Control Bulbs Research Articles

First Report of Fusarium proliferatum Causing Basal Rot and Dry Rot on Onion Bulbs (Allium cepa) in Spain.

Spain is the second largest onion-producing country in Europe with 1,465,430 tons and an export value of 584 million € in 2021 (MAPA 2022). In summer 2022 rot bulb symptoms were observed in five commercial fields and during the storage of cultivars 'Orlenda', 'Veleta', 'Mallory', 'Citation' and 'Pantano' from La Roda in Albacete (Castilla-La Mancha, Spain). Approximately 20% of sampled bulbs (113 bulbs analyzed) were affected with dry scales showing brown to dark brown rot on the top and basal plate of the onion bulbs. Occasionally, white to light pink fungal mycelium was observed between rotten scales and the plate basal. Sections of dry scales (5-10 mm) of the apical and basal plate were cut and placed on potato dextrose agar (PDA) and Komada medium (Komada 1975). From 5-day-old cultures typical white to light pink mycelium with microconidia in chains formed on polyphialides and macroconidia resembling Fusarium proliferatum (Nelson et al. 1983). To confirm the pathogen identity, partial translation elongation factor 1-alpha (TEF1) and RNA polymerase II subunit 2 (RPB2) genes were amplified and sequenced using primers reported in O´Donnell et al. (1998) and Samuels et al. (2002) for TEF1 and Liu et al. (1999) for RPB2. In BLAST analyses, the sequences showed 100% identity to the corresponding region of F. proliferatum (KP964908 and JF740801). Sequences were submitted to GenBank, and registered accession numbers are OR061014-16 for TEF1 and OR061017-19 for RPB2. Pathogenicity tests were conducted by inoculating healthy onion bulbs (five replicates per treatment) on the apical and basal plate by placing a 7-day old mycelial plug (10 mm diameter) from PDA cultures. Two onion cultivars ('Pandero' by Nunhems USA and 'Mallory' by Bejo The Netherlands) were inoculated separately with three isolates (PRO1, PRO9, PRO12). Control bulbs were inoculated with sterile PDA. The experiment was carried out twice. All bulbs were placed in a moist chamber and incubated at 25°C in the dark. After 15 days, bulbs inoculated with mycelial plugs showed similar symptoms to those of the original diseased bulbs. Browning dry rot was observed on the apical and basal plate of bulbs. When bulbs were cut longitudinally inner progressing rot was observed. Control bulbs remained symptomless. In both experiments, F. proliferatum was successfully re-isolated and morphologically confirmed from symptomatic bulbs to fulfill Koch's postulates. These results confirmed that isolates PRO1, PRO9 and PRO12 were the pathogen causing basal and dry rot on onion bulbs. This pathogen has recently been identified in China on Allium cepa L. var. agrogatum (Liu et al. 2022) and Idaho on onion (Beck et al. 2020) and could become a serious threat to onion production in Spain, reducing the quality and yield of onion.

Early Detection of Fusarium Basal Rot Infection in Onions and Shallots Based on VOC Profiles Analysis.

Gas chromatography ion-mobility spectrometry (GC-IMS) technology is drawing increasing attention due to its high sensitivity, low drift, and capability for the identification of compounds. The noninvasive detection of plant pests and pathogens is an application area well suited to this technology. In this work, we employed GC-IMS technology for early detection of Fusarium basal rot in brown onion, red onion, and shallot bulbs and for tracking disease progression during storage. The volatile profiles of the infected and healthy control bulbs were characterized using GC-IMS and gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS). GC-IMS data combined with principal component analysis and supervised methods provided discrimination between infected and healthy control bulbs as early as 1 day after incubation with the pathogen, classification regarding the proportion of infected to healthy bulbs in a sample, and prediction of the infection's duration with an average R2 = 0.92. Furthermore, GC-TOF-MS revealed several compounds, mostly sulfides and disulfides, that could be uniquely related to Fusarium basal rot infection.

Sustainable nano-interventions to enhance crop yield, anthocyanin content, and marketability of onion (Allium cepa)

