Diversity of onion nematode fauna in agrocenoses of different altitudinal zones in Fergana Valley, Uzbekistan

Altitudinal and seasonal variation in herbage composition and energy and protein content of grasslands on Mt Varnoudas, NW Greece

The composition and structure of forest stands in the Tatra National Park were examined using data gathered in 2016 and 2017 from 617 circular sample plots (0.05 ha each). The diameter at breast height of all living trees, standing dead trees, snags, and wind throws was measured along with diameters and lengths of fallen logs within the plot boundaries. Tree height was measured for all living trees within the core (0.01 ha) of the sample plots. Using the obtained data, height-diameter curves were calculated for all major tree species and in the case of spruce, the height-diameter relationships were also calculated separately for each of the three elevation zones (up to 1200 m, between 1200 and 1400 m, above 1400 m). For each elevation zone and park protection zone, we also determined the volumes of live and dead trees. The volume of living trees in the Tatra National Park amounted to 259 m3/ha, which was higher than the volume of dead trees (176 m3/ha). Snags constituted the largest part of the dead wood whilst over 97% of the standing dead trees were spruce Picea abies. Among living trees, the share of spruce ranged from 81% in the low elevation zone to 98% in the middle zone. Other significant species in the lower zone were Abies alba (11%) and Fagus sylvatica (4.5%), while in the middle and upper elevation zones only Sorbus aucuparia occurred in significant numbers. Furthermore, in the lower elevation zone, Fagus sylvatica was the only species displaying significantly higher volumes in the ‘strict protection’ zone compared to the other park areas. In the ‘landscape protection’ zone, Picea abies was the most dominant species and the share of other species in the lowest elevation zones calculated based on tree density was smaller than calculated based on tree volume, indicating problems with stand conversion from spruce monoculture to mixed forest.

Satellite based remote sensingRemote sensing is a convenient tool for the study of cryosphere that allows to carry out investigations over large and inaccessible areas. The present investigation has been carried out to monitor seasonal variation in the Snow Cover Area (SCA) for the upper Bhangirathi basin, located in the Garhwal region of Indian HimalayaIndian Himalaya . This analysis has been done using Moderate-Resolution Imaging Spectroradiometer (MODIS)MODIS satellite data for the past 11 years (2000–2010); the temporal snow cover being derived using the Normalized Difference Snow Index (NDSINDSI ). The entire study basin has been divided into nine elevation zones, on the basis of Digital Elevation Model (DEM), for estimating the SCA for each zone. Zones 1–9 cover different elevation ranges: (1) above 6,500 m, (2) between 6,000 and 6500 m, (3) 5,500–6000 m, (4) 5,000–5500 m, (5) 4,500–5000 m, (6) 4,000–4500 m, (7) 3,500–4000 m, (8) 3,000–3500 m, and (9) below 3,000 m. Mann Kendall and linear regression methods have been employed to identify trends in the SCA during the period 2000–2010. The snow cover depletion analysis depicts a shift in the duration of ablation and accumulation during the study period in the basin. The analysis indicated 13–21 % increase in SCA in the middle elevation zones (4 and 5) and 2–9 % decline in SCA in the lower elevation zones during autumn. SCA was found to increase across all the elevation zones in winter; the rate of increase was particularly high (14–21 %) in the lower elevation zones as compared to higher (2–3 %) and middle elevation zones (4–10 %). Similarly, an increase of 2–3 % in the higher elevation zones, 6–14 % increase in the middle elevation zones and 2–6 % decline in the lower elevation zones was observed in respect of SCA during spring. However, no significant variation in SCA was observed during the summer season. Decadal variation in SCA showed mean annual increase of 8–15 % in the middle elevation zones (3–5). In the lower elevation zones (<4,500 m), mean annual SCA showed increase of 11–14 % between 2000 and 2005, followed by 6–8 % decrease in the upper Bhagirathi Basin.

