Bulb Maturity Research Articles

Participatory variety evaluation and selection of improved onion (Allium cepa L.) varieties for bulb yield under supplementary irrigation condition at Basketo Special District, Southern Ethiopia

Onion is one of the most important vegetables and high economic crops, but grown by a few small-scale farmers in Basketo special district (woreda). Likewise, productivity of the crop in the district is very low. Lack of improved onion varieties and the use of inappropriate agronomic practices are among the major factors that limit the productivity of onions in the study area. Hence, this study was conducted at Basketo special woreda in 2019 and 2020 cropping seasons under supplementary irrigation to evaluate adaptability and to select high yielding onion varieties using farmers’ selection criteria. The experiment consisted of five improved onion varieties, namely; Adama red, Bombay red, Nafis, Adama Red, Robaf and Nasik Red and arranged in Randomized Complete Block Design in three replications. The results revealed that onion varieties exhibited differential performance in the two cropping seasons in the study area. Accordingly, Nasik red variety gave the highest bulb weight, marketable and total bulb yield (13.23 and 1.75 t/ha) and took a short period for bulb maturity compared to other onion varieties in the two cropping seasons. On the other hand, variety Bombay red produced 11.7 and 11.3 t/ha during the year. However, variety ‘Nafis’ was also selected by the farmers through their criteria. Therefore, onion varieties Nasik red (129.9Q/ha) and Nafis (106.1 Q/ha) are selected and recommended for the onion growers in the study area for better bulb yield.

Evaluation of onion cultivars as affected by bulb maturity and bulb characteristics of intermediate-day yellow onions in South Korea

ABSTRACT This study evaluated the performance of 55 intermediate-day onion cultivars (Allium cepa L.) in southeastern Korea, and clustered the cultivars based on bulb maturity and marketable bulb yield (MBY). Days from transplanting to bulb initiation (DTB) ranged from 146 to 177. Fresh bulb weight (FBW) and MBY were lower in early or mid-maturing cultivars than in late-maturing ones. The cultivar ‘Eomcheongnan’ produced the greatest FBW and MBY in the mid-maturing cultivars. Of the late maturing cultivars, ‘Art’, ‘K-star’, ‘Okkimaru’, ‘Cheonjujunggo’, ‘Worldstar’, and ‘Johwang’ ranked for MBY with more than 73.0 Mg ha−1. Only 10 late-maturing cultivars including 6 cultivars with more than 73.0 Mg ha−1, ‘Dekanmaru’, ‘Newmars’, ‘Hanaro’ and ‘Strike’ had a significantly greater than 4 cultivars (‘Volve’, ‘SuperRich’, ‘Marathoner’, and ‘Gangwon 1 ho’) with the lowest MBY, which might be due to difference in maturity too short with 14–26 April for bulb initiation, and 3–13 June for harvest. Higher air temperature and lower rainfall during bulb development stage did not affect days from transplanting to harvest (DTH), but negatively affected FBW. In 47 cultivars except for early and mid-maturing cultivars which started bulb initiation before 10 April, MBY was positively correlated with only DTH (R = 0.401) and FBW (R = 0.960). All the 55 cultivars were classified into 5 clusters, but there were close distances in clusters among late-maturing cultivars.

Determination of the maturity stage and the most suitable age for harvesting of sweet fennel (Foeniculum vulgare var. dulce, Mill)

Sweet fennel is a native Mediterranean plant and has widely naturalised and escaped from cultivation worldwide. We aimed to study the changes occurred in the physical, chemical and biochemical characteristics during development and under cold storage to determine the maturity stage and the most suitable age for harvesting. Two experiments were carried out on sweet fennel cultivar in the winter seasons of 2016-2017 and 2017-2018 at a private farm located in Behiera Governorate. Bulbs of 70, 90, 110, 130, 150 and 170 days age from seed sowing were examined The obtained results showed that there were gradual increases in the bulb fresh weight, size and diameter till the age of 130 days after which a rapid increase took place up to the last examined age of170 days exhibiting statistically a curvilinear pattern. However, the bulb firmness increased gradually with the age proceeding till 170 days age. Moreover, an increase in the T.S.S, ascorbic acid and antioxidant activity was detected up to the age of 130 days then followed by a decline up to the age of 170 days showing statistically a curvilinear shape. Furthermore, storing the developmental stages at 15oC and 95% RH showed that the bulbs of 130 days age reflected the minimum loss in weight and the lower unmarketable percentage during storage and the highest contents of T.S.S, ascorbic acid and antioxidant activity. From the obtained results, it was clear that the bulb maturity stage of the variety Florence of sweet fennel was reached after 130 days and this age was fortunately the most suitable age for harvesting.