Introduction: Agriculture predominantly follows three farming systems: natural, organic (organic manures for soil nutrition), and agrochemical intensive. Agrochemical-intensive farming uses synthetic fertilizers, insecticides, pesticides, and weedicides. It holds the most prominent place in the modern agriculture business. Humankind realizes that over-reliance on synthetic agrochemicals has resulted in the declining health of the ecosystem’s soil, water, and living species. It must explore strategies to reduce synthetic agrochemicals without compromising agricultural production to restore the ecological balance. Nano-formulations help lower dosages of agrochemicals, leading to the emergence of nano-agriculture. However, the critical challenge is how we could exploit nanomaterials’ power to selectively improve crop plants’ metabolic performance so that it has a better competitive edge in the field to withstand the nutrient-seeking pressure exerted by other plants.Methods: Here we have achieved the same by root treatment of the onion crop and then growing them in the presence of organic goat manure.Results: In a 2 years field trial with onion crops, we report an increase in yield through root treatment with nano-pyrite (FeS2) plus soil application of goat dropping (Test) as compared to the use of goat dropping alone (Control). In the first-year field trial (November 2018- April 2019), the total biomass (bulb + leaf) weight of the test sample was 4.75 kg (n = 86), while control samples weighed 3.5 kg (n = 83). The total bulb weight for the control and test was 2.6 and 3.6 kg, respectively. In the second-year field trial (December 2019- April 2020), the total biomass of the test sample was 2.65 kg (n = 64), while control samples weighed 2.30 kg (n = 64). We observed a yield-boosting effect of root treatment with nano-pyrite plus soil application of goat dropping in onion crops. As monitored by spectroscopic absorbance, there is a significant increase in the anthocyanin content in test bulbs (0.069) compared to control bulbs (0.02). Similarly, the relative flavanol content in test leaves (0.253) was significantly higher compared to the control samples (0.086). We have integrated nano-agriculture and organic farming, resulting in a hybrid form; nano-organic farming bolsters the metabolic fitness of the onion (Allium cepa) to achieve sustainable food production.

First Report of Neck Rot Caused by Botrytis aclada on Onion (Allium cepa L.) in Gansu Province, China.

Onion (Allium cepa L.) is one of the most important cultivated vegetable crops in many countries, including China (Hanci 2018; Steentjes et al. 2021). Gansu, in the northwest region of China, is a major area of onion production (Zhang et al. 2022). In October 2021, typical symptoms of neck rot were observed on stored onion bulbs (cv. Honghe) in Jiuquan, Gansu Province, China. Further surveys of 20 bags of onion bulbs randomly selected in a storage facility with bulbs harvested from 73 ha indicated that approximately 5% of the bulbs had typical neck rot symptoms. The neck of infected bulbs developed a water-soaked decay, with softened and discolored inner scales with white to gray mycelium in the neck. Infection usually began in the neck and sometimes spread through the entire bulb. In severely affected bulbs, the fleshy scales were span style="font-family:'Times New Roman'">decayed and the bulbs had shrunk, with black sclerotia between the rotting scales in the neck and shoulders of the bulb. Small pieces cut from the margins of lesions were surface-disinfested with 75% ethanol for 10 s, and 1% NaClO for 1 min, rinsed three times in sterile distilled water, dried on sterile filter paper, placed onto potato dextrose agar (PDA), and incubated at 20 ± 1℃ for 5 days in the dark. Ten pure cultures were obtained by single-spore isolation (one from each of 10 bulbs). All 10 isolates produced colonies that initially were white, and became gray to dark in color with gray mycelium that was covered with abundant conidia resembling Botrytis species when cultured on PDA at 20 ± 1℃ for 10 days in the dark. Conidia (n = 100 per isolate) were one-celled, ellipsoid or ovoid, beige to dark brown, and 5.6 to 14.8 × 3.9 to 8.5 μm. Sclerotia were not produced by any of the isolates on PDA after incubation at 20 ± 1°C for 30 days. The internal transcribed spacer (ITS) region of ribosomal DNA, glyceraldehyde-3-phosphate dehydrogenase (G3PDH) gene, heat shock protein 60 (HSP60) gene, and DNA-dependent RNA polymerase II core subunit (RPB2) gene of two representative isolates, JQ21AC03 and JQ21AC09, were amplified and sequenced with primers ITS1/ITS4, G3PDH-F/G3PDH-R, HSP60-F/HSP60-R, and RPB2-F/RPB2-R, respectively (Staats et al. 2005), and deposited in GenBank (ITS: OP604277 and OP604283; G3PDH: OP627512 and OP627515; HSP60: OP627513 and OP627516; and RPB2: OP627514 and OP627517). BLASTn analysis of the resulting sequences showed 98 to 100% similarity with those of Botrytis aclada. A maximum likelihood phylogenetic tree generated by combining the sequenced loci using MEGA11.0, clustered isolates JQ21AC03 and JQ21AC09 with B. aclada with 99% bootstrap support. Based on these results, isolates JQ21AC03 and JQ21AC09 were identified as B. aclada. Pathogenicity of the two isolates on the onion cv. Honghe was confirmed by inoculating 30 heathy onion bulbs per isolate with 100 μL of conidial suspension (1×105 conidia/ml), while control bulbs were inoculated with 100 μL sterile distilled water. All 30 bulbs inoculated with each isolates developed neck rot symptoms after 30 days incubation at 15 ± 1ºC in the dark, with symptoms identical to those observed in the original storage facility, whereas control bulbs remained symptomless. The pathogen was re-isolated from the symptomatic tissue of inoculated bulbs, fulfilling Koch's postulates. hang et al (2008) documented this pathogen causing bulb rot of onions in Wuhan, Hubei Province, 1,700 km from Gansu. To the best of our knowledge, this is the first report of B. aclada causing neck rot on onion bulbs in storage in Gansu Province, which is the main onion production region in China. Considering that onion is the main source of income for growers in Gansu, further studies will be required to understand the epidemiology of this disease and foster appropriate disease management measures to avert disease outbreaks in the future.

