumer demand for high-quality and nutritious foods is increasing rapidly. A 2-year field study evaluated growth, yield, and bulb quality in response to precision planting density and deficit irrigation of onion (Allium cepa L.) in southwest Texas. Seeds of short-day sweet onion cv. Texas Grano 1015Y were planted in the field on 11 Nov. 2007 and 30 Oct. 2008 at two planting densities (PDs), 397,000 (standard) and 484,000 (high) seeds/ha. Three irrigation rates using growth stage-specific crop coefficients and subsurface drip were imposed after plants were fully established, 100%, 75%, and 50% crop evapotranspiration rates (ETc). Total rainfall plus irrigation received for each irrigation rate were 594, 501, and 413 mm in 2008 and 662, 574, and 486 mm in 2009. In both seasons, there were consistent trends in growth, yield, and quality parameters. Leaf fresh weight was unaffected by PD but was reduced by deficit irrigation at 50% ETc. Although increasing planting density reduced the average bulb size by 12%, it increased the number of marketable bulbs by 21% to 33% and marketable yield by 7% to 14%. In contrast, deficit irrigation showed a trend to reduce both the number of bulbs and bulb size with yield reductions of 8% to 13% at 75% ETc and 19% to 27% at 50% ETc. Neither planting density nor deficit irrigation rate had a significant effect on soluble solids content, pungency, or quercetin contents. These results suggest that growers of short-day onions in semiarid regions could adjust PDs to target high-value bulb sizes. Implementing water-conserving practices (deficit irrigation at 75% ETc rate) would result in a decrease of high-value bulb grades and modest losses in yield but not flavor or nutritional components.

Determining Redundancy of Short-day Onion Accessions in a Germplasm Collection Using Microsatellite and Targeted Region Amplified Polymorphic Markers

The U.S. National Plant Germplasm System is one of the world's largest national genebank networks focusing on preserving the genetic diversity of plants by acquiring, preserving, evaluating, documenting, and distributing crop-related germplasm to researchers worldwide. Maintaining viable germplasm collections is essential to world food security but comes at a cost. Redundancy within the collection can incur needless expense and occurs as a result of donations of similar material under different names from different donors. Alternatively, similarly named accessions from different donors can actually be genetically distinct. We evaluated 35 short-day onion (Allium cepa) accessions using microsatellite and targeted region amplified polymorphic (TRAP) molecular markers to compare newly acquired germplasm with existing accessions in the collection to determine differences and redundancies and to compare the use of each marker type in distinguishing the onion accessions. Both marker types distinguished differences and found similarities, but the results did not always agree. TRAP markers found one of the Italian Torpedo entries to be different, whereas the 10 microsatellite loci analyzed found no differences. In contrast, microsatellite analysis found all three Red Grano entries to be different, whereas TRAP analysis distinguished only one accession. The eight White Grano entries were separated into four groups by microsatellite markers and five groups by the TRAP markers. Discriminating among closely related accessions using molecular markers can require a large number of random marker loci, especially when differences may be limited to a single trait. TRAP markers were more efficient, uncovering ≈10 random polymorphic loci per primer pair, whereas microsatellite markers each uncovered differences at a single locus.

Evaluation of Poultry Litter and Organic Fertilizer Rate and Source for Production of Organic Short-day Onions

In a 3-year study of poultry litter applications on short-day onion (Allium cepa) production, where rates ranged from 0 to 10 tons/acre, there was an increasing linear effect on total onion yield. Jumbo (≥3 inches diameter) onion yield did not differ with increasing poultry application rates, while medium (≥2 and <3 inches diameter) yields decreased with increasing applications of poultry litter. In addition, organic-compliant fertilizers, 4N–0.9P–2.5K at 150 to 250 lb/acre nitrogen (N), as well as 13N–0P–0K at 150 lb/acre N and in combination with 9N–0P–7.5K totaling 150 lb/acre N were evaluated. Comparison of these commercial organic-compliant fertilizers indicated that there were no differences in total or jumbo yields, while medium yields generally decreased with increased N fertilizer rate.

Quantification of Quercetin Glycosides in 6 Onion Cultivars and Comparisons of Hydrolysis‐HPLC and Spectrophotometric Methods in Measuring Total Quercetin Concentrations

This study was performed to purify and quantify quercetin glycosides (QG) and aglycone (free) quercetin (Q) in 6 selected onion cultivars and to compare analytical approaches based on high-performance liquid chromatography (HPLC) and spectrophotometry for the quantification of total quercetin (TQ) concentrations. Individual mono- and di-glycoside Q compounds were purified using a semipreparative HPLC and identified by comparing spectral data and by confirming corresponding peaks of QG and Q after incomplete enzyme-hydrolysis. Purified QG were quantified as Q by enzyme-hydrolysis/HPLC. TQ concentrations obtained from 20 onion bulbs with enzyme-hydrolysis/HPLC, no-hydrolysis/HPLC, and a spectrophotometric method without prior hydrolysis were significantly correlated (r(2)= 0.99) and were about 15% higher, identical, or 10% less than those concentrations by a standard acid-hydrolysis/HPLC method, respectively. During enzyme-hydrolysis of onion extracts, progressive reduction of the QG and formation of the corresponding mono-glycosides and Q were monitored using an analytical HPLC. TQ ranged from 83 to 330 microg/g F.W. in 6 selected cultivars of long-day or short-day onions. Q3,4'G and Q4'G were the 2 major compounds and comprised approximately between 94% and 97% of TQ in onions.