Evaluating the Effects of Deficit Irrigation on Yield and Water Productivity of Furrow Irrigated Onion (Allium cepa L.) in Ambo, Western Ethiopia

The objective of this study was, to evaluate the effects of deficit irrigation on yield and water productivity (WP) of onion crop grown under Ambo condition. Field experiment was conducted at Ambo Agricultural Research Center in Ethiopia. The treatments consisted of nine different treatments replicated three times arranged in RCBD. The experiment involved two categories of deficit with different timings: 1) skipping of irrigation during one particular phenological stage and application of 75% ETc during the rest of the growing stages and 2) no watering during specific phenological stage and watering with 50% ETc during the remaining stages. Amount of water applied was monitored using standard Parshall flume. The highest total onion yield (46.7t/ha) was obtained from full irrigated treatment, which was not statically different from treatments that were not irrigated during initial growth stage and irrigated with 75% ETc during the rest of phenological stages (T2) and treatment with no irrigation during bulb maturity stage and irrigated with 75% ETc otherwise (T5) (P<0.05). The second category of treatment (irrigation with 50% ETc) resulted high water saving and yield reduction which may not be attractive for producers. WP varied from 7.7 kg/m3 for control and 14.9 kg/m3 for the 50% stressed and not irrigated during maturity stage. T2 and T5 produced WP values of 10.8 and 13.1 kg/m3 respectively. From resources conservation point of view, maximum water productivity may be of interest, which could be obtained under sever deficit irrigation. However, such consequences on yield may not be tolerable from producers view point. The recommended depth of irrigation would be 75% ETc during development, bulb formation, maturity stages and skipping during initial growth stage. Skipping irrigation during maturity stages and irrigating with 75% ETc otherwise has more water saving and WP enhancement potential with tolerable level of yield reduction.

New phenological growth stages of garlic (Allium sativum)

AbstractThe advantages of using Biologische Bundesanstalt, Bundessortenamt and Chemische Industrie (BBCH) phenological scales are well‐known in the field of agronomy. Currently, specific scales exist for the majority of crops. Although garlic has international importance due to its worldwide cultivation, a specific phenological scale has not been developed; in general, garlic is integrated into the BBCH description for onion. While garlic and onion belong to the same genus, this generalisation should be avoided due to their many differences. The means of propagation of garlic is vegetative, from cloves of the previous cycle, and the concurrence of the bulbing phase and the emergence of the inflorescence (bolting types) cause garlic to perpetually remain in a ‘second year stage’ of its biological cycle. In contrast, onions and other bulbous Liliaceae that produce seeds undergo biannual development. In addition to this complexity, its physiological complex is strongly influenced by environmental factors, such as temperature and photoperiod; distinct conditions are required for overlapping or simultaneously occurring phases (bulbing/flowering). Nevertheless, ambiguity and lack of consensus exist concerning the start of different phenological phases due to the complex morphology of the bulb (composed of a bulb of bulbs/cloves). During bulbing, for example, two distinct, consecutive processes are involved: the differentiation of lateral buds and inflorescence (bolting types) and the thickening of the storage leaf of each bud (cloves). In the present study, an extended BBCH scale was developed for garlic (Allium sativum). Seven principal growth stages divided into secondary growth stages are described in detail and are represented by a two‐ or three‐digit code. Descriptions begin with garlic cloves in a stage of dormancy, destined for planting and end with complete bulb maturity. The most complex growth stages of garlic were described from a morphological and physiological perspective, that is complete bolting types (hard‐neck cultivars). Illustrations of different stages are included to clarify the application of the code system. The proposed BBCH garlic scale aims to fill gaps in the knowledge of this important crop and will serve as a useful tool for researchers, technicians and farmers. Thus, experimental findings may be standardised and complementary, which may lead to improvements in management practices and their comparisons.