The effects of chitosan‐TiO2 and chitosan‐TiO2‐ZnO‐MgO hybrid coatings on the shelf life of jackfruit bulbs (Artocarpus heterophyllus Lam)

SummaryThis study evaluated the effect of chitosan hybrid coatings on the shelf life and quality of jackfruit bulbs. The treatments include control bulbs, bulbs with the chitosan coating (CS bulbs), bulbs with the chitosan‐TiO2 hybrid coating (CSTiO2 bulbs) and bulbs with the chitosan‐TiO2‐ZnO‐MgO hybrid coating (CSTZM bulbs). Bulbs were stored at 4 °C. Shelf life of control, CS, CSTiO2 and CSTZM bulbs were 4, 10, 13 and 15 days, respectively. The CSTZM bulbs exhibited < 1% weight loss, a decrease in the pattern of respiration, the highest levels of vitamin C (28.27 mg/100 g), carotenoids (10868.91 μg/100 g), phenolic compounds (31.31 mg/100 g) and antioxidant capacity (283.49–444.36 mmol/100 g). According to the Artemia salina test, all coatings were non‐toxic. In conclusion, the chitosan‐TiO2‐ZnO‐MgO hybrid coating was the best alternative to extend the shelf‐life of fresh‐cut jackfruit.

Elicitation and Enhancement of Phenolics Synthesis with Zinc Oxide Nanoparticles and LED Light in Lilium candidum L. Cultures In Vitro

In this study, we identified and determined the content of phenolic compounds in Lilium candidum adventitious bulbs formed in vitro. HPLC analysis revealed the presence of four phenolic acids: chlorogenic, caffeic, p-coumaric, and ferulic acid. Phenolic acid content was assessed in adventitious bulbs formed in vitro on media supplemented with zinc oxide nanoparticles (ZnO NPs at 25, 50, and 75 mg/L) under fluorescent light (FL) or in darkness (D). The second experiment analyzed the effects of light-emitting diodes (LEDs) of variable light spectra on the formation of adventitious bulbs and their contents of phenolic acids. Spectral compositions of red (R; 100%), blue (B; 100%), red and blue (RB; 70% and 30%, respectively), a mix of RB and green (RBG) in equal proportions (50%), and white light (WLED, 33.3% warm, neutral, and cool light, proportionately) were used in the study. FL and D conditions were used as controls for light spectra. Bulbs grown in soil served as control samples. The most abundant phenolic acid was p-coumaric acid. Treatment with LED light spectra, i.e., RB, RBG, WLED, and B, translated into the highest p-coumaric acid concentration as compared with other treatments. Moreover, all the bulbs formed in light, including those grown on the media supplemented with ZnO NPs and under FL light, contained more p-coumaric acid than the bulbscales of the control bulbs grown in soil. On the other hand, control bulbs grown in soil accumulated about two to three times higher amounts of chlorogenic acid than those formed in vitro. We also found that the levels of all examined phenolics decreased under FL, R, and D conditions, while the bulblets formed in vitro under RB light showed the highest phenolic content. The use of ZnO NPs increased the content of p-coumaric, chlorogenic, and caffeic acid in the bulblets formed under FL as compared with those grown in darkness.

First Report of Rhizopus arrhizus (syn. R. oryzae) Causing Garlic Bulb Soft Rot in Hebei Province, China.

