Thelytokous Reproduction of Onion Thrips, Thrips tabaci Lindeman 1889, Infesting Welsh Onion and Genetic Variation among Their Subpopulations

Parthenogenesis is not uncommon in thrips. This asexual reproduction produces males (arrhenotokous) or female (thelytokous). Only females are found in the onion thrips (Thrips tabaci Lindeman 1889) infesting Welsh onion (Allium fistulosum) in several areas of Korea. To determine the reproduction mode of T. tabaci, thrips infesting Welsh onion were collected from different localities in Korea. Cytochrome oxidase I (COI) sequences were then assessed. Results showed that all test local populations had signature motif specific to a thelytokous type. These COI sequences were clustered with other thelytokous populations separated from arrhenotokous T. tabaci populations. In a laboratory test, individual rearing produced female progeny without any males. These results support that Korean onion thrips infesting Welsh onion have the thelytokous type of parthenogenesis. Local thrips populations exhibited significant variations in susceptibility to chemical and biological insecticides. Random amplified polymorphic DNA (RAPD) analysis indicated genetic variations of local populations. However, the genetic distance estimated from RAPD was independent of the actual distance among different local populations. These results suggest that genetic variations of T. tabaci are arisen from population subdivision due to asexual thelytokous reproductive mode.

Effect of Welsh Onion on Taste Components and Sensory Characteristics of Porcine Bone Soup

To investigate the effect of welsh onion on taste components and sensory characteristics in porcine bone soup, the stewing condition was as follows: the material–liquid ratio (m/V) was 1:1, the stewing time was 5.0 h, and the ratio of welsh onion was 2.5%. Then, the content of taste components was measured. The content of free amino acids in porcine bone soup with welsh onion (PWS) was higher than the sum of welsh onion soup (WS) and porcine bone soup (PS); particularly, the umami amino acids increased by 35.73% compared with PS. Significant increases in four organic acids (lactic acid, pyroglutamic acid, citric acid and ascorbic acid), two 5′-nucleotides (5′-AMP and 5′-GMP) and three mineral elements (K, Ca and Mg) were observed in PWS. Compared with PS, the equivalent umami concentration (EUC) value was increased from 79.09 to 106.47 mg MSG/100 g in PWS, which was due to the high content of umami amino acids and the synergistic effect with 5′-nucleotides. The results of the sensory analysis indicated a certain enhancement of umami taste in PWS, and the sweet and salty tastes were also increased with the addition of welsh onion. The correlation analysis was consistent with the variation of the components tested above.

Effects of nitrogen levels on gene expression and amino acid metabolism in Welsh onion

Background Welsh onion constitutes an important crop due to its benefits in traditional medicine. Nitrogen is an important nutrient for plant growth and yield; however, little is known about its influence on the mechanisms of Welsh onion regulation genes. In this study, we introduced a gene expression and amino acid analysis of Welsh onion treated with different concentrations of nitrogen (N0, N1, and N2 at 0 kg/ha, 130 kg/ha, and 260 kg/ha, respectively). Results Approximately 1,665 genes were differentially regulated with different concentrations of nitrogen. Gene ontology enrichment analysis revealed that the genes involved in metabolic processes, protein biosynthesis, and transportation of amino acids were highly represented. KEGG analysis indicated that the pathways were related to amino acid metabolism, cysteine, beta-alanine, arginine, proline, and glutathione. Differential gene expression in response to varying nitrogen concentrations resulted in different amino acid content. A close relationship between gene expression and the content of amino acids was observed. Conclusions This work examined the effects of nitrogen on gene expression and amino acid synthesis and provides important evidence on the efficient use of nitrogen in Welsh onion.