Application of extra sulfur to high-sulfur soils does not increase pungency and related compounds in shortday onions

Sulfur (S) nutrition has a strong influence on onion pungency, and the production of sweet onions in the high-sulfur soil of Texas is a challenge to growers. This study was performed to determine the effects of S applications to fields already having sufficient levels of soil S on pungency and related compounds in four shortday onion cultivars. The onion cultivars ‘Cougar’, ‘Legend’, ‘Texas Early White’, and ‘Texas Grano 1015Y’ were grown in three commercial fields at Edinburg, Mercedes, and Weslaco of the Rio Grande Valley of South Texas with applications of sulfur at 0, 13, and 26 kg S/ha. Pyruvic acid, bulb weight, extractable S in soil and total S in bulb, soluble solids content (SSC), flavor precursor compounds [also called S-alk(en)yl- l-cysteine-sulfoxides (ACSOs)], and total sugars were measured. The pyruvic acid level of onions was not increased by the S applications and showed no significant correlation with soil S levels in any of the cultivars at locations having 30 or 235 ppm S. The SSC, total S in bulbs, total sugars, and total ACSO content also showed no correlation with the S applications and soil S levels. Onion pungency and content of flavor precursor compounds were significantly influenced by cultivar and cultivar × location interaction. We conclude that onion pungency is not increased by application of extra S fertilizer to commercial fields already containing sufficient levels of soil sulfur.

Evaluation of field performance and storage of some tropical short-day onion (<i>Allium cepa</i> L.) cultivars

The storage of bulbs of onion (Allium cepa L.) is very crucial to ensure its availability throughout the year. Experiments were conducted at Sokoine University of Agriculture to evaluate the growth and yield characteristics of some tropical short–day onion cultivars and the storability of their bulbs after harvest. The first experiment in 1994 involved 21 cultivars evaluated for their growth and yield variables. The second experiment, involving six cultivars, was carried out in 1996 and in addition to performance evaluation, the storability of bulbs was investigated. Results showed significant differences among the cultivars in yield, yield components and storability. Granex 429 had the highest yield among cultivars in both trials, but had very poor storability. Serrana and XPH 6074 had long storability and maintained more than 50% of their weight after 5 months of storage. These two cultivars are promising as good sources of genes to incorporate storage traits in other cultivars of onion

Characterization of Shortday Onion Cultivars of 3 Pungency Levels with Flavor Precursor, Free Amino Acid, Sulfur, and Sugar Contents

This study was conducted to characterize shortday onions of 3 pungency levels with regard to the composition of flavor related compounds. A total of 9 onion breeding lines/cultivars were selected, per each of low, medium, and high pungency level, with pyruvic acid contents of 1.9 to 2.8, 4.8 to 5.4, and 7.2 to 8.3 micromoles/mL, respectively. The contents of flavor precursors (S-1-propenyl-L-cysteine sulfoxide [1-PeCSO] and S-methyl-L-cysteine-sulfoxide [MCSO]), free amino acids, free sugars, soluble solids (SSC), and total sulfur (S) in onion bulbs were measured. The flavor precursor contents ranged from 0.03 to 0.16 mg/g fresh weight (FW) for MCSO, 0.07 to 0.65 mg for 1-PeCSO, and 0.12 to 0.77 mg in total, and precursor contents increased with the pungency levels. Onions of different pungency levels did not differ in the contents of individual or total free amino acids, and the most abundant amino acids were glutamine and arginine. The total sugar contents ranged from 50 to 75 mg/g FW, and total S contents (3.5 to 5.1 mg/g dry weight) were not correlated with the pungency levels. However, pungency levels were correlated inversely with bulb weight and positively with SSC, presumably by the effect of dilution. This study indicates that onion pungency is primarily determined by the content of flavor precursor compounds and not by total S, total sugars, or individual/total free amino acids in shortday bulbs.

Plant Population, Transplant Size, and Variety Effect on Transplanted Short-day Onion Production

Onions (Allium cepa) produced in southeastern Georgia's Vidalia-growing region are primarily grown from on-farm–produced bareroot transplants, which are usually sown the end of September. These transplants are pulled midwinter (November–January) and are reset to their final spacing. This study was to evaluate transplant size and spacing effects on yield and quality of onions. Large transplants (260–280 g per 20 plants) generally produced the highest yield. Medium transplant size in the range of 130 to 150 g per 20 plants produced satisfactory yield while maintaining low numbers of seedstems (flowering) and doubled bulbs, which are undesirable characteristics. Smaller transplant size (40–60 g per 20 plants) have reduced yields and lower numbers of seedstems and double bulbs. Increasing plant population from 31,680 to 110,880 plants/acre can increase yield. In addition, plant populations of 110,880 plants/acre can increase yields compared with 63,360 plants/acre (industry standard), but only when environmental conditions favor low seedstem numbers. Seedstems can be high because of specific varieties, high plant population, or more importantly, in years with environmental conditions that are conducive to their formation. ‘Sweet Vidalia’ was the only variety that had consistently reduced quality and high numbers of seedstems. ‘Sweet Vidalia’ has a propensity for high seedstem numbers, which may have influenced results with this variety. A complete fertilization program that included 133 or 183 lb/acre nitrogen did not affect onion yield, regardless of variety or population density.