Aspects of interspecific hybridization within edible <Emphasis Type="Italic">Alliaceae</Emphasis>

Crossing experiments within the genus Allium have been carried out for many years. Usually, with the aim of widening genetic variation, edible Alliaceae such as bulb onion, Japanese bunching onion, leek, garlic and shallot have been crossed with each other or with distant vegetable Allium crops. Interspecific hybridization, especially with wild relatives is considered as the best way of introgression desirable traits to the crops. By using sexual or somatic hybridization, many important characters, such as: disease and pest resistance, important metabolites and cytoplasmic male sterility have been transferred to other Allium crops. This review summarises some aspects of the directions of interspecific hybridization in edible Alliaceae and the significance and perspectives of using these hybrids in breeding programmes.     

Quercetin-4′-glucoside: a physiological inhibitor of the activities of dominant glutathione <Emphasis Type="Italic">S</Emphasis>-transferases in onion (<Emphasis Type="Italic">Allium cepa</Emphasis> L.) bulb

The onion (Allium cepa L.) bulb has a high level of glutathione S-transferase (GST) activity, and it is a rich source of sulfur compounds as well as flavonoids. To investigate interactions between onion bulb GSTs and metabolites, we separated onion bulb GSTs (GSTa and GSTb as minor GSTs and GSTc, GSTd and GSTe as dominant GSTs) by DEAE-cellulose chromatography. In Western blot analysis with anti-CmGSTF1 antiserum, GSTc and GSTd fractions showed a thick band. A cDNA (AcGSTF1) corresponding to GSTc was immunoscreened with the same antiserum from an onion bulb cDNA library and its bacterial expression product was also subjected to investigation. Among the sulfur compounds, nonphysiological compounds, S-hexyl glutathione (GSH) and S-butyl GSH, showed strong inhibitory effects on 1-chloro-2,4-dinitrobenezene (CDNB)-conjugating activities of GSTa, GSTb and GSTe. However, physiological sulfur compounds, S-methyl GSH, S-propyl GSH, S-lactoyl GSH and S-ethyl-l-cysteine sulfoxide, had small or almost no inhibitory effects. Therefore, onion sulfur compounds might have the least possibility to be substantial inhibitors of onion GSTs. On the other hand, the activities of GSTc, GSTd and AcGSTF1 were strongly inhibited by flavonoids, quercetin, luteolin, apigenin and kaempferol. Ethylacetate (EtOAc) extract of onion bulb contained quercetin-4′-glucoside as a major inhibitory substance. The strong inhibitory effects of quercetin-4′-glucoside on GSTc and GSTd as well as on AcGSTF1 (50% inhibitory concentration (IC₅₀): 9.5, 7.5 and 11.2 μM, respectively) along with its high concentration (226 μM) in the onion bulb indicates that quercetin-4′-glucoside is a physiological inhibitor of dominant GSTs in the onion bulb.     

Molecular characterization of European and Egyptian isolates of Sclerotium cepivorum,the incitant of onion white rot

Abstract

The tested European and Egyptian isolates of Sclerotium cepivorum were able to infect Giza 6 onion cultivar causing white rot disease with a different degrees of disease severity (ranging from sever to weak). The pattern of esterase isozymes produced by the tested isolates of the pathogen showed two main bands (arrows) which were different in density. Such differences in density of bands were present in every run and therefore appear to be indicators for differences among the tested isolates. Analysis of the protein pattern of the tested isolates of the pathogen indicated that the tested isolates had major proteins of a molecular weight of 52, 36, 23 and 16 kDa. Variation between isolates was detected by presence of bands of low molecular weight. Isolate Nos. 1, 4, 5, 7, 8, 9, 10 and 13 had a band at 17 kDa, whereas isolate Nos. 2, 3, 6, 11, 12, 14, and 15 had a band at 20 kDa. Using RAPD analysis to evaluate the genetic diversity of the tested isolates indicated that the tested field population of the pathogen was genetically heterogeneous but shared a number of common bands with molecular weights ranging from 650 to 2500 bp. Based on the DNA banding pattern the tested isolates can be assigned to seven genetically different groups. All tested isolates produced a band at 2500 bp except isolate No. 7. No correlation was exibited between patterns esterase isozmes, protein and DNA patterns of S. cepivorum isolates and their virulence or geographical origin.     

A Comparison of Pectinases from Ditylenchus dipsaci and Allium cepa Callus Tissue

Ground and whole Ditylenchus dipsaci maintained on onion callus contain no culturable micro-organisms when tested with five check media. Healthy onion callus does not produce pectolytic enzymes. Pectolytic enzymes are present in infected callus. These enzymes are, however, associated with resident nematodes and not host tissues. These results suggest that D. dipsaci is the actual source of the endo-polygalacturonase and endo-pectinmethyltrans-eliminase extracted from them.     