BackgroundOnion thrips (Thrips tabaci Lindeman) are a main threat to onion (Allium cepa L.) production worldwide. Entomopathogenic nematodes (EPNs) are recommended as environmentally acceptable alternatives to chemical management for a wide range of economic insect pests. EPNs are widely used and provide good control over insect pests that live in the soil. Adjuvant-based formulation of EPN solutions has enhanced longevity and potency on foliage. In this study, tests were performed to compare two EPN application techniques for controlling the onion thrips in the open field. The first technique was the traditional spray technique, while the second one was the nematode-infected insect technique. Side experiments were conducted to investigate the influence of different adjuvants on the persistence of Steinernema feltiae (Filipjev) sprayed on onion plants in a semi-field setting.ResultsIn semi-field experiments, the results suggested that Tween 80 or Xanthan was suitable for increasing the persistence of S. feltiae on onion plants. In the spray technique, application of Heterorhabditis bacteriophora (Poinar), at 1000 infective juveniles (IJs)/ml, combined with 0.3% Tween 80, reduced the thrips population on onion leaves by 63% in three days. However, it remained effective for only three days post-application. Using the nematode-infected insect approach, a single application of 10 H. bacteriophora-infected Tenebrio molitor L. larvae per 1 m of the row (70 cm between rows) remained effective in the onion field for 5 weeks, following treatment, generating a pest population reduction of up to 77%, while the same rates of S. feltiae reduced the pest population by up to 59%.ConclusionsIn onion fields, the nematode-infected insect technique was proved to be more effective and long-persisted than the traditional spray technique for controlling T. tabaci in onion fields. Further research work is still needed to improve the ease of use of the recommended approach.

Plant parasitic nematode populations on upland and hydromorphic rice in Côte d’Ivoire: relationship with moisture availability and crop development on a valley slope

Onion (Allium cepa L) is an important vegetable crop in Chile with 3.675 ha (ODEPA, www.odepa.gob.cl). Since 2017, a series of symptoms has been increasingly observed, mainly in mature bulbs which include water-soaked lesions on mature leaves and external and central cataphylls, which evolve to necrotic lesions and rot, reducing yields and affecting the postharvest life. As the season progresses over 90% incidence has been estimated in severely affected fields. Symptomatic plants were collected for disease identification in summer (February 2022) in Santa Cruz, O´Higgins, Chile, (34º41'32"S and 71º27'17"W). Isolations were done on semi-selective OEM medium (Zaid et al. 2012) and isolated colonies were transferred and maintained on King's B (KB) medium. Colonies on OEM medium were yellow slightly green in the center, circular to irregular shape, elevated, smooth margin, and mucoid texture (Tho et al. 2015). On KB medium colonies were yellow cream, slightly darker in the center, with smooth margins and circular or slightly irregular. Two isolates (CHS B3, CHS B1), obtaining in three different onion fields, were further identified by PCR amplification of partial 16S rRNA using primers 27F/1492R (Frank et al., 2008). The resulting sequencing were deposited in GenBank under accession numbers OP934962.1 and OP934961.1. A BLAST search of GenBank showed that these sequences exhibited 99,89 to 100 % nucleotides similarities with multiple Pantoea agglomerans sequences. Three isolates were used to test pathogenicity on detached cataphylls and onion plants tests in the laboratory and greenhouse, respectively. Cataphylls (n=10) were surface disinfected with 2% NaOCl for 2 min, placed in sterile Petri dishes, and injected with 50 µL (106 UFC/mL) inoculum suspension with the aid of a hypodermic syringe. Cataphylls were incubated in humid chamber at 22 + 2ºC for 14 days. Additionally, three-month-old onion plants (n=10), growing in pod, were inoculated by injecting leaves with 1 mL inoculum suspension (106 UFC/mL). Plant were incubated under greenhouse for 30 days to 28ºC. An equal number of cataphylls and onion plants, injected with sterile water, were left as controls. Water soaked lesions on inoculated cataphylls appeared five days after inoculation. While onions plants develop water soaked lesion 1- 4 days after inoculation. Blight and bulb rot were observed only on inoculated plants. Symptoms were identical to those previously observed in the field. Reisolations were accomplished for 100% of the inoculated cataphylls and leaves fulfilling Koch's postulates (Biochemical characterization and PCR amplification of partial 16S rRNA). Previously, Pectobacterium carotovorum was reported causing a similar disease in Chile (Acuña 2008). However, to our knowledge this is the first report of P. agglomerans causing onion leaf blight and bulb rot in O'Higgins Region, Chile. In agreement with other reports (De Armas et al. 2015, Tho et al. 2015), leaf blight and bulb has been a very aggressive disease in Chile. These results do not exclude the possibility that other Pantoea species (Armas et al. 2015) may be involved in the leaf blight and bulb rot of onions.