Rhizopus soft rot occurs on the succulent tissues of vegetables, fruits, and ornamental plants throughout the world (Cui et al. 2019). When the garlic is in the seedling stage in the fields (Fig. S1) in November 2021, a disease outbreak on garlic bulbs suspected as Rhizopus soft rot occurred in Daming County, Handan City, Hebei Province of China (N 36°17', E 115° 13'). This disease symptom was first found in the garlic seedling stage in China. Disease incidence was 10% to 30% in cultivated garlic bulbs. There were soft water-soaked lesions on the surface of diseased garlic bulbs and the interiors were brown and soft. In the disease severe field, white to gray mycelia were observed on the diseased garlic bulbs. Infected garlic bulbs were sampled to isolate and determine the identity of the disease-causing organism. Symptomatic bulbs were surface sterilized with 1% NaClO for 2 min, dipped in 75% ethanol for 3 min and rinsed three times with autoclaved distilled water. Small pieces of the inner decayed tissue were removed and cultured on potato dextrose agar (PDA) at 28°C for 2 to 3 days. Five white colonies grew on PDA and then they became brownish gray to blackish-gray mycelium. The fungal strains were purified by hyphal-tip isolation method. To determine the identity of the five isolated fungi, we analyzed their internal transcribed spacer (ITS) region sequences (Jung et al. 2012). BLAST analysis of the ITS sequences from DSF-0-2 (accession no. ON706022), DSF-0-3 (accession no. ON706021), DSF-0-4 (accession no. ON706020), DSF-0-5 (accession no. ON706019) and DSF-0-6 (accession no. ON706018) were all 100% identical with Rhizopus arrhizus (syn. Rhizopus oryzae). Phylogenetic trees were constructed using the neighbor-joining method of MEGA11 based on the sequences of ITS rRNA gene (Walther et al. 2013). Phylogenetic trees indicated that isolates were most likely Rhizopus arrhizus (syn. Rhizopus oryzae) (Fig. S2). We selected one isolated strain, DSF-0-2, for characterize the morphology and test its ability to cause garlic bulb soft rot. Under the microscope, nonseptate rhizoids, sporangia, and sporangiospores were observed (Fig. S1). Sporangiospores were unequal, subglobose, numerous irregular, or oval, and 9.7 (6.2 - 12.5) × 6.5 (4.1 - 8.5) μm (n = 50) in diameter. The sporangia were globose, black, 121.5 (65 - 198) μm (n = 50) in diameter. Based on the rDNA-ITS sequencing and the morphological characteristics, the DSF-0-2 isolate was identified as Rhizopus arrhizus (syn. Rhizopus oryzae) (Zheng et al. 2007; Abeywickrama et al. 2020). To complete Koch's postulates, surface-sterilized healthy garlic bulbs were inoculated with R. arrhizus isolate DSF-0-2. A 1.0-ml sterile syringe was used to inject 50 μl of a 106 conidia/ml suspension into each of five healthy bulbs. As a control, garlic bulbs were treated with sterile distilled water. The inoculated and control bulbs were incubated at 28°C for 7 days. The bulbs inoculated with R. arrhizus DSF-0-2 showed symptoms of water soaking, and the tissues were brown and soft throughout the bulb at 7 days (Fig. S1). Results of the three trials were the same. No symptoms were observed in the control group. R. arrhizus was reisolated from the symptomatic garlic bulb and confirmed as such based-on colony and sporangia morphology and ITS sequence. There were some reports that R. arrhizus infects cassava tubers and potato tubers (Amadioha and Markson 2007; Cui et al. 2019). To our knowledge, this is the first report of R. arrhizus (syn. Rhizopus oryzae) associated with soft rot on garlic bulb in the seedling stage in China. This disease has posed a potential threat during garlic seedling stage in the field. Management measures should be considered before this disease outbreaks widely. Garlic bulbs died in the seedling stage, which caused production reduction, serious economic loss and soil pollution. This finding may help to take effective control measures for this disease.

Effects of Substrates and Buckling on the Rejection Capacity of Plantain (Musa sapientum L.) under the Eco-climatic Conditions of Gbado-Lite, Democratic Republic of the Congo

Compost and flambéing on the plantain (Musa sp. cv. AAB, var Ngbangele) offshoot power studied under the conditions of Gbadolite in the Democratic Republic of Congo, remain among the techniques that protect the soil and increase production in the face of factors limiting such as climate change and soil destroyer including NPK. The experimental device chosen was that of complete randomized blocks comprising 3 repetitions and 4 plots 3 m long. The plots were arranged so that the flamed cultivars were adjacent depending on the substrates including T0: control substrate or unamended plot; T1: substrate from sawdust; T2: substrate from rice husk; T3: substrate from slush. Each plot contained 10 sample suckers of plantains. The greenhouse was installed after applying the buckling technique. It was observed that a bulb produced an average of 4 weaned suckers in the control bulbs; 8 suckers weaned on bulbs installed on substrates originating from slush; 9 suckers weaned on bulbs planted on substrates made from sawdust and rice husk. The releases installed on the control plot experienced a post-buckling recovery rate of 66.7%; those planted on sawdust and rice husk gave 83.3% and the subjects planted on the substrate from slush experienced a recovery rate of 80%; these results showed that the flame suckers adapted to the greenhouse conditions. In view of these results, it should be noted that this technique remains a major asset for the production of healthy suckers and in large quantities.