Determination of physical properties of onions (Arka kirthiman)

India produces about 13 per cent of total worlds onion product and ranked second after China. Onion is grown in an area of 1.0 mha in India with the production of 15.1 million tonnes and productivity of 14.2 tonnes/ hectare. Broad casting method of growing onion seeds results in the higher amount of seed rate, non-uniform distribution of seeds, poor bulb maturity and higher nutrient competition. To overcome these constraints there is a need to develop animal drawn onion seeder, which is more adaptable for small scale farmers under rainfed cultivation with reasonable cost of operation. To develop the desired seed metering unit of animal drawn seeder some of the onion seed physical properties viz. , seed dimensions, weight and mechanical properties were determined. The length, width and thickness of Artthi Kirthiman onion variety were in the range of 2.50-2.95 mm, 1.75-2.24 mm and 1.33-1.53 mm, respectively. Geometric mean diameter, spherisity, weight, bulk density, true density, porosity and angle of repose were found to be 1.96 mm, 0.71 cm, 3.69 g, 520 kg/m ³ , 975.4 kg/m ³ , 48 per cent and 48.69°, respectively. The Co-efficient of static friction on glass and mild steel were found to be 0.521 and 0.556, respectively.

Molecular and Functional Characterization of FLOWERING LOCUS T Homologs in Allium cepa.

Onion bulbing is an important agricultural trait affecting economic value and is regulated by flowering-related genes. FLOWERING LOCUS T (FT)-like gene function is crucial for the initiation of flowering in various plant species and also in asexual reproduction in tuber plants. By employing various computational analysis using RNA-Seq data, we identified eight FT-like genes (AcFT) encoding PEBP (phosphatidylethanolamine-binding protein) domains in Allium cepa. Sequence and phylogenetic analyses of FT-like proteins revealed six proteins that were identical to previously reported AcFT1-6 proteins, as well as one (AcFT7) with a highly conserved region shared with AcFT6 and another (comp106231) with low similarity to MFT protein, but containing a PEBP domain. Homology modelling of AcFT7 proteins showed similar structures and conservation of amino acids crucial for function in AtFT (Arabidopsis) and Hd3a (rice), with variation in the C-terminal region. Further, we analyzed AcFT expression patterns in different transitional stages, as well as under SD (short-day), LD (long-day), and drought treatment in two contrasting genotypic lines EM (early maturation, 36101) and LM (late maturation, 36122). The FT transcript levels were greatly affected by various environmental factors such as photoperiod, temperature and drought. Our results suggest that AcFT7 is a member of the FT-like genes in Allium cepa and may be involved in regulation of onion bulbing, similar to other FT genes. In addition, AcFT4 and AcFT7 could be involved in establishing the difference in timing of bulb maturity between the two contrasting onion lines.

Developed Water Stress and Crop Coefficients of Dripped-Onion Crop under Arid Conditions of Egypt

The aims of this study were to develop out crop and water-stress coefficients of onion crop under deficit conditions of arid regions. Therefore, field experiments of fully irrigated and deficit conditions with standard agronomic practices of onion crop had been conducted in two successive growing seasons in 2011-2012 and 2012-2013 in order to develop out the crop coefficients of onion plants at different growing stages. Results revealed that crop coefficient values at different growing stages under different management parameter considerations indicated that the observed values of kc are ranged above and dawn of the estimated values of FAO. Meanwhile, data analysis revealed that a general trend of increasing CWU and attributed SCWR from the beginning of cultivation up to the end of bulb formation stage (72 days after sowing seeds), then it decreasing within bulb enlargement and maturity stage.

Screening Onion Plant Introduction Accessions for Tolerance to Onion Thrips and Iris Yellow Spot

