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Plant population and weed management are among major factors constraining onion production. Therefore, field trial was conducted in Birnin Kebbi, Nigeria during the 2017/2018 and 2018/2019 dry seasons to assess the bulb size distribution of onion under the influence of plant population and weed control practice. The treatments was made of three plant population (500,000, 333,333 and 250,000 plants/ha) and weed control methods (pendimethalin @ 1.0 kg a.i. ha-1 + 1 Hw: pendimethalin @ 1.5 kg a.i. ha-1: pendimethalin @ 2.0 kg a.i. ha-1: butachlor @ 2.0 kg a.i. ha-1 + 1 Hw: butachlor @ 2.8 kg a.i. ha-1: butachlor @ 3.6 kg a.i. ha-1: fluaxifop-P-butyl @ 2.0 kg a.i. ha-1: oxyfluorfen @ 1.0 kg a.i. ha-1 + 1 Hw: two weeding at 3 and 6 weeks after transplanting (WAT): three weeding at 3, 6 and 9 WAT: weed free and weedy check). The experiment was laid out in Randomized Complete Block Design and replicated three times. Results showed that onion bulb size distribution was not significantly affected with plant population treatments. The use of pendimethalin and butachlor at 1.0 and 2.0 kg a.i. ha-1 two days after transplanting followed by one hoe weeding respectively at 6 WAT recorded the highest bulb size distribution of onion. Weeding 3 times was second best and it can serve as an alternative to the aforementioned practice. It can be concluded that the integration of two methods such as pendimethalin at 1.0 kg a.i ha-1 or butachlor at 2.0 kg a.i ha-1 followed by one hoe weeding at 6 WAT was significantly superior to other methods and therefore, recommended for onion farmers in the study area as best practice for weed control.

The effect of planting time (September, October and November) and the size of flower bulbs (12.1-14, 10.1-12 and 8.1-10 cm) on flower quality and flowering period of natural Narcissus tazetta naturally grown in Ordu in Black Sea region were investigated. Tepal width, tepal length, corona diameter, corona length, perianth tube length, flower size, flower stem length, flower stem diameter, the pedicel length, ovary length, the number of flowers per stem, flower diameter, number of leaves, leaf width, leaf length, vase life, yield and flowering period were determined. The best quality of flowers as well as the highest flowering rate was obtained from the flower bulbs with a circumference of 12-14 cm. The smaller bulbs with a circumference of 10-12 cm gave only a few flowers whereas the smallest ones did not give any flowers. Therefore, it is suggested that the minimum circumference of the bulbs should be at least 12-14 cm for cut flower production of Narcissus tazetta. September was the best planting time for Narcissus tazetta cut flower production as to the flower quality and harvest period. The flowering period was extended to about 3 months from January 15 to April 11 by planting the bulbs at 3 different times. © 2019 International Society for Horticultural Science. All rights reserved. This research project (PYO.ZRT. ? ? ? ?. ? ?. ? ? ?) was supported by Project Management Office of Ondokuz Mayis University in Samsun, Turkey.

Experiments were conducted at Horticulture Research Division (HRD), Khumaltar, Lalitpur; and Horticulture Research Station (HRS), Kimugaun, Dailekh in 2017/18 to evaluate the high yielding open pollinated genotypes of onion in mid hills of both locations. Five onion genotypes namely AVON-1016, AVON-1027, AVON-1028, AVON-1052, AVON-1074 and AVON-1103 received from Asian Vegetable Research and Development Centre were evaluated with local check variety and recommended variety Red Creole in both locations in randomized complete block design with 4 replications. The main objective of the experiment is to findout the high yielding open pollinated onion genotypes for mid hill condition.The pooled analysis of data over locations showed significant differences on plant height, neck diameter, bulb diameter, weight of bulbs and adjusted bulb yield per hectare. Introduced genotypes AVON 1027 (38.83 t/ha), AVON 1052 (31.97 t/ha) and AVON 1028 (31.48 t/ha) produced significantly higher yield than recommended and commercially cultivated check variety Red Creole (27.04 t/ha). Therefore the genotype AVON 1027 can be selected as the best genotype for growing in mid hills of Nepal