Pectinases in Aqueous Extracts of Ditylenchus dipsaci

Aqueous extracts of a population of Ditylenchus dipsaci isolated from onion and maintained monoxenically on onion callus contained endo-polygalacturonase (endo-PG) and endo-pectinmethyltranseliminase (endo-PMTE). In viscometric tests pH 4.2 and 4.0 were optimal for degradation of sodium polypectate and pectin N.F., respectively, by endo-PG. Endo-PMTE reduced viscosity of pectin N.F. optimally at pH 8.5 or above. Activity was dependent on CaCl₂. Pectinmethylesterase activity was not detected in water, NaCl, or sucrose extracts of these nematodes. The extracts macerated potato tuber tissue, onion cotyledonary tissue, and strips of onion epidermis from the ventral surface of onion bulb scales at pH 4.2, 5.3, and 6.2. Pectin could not be localized with hydroxylamine-ferric chloride reagent in macerated tissues treated for 24 hr with active extract.     

DNA polymorphism in Allium cepa cytoplasms and its implications concerning the origin of onions

Summary Mitochondrial and chloroplast DNA was isolated from fertile and cytoplasmic male sterile cultivars of cultivated onions. Restriction fragment length polymorphism led to the distinction between cytoplasms S and M. Mitochondrial DNA patterns from S cytoplasms appeared dentical and characterized mostly male sterile lines. An open-pollinated variety was found to bear this cytoplasm and thought to be the origin of S types. Mitochondrial DNA patterns from M cytoplasms were subdivided into four types, M₁ and M₂ corresponding to normal N cytoplasm, M₃ and M₄ probably corresponding to T cytoplasms. S and M cytoplasms were also distinguished by chloroplast DNA restriction patterns. Our results confirm previous genetic distinction between S, N and T cytoplasms.     

Performance of down-flow hanging sponge (DHS) reactor coupled with up-flow anaerobic sludge blanket (UASB) reactor for treatment of onion dehydration wastewater

In this study, a promising system consisting of up-flow anaerobic sludge blanket (UASB) reactor followed by down-flow hanging sponge (DHS) reactor was investigated for onion dehydration wastewater treatment. Laboratory experiments were conducted at two different phases, i.e., phase (1) at overall hydraulic retention time (HRT) of 11 h (UASB reactor: 6 h and DHS reactor: 5 h) and phase (2) at overall HRT of 9.4 h (UASB reactor: 5.2 h and DHS reactor: 4.2 h). Long-term operation results of the proposed system showed that its overall TCOD, TBOD, TSS, TKN and NH₄N removal efficiencies were 92 ± 5, 95 ± 2, 95 ± 2, 72 ± 6 and 99 ± 1.3%, respectively (phase 1). Corresponding values for the 2nd phase were 85.4 ± 5, 86 ± 3, 87 ± 6, 65 ± 8 and 95 ± 2.8%. Based on the available results, the proposed system could be more viable option for treatment of wastewater generated from onion dehydration industry in regions with tropical or sub-tropical climates and with stringent discharge standards.     

Fluctuations in concentration of two potyviruses in garlic during the growing period and sampling conditions for reliable detection by ELISA

To optimise sampling conditions for the detection by ELISA of Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV), the most important viral pathogens of garlic worldwide, relative virus concentrations were determined during the growing period and in different leaf parts by DAS‐ELISA. Both viruses were found to have uneven distributions in garlic plants, with the tips of the two latest fully developed leaves showing the highest concentrations and the oldest leaves the lowest concentrations. The tips of the youngest leaves were found to have higher virus concentrations than their middle and basal sections. In the older leaves, viruses were distributed more uniformly in the three leaf sections. In the oldest leaves virus levels in the leaf tips were significantly decreased. The concentrations of OYDV and LYSV increased until March, whereas later on they decreased. During storage of leaf samples at 6°C for 15 days, a loss was found of both virus antigens of more than 80%, and during 109 days of storage at ?30°C a loss of more than 90% was found.     

Molecular characterisation of Onion yellow dwarf virus (OYDV) infecting garlic (Allium sativum L.) in Israel: Thermotherapy inhibits virus elimination by meristem tip culture

Garlic (cv. Shani) was tested using single step RT‐PCR and digoxygenin (DIG) labelled dot‐blot for a number of viruses. Following sequence analysis it was shown that at least three different polymorphs of the potyvirus Onion yellow dwarf virus (OYDV) infect the same plant simultaneously, together with the potyvirus Leek yellow stripe virus (LYSV), the carlavirus Garlic common latent virus (GCLV) and a multitude of allexiviruses (Shallot virus X (ShVX) related viruses]. Several garlic plants free of all the viruses tested were obtained through meristem‐tip culture. Plants infected with single viruses or with different combinations of viruses were similarly obtained. Meristem‐tip culture was confirmed as a satisfactory method of virus eradication, while thermotherapy treatment given to mother plantlets before meristem excision was found to specifically antagonise OYDV eradication. This work uses molecular methods for the first time to examine the effectiveness of meristem‐tip culture for the eradication of multiple viruses from garlic.