First Report of Pythium Cluster B2a Species Causing Root Rot in Welsh Onion

Hiroshima Prefecture has the highest production area of hydroponically grown Welsh onions (Allium fistulosum L.) in Japan. Since the cultivation began in 1988, root rot (Fig. 1A) followed by leaf browning (Fig. 1B) has caused significant economic losses. Approximately 80% (loss of 45 million JPY) of plant loss occurred from May to Sep 2009 (Shimizu, unpublished), and the disease was observed again in 2020. Diseased Welsh onions (five to six leaf stage) were collected in 2009. Abundant nonseptate hyphae of Pythium-like organisms were observed in the rotted roots (Fig. 1C). Disinfected symptomatic tissue samples were placed on NARF medium (Morita and Tojo 2007) and incubated at 25°C for 3 to 7 days. Six Pythium-like organisms were isolated, and their morphological features on a grass blade culture, potato carrot agar (PCA) (van der Plaats-Niterink 1981), cornmeal agar (CMA) and V8 juice agar (Miller 1955) were examined. Hyphal growth rates from 1–46°C were measured by culturing on PCA. The ribosomal internal transcribed spacer (ITS) regions and mitochondrial COI of the isolates were amplified and sequenced according to Ueta and Tojo (2016). All six isolates obtained showed similar morphology, hyphal growth rates, and sequences of ITS and COI. Detailed descriptions are provided here for the representative isolate 72 (MAFF246451). The isolate produced asexual structures but did not form sexual structures, including oogonia, antheridia, and oospores on all the media used. Hyphae were up to 6.8 μm wide. Appressoria were knob-like terminations (Fig. 1D). Sporangia were filamentous and indistinguishable from the hyphae. Zoospores (Fig. 1E) were formed at 5–25°C. The diameter of encysted zoospores ranged 7.4–10.1 (av. 8.9) μm (Fig. 1F). Cardinal temperatures for hyphal growth on PCA were 5°C min, 28–31°C opt, and 35°C max. The daily growth rate at 25°C was 15.0 mm per day. The sequence analysis of all isolates, including isolate 72 (GenBank ac nos AB700596 for ITS, LC630955 for COI) showed the present isolates belonged to Pythium Cluster B2a (Robideau et al. 2011) (Fig. 2). Based on these features, the six isolates were identified as Pythium Cluster B2a sp. In the inoculation test, isolate 72 was cultured on CMA at 25°C for 5 days. Mycelium disks (5 mm diam) obtained from the culture were placed on the primary roots of 8-day-old Welsh onion seedlings (cv Koutou), which were grown at a density of six plants on rock wool cubes moistened with tap water in a 50 mL plastic pot. The inoculated and non-inoculated plants were grown at 28°C for 7 days in a growth chamber. The experiment was repeated twice using three pots per replication. The plants inoculated with isolate 72 wilted, and their roots rotted 7 days after inoculation. No disease was found observed on the non-inoculated plants. The isolate of Pythium Cluster B2a sp. was consistently re-isolated from the diseased plants, thus, fulfilling Koch’s postulates. Pythium Cluster B2a sp. causing stem rot on lettuce has been recorded in Italy (Garibaldi et al. 2017). To our knowledge, this is the first report of Pythium Cluster B2a sp. on Welsh onions. Since significant losses to root rot of Welsh onion have occurred in Japan, identification of the causal organism will enable the development of management practices to reduces losses.

Stemphylium Leaf Blight of Welsh onion (Allium fistulosum): An Emerging Disease in Sanxing, Taiwan

Welsh onion (Allium fistulosum L.) is one of the main and oldest vegetable crops grown in Taiwan. A severe epidemic of leaf blight in Welsh onion caused by a Stemphylium-like pathogen was found in Sanxing, Taiwan, from 2018 to 2020. However, correct species identification, biology and control of Stemphylium leaf blight (SLB) of Welsh onion is not well established. Therefore, the main objective of this study was to investigate the causal agent of SLB in Sanxing and evaluate the in vitro sensitivity of Stemphylium-like pathogen to commonly used fungicides. Phylogenetic analysis based on combining the internal transcribed spacer (ITS) region, and glyceraldedyhe-3-phosphate dehydrogenase (gapdh) and calmodulin (cmdA) gene sequences together with morphological features, identified S. vesicarium as associated with SLB in Sanxing. When inoculated onto Welsh onion leaves, the isolates caused symptoms identical to those seen in the field and S. vesicarium was reisolated, confirming Koch’s postulates. We observed a higher incidence of SLB symptoms on the oldest leaves compared with younger leaves. The maximum and minimum temperatures for in vitro mycelial growth and conidial germination (%) of S. vesicarium were 20 to 30°C and 5°C respectively. Sixteen fungicides were tested for their effectiveness to reduce the mycelial growth and conidial germination of S. vesicarium in vitro. Boscalid + pyraclostrobin, fluopyram, fluxapyroxad, fluxapyroxad + pyraclostrobin were highly effective at reducing mycelial growth and conidial germination in S. vesicarium. However, strobilurin fungicides (azoxystrobin and kresoxim-methyl) commonly used in Welsh onion production in Sanxing were ineffective. This study discusses the emergence of SLB caused by S. vesicarium in the foliar disease complex affecting Welsh onion and the management of the disease using fungicides with different modes of action in Taiwan. The research will underpin the sustainable management of SLB in Sanxing, Taiwan, however further field assessments of the fungicides are warranted.

Thiolane-type sulfides from garlic, onion, and Welsh onion

In this paper, we review our work in the last 10 years wherein we examined the sulfides in the acetone extracts of garlic (Allium sativum), onion (A. cepa), and Welsh onion (A. fistulosum), obtained and characterized the structures of new sulfides, three 3,4-dimethylthiolane-type sulfides from onion and Welsh onion, respectively, and four acyclic-type, nine 3,4-dimethyl- thiolane-type, four 2-methylthiolane (and thiane)-type, two 1,2-dithiolane-type, and two 2-oxothiolane-type sulfides, together with (E)-ajoene and one kujounin-type sulfide from garlic. During this process, structural corrections were made in onionin A group, garlicnin A, and garlicnin B group in some 3,4-dimethylthiolane-type sulfides. Next, hypothetical pathways for the production of the aforementioned sulfides were proposed. Furthermore, it was revealed that a typical 3,4-dimethylthiolane-type sulfide, onionin A1 obtained from onion, having the isomeric structure of garlicnin B1 obtained from garlic, decreased tumor proliferation and controlled tumor metastasis. These results showed that onionin A1 is an effective agent for controlling tumors, and that the antitumor effects observed in vivo are likely caused by reversing the antitumor immune system. Activation of the antitumor immune system by onionin A1 might be an effective adjuvant therapy for patients with osteosarcoma, ovarian cancer and other malignant tumors.