Soil nematode populations in a grassland plant diversity experiment run for seven years

‘Vidalia’ onions are sweet, short day, low pungency, yellow Granex-type bulbs that are popular in the United States. The relationships of sweet onion bulb yield and quality with potassium (K) and sulfur (S) concentrations are not fully understood. The objective of this study was to evaluate the effects of K and S fertilization rates on sweet onion plant growth and bulb yield and quality. Experiments were conducted at the Horticulture Farm, Tifton Campus, University of Georgia, in the Winters of 2012–13 and 2013–14. The experiment had five treatments (K/S rates: 56/80, 112/126, 168/172, 224/218, and 280/264 kg·ha −1 of K and S, respectively). K/S rates had no effect on onion biomass of roots, bulbs, and shoots during the growing season. Marketable and total number and weight of onion bulbs and individual bulb weight were also unaffected by K/S rate. Incidences of bolting, double bulbs, Botrytis leaf blight ( Botrytis cinerea ), and sour skin ( Burkholderia cepacia ), and bulb dry weight, soluble solids content (SSC), and pungency (pyruvate concentration) were unaffected by K/S rates. In conclusion, K/S rates had little effect on plant growth and bulb yield and quality. The lack of response of onion plants to K/S rates, even at the lowest rate suggests that some of the K absorbed by plants originated from K already present in the soil before planting. The average K content of sweet onion whole plants was 80 kg·ha −1 K. Thus, under our experimental conditions, application of K rates above the recommended value (84 kg·ha −1 K) are unnecessary and will likely not improve plant growth, yield, or quality. Regarding S, rates higher than 80 kg·ha −1 S are probably unnecessary and will not enhance either plant growth or bulb yield or quality of sweet onion.

Although, olive oil industry is crucial for Turkey, olive oil solid waste or olive vegetation water, a by-product of the industry, leads to environmental pollution during olive oil production. This study investigated the fields where olive oil solid waste was used as an organic substance. Olive oil solid waste in different concentrations (0, 10, 20, 30 and 40 t ha-1) were applied to faba bean, onion and radish plants grown (in 1 m2 plots) in the field conditions. Germination rates and growth of the plants were monitored. The application at the rates of 10 to 30 t ha-1were determined as the most appropriate rates for both faba bean and onion. The higher rates of application negatively affected germination and growth of plants. The application at 20 t ha-1 concentration of olive oil solid waste provided the best results for faba bean and onion plants. However, none of the application rates were found suitable for radish. Keywords: Olive oil solid waste; germination; plant growth; plant analysis

The present study was conducted to investigate the toxicity of Aerosil 200® (fumed silica nanoparticles) and leaf extracts of four plants, Cinnamomum camphora, Matricaria chamomilla, Mentha arvensis, and Trigonella foenum-graecum against Thrips tabaci (Lind.) (Thysanoptera: Thripidae) in onion fields, as well their allelopathic effects on onions; moreover, the chlorophyll, phenol, and protein contents were determined in onions. This study was performed in completely randomized plots. After a growth period of 1 month, bioassay investigations and molecular polymorphism in T. tabaci by RAPD-PCR were performed, and total chlorophyll, phenol, and protein concentrations were investigated in onion plants posttreatment as well. The initial reduction% of the T. tabaci population in onion fields after application of a high concentration of nanoparticles (Aerosil 200® (4 ml/l)) and 8000 ppm concentrations of the four plant extracts were 83.66, 81.08, 86.92, 74.49, and 91.38%, respectively, whereas their persistence effects were 73.18, 67.78, 71.46, 66.94, and 78.29%, respectively. Furthermore, the total chlorophyll contents in onions treated with the nanoparticles and four plant extracts were 1.35, 1.17, 1.09, 1.07, and 1.18 mg/g, respectively; additionally, the concentrations of phenols were 4.65, 3.15, 3.15, 2.85, and 3.70 mg/g in onions treated with C. camphora, M. chamomilla, M. arvensis, T. foenum-graecum, and Aerosil 200®, respectively. The C. camphora extract was the most potent, as it increased the protein content in the onion plants, while the Aerosil 200® decreased the protein content in onions. In addition, DNA-RAPD showed that the polymorphism percentages were 73, 71, and 67% when treated with high concentrations of C. camphora and M. arvensis extracts and Aerosol 200®, respectively. T. foenum-graecum and M. chamomilla extracts induced the least polymorphism (17 and 16%, respectively). Overall, this study indicated that these plant extracts as well as the nanoparticles in Aerosil 200® could be used to reduce onion infestations of T. tabaci in the field environment.

