Variation in economically and ecologically important traits in onion plant organs during reproductive development

The spatial distribution of organosulphur compounds throughout the onion (Allium cepa L.) plant body during reproduction is of ecological and horticultural interest. These secondary metabolites are associated with both pest resistance and many of the vegetable's culinary and medicinal properties, including the ability to inhibit platelet aggregation. Inhibition of platelet aggregation can be of benefit to human cardiovascular health. Organosulphur compound concentrations are associated with elemental sulphur, pungency, soluble solids and effect on human platelet aggregation. These parameters were evaluated in extracts collected separately from bulb scales, leaf blades, scapes and umbels biweekly throughout the reproductive phase of the life cycle of the onion. Significant variation in pungency, platelet inhibition, total sulphur content and soluble solids existed among samples of organs and within organs over time during reproductive growth. Furthermore, some extracts from leaf, scape and bulb induced rather than inhibited platelet aggregation.     

Seed quality effects in bulb onions (Allium cepa L.)

The nature and persistence of seed quality effects produced by a range of seed production treatments was investigated in the autumn-sown onion crop. Genotypically equivalent seed lots raised in different glasshouses within the same year were found to germinate at significantly different rates. The seed lot which emerged earlier produced larger seedlings and this difference in size persisted throughout the growing period. In a comparison between the effects of hand crossing and self-pollination techniques the hand crossing method produced a much lower total seed yield but heavier seeds and larger plants. The induced effects persisted throughout the year but were not significant in the mature bulb characters. The implications of these results upon the control of seed production for plant breeding and genetical experiments is discussed.     

洋葱花器数目变异研究

以洋葱JQS-1、MST-140、Red beauty 3个常规栽培品种的鳞茎为试材,观察统计洋葱花器数目的变化,探讨花器数目的变异与植物花器多样性的关系,为植物花器发育模式以及植物分类和系统发育研究提供依据。结果表明:(1)洋葱花序中正常的洋葱小花含有6枚雄蕊,一些异常小花雄蕊的数目减少到5枚或增加到7~11枚;正常花药中的花粉粒数量大、形状规则、分散均匀,而异常花药中的花粉粒形状不规则。(2)雌蕊数目也发生变异,子房由正常的3室,变成了2室、4室或6室;花柱从正常1枚,增加到2枚或3枚。(3)正常小花含有6片花被片,异常小花的花被片数目从5片到10片。(4)花被片与雄蕊数目的变异有同步增减和非同步增加2种类型。     

Cytotoxic and genotoxic effects of dioxacarb by human peripheral blood lymphocytes CAs and Allium test

Dioxacarb (Elecron, Famid) is a phenyl methylcarbamate insecticide and in vitro cytotoxic and genotoxic effects of this pesticide on human peripheral blood lymphocytes and Allium root meristematic cells were investigated by chromosomal aberrations (CAs) and Allium test. Human lymphocytes were treated with 62.5, 125, 250 and 500 ppm doses of dioxacarb for CAs. CA/cell, abnormal cell % and mitotic index % (MI %) data were obtained from these concentrations in 24 and 48 h treatment periods. Dioxacarb did not increase the CA/cell frequency significantly, so this insecticide was not identified as genotoxic. But it was found cytotoxic especially at 250 and 500 ppm concentrations because of the reduced the MI % and increased the abnormal cell %. In Allium test, 25 ppm (EC50/2), 50 ppm (EC50) and 100 ppm (EC50 × 2) concentrations were used for root growth inhibition (EC50 determination) and Allium mitotic index (MI) determination tests. The used concentrations of dioxacarb induced dose-dependent inhibition of MI and root growth on root meristems. Mitotic inhibition of dioxacarb was found significantly higher than for the positive control. These Allium results indicated the high cytotoxicity of dioxacarb. The present study is the first research on cytotoxicity and genotoxicity of dioxacarb by human lymphocyte CAs and Allium test.     

Contrasting responses to Pleistocene climate changes: a case study of two sister species Allium cyathophorum and A. spicata (Amaryllidaceae) distributed in the eastern and western Qinghai–Tibet Plateau

It has been hypothesized that species occurring in the eastern and the western Qinghai–Tibet Plateau (QTP) responded differently to climate changes during the Pleistocene. Here, we test this hypothesis by phylogeographic analysis of two sister species, Allium cyathophorum and A. spicata. We sequenced two chloroplast DNA (cpDNA) fragments (accD‐psaI and the rpl16 intron) of 150 individuals, and the nuclear (ITS) region of 114 individuals, from 19 populations throughout the distributional ranges of these species. The divergence between the two species was dated at 779 ‐ 714 thousand years before the present and was likely initiated by the most major glaciation in the QTP. Analysis of chlorotype diversity showed that A. spicata, the species occurring in the western QTP, contains much lower genetic diversity (0.25) than A. cyathophorum (0.93), which is distributed in the eastern QTP. Moreover, multiple independent tests suggested that the A. spicata population had expanded recently, while no such expansion was detected in A. cyathophorum, indicating a contrasting pattern of responses to Pleistocene climate changes. These findings highlight the importance of geographical topography in determining how species responded to the climate changes that took place in the QTP during the Pleistocene.     

The influence of intercropping with Allium on some insect populations in potato (Solatium tuberosum)

Two field experiments were conducted in West Java, Indonesia to investigate the effects on insect populations in a potato crop of intercropping with Allium cepa or A. sativum. Intercropping reduced populations of Myzus persicae, Aphis gossypii and Empoasca spp. when less than 0.75 m separated the potato plants and Allium spp. Leaf damage to potato by Henosepilachna sparsa was also reduced at this spacing; but populations of Thrips palmi or T. parvispinus were increased. The implications of these trends are noted.