Aqueous extract of Moringa oleifera Lam. induced mitodepression and chromosomal aberration in Allium cepa, and reproductive genotoxicity in male mice

Moringa oleifera is a multipurpose plant with nutritional and medicinal value. Despite its widely acclaimed therapeutic benefits in traditional medicine, there are reports on its toxicity in living cells. Information is however, limited on toxic effect of the plant on the genetic component and male reproductive cells. We evaluated genotoxicity of aqueous extract of the leaves of M. oleifera using the Allium cepa chromosome aberration (CA) and mouse sperm morphology assays. Roots of onion bulbs were exposed to 0.5–20% of the extract for analysis of root growth inhibition, mitotic index (MI) and CA. Swiss male mice orally exposed to the aqueous extract (50–800 mg/kg) for 35 consecutive days were analysed for body and testes weight, testicular histology and sperm morphology. There was a significant (p < 0.05) root growth inhibition, decrease in MI and induction of CA compared to the negative control bulbs. The extract did not cause adverse effect on body and testes weight, but maturation arrest, atrophy and germ cell sloughing and degeneration were observed in testicular sections of exposed mice. A significant increase in sperm morphology was observed in exposed mice relative to the control group. Aqueous extract of M. oleifera was cytotoxic, mitodepressive and genotoxic in A. cepa. It induced DNA damage in the sperm head and interfered with spermatogenesis. This suggests potentials of M. oleifera to modulate somatic cell cycle and impact male fertility.

The Effects of Green Tea Leaf Extract on Cytogenetical and Physiological Parameters of Allium cepa L. exposed to Salinity

The aim of this study investigated the effects of 50 mg L-1 green tea leaf extract in decreasing harmful effects of 0.175 M salinity stress on the mitotic activity, chromosomal aberrations, seedling growth (fresh weight, radicle length and radicle number), micronucleus frequency which is the simplest indicator, the most effective of cytological damage and bulb germination of A. cepa L. In only green tea leaf extract medium, the radicle length and radicle number of bulbs were partially reduced compared to the control bulbs germinated in the distilled water medium. While their germination percentage and fresh weight statistically indicated the same values. Besides, the mitotic index and chromosomal abnormalities in the root tip meristematic cells of Allium cepa bulbs germinated in alone green tea leaf extract medium increased compared to germinated control bulbs in the distilled water medium, whereas the micronucleus frequency showed statistically the same value compared to the control. In other words, it can be said that salt stress significantly inhibited the seedling growth and bulb germination of Allium cepa. What’s more, it significantly reduced the mitotic index in the root tip meristems of the bulbs and increased the number of chromosomal abnormalities and micronuclues frequency. On the other hand, inhibitory effects of salt on the mitotic activity, seedling growth, bulb germination, chromosomal abnormalities and micronuclues frequency significantly decreased with the application of green tea leaf extract. The germination percentage, radicle lenght, radicle number, fresh weight, mitotic index, micronuclues frequency and chromosomal aberrations of the seedlings grown in 0.175 M salinity were 23 %, 10.3 mm, 12.7, 7 g, 1.2 %, 13 % and 17 % respectively, while these values became 75 %, 13.4 mm, 17.2, 13.8 g, 6.3 %, 9 % and 9.3 % in the seedlings treated with 50 mg L-1 green tea leaf extract.

Silver nanoparticles preplant bulb soaking affects tulip production

ABSTRACTNanomaterials and particularly silver nanoparticles (AgNPs) have increased great interest in many fields of science. The element may affect plant growth and development but so far research studies have been scarce and their results disparate. Tulip is one of the most important ornamental plants and its production technology is constantly being improved. The aim of this study was to investigate the effects of AgNPs on growth and yield attributes of tulip cv. ‘Pink Impression’. Before planting, the tulip ‘Pink Impression’ bulbs were soaked in the following concentrations of AgNPs: 25, 50, 100 and 150 mg L-1. Control bulbs were soaked in deionized water. The plants were forced in a greenhouse for two growing seasons. The tulips treated with 100 mg L−1 AgNPs flowered earlier, had longer cut-flower stem, larger petals, greater stem diameter and cut-flower fresh weight. Moreover, at this concentration of AgNPs, they showed increased leaf greenness index (SPAD), stomatal conductance, root fresh weight, root length and produced daughter bulbs of the greatest weight. The study outcomes indicate that AgNPs may be used as plant growth promoters in horticulture.