Aim Data on spatial and temporal turnover in species composition within a region is essential to design regional protected areas. Montane systems are often recognized as biodiversity hotspots. The primary objective of this study is to identify patterns of montane bird diversity across multiple spatial and temporal scales using an additive diversity partitioning framework.Location The Ailao Mountains, central Yunnan Province, China.Methods We used point counts to sample bird communities in four elevational zones, on eastern and western slopes, during both the breeding and the non‐breeding seasons. Diversity (richness and Shannon) was partitioned across space (points, elevational zones and slopes) and time (seasons). We used permutation tests to compare observed values to values expected by random chance. A complementary cluster analysis was also used to evaluate beta diversity.Results Overall, the gamma diversity was attributed to significantly higher beta diversity (relative to that of randomization tests) among elevational zones and, to a lesser extent, between slopes. For Shannon–Wiener Index, beta diversity between seasons was significantly higher than expected and had a similar contribution to the gamma diversity as with beta diversity between slopes. Hierarchical cluster analysis supported the findings for Shannon–Wiener Index. The contribution of beta diversity among points to gamma diversity within each elevational zone generally lessened with increasing elevation.Main conclusions Our results show significantly high levels of beta diversity among elevational zones and between slopes, as well as between seasons for Shannon diversity, in a small area of the Ailao Mountain range. Thus, a regional montane reserve system should cover the entire elevational gradient and multiple slopes, rather than only the montane crest. Furthermore, higher pattern diversity in lower elevational zones suggests that larger areas should be preserved at lower elevational zones. Finally, the design of regional reserve systems require more studies conducted at multiple seasons at a regional scale.

Iris yellow spot virus (IYSV) poses a significant threat to dry bulb onion, Allium cepa L., production and can lead to substantial yield reductions. IYSV is transmitted by onion thrips, Thrips tabaci (Lindeman), but not via seed. Transplanted onion fields have been major early season sources of IYSV epidemics. As onion thrips tend to disperse short distances, seeded onion fields bordering transplanted onion fields may be at greater risk of IYSV infection than seeded fields isolated from transplanted ones. Additionally, seeded onion fields planted early may be at greater risk of IYSV infection than those seeded later. In a 2-year study in New York, we compared IYSV incidence and onion thrips populations in seeded onion fields relative to their proximity to transplanted onion fields. In a second study, we compared IYSV incidence in onion fields with either small or large plants during midseason. Results showed similar IYSV incidence and onion thrips populations in seeded onion fields regardless of their proximity to transplanted onion fields, while IYSV incidence was over four times greater in large onion plants than in small ones during midseason. These findings suggest a greater risk of onion thrips-mediated IYSV infection in onion fields with large plants compared with small ones during midseason and that proximity of seeded fields to transplanted ones is a poor indicator of IYSV risk. Our findings on IYSV spread dynamics provided valuable insights for developing integrated pest and disease management strategies for New York onion growers.