Iris yellow spot is an economically important disease of onion that reduces bulb size and yield and is difficult to control. The disease is spread by Thrips tabaci (onion thrips) and disease symptoms are exacerbated by hot, dry climatic conditions that also favor rapid thrips multiplication and make control programs less effective. Currently, no onion cultivar is resistant to the disease and/or thrips. Certain onion foliar characteristics have shown nonpreferential feeding activity by thrips and may be the first step in developing Iris yellow spot (IYS)-tolerant onion cultivars. Seventy-five onion PI accessions from the U.S. germplasm collection were evaluated for leaf color, waxiness (bloom), and axil pattern; thrips number per plant; and IYS disease severity under conditions that favored thrips and disease buildup. Plants of PI 289689 were less attractive to thrips and had a lower number of thrips per plant than plants of most other accessions. These plants were rated as having light green to green-colored foliage and a relatively low amount of epicuticular leaf wax. Plants of PIs 239633 and 546192 generally exhibited less severe IYS disease symptoms than those of other accessions. Individual plants, that exhibited less leaf area exhibiting IYS disease symptoms, were selected at bulb maturity from 22 different accessions with PI 546140 producing the largest number of selected bulbs. Physiological plant development, environmental conditions, and tolerance to plant stress may influence the degree of disease symptom expression. Further work that examines the role of plant maturity and host plant tolerance to stress with respect to disease expression is needed.

Improvement of the seed germination, growth and yield of onion plants by extremely low frequency non-uniform magnetic fields

The effects of pre-sowing magnetic treatments on germination under laboratory conditions and emergence, growth and yield of onion (cv Red Creole) plants under field conditions were investigated. Onion seeds were exposed to 60Hz full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 160mT for 15 and 20min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (2.4m2) and were cultivated according to standard agricultural practices. During vegetative stage and bulb forming, samples were collected at regular intervals for growth rate analyses. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters determined. Under laboratory conditions, the magnetically treated seeds showed a higher germination percentage than the control seeds. Significant differences were found between both treatments and the best finding was found for 160mT for 15min. In field experiments, the treatments led to a significant increase in seedling emergence, root length, seedling height, seedling dry weight and leaf area per plant. Also, at the vegetative stage, the leaf and root relative growth rates of plants derived from magnetically treated seeds were greater than those of the control plants. At the bulb forming stage, bulb relative growth rates from magnetically exposed seeds were greater than those of controls. At the bulb maturity stage, all magnetic treatments significantly increased mean bulb weight, bulb yield per area, number of tunics per bulb, bulb diameter and dry bulb weight in comparison to the controls. The results suggest that pre-sowing extremely low-frequency non-uniform MF treatment has the potential to improve crop productivity of onion through the enhancement of germination, seedling emergence, plant growth, bulb formation and yield.

Effect of deficit irrigation on crop growth, yield and quality of onion in subsurface drip irrigation

India has the largest area under onion (Allium cepa) crop but its average productivity (14.21 t ha -1 ) is considerably lower than the world’s average of 19.4 t ha -1 . Besides low productivity, irrigation efficiencies are also very low i.e. 30-35% in India. Managing onion crop with less than adequate irrigation water availability is a challenge in several parts of the country. Options of i) deficit irrigation (DI) i.e. 20% or 40% less water application at one of the growth stages of the crop and ii) controlled deficit of 20% or 40% on all growth stages i.e. regulated deficit irrigation (RDI) were explored for maximizing IWUE of onion under deficit water application through subsurface drip irrigation. A field experiment was conducted on onion (var. Agrifound light red) for three years from October to May in 2007-08, 2008-09 and 2009-10 to study the effect of DI and RDI on onion yield and its quality under subsurface drip irrigation. In DI treatments, the crop was provided the irrigation with 60% and 80% of ETc creating water stress of 40 and 20%, respectively at developmental (2 nd ), bulb formation (3 rd ) and bulb maturity (4 th ) crop growth stages. In case of RDI treatments, 20% and 40% water stress was created throughout the crop season by applying the irrigation water at 80% and 60% ETc. The maximum yield (44.7 t ha -1 ) was obtained in the full-irrigation treatment (T1). In RDI, 20 and 40% deficit water application saved 19.2 and 41.7% water and resulted in 20 and 32% reduction in yield, respectively. In DI, 20% water deficit in the growth stages of 2 nd , 3 rd and 4 th saved 2.1, 13.2 and 4.6% of water with 19.8, 18.3 and 11.2% reduction in yield, respectively in comparison to full irrigation water application. This suggests that RDI is better option of water saving than DI. Saving of water through RDI may be used to irrigate additional cropped area. Strategy suggested for productions of onion crop can be adopted in large scale to offset high cost of onion, which is cause of concern for all stake holders.

