Sequence heterogeneity of the ribosomal DNA inAllium cepa (Liliaceae)

Summary Southern blot hybridizations were performed to investigate the ribosomal DNA structure inAllium cepa (Liliaceae). The analysis of single and double digestions with Eco RI, Hind III, and Bam HI endonuclease restriction enzymes showed the presence of at least two types of repetitive units. The gene types were present in each single individual ofAllium cepa analyzed, notwithstanding the variation of the ribosomal gene number from 5,500 to 11,900 and the NOR number from 2 to 4. The first and the second gene type are 12.7 kb long and the first type is much more represented inAllium cepa genome. The differences between the two gene types consist in the position of the Hind III restriction sites in the external spacer.Work supported by CNR contract no. 74/0267.     

The plasmalemma surface area exposed to the soil solution is markedly reduced by maturation of the exodermis and death of the epidermis in onion roots

The dimorphic exodermis of the root of onion (Allium cepa L.) consists of long and short cells, both of which have Casparian bands. The long cells and some of the short cells also have suberin lamellae. The proportion of short cells with lamellae increases with distance from the root tip and with plant age, but is not influenced by drought stress. In young regions of onion roots, characterized by a mature endodermis and an immature exodermis, the plasmalemma surface area that can be contacted by the soil solution is 90·9 mm² per mm length of root, i.e. the sum of the plasmalemma surface areas of the epidermis, immature exodermis, cortical parenchyma and endodermis external to the Casparian band. This is reduced to 14·5–14·7 mm² by the development of a Casparian band in the exodermis, which cuts off access to the cortical parenchyma, and by the development of suberin lamellae, which cut off access to the plasmalemmae of the long and some of the short cells of the exodermis. Death of all the epidermal cells, a consequence of drought, further reduces this area to 0·205–0·0183 mm², i.e. the area of the outer tangential plasmalemmae of the short cells without suberin lamellae. In this condition, the root's capacity for ion uptake should be reduced but its capacity to resist water loss to the soil should be increased.     

SC-formation in someAllium species,and a discussion of the significance of SC-associated structures and of the mechanisms for presynaptic alignment

Earlier observations on synaptonemal complex (SC) formation inAllium are supplemented by data from diploidA. sphaerocephalon, pentaploidA. oleraceum and allotetraploidA. senescens. Accumulating information about structures like lateral element thickenings and -doublings allows to draw conclusions about their nature. The occurrence of discrete intercalary and terminal homologous associations prior to synapsis is confirmed for a range ofAllium species and it is argued that they are a general phenomenon. Several hypotheses on homologous recognition and/or attraction are discussed in the light of the observations on homologous alignment inAllium. Gratefully dedicated to my highly respected mentor, Prof. DrElisabeth Tschermak-Woess, on the occasion of her 70th birthday.     

Discrimination amongst Alliums using an electronic nose

Pyruvic acid content determination and, to lesser extents, thiosulphinates determination and organoleptic tests are used for assessing the eating characteristics of onions and other Allium spp. Each of these methods has inherent limitations, especially when large numbers of samples are to be evaluated. With a view to developing a more convenient quality evaluation method, an electronic nose was used to discriminate flavour and aroma characteristics amongst garlic, leek, shallot, bulb onion and spring onion. Differences in relative sensor response to headspace volatiles over macerated samples of these five different Allium types were recorded. Principal Component Analysis (PCA) showed some separation among the five types. PCA and Mahalanobis' D² statistic suggested similarities in headspace volatiles for shallot, spring and bulb onions and differences for leek and, especially, garlic. Multiple linear regression analyses (Y =α+β₁X₁+β₁X₂; N_{(x, Y)}=5) of the first two principal component values (PCA 1 [X₁] and PCA 2 [X₂]) accounted for not less than 90% of the total variation in pyruvic acid concentration (Y1), total soluble solids content (Y2) and percentage dry matter content (Y3) of the Allium types. These relationships suggest that electronic nose discrimination was on the basis of quality characteristics that relate to Allium flavour. This work has shown that the electronic nose has potential for flavour characteristic‐based discrimination amongst Allium types. Future work will explore this potential within a single Allium spp.     

The onset of cell proliferation is stimulated by ascorbate free radical in onion root primordia

Summary— Ascorbate free radical (AFR) accelerates the quiescency-proliferation shift in onion root primordia. The acceleration was detected by the increase of [³H]thymidine incorporation and by the anticipated kinetics of the increase in the labeling index. The shortening of the onset of cell proliferation is attributted to the role of AFR in the energization of the plasma membrane.     

Elucidation of an α-glucosidase inhibitor from the peel of Allium cepa by principal component analysis

We conducted liquid chromatography-mass spectrometry measurements on hot-water extracts of peel from different varieties of Allium cepa. Some quercetin glycosides were identified as potential α-glucosidase inhibitors by principal component analysis of the liquid chromatography-mass spectrometry data. α-Glucosidase inhibitory activity assays identified quercetin-4?-O-glucoside as an α-glucosidase inhibitor.     

Infestation of leek by Thrips tabaci as related to spatial and temporal patterns of undersowing

Full field undersowing of leeks with clovers suppresses populations of adult and larval Thrips tabaci. To explore the conditions for application of this approach of IPM in commercial practice, variations in the spatial and temporal pattern of clover undersowing were studied. Effects on thrips populations, crop growth and the development of thrips feeding symptoms were recorded. Assessment of the yield in quantity and quality was made. Sowing clover (Trifolium fragiferum) between rows resulted in significant and sufficient thrips population suppression and good yields. Similar results were achieved by full field sowing of clover simultaneous with leek crop planting. Reduced thrips feeding symptoms were found in intercropped leeks.     

Effect of 1,10-phenanthroline on peroxidase and catalase activity and chlorophyll, sugar, and ascorbic acid contents

Changes in the peroxidase (EC 1.11.1.7) and catalase (EC 1.11.1.6) activities, and total chlorophyll, soluble sugars, and ascorbic acid contents of leek leaves treated with the herbicide 1,10-phenanthroline (Phe) in concentrations 0.5, 2.5, 5.0, 7.5, and 10.0 mM have been determined. Plants treated with Phe were characterised by a higher activity of peroxidase and a lower activity of catalase and lower contents of chlorophyll, soluble sugars, and ascorbic acid as compared to non-treated plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Simplified rapid differentiation of Liriomyza chinensis Kato (Diptera; Agromyzidae) genotypes A and B using PCR-RFLP

The stone leek leafminer Liriomyza chinensis Kato is one of the most important pests of Allium spp. In recent years, a new genotype of L. chinensis, genotype B, has been shown to cause more severe damage to Allium spp. compared with the native genotype A in Japan. Thus, identification of the genotypes is important for establishing L. chinensis control strategies. In this study, we developed a simple and rapid method of genotype identification using PCR-restriction fragment length polymorphism (RFLP). Primers were designed to mitochondria cytochrome oxidase subunit I gene (mtCOI) nucleotide sequences from both genotypes. Genotypes A and B were successfully identified using the restriction enzymes PvuI and DdeI, respectively. Using PCR-RFLP, we identified the genotype of L. chinensis samples (n = 108) collected in seven Japanese bunching onion fields in Ibaraki Prefecture, Japan. All individuals were shown to be genotype B, as expected.