Lilium longiflorum is a wild Lilium, and its flowering transition requires a long period of cold exposure to meet the demand of vernalization. The responses of different sized bulbs to cold exposure and photoperiod are different, and the floral transition pathways of small and large bulbs are different. In this study, small and large bulbs were placed in cold storage for different weeks and then cultured at a constant ambient temperature of 25 °C under long day (LD) and short day (SD) conditions. Then, the flowering characteristics and expression patterns of key genes related to the vernalization and photoperiod pathways in different groups were calculated and analyzed. The results showed that the floral transition of Lilium longiflorum was influenced by both vernalization and photoperiod, that vernalization and LD conditions can significantly improve the flowering rate of Lilium longiflorum, and that the time from planting to visible flowering buds’ appearance was decreased. The flowering time and rate of large bulbs were greatly influenced by cold exposure, and the vernalization pathway acted more actively at the floral transition stage. The floral transition of small bulbs was affected more by the photoperiod pathway. Moreover, it was speculated that cold exposure may promote greater sensitivity of the small bulbs to LD conditions. In addition, the expression of LlVRN1, LlFKF1, LlGI, LlCO5, LlCO7, LlCO16, LlFT1, LlFT3 and LlSOC1 was high during the process of floral transition, and LlCO13, LlCO14 and LlCO15 were highly expressed in the vegetative stage. The expression of LlCO13 and LlCO14 was different under different lighting conditions, and the flowering induction function of LlCO9 and LlFT3 was related to vernalization. Moreover, LlFKF1, LlGI, LlCO5, LlCO16, LlSOC1 and LlFT2 were involved in the entire growth process of plants, while LlCO6, LlCO16 and LlFT1 are involved in the differentiation and formation of small bulblets of plants after the inflorescence stage, and this process is also closely related to LD conditions. This study has great significance for understanding the molecular mechanisms of the vernalization and photoperiod flowering pathways of Lilium longiflorum.

Khon Kaen Agriculture Journal, 49, 6, 1563-15571

Constraints are reported for the low productivity and quality of onion seed production in Ethiopia. Therefore, a field experiment was conducted at Kobo sub-center research station and Libso investment farm to study the influence of planting date and onion bulb size on yield and quality of onion seed. The experiment was laid out in Randomized Complete Block Design with three replications and involved three levels of onion bulb sizes and four levels of planting dates. The results of the study revealed that significant interactions between planting date and mother bulb size on seed yield ton ha-1, germination percentage, seed vigor index I and seed vigor index II. The highest seed yield (2.8 tons ha−1) was recorded from large onion bulbs of a size planted at Kobo early—October. Planted onion bulbs early-October increased seed yield (ton ha−1 by 21.7%) than planted early-November. Regarding onion bulb size, large bulbs increased seed yield (ton ha−1 by 40%) than the small bulbs. The highest (97.3) germination percentage was recorded from large onion bulbs planted at Kobo in early-October. Therefore, for the production of better yield and quality of onion seeds, early-October planting and large onion bulbs (4.1–5 cm) can be recommended in the study areas and other similar agro-ecology areas of the country.

The combined application of humic substances and mycorrhizal inocula under increased CO in the air is a promising horticultural technique for improving the quality of greenhouse-grown onion seedlings. The objective of this study was to evaluate if the development and qualitative characteristics of bulbs from the yellow onion Allium cepa L. Alfa São Francisco improved with the application of the abovementioned agronomic, biotic, and environmental factors. The lowest dry matter was achieved in bulbs of onions not inoculated with mycorrhizal fungi, non-amended with humic acids (HA), and grown at ambient CO. Mycorrhizal inoculation significantly increased bulb biomass in plants cultivated at ambient CO, and not fertilized with HA, which may be a consequence of the enhanced acid phosphatase activity in roots. The application of HA always increased bulb dry matter, which were more evident at elevated rather than ambient CO conditions and correlated with improved acid phosphatase activity in the plants at elevated CO. Mycorrhizal inoculation, HA supplementation, and elevated CO in the air had an additive effect of increasing the content of soluble sugars, proteins, and phenolics in bulbs. While high levels of sugars and proteins enhanced the energetic value of onions, the increase in phenolics improved their antioxidant properties. The triple interaction between mycorrhization, HA fertilization, and elevated CO also increased the ratio between soluble solids and total titratable acidity, which may enhance the perception of sweetness and make onions more pleasant for consumption., This study has been supported by the ‘Ministerio de Ciencia e Innovación’ (Spain) (BFU2011-26989). Marcelle M. Bettoni received a grant from ‘Los CAPES y Coordenação do Programa de Pós-graduação em Agronomia - Produção Vegetal’ from the Brazilian Government.