Effect of controlled atmospheres on the quality of white onion (Allium cepa L)

Onion is one of the oldest and most consumed crops in the world. Its quality deteriorates gradually during prolonged storage. In the present study, white onions of the variety "Sierra Blanca" were stored in a controlled atmosphere (CA) for 7months. The color, total pungency, microbiological load and total carbohydrates were evaluated. Three treatments were applied: control treatment (CT), regular atmosphere at 2.5°C without controlled relative humidity (RH); (T1)1% O2 + 1% CO2 at 2.5°C and 60-75% RH and (T2)3% O2 + 5% CO2 at 2.5°C and 60-75% RH. The statistical analysis showed a significant effect of the treatments and storage time in most of the variables analyzed. The CA managed to preserve the quality of the onion during the storage period while the control bulbs exhibited greater deterioration. These increased 2.9 times their level of pungency, had a higher microbial load and showed a very noticeable color change at the end of storage with respect to freshly harvested onions and those stored in a CA. They had a more yellow-green coloration. Both CA treatments were effective in preserving onion quality, but a more positive effect for T1 than T2 was observed on most of the parameters evaluated.

FIRST REPORT OF PSEUDOMONAS AERUGINOSA CAUSING INTERNAL BROWN ROT OF STORED ONION BULBS IN TAIWAN

Onion (Allium cepa L.) may suffer from various bulb rot diseases during postharvest storage, including internal brown rot caused by Pseudomonas aeruginosa (Cother et al., 1976). Onion bulbs, stored at room temperature, were sampled in Chiayi city, Taiwan in July 2017. The bulbs were externally asymptomatic but symptoms of internal brown rot occurred in 6% of bulbs. Repeatedly a bacterium was isolated on nutrient agar from surface-sterilized tissue of diseased onion bulb and fluoresced under UV light while cultured on King’s B plates. Several isolates were purified and maintained on King’s B plates, and produced fluorescence. Two isolates, OP01 and OP03, were stored in Luria-Bertani broth with 20% glycerol at -80°C. They were identified as Pseudomonas aeruginosa by API 20 NE system (Biomerieux) and phenotypically similar to a reference strain of P. aeruginosa (ATCC 27853). Furthermore, the 16S rDNA sequence of the strain OP01 was amplified using the primers fD1/rP1 (Weisburg et al., 1991) and sequenced (GenBank accession number MF946565). Blastn analysis of 16S rDNA indicated that the onion-pathogenic strain was P. aeruginosa (100% identity to P. aeruginosa ATCC 27853, AB594760). For pathogenicity assay, surface-sterilized onion bulbs were injected with a bacterial suspension (Schwartz and Otto, 2000). P. aeruginosa ATCC 27853 was included as a control strain. After incubation at 28°C for 14 days in closed plastic bags in the dark, the artificially inoculated bulbs exhibited symptoms indistinguishable from those observed in natural infections, but not the control bulbs. The same fluorescent bacterium could be consistently re-isolated from the inoculated bulbs, fulfilling Koch’s postulates. To our knowledge, this is the first report of P. aeruginosa causing internal brown rot of stored onion in Taiwan.

An Outbreak of Onion Center Rot Caused by Pantoea ananatis in Korea.

Symptoms typical of center rot of onion (Allium cepa L.) were observed in farmers' fields in spring of 2009 and 2010 in Hamyang, South Korea, at an incidence of 30 to 50% (five affected fields representing approximately 6 ha). The symptoms were identical to those reported from infected onions in Georgia in 1997 (1). Harvested bulbs of symptomatic plants had reddish, collapsed scales near the neck. Symptomatic bulb tissues were surface-sterilized by immersing sections of the tissue for 30 s in 1% NaOCl, then rinsing the sections with sterilized, distilled water. Tissues were then macerated in 1 ml of sterilized, distilled water in a 1.5 ml Eppendorf tube using a sterile scalpel. The macerated tissue was left to soak for 10 min, after which a 5 μl suspension from each section was streaked onto plates of nutrient agar (NA). Gram-negative, rod-shaped, yellow bacteria were consistently recovered on NA. Three bacterial isolates recovered were each facultative anaerobes and induced a hypersensitive reaction on tobacco leaves. The biochemical test, API 20E (Biomérieux, Marcy l'Etoile, France), was also used for identification. All three strains tested positive for β-D-galactosidase, utilization of citrate, and production of acetoin, catalase, and indole. All three strains tested negative for ornithine decarboxylase, lysine decarboxylase, urease, and oxidase. All produced acid from arabinose, glucose, mannitol, and sorbitol; while none produced acid from melibiose, inositol, and rhamnose. These characteristics are consistent with those of P. ananatis (1,2). Five bulbs were each surface-disinfested with 70% ethanol, dried, and injected with 50 μl of the appropriate bacterial suspension containing ~108 CFU/ml, using a syringe. The bulbs were placed in plastic boxes with four sheets of wet paper towel to maintain the relative humidity at 100%, and incubated at 25°C for 2 weeks. Three onion bulbs treated similarly but injected with sterilized, distilled water served as replicates of the control treatment. After 1 week of incubation, inoculated onion bulbs developed a brown discoloration and decay of the internal, fleshy scales matching those observed in the original farmers' fields. The control onion bulbs remained asymptomatic. Bacteria reisolated from lesions in the fleshy bulb scales of the inoculated bulbs had the same characteristics as the original isolates inoculated, proving Koch's postulates. Bacteria were not reisolated from any of the control bulbs. To confirm identity of the isolated bacteria, 16S rRNA and recA genes were amplified with primers 27mF: 5'-AGAGTTTGATCMTGGCTCAG-3' and 1492mR: 5'-GGYTACCTTGTTACGACTT-3', and PAGRECA21: 5'-GGTGAAGACCGCTCAATGGA-3' and PAGRECA621: 5'-CACCGATACGGCGGATATCA-3', respectively (3). Amplification of the 16S rRNA gene generated a 1,506-bp consensus sequence (GenBank Accession No. JQ762264), and amplification of the recA gene generated a consensus sequence of 601 bp (JQ762265). The 16S rRNA and recA gene sequences shared 99% nucleotide identity with those of a P. ananatis strain in GenBank (DQ195523 and AY219004, respectively). Based on symptoms, biochemical tests, and molecular analyses, the bacterium responsible for the onion symptoms in Korea was identified as P. ananatis. To our knowledge, this is the first report of center rot of onion caused by P. ananatis in Korea.