Effect of set-size and planting time on the incidence of bolting, bulbing, and seed yield in two onion cultivars

SummarySets of two onion (Allium cepa L.) cultivars (‘Hygro’ and ‘Delta’), graded into three size classes (12.5, 17.5 and 22.5 mm in diameter) were planted at seven 15-d intervals from 5 December 1995 to 5th March 1996. Flowering and seed production were influenced by set-size. Small sets (12.5 mm in diameter) showed little or no bolting, while the bolting percentage increased with increasing set-size, following a linear relationship. The seed yield per umbel increased with increasing set-size from 12.5 mm to 22.5 mm diameter. Following initiation, inflorescence development (i.e., emergence and floret opening) occurred earlier in plants grown from larger onion sets than from smaller sets. Bolting percentage tended to decrease with late planting of sets (5 March). Maximum seed yield per umbel was observed from the earliest planting (5 December). Delaying planting until 5 March had an enhanced effect on bulb yield. Large sets, being prone to bolting, produced smaller bulb yields than medium or small onion sets. In the earliest planting (5 December), bulbs matured earlier, while the time to bulb maturity was delayed in later plantings.

Effect of temperature and photoperiod on the incidence of bulbing and bolting in seedlings of onion cultivars of diverse origin

SummaryThe effects of temperature and photoperiod on bulbing and bolting in onion (Allium cepa L.) cultivars: ‘Senshyu Yellow’, ‘Jaune Espagnol’, ‘Hygro’, ‘Sito’, ‘Delta’, ‘Australian Brown’, ‘Rijnsburger Balstora’, and ‘Phulkara’ from Japan, Turkey, The Netherlands, The United Kingdom, Australia, and Pakistan were examined under controlled environments in glasshouse conditions in the UK. Plants of each cultivar, at the three-leaf stage, were transferred to a wide range of photo-thermal regimes consisting of six-set point temperatures (6°, 10°, 14°, 18°, 22° or 26°C) and four photoperiods (8, 11, 14 or 17 h d–1). The bulbing ratio in all cultivars increased curvi-linearly with increasing temperature and lengthening photoperiod. Increasing photoperiod promoted bulbing, while under very short photoperiods (8 h d–1) no cultivars bulbed, even after 60 d of growth. The time to bulb maturity decreased linearly with increasing temperature and lengthening photoperiod. Under low temperatures, the time to floral initiation shortened with lengthening photoperiods (8 – 14 h d–1). Under photo-thermal regimes favouring floral initiation, leaf number increased with both increasing temperature and lengthening photoperiod.

Mycorrhizal colonization improves onion ( Allium cepa L.) yield and water use efficiency under water deficit condition

Most plants benefit from mycorrhizal symbiosis through improvement of water status and nutrient uptake. A factorial experiment with complete randomized blocks design was carried out in greenhouse at Tabriz University, Iran in 2005–2006. Experimental treatments were (a) irrigation interval (7, 9 and 11 days), (b) soil condition (sterile and non-sterile) and (c) arbuscular mycorrhizal fungi (AMF) species ( Glomus versiforme, Glomus intraradices, Glomus etunicatum) and non-mycorrhizal (NM) plants as control. Onion ( Allium cepa L. cv. Azar-shahr) seeds were sown in sterile nursery and inoculated with fungi species. One nursery left uninoculated as control. Nine weeks old seedlings then were transplanted to the pots. Average pre-irrigation soil water contents reached to about 67, 61.6 and 57.5% of FC corresponding to 7, 9 and 11 days irrigation intervals, respectively. At onion bulb maturity stage (192 days after transplanting), yield, water use efficiency (WUE) and yield response factor ( K y ) were determined. The results indicated that AMF colonization increased soil water depletion significantly. G. versiforme under both soil conditions (sterile and non-sterile) and G. etunicatum in sterile soil depleted soil water effectively ( P < 0.05). Mycorrhizal fungi improved WUE significantly ( P < 0.0001) in both soil conditions. It raised by G. versiforme about 2.4-fold (0.289 g mm −1) in comparison with the control (0.117 g mm −1). G. intraradices and G. etunicatum also had significantly higher WUE than control. Apparently water deficit in 11-day irrigation interval led to lower yield and WUE compared to 9-day interval; the later resulted highest WUE (0.254 g mm −1). Mycorrhizal plants increased seasonal ET significantly due to enhancing in plant growth; G. versiforme in both sterile and non-sterile soil and G. etunicatum in sterile soil had the highest ET. Bulb yield was influenced by irrigation period and fungi species. G. versiforme produced higher yield than other treatments (135.27 g/pot). Mycorrhizal plants in 11-day irrigation interval in spite of suffering from water stress had more bulb yield than non-mycorrhizal plants in all irrigation intervals. Yield in general was higher in 9-day treatments than other irrigating internals significantly ( P < 0.05). Onion yield response factor ( K y ) was decreased by AMF colonization; implying that symbiosed plants become less responsive to water deficit (longer irrigation interval) compared to the control ones.