The effects of planting time and bulb size on the plant growth and development characteristics of Narcissus tazetta (‘Paperwhite’, ‘Bunch-Flowered Narcissus’) flowers were investigated as one of the first studies on quantitative analysis of bulbous flowers. Narcissus tazetta bulbs, which were removed from their native habitat in August, were divided into three sizes (12.1 to 14, 10.1 to 12 and 8.1 to 10 cm) according to the circumference and planted at 3 different times (September, October and November). After harvest, stem weight ratio, leaf weight ratio, leaf area ratio, specific leaf area, leaf thickness were determined as quantitative measurements. Leaf area was measured by planimeter. Dry weights of plant samples were determined and plant growth parameters were calculated according to the models adapted to the bulbous plants. Results on growth parameters showed planting time significantly affected the leaf thickness, leaf weight ratio and stem weight ratio. The differences among the bulb sizes were not statistically significant on quantitative measurements. Planting time and bulb size did not affect the leaf area ratio and specific leaf area. The results showed that plant growth parameters can be used in modeling studies on cut flower production of bulbous flowers. © 2019 International Society for Horticultural Science. All rights reserved. These results are belong to the master research project (PYO.ZRT. ? ? ? ?. ? ?. ? ? ?) supported by Project Management Office of Ondokuz Mayis University in Samsun, Turkey.

An experiment was conducted aiming to find out the seed production potentiality of 19 local and exotic onion cultivars. The analysis of variance showed significant differences among the genotypes for all characters except sprouting percentage, number of flowers per umbel and number of umbel per bulb. Maximum number of days to 50% bolting (52.67) was exhibited by the genotype G2 and minimum by G6 (27.00 days). The larger bulb size after harvest was obtained from G14 and G19 (18.11 g). Genotypes G4 and G11 required the maximum (16.66) and the minimum (9.00) days for 100% sprouting, respectively. The highest stalk length was found in the genotype G1 (67.23 cm) and the lowest in G8 (38.47 cm). Maximum number (5.75) of stalk was produced by the genotype G7 and minimum number (2.09) of stalk by the genotype G11. The genotype G1 produced the highest number of seeds per umbel (1395.92) and seed yield per plant (4.29 g). The lowest (0.45 g) seed yield per plant and maximum bulb weight was obtained by the genotype G8.

Hippeastrum flowers in the spring, but the exact flowering time can be controlled by applying specific thermal regime to large sized bulbs. To control the flowering time, and improve quality and size of Hippeastrum (Hippeastrum hybridum, cv. Red Lion) bulbs, the effect of temperature regime was investigated. The objectives of this research were to study the effect of ambient temperature on the growth rate of bulbs, the effect of soil temperature on the growth rate of bulbs and the susceptibility of several bulbs' sizes to various thermal regimes. Two sets of experiments were conducted: A phytotron experiment with six day/night temperature combinations and a controlled greenhouse experiment in which five levels of minimum soil temperature treatments were imposed. Temperature had a strong effect on bulb and leaf development. Temperatures of 27℃ were optimal for leaf area development while temperatures of 22℃ were optimal for bulb development. Different patterns of bulb growth rate were found when bulbs of different initial sizes had grown under the same minimum growing temperature (22℃): The small bulbs (initial diameter of 5.4cm) had grown about two cm throughout the season (180 growing days) while the large bulbs (initial diameter of 7.9cm) had grown less the one cm. The growth rate of the other three initial bulb size categories (6.1, 6.7 and 7.3cm) varied between these two rates. A high linear temperature dependent correlation was found between leaf area and bulb size. The distribution of the fresh matter among the roots, leaves and bulbs was also found to be temperature dependent.