During the 2021-22 and 2022-23 seasons (December to February), onion plants (Allium cepa L.) showing decay, leaf blight, chlorosis and water soak lesions were collected in Central Chile. Five symptomatic plants were sampled from 20 different onion fields. Brown rot of the external scales was observed in bulbs from two fields: one planted with the cv. Campero (20 ha; O'Higgins Region), and another with cv. Marenge (2 ha; Metropolitan Region). The disease incidence in these fields ranged from 2% to 5%. Isolations were carried out from symptomatic leaves and bulbs from these fields on King's B medium, resulting in small white colonies with smooth margin. Three isolates were selected, two from first field (QCJ3A & QCJ2B), and one from second field (EPB1). A preliminary identification based on 16S rRNA sequences was conducted. BLAST analyses of strains QCJ3A, QCJ2B and EPB1 (GenBank Accession No. PP345601 to PP345603) against the NCBI Database resulted in a match with strains (GenBank Accession No. ON255770.1 and ON255825.1) isolated from infected bulbs in Texas, USA identified as Erwinia spp. (Khanal et al. 2023), with 100% coverage and 100% identity (707 bp out of 707). To evaluate the pathogenicity of these three strains, onion bulbs were inoculated (Guajardo et al. 2023). Toothpicks previously immersed in a bacterial suspension at ~ 108 colony forming units (CFU)/mL were pricked at a 4 cm depth into the shoulders of onion bulbs bought from commercial store and incubated at room temperature. Bulbs inoculated with sterile water served as negative control. A known onion bulb rotting bacterial strain of Dickeya sp. was used as a positive control. At the end of the incubation period (20 days), bulbs were opened longitudinally across their inoculation site, showing that the external scales had a brown color. Negative control remained asymptomatic. Strains were re-isolated from damaged tissue and identified as Erwinia sp. This assay was repeated three times with the same results. For further identification, genomic DNA extraction was carried out using the Blood & Cell Culture DNA Kit (Qiagen), and genome sequencing was performed in the Illumina HiSeq 2500 platform. The Whole Genome Shotgun project for strains QCJ3A, QCJ2B and EPB1 have been deposited at DDBJ/ENA/GenBank under the accession JBANEI010000000, JBANEJ010000000 and JBANEK010000000. The average nucleotide identity (ANI) values were 99.6% (EPB1), 98.2% (QCJ2B), and 99.6% (QCJ3A) and DNA-DNA hybridization (dDDH) values were 96.9% (EPB1), 83.7% (QCJ2B), and 97.1% (QCJ3A), when compared with the type strain Erwinia aphidicola JCM 21238 (GenBank accession No. GCF_014773485.1). The three strains were deposited in the Chilean Collection of Microbial Genetic Resources (CChRGM). Erwinia aphidicola has been previously described causing diseases in common bean (Phaseolus vulgaris) and pea (Pisum sativum), in Spain (Santos et al. 2009) and in pepper (Capsicum annuum) in China (Luo et al. 2018). Its close relative E. persicina has been reported causing bulb rot in onion in Korea (Cho et al. 2019) and garlic in Europe (Galvez et al. 2015). To our knowledge, this is the first report of E. aphidicola causing a bulb rot of onion in Chile. Although the distribution and prevalence of this bacterium in Chilean agroecosystems is not known, it can be a potential cause of losses in onions and other crops such as beans, peas, and peppers. Additional studies should be conducted to determine the host range of Chilean Erwinia aphidicola strains.

A biotic and biotic stresses can cause severe damages to leaves and/or roots of plants leading to reduction in productivity and plant death. A greenhouse pot-experiment was performed to determine the interactive effects of leaf and root damages on onion (Allium cepa L. ‘Braddock’) plant growth and productivity. The treatments were: 1) leaf damage (LD: 0, 25, 50, 75 and 100%); and 2) root damage (RD: 0, 50 and 100%) at transplanting. Onion plants with LD 75% or 100% under severeRD100% exhibited the least plant growth rate, and reduced bulbing ratio and bulb fresh weight compared to control intact plants. Moderate leaf damage i.e., LD 25%combined with severe root damage RD 100% had the highest plant growth rate and bulbing ratio compared to the other treatments suggesting that plants with severe root damage, but moderate leaf damage promoted onion plant growth. In conclusion, this preliminary study showed that combined leaf and root damage or root damage alone significantly (P<0.05) reduced onion plant growth and productivity. However, leaf damage alone did not significantly (P>0.05) reduce onion plant growth and productivity. Future work will investigate plant morpho-physiological response.

In New York, onion [Allium cepa L. (Alliaceae)] fields often border woods or other vegetable fields. Because onion maggot adults, Delia antiqua (Meigen) (Diptera: Anthomyiidae), spend a significant portion of their time outside of onion fields, surrounding habitat may affect patterns of fly activity and oviposition within onion fields. To better understand these patterns throughout the onion‐growing season, first‐, second‐, and third‐flights maggot adult (male and female) activity was monitored using yellow sticky cards. Half of the monitored fields bordered woods, whereas the other half bordered other onion or vegetable fields. Within all fields, yellow sticky cards were placed at five distances along a transect beginning at the onion field edge extending into the field center. First‐flight male and female adult activity was greatest along onion field edges and was especially high along edges bordering woods. This pattern diminished during the second flight and was absent during the third. To determine if spatial patterns of onion maggot oviposition by first‐flight onion maggots were similar to first‐flight adult activity patterns, potted onion plants were placed in onion fields that bordered or did not border woods in late May and early June 2003. The number of eggs laid in the soil at the base of each plant was recorded. Unlike spatial patterns of first‐flight adult activity, oviposition patterns were not affected by bordering habitat or distance from the field edge. Based on the activity of onion maggot adults in onion fields, future and existing control strategies should consider targeting first‐flight adults along field edges rather than across entire fields, especially in fields that border woods. In contrast, based on spatial patterns of oviposition within onion fields, controls targeting onion maggot larvae should be applied on a fieldwide basis.