Induction of bulb maturity of Ornithogalum thyrsoides

The influence of bulb maturity at bulb harvest on growth and flowering response of Ornithogalum thyrsoides Jacq. ‘Chesapeake Starlight’ was investigated. Experiments were designed to determine if bulb maturity can be induced by bulb storage temperatures and whether bulb maturity can be evaluated by flowering responses. Bulbs with all senesced leaves at harvest were considered “mature” or with emerging young leaves and re-growing young roots were considered “immature”. Bulbs were potted after 0, 3, and 6 weeks of 30 °C or 2 weeks of 10 °C given either in the middle or at the end of 6 weeks of 30 °C. Mature bulbs, as compared to immature bulbs, took longer for leaves to emerge when control bulbs that did not receive any temperature treatment after harvest were planted upon harvest. Leaf emergence of the immature bulbs was significantly earlier than that of the mature bulbs. Mature bulbs which received 30 °C for 3 weeks (30 °C/3 week) flowered 31 days faster than immature bulbs and all bulbs flowered. Leaf emergence and flowering of mature and immature bulbs that received 30 °C/6 weeks or 2 weeks of 10 °C in the middle of 6 weeks of 30 °C (30 °C/2 weeks–10 °C/2 week–30 °C/3 weeks) did not differ from each other. Maturity can be induced by storing immature bulbs at 30 °C/6 weeks. Maturity, as evaluated by flowering percentage and days from leaf emergence to flowering, can be induced in O. thyrsoides. Immature bulbs can, therefore, be harvested for later forcing as long as bulbs are treated with 30 °C/6 weeks. It is proposed that maturity can be correlated with the speed of flowering and bulbs can be harvested at immature physiological state for forcing. Postharvest high-temperature treatment can be used to force immature bulbs that were harvested before the senescence of the leaves.

Response of onion (Allium cepa L.) to combined application of biological and chemical nitrogenous fertilizers

A field experiment was conducted during the summer season of 2000-2001 at the Vegetable Research Farm of Indian Agricultural Research Institute (I.A.R.I.), New Delhi (India) to test the efficacy of three Azotobacter strains as a potential supplement to nitrogenous fertilizer in improving growth and yield of onion cv. Pusa Madhvi. The treatments consisted of factorial combination of four levels of nitrogen (0, 25, 50 and 75 kg N ha -1 ) and three Azotobacter strains (CBD-15, AS-4 and M-4) with two uninoculated controls one with full dose of N (100 kg ha -1 ) and the other without NPK. Application of 75 kg N ha -1 along with inoculation of CBD-15 was found to have significantly increased most of the growth and yield parameters, soil available nitrogen, and nitrogen content in the bulb followed by M-4 inoculation as compared to application of full dose of nitrogen without the inoculation. Days to bulb initiation were significantly reduced due to inoculation with CBD-15 or M-4 along with 50 kg N ha -1 whereas days to bulb maturity were significantly reduced due to inoculation with any of the strains along with the same N rate (50 kg ha -1 ) as compared to application of full dose of nitrogen without the inoculation. The finding demonstrated a saving of 50 kg N ha -1 without significantly affecting yield and an average increase of 13.5% marketable yield due to Azotobacter inoculation in the presence of 75 kg N ha -1

Within- and Between-family Variability for Important Bulb and Plant Traits among Sexually Derived Progenies of Garlic

Until recently, there has been no large-scale production of true seeds in garlic (A. sativum L. and A. longicuspis L.). The recent discovery of male fertile garlic accessions stimulated research on the genetics and breeding of garlic. However, there is no information regarding the phenotypic characteristics of garlic populations generated from true seeds. We evaluated the first generation of sexually derived families of garlic for bulb and clove weight, number of cloves per bulb, flower stalk height, number of leaves, plant height, and days required to achieve bulb maturity. Significant variations were observed within and among families for these important traits.