One of the major problems of Hippeastrum is the large amount of labor involved in its production. There are three common methods for the propagation of the Hippeastrum: Seeds, offset bulblets and twin scaling. Study on various cutting methods for the propagation of Hippeastrum was conducted in the Northern Israeli Negev Desert during two consecutive years. Fewer bulblets were developed when the mother bulb was divided into un-separated sections, compared to twin scales. Increasing the number of sections into which the bulb was divided resulted in larger number of bulblets. No correlation between the number of sections and the average weight of bulblets was found. The total weight of all the bulblets derived from one bulb, doubled after one growing year. Propagation coefficient, defined as the ratio between the bulblets number to the number of section into which the bulb was divided, was larger than one unit when the bulbs were cut into un-separated sections and smaller than one unit when the twin scaling method was used. Higher economic profit was found when the bulbs were divided into un-separated sections. By using the un-separated section method, it was possible to receive bulbs ready for marketing one year sooner, when compared to the twin scaling method. The greatest economical profit is expected when the mother bulb was divided into eight un-separated sections.

Flowering time of Hippeastrum can be controlled by applying specific thermal regime to large sized bulbs. Due to high-energy costs, the aim of this study was to examine the possibility to reduce soil heating and keep high bulb growth rate by increasing the CO_2 concentration. Two sets of experiments were carried out in a controlled greenhouse at the North-Western Israeli Negev Desert. In both experiments, bulbs of different initial sizes were grown under two levels of CO_2 concentrations (ambient, 350ppm and elevated, 1000ppm) combined with different minimum soil temperature regimes. In the first experiment three temperature regimes (16℃, 22℃ and 24℃) were tested, while in the second experiment only one minimum soil temperature regime (22℃) was investigated. In both experiments, raising CO_2 concentration from the ambient level to elevated one, or increasing soil temperature resulted in a higher bulb growth rate. Temperatures, CO_2 concentration and initial bulb size significantly influenced the final diameter of the bulbs. A significant difference in final bulb diameter was obtained only between the 16℃ treatment and the 22℃ and 24℃ treatments, but not between the two high temperatures tested. The area of the largest leaf was significantly affected only by the soil temperature treatments. No effect of CO_2 concentration on leaf area development was detected. The number of leaves, however, was affected by the CO_2 but not by the temperatures. Bulbs grown under elevated CO_2 had a higher flowering rate compared to ambient CO_2. This was effective both in shortening the period of time from replanting until flowering and by the significant high number of flowers compared to the ambient CO_2 conditions.

Environmental, genotypic and agronomic factors have an effect on the yield value of an onion crop, which is determined primarily by number, weight and size of bulbs. Spatial variability of soil properties affects crop yield. Remote sensed hyperspectral vegetation indices (VIs), calculated using crop reflectance at field scale can be used either as an index of the plant biophysical status, or as a tool to estimate crop variability. The aim of the study was to evaluate the relationships among traditional agronomic measurements of two irrigated onion hybrids (Cometa and Red Mech) with spectroradiometric measurements taken at field scale. The two hybrids differed significantly either for agronomic response (yield, yield components and distribution of yield classes) or for their spectral properties. Cometa showed significant higher yield and biomass than Red Mech, as well as significant higher VI values, although no correlations were found among agronomic parameters and spectroradiometric indices. On the contrary, Red Mech showed significant correlation among biomass, yield and bulb weight with VIs. Differences between the two onion hybrids in the spectroradiometric readings and agronomic traits underlined the importance of ground truth data verification when air-born images or satellite data are taken over onion crop field. © 2013 Elsevier B.V.

[EN] 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 co- efficients 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.