SHORT TREATMENT WITH ETHYLENE AND 1-METHYLCYCLOPROPENE IN COMBINATION PRIOR TO STORAGE IS SUFFICIENT TO REDUCE SPROUT GROWTH IN ONION (ALLIUM CEPA L.)

To eliminate the use of chemical sprout suppressants such as maleic hydrazide, onions intended for long term storage in the UK are held in continuous ethylene (10 µl L-1). That said, short treatments for 24 h with ethylene or the ethylene binding site inhibitor, 1-methylcyclopropene, have both been found to reduce sprout growth compared with onions stored in air. The aim of this study was to investigate whether the application of ethylene (10 µl L-1) and 1-MCP (1 µl L-1) in combination for 24 h before or after curing would suppress sprout growth of ‘Sherpa’ onions following long term storage at 1°C in 2008-2009 and at 1 or 6°C in 2009-2010. In both years, treatment with ethylene and 1-MCP before curing resulted in an increase in respiration rate whereas the same treatment applied after curing resulted in no significant change in respiration rate. In 2008-2009 and 2009-2010, onions treated with ethylene and 1-MCP in combination after curing had significantly shorter sprouts 25 and 19 weeks after harvest, respectively, compared with the control bulbs. Previously, studies have shown that ethylene and 1-MCP applied individually before curing were more successful at reducing sprout growth compared with application after curing possibly due to the a change in the skin composition following curing. Yet, results herein suggest that when used in combination, application after curing resulted in significantly shorter sprout growth compared with the control bulbs and those treated with both ethylene and 1-MCP before curing. It is possible that when applied in combination, lower concentrations of each treatment are more successful at reducing onion sprout growth hence when treated after curing the difference in skin composition may provide a greater barrier allowing a lower influx of ethylene and 1-MCP and therefore resulting in no increase in respiration rate compared with the control. In conclusion, providing 1-MCP is approved for use on onions, the application of ethylene and 1-MCP in combination to onions post-curing could provide a safer and cheaper alternative to current onion sprouting suppressants.

Postharvest application of ethylene and 1-methylcyclopropene either before or after curing affects onion ( Allium cepa L.) bulb quality during long term cold storage

The storability of onion bulbs is dependent on the incidence and rate of sprout growth. Exogenous ethylene applied continuously has been demonstrated to act as a sprout suppressant in onion. However, the ethylene binding inhibitor, 1-methylcyclopropene (1-MCP), can also suppress sprouting in onion. Given this seemingly contradictory result, the precise role that ethylene plays during onion storage and the effect of curing on its efficacy is not understood. ‘Sherpa’ and ‘Wellington’ onion bulbs were treated before or after curing (28 °C for 6 weeks) with a single dose of 10 μL L −1 ethylene or 1 μL L −1 1-MCP for 24 h at 20 °C, or no treatment (control). Replicated out-turns were sampled during 38 weeks storage at 0–1 °C. Sprout growth (31 weeks after harvest) was reduced in ‘Sherpa’ treated before curing with ethylene or before or after curing with 1-MCP. However, sprout growth of ‘Wellington’ was not affected by any treatment. Following treatment, the cured, thick-skinned ‘Wellington’ released a lower concentration of treatment gas compared with the newly harvested, thin-skinned ‘Sherpa’. Onion bulb respiration rate increased immediately after being treated with ethylene but to a lesser extent or not at all when treated with 1-MCP. Fructose concentrations of onions treated with ethylene or 1-MCP before curing were not significantly different, however, after curing concentrations were about 2-fold higher compared with the control. Mean glucose and sucrose concentrations for both cultivars were higher immediately after being treated before curing with ethylene or 1-MCP than control bulbs. It appears that inhibition of sprout growth can be achieved using just a short 24 h treatment with ethylene or 1-MCP. However, skin thickness or permeability, which is dependent on cultivar and curing, may affect ethylene or 1-MCP influx and therefore efficacy of sprout suppressant action.