Selection for bulb maturity in onion

It is possible to produce onions (Allium cepa) all over the year in Brazil, but most of the Brazilian cultivars have poor quality bulbs, a fact that favours onion imports from Argentina, a producer of Valenciana type cultivars that does not bulb in Brazil, but please Brazilian consumers. To study the effect of selection for bulb maturity, seventeen half sib progenies selected for early maturity and twenty five for late maturity, from the intervarietal triple cross [Crioula x (Pira Ouro x Valenciana Sintetica 14)] were grown, along with the triple cross itself and the cultivars Pira Ouro (short-day), Crioula (intermediate-day) and Armada (long-day). A total of forty six treatments were tested in a randomized block design with three replications of 32 plants per plot. The progenies selected for earliness had cycles from 67 to 83 days, whereas those selected for lateness had cycles of 85 to 103 days. This difference was evident when comparisons were made for the percent thick neck bulbs, which varied from 0 to 6.2% and from 8.1 to 59.8% for the early and late progenies, respectively. High heritability estimates were obtained for all characters and they varied from 0.65 (thick neck percentage, in the late selection) to 0.80 (average bulb weight, in the early selection). Progenies of higher bulb weight and maturity similar to the standard cultivars were obtained. Selection for maturity was highly efficient and the population selected for early maturity has potential to originate adapted cultivars, with bulb yield and quality superior to the available cultivars.

Nitrogen Use Efficiency and Onion Yield Increased with a Polymer-coated Nitrogen Source

Nitrogen (N) losses can be substantial in furrow-irrigated onions (Allium cepa L.). Polymer-coated urea (PU) may reduce N losses and result in an increase in productivity. In this study, we investigated the effects of different rates and blends of urea and PU on onion yield and N use for two cropping seasons. Nitrogen was applied at 112, 168, and 224 kg·ha-1 as PU or urea. In addition, three PU/urea blends equal to 224 kg·ha-1 of N were compared. Plant growth and N concentration, soil nitrate concentrations, and bulb yield were evaluated each year. Onion yield decreased by 95 Mg·ha-1 for each 25% increase in the proportion of urea in the fertilizer blends. Reducing the N rates from 224 to 112 kg·ha-1 had minimal effect on bulb yield when all the fertilizer was supplied by urea. A reduction of N applied from 224 to 168 kg·ha-1 had little effect on yield, although a further reduction to 112 kg·ha-1 did significantly reduce bulb yield when the entire N was supplied from PU. Nitrogen source and rate had no effect on bulb maturity and only minor effects on leaf area and storage potential. Soil sampling indicated that more N was retained in PU-treated onion beds than in urea-treated beds, which improved nitrogen use efficiency. In addition, N use efficiency improved when there was more PU in the blend and when PU was compared with urea at the same rate. We conclude that the use of PU can dramatically improve N use efficiency and productivity in direct-seeded onions.

'NuMex Chaco' Onion

Additional index words. Allium cepa, vegetable breeding, Phoma terrestris tion of yellow and white bulbs. Six families that produced only yellow bulbs were selected and recombined in 1989. In 1991, 1993, 1995, and 1997, selections were made using recurrent selection and each year’s selections were intercrossed to form the next generation. The selection criteria were the same as mentioned previously except that the last three generations were also selected for the production of single growing points per bulb (single center). Selection for bolting resistance was done from field plantings that possessed 70% or more plants with seedstalks. Seeds were planted on an early planting date (around 1 Sept.) to induce seedstalk production. This date is three to four weeks earlier than the earliest recommended planting date for fall-planted onions in southern New Mexico. Selection for pink root resistance was accomplished by planting selections in fields that were severely infested with P. terrestris. At bulb maturity, bulbs were rated for the incidence of pink root on their root system. Only bulbs that possessed a healthy root system with minimal symptoms of pink root were selected. Selection for bulb shape was for a medium depth grano shape, and for a bulb that was more rounded, with less pronounced shoulders and taper than a typical grano shape. Selection for bulb shape uniformity was for