An experiment was conducted aiming to find out the seed production potentiality of 19 local and exotic onion cultivars. The analysis of variance showed significant differences among the genotypes for all characters except sprouting percentage, number of flowers per umbel and number of umbel per bulb. Maximum number of days to 50% bolting (52.67) was exhibited by the genotype G2 and minimum by G6 (27.00 days). The larger bulb size after harvest was obtained from G14 and G19 (18.11 g). Genotypes G4 and G11 required the maximum (16.66) and the minimum (9.00) days for 100% sprouting, respectively. The highest stalk length was found in the genotype G1 (67.23 cm) and the lowest in G8 (38.47 cm). Maximum number (5.75) of stalk was produced by the genotype G7 and minimum number (2.09) of stalk by the genotype G11. The genotype G1 produced the highest number of seeds per umbel (1395.92) and seed yield per plant (4.29 g). The lowest (0.45 g) seed yield per plant and maximum bulb weight was obtained by the genotype G8., Istraživanje je provedeno s ciljem utvrđivanja potencijala sjemenske proizvodnje 19 domaćih i stranih kultivara luka. Analiza varijance pokazala je signifikantne razlike između genotipova za sva svojstva, osim postotka naklijavanja, broja cvjetova po štitastom cvatu i broja štitastog cvata po lukovici. Maksimalan broj dana do 50% naklijavanja (52,67) je svojstvo genotipa G2, a minimalan (27,00 dana) je svojstvo genotipa G6. Nakon vađenja utvrđena je veća lukovica kod genotipova 14 i 19 (18,11 g). Genotipovi G4 i G11 trebali su maksimalno 16,66 dana, odnosno minimalno 9,00 dana za 100% naklijavanja, redosljedom. Genotip G1 imao je najdulju (67,23 cm), a G8 najkraću (38,47 cm) stabljiku. Maksimalan broj stabljika (5,75) ustanovljen je kod genotipa G7, a minimalan (2,09) kod genotipa G11. Ustanovljeno je da G1 ima najveći broj sjemena po štitastom cvatu (1395,92) i prinosa sjemena po biljci (4,29 g). Najniži prinos sjemena (0,45 g), kao i najteža lukovica po biljci dobiveni su od genotipa G8.

Two field experiments were carried out. In the first experiment, 13 variables were studied for 3 inbred groups as influenced by genetic differences, source of pollen, soil moisture, fertilizers , and size of bulbs. Path-coefficient analysis was made of var ious insect pollinators influencing seed yield in different inbreds, and of components of seed production in all inbreds together. In the second experiment, 4 variables were studied for one male-sterile inbred and one male-fertile inbred as influenced by soil moisture and fertilizers. Genetic differences among inbreds were the most important source of variation in seed yields. This points out that a major portion of the onion seed problem could be solved through plant breeding. The inbreds differed very significantly in t heir attractiveness to pollinating insects, probably as a result of varying genetic vigor which influenced nectar formation. Most of the inbreds had negative correlation or no correlation between the number of honey bee nectar collectors and seed yield. The separation of correlation with honey bee nectar and pollen collectors into components of direct and indirect effects indicates that the number of pollinating insects was excessive for all inbreds in the experiment. Negative direct effects on seed yield and negative indirect effects through percent fertilized flowers and seeds per fertilized flower disclose some important aspects as possible causes for low onion seed yields: 1. Depletion of assimilated food needed for the development of fertilized ovules through an overdraw on nectar by nectar collectors. 2. Water deficit affecting fertilized developing ovules due to increased transpiration resulting from overhandling of flowers by honey bees, especially by pollen collectors, which through nervous search for pollen on male- sterile lines might cause enough physical damage to increase transpiration even at low visitation levels. At high visitation levels, pollen collectors might also harm male-fertile lines. 3 . Removal of pollen from the stigmas of male-sterile flowers by high populations of pollen collecting honey bees. Compatibility of the pollen parents with the male-sterile inbreds was influenced by soil moisture levels. At high moisture, M611C increased seed yields while B12115-2C decreased them. At low moisture the reverse was true. In the first experiment there was no significant yield response to varying soil moisture levels due to contrasting effects of high soil moisture on compatibility with pollen parents. In the second experiment, the pollen parent B2215C was used and a significant favorable response to high soil moisture was obtained. Salinity aspects and the effects of indiscriminate use of fertilizers were tested through the method of fertilizer placement. While fertilizers reduced seed yield , high soil moisture tended to reduce the negative effects of nitrogen and to produce favorable response to phosphorus. Seed yield followed the trend in plant survival as affected by the induced salinity x moisture relationships. The size of bulbs had a great influence on seed yields, mainly through an increased number of umbels per plant. It seems that the number of umbels per plant had more influence on the number of flowers per row than did the number of flowers per umbel. Path-coefficient analysis of components of onion seed production indicates that the percentage of fertilized flowers is the most important criterion for selection to improve seed yield. It would be ideal to combine both high percentage of fertilized flowers and large number of flowers per umbel, but if compromise has to be made, selection would best be considered on the basis of greater percentage of fertilized flowers in the umbel. Plants which have a large percentage of fertilized flowers can be easily detected at the pre-seed harvest stage.