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.

Efeito anti-proliferativo das infusões de Achyrocline satureioides DC (Asteraceae) sobre o ciclo celular de Allium cepa

Achyrocline saturoides (marcela) is used in Brazilian folk medicine as a tea in the treatment of digestive and inflammatory diseases. The anti-proliferative effect of infusions of marcela on onion cell cycle was evaluated by using the inflorescences of recently collected marcela and after the storage for 30 months. Marcela inflorescences were collected for the infusion preparations in 2003 and in 2005 (used still fresh). We prepared the infusions at two concentrations 5.0 mg/mL (concentration used as tea) and 20 mg/mL. We used two groups of six onion bulbs for each population of marcela, and one group of bulbs of each population was withdrawn as a control group. All bulbs rooted in distilled water and after they were transferred to the extracts of marcela and they were kept there for 24 hours (control bulbs remained under water). The root tips were collected, after fixed in ethanol acetic acid (3:1) for 24 hours and, stored under alcohol 70%. A total of 6000 cells per group of bulbs was analyzed, and the mitotic indexes were calculated and undergone to statistical analysis by using c2 at 5%. The conclusions were that the infusions of marcela have anti-proliferative action on the cell cycle of onion and that this inhibitory action on the cell division increases according to the increase of the infusion concentration, after storage as well.

VARIATION IN FUSARIUM-INDUCED ETHYLENE PRODUCTION AMONG TULIP CULTIVARS

Ethylene evolution is a well-known consequence of Fusarium infection of tulip (Tulipa gesneriana) bulbs, yet little is known about the bulb-pathogen interactions involved in the induction or the time course of ethylene production in the infected bulb. Bulbs of 36 tulip cultivars were wounded, inoculated with a liquid Fusarium suspension (isolated from infected bulbs, and grown on agar plates) and held at 21°C. Control bulbs were wounded, but not inoculated. Ethylene production was monitored by headspace accumulation and gas chromatography. The results indicated that ethylene could increase rapidly after a lag phase of at least 8 days after inoculation, but there was a great variability in ethylene production among cultivars. Of the cultivars tested, the highest ethylene producer was ‘Furand’, which evolved more than 340 µl/kg fwt wt/h (ca. 250 µl/bulb/day) on the 12 th day after infection. By 19 days, inoculated ‘Furand’ and ‘Nashville’ produced ethylene at ca. 800 µl/bulb/day. Approximately 40% of the cultivars produced ethylene at rates greater than 150 µl/bulb/day, and only 11% of them produced less than 5 µl/bulb/day. These results suggest high-ethylene producing tulips should be stored separately from other cultivars, or that increased ventilation should be maintained during storage or transportation. Knowledge of cultivar variation might also be useful in breeding programs.

Light, moisture, and atmosphere interact to affect the quality of dry-sale lily bulbs

Abstract The interactions of moisture and light with low oxygen (1%) storage of dry sale lily bulbs at 22–25 °C for 4–5 weeks have been studied as part of a continuing evaluation of modified atmospheres (MA) to lengthen shelf life. Conditions that promoted development in storage (light, moisture, and air) were detrimental to final plant quality, resulting in short plants with many aborted flowers and poor foliage development. One percent O2 suppressed pre-plant development compared to storage in air, irrespective of light and moisture. When bulbs were forced under conditions that accelerated growth (high temperatures and light), bulbs stored in darkness, air, and dry (without peat) were comparable in quality (producing normal flowers and having adequate height and foliage development) to bulbs stored with 1% O2 without peat. Exclusion of light is beneficial to bulbs stored in air but is not practical for marketing. The quality of dry-sale bulbs was always inferior to un-treated control bulbs that remained in the cooler during the dry-sale storage period. Untreated bulbs produced taller plants with more flowers and superior foliage development compared to bulbs stored under dry-sale conditions, regardless of the combination of light, moisture, and atmosphere.