Phage Biocontrol of Bacterial Leaf Blight Disease on Welsh Onion Caused by Xanthomonas axonopodis pv. allii

Bacterial leaf blight, which is caused by Xanthomonas axonopodis pv. allii, annually causes significant yield losses to Welsh onion in many producing countries, including Vietnam. In this study, we isolated and characterized lytic phages ɸ16, ɸ17A and ɸ31, specific to X. axonopodis pv. allii and belonging to a new phage species and genus within the Autographiviridae, from four provinces in the Mekong Delta of Vietnam. Moreover, we evaluated their efficacy for the biocontrol of leaf blight in greenhouse and field conditions. When applying the three highly related phages individually or as a three-phage cocktail at 108 PFU/mL in greenhouse conditions, our results show that treatment with ɸ31 alone provides higher disease prevention than the two other phages or the phage cocktail. Furthermore, we compared phage concentrations from 105 to 108 and showed optimal disease control at 107 and 108 PFU/mL. Finally, under field conditions, both phage ɸ31 alone and the phage cocktail treatments suppressed disease symptoms, which was comparable to the chemical bactericide oxolinic acid (Starner). Phage treatment also significantly improved yield, showing the potential of phage as a biocontrol strategy for managing leaf blight in Welsh onion.

Detection of Two Biotypes of Liriomyza chinensis (Diptera: Agromyzidae) in Japan

The larva of stone leek leafminer, Liriomyza chinensis (Kato), is known to infest alternately just below the epidermis and inner surface of hollow cylindrical leaves of allium crops, resulting in the formation of discontinuous linear mines (mine form: discontinuous). However, after the fall of 2016, a novel mine form of the same species (mine form: continuous) was detected in Welsh onion fields of Kyoto Prefecture, Japan. We hypothesized that these mine forms were associated with flies having different genetic backgrounds; hence, we compared the mine forms and the partial mtCOI gene of flies collected from Welsh onion fields from 2018 to 2019. The results demonstrated that the flies that emerged from different mine forms could be classified into two haplogroups, i.e., flies displaying a discontinuous mine form were of haplogroup A, whereas those that displayed continuous mines were of haplotype B. Additionally, using populations of these flies reared in the laboratory, we confirmed that the mine form of the larvae of haplotype A on Welsh onions was discontinuous, whereas that of haplotype B was continuous. We named the population that exhibited a discontinuous mine form as biotype A and the population displaying a continuous mine form as biotype B.

Phytochemical Analysis and In Vitro Effects of Allium fistulosum L. and Allium sativum L. Extracts on Human Normal and Tumor Cell Lines: A Comparative Study

Allium sativum L. (garlic bulbs) and Allium fistulosum L. (Welsh onion leaves) showed quantitative differences of identified compounds: allicin and alliin (380 µg/mL and 1410 µg/mL in garlic; 20 µg/mL and 145 µg/mL in Welsh onion), and the phenolic compounds (chlorogenic acid, p-coumaric acid, ferulic acid, gentisic acid, 4-hydroxybenzoic acid, kaempferol, isoquercitrin, quercitrin, quercetin, and rutin). The chemical composition determined the inhibitory activity of Allium extracts in a dose-dependent manner, on human normal cells (BJ-IC50 0.8841% garlic/0.2433% Welsh onion and HaCaT-IC50 1.086% garlic/0.6197% Welsh onion) and tumor cells (DLD-1-IC50 5.482%/2.124%; MDA-MB-231-IC50 6.375%/2.464%; MCF-7-IC50 6.131%/3.353%; and SK-MES-1-IC50 4.651%/5.819%). At high concentrations, the cytotoxic activity of each extract, on normal cells, was confirmed by: the 50% of the growth inhibition concentration (IC50) value, the cell death induced by necrosis, and biochemical determination of LDH, catalase, and Caspase-3. The four tumor cell lines treated with high concentrations (10%, 5%, 2.5%, and 1.25%) of garlic extract showed different sensibility, appreciated on the base of IC50 value for the most sensitive cell line (SK-MES-1), and the less sensitive (MDA-MB-231) cell line. The high concentrations of Welsh onion extract (5%, 2.5%, and 1.25%) induced pH changes in the culture medium and SK-MES-1 being the less sensitive cell line.