Pseudomonas alliivorans sp. nov., a plant-pathogenic bacterium isolated from onion foliage in Georgia,USA

This study provides a taxonomic characterization of three bacterial strains isolated from onion seedlings in Georgia USA. Yellow-colored colonies were isolated, and a diffusible fluorescent pigment was visible under ultraviolet light on King’s medium B. Preliminary analysis of the basic phenotype tests and 16S rRNA gene sequence analysis indicated the onion strains were closely related to Pseudomonas viridiflava with the highest similarity to P. viridiflava DSM 6694^T (99.6%). The phylogenomic analyses based on whole genome sequences showed that the onion strains formed a separate monophyletic clade from other species with P. viridiflava as the closest neighbor. When the onion strains and the P. viridiflava type strain were compared, the average nucleotide identity values was 91.6%. Additionally, the digital DNA–DNA hybridization values of the onion strains were 45.8% or less when compared to the type strains of their close relatives, including P. viridiflava. In addition, biochemical, physiological features, and cellular fatty acid compositions were determined for a polyphasic taxonomic analysis. The results supported that the three onion strains represented a novel Pseudomonas species. We propose a new species as Pseudomonas alliivorans sp. nov., with 20GA0068^T (=LMG 32210^T = CFBP 8885^T) as the type strain. The DNA G + C content of the strain 20GA0068^T is 59.1 mol%.     

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.     

Onion yield as affected by plant density,nitrogen level and loss of leaf area

Onion (Allium cepa) is an important horticulture crop because of its value as a food with a long shelf life being a relatively non-perishable product. It is very helpful to understand the growth response of the seeded onion crop to conduct appropriate field practices in attaining the highest or optimum yields. A three year field experiment was conducted using a variety of onion Valcatorce INTA, in a randomized block design with five replicates. Treatments were two plant densities and three rates of N application. The bulb growth followed a classical sigmoid curve. During the rapid growing period, the crop had the greatest leaf area (LA) with at least six leaves per plant. Increasing plant density increased yield in kg/ha, but decreased bulb size. Defoliating 40 to 60% of the LA had a significant impact on bulb production only at early growth stages. Late in the growing period, the remaining LA was apparently large enough for producing sufficient amounts of metabolites to feed new leaves, increasing their photosynthesis efficiency for the benefit of bulb production.     

洋葱大葱种间杂种鉴定方法建立与应用

以洋葱、大葱及其杂种F1为材料,利用PCR-RFLP技术对其核糖体DNA内部转录间隔区（ITS）和细胞质线粒体DNA的srRNA基因V7进行分析,试图建立洋葱大葱种间杂种的鉴定方法。结果显示：大葱ITS序列没有DdeⅠ酶切位点;而洋葱被DdeⅠ酶切成两个大小不同的片段;F1杂种具有两亲本的ITS序列酶切模式。细胞质线粒体srRNA基因的V7区域的扩增表明F1杂种和亲本有大小一致的单一片段,经RsaI酶切后,大葱有约0.3 kb条带,比洋葱的稍小,两亲本都含有另外一条小条带（约0.1 kb）。对25份杂种材料进行鉴定,22份的母本为大葱,3份为假杂种。本研究在分子水平上建立了洋葱大葱种间杂种的鉴定方法,快速、准确的辨别杂种一代的真假性。     

洋葱鳞茎薄壁细胞原生质体胞质肌动蛋白质微丝骨架的形态与结构

使用四甲基罗丹明标记的鬼笔环碱(TRITC-Ph)探针,以新分离的洋葱鳞茎薄壁细胞原生质体为材料,观察了细胞胞质肌动蛋白微丝骨架的结构与形态。研究结果发现洋葱鳞茎内部细胞的细胞质内存在极丰富而精细的肌动蛋白微丝束。这些肌动蛋白微丝束的直径约1.0—4.5μm,有下列四种不同的排列形式:(1)相互平行排列,方向大体与细胞的长轴垂直;(2)从一些结合位点辐射而出,并向四周延伸,然后再相互交织在一起,形成一个非常密集而复杂的网络;(3)细而稀疏,相互交织成网状,两端分别与质膜不同位置上的结合位点相连;(4)粗而稀疏,相互交织成网状,两端都与质膜相连,或一端与质膜相连,另一端与细胞核周围的微丝束网络相连。部分微丝束具有“Y”形分支。     

离子胁迫诱导洋葱鳞茎内表皮细胞凋亡

通过不同浓度离子胁迫诱导剂(NaCl、CaCl2)对洋葱鳞茎内表皮细胞进行不同时间的处理,发现0.1M、0.5M的NaCl和CaCl2处理2小时即可诱导出细胞凋亡现象,随处理时间延长直至10小时,细胞核凋亡的形态学变化和凋亡小体更加明显,基因组DNA降解更加梯状条带化。本实验对离子诱导的洋葱鳞茎内表皮细胞凋亡现象做了较系统的描述,为植物细胞凋亡的研究及细胞凋亡实验教学提供了经济、快捷、有效的诱导方法。     

Harvesting of Onion Grass,Romulea rosea L. by Sulphur‐crested Cockatoo,Cacatua galerita Latham

The harvesting of Onion Grass (Romulea rosea) corms by flocks of Sulphur‐crested Cockatoo (Cacatua galerita) is well known. Individual birds and large flocks feed on the weed in pastures, grasslands and recreational turf. Flocks of Sulphur‐crested Cockatoo were observed feeding on Onion Grass at seven sites along the Maribyrnong River at Keilor, Victoria. Flock size and feeding habits were noted, as were the depth of corms, the time taken to remove corms from the ground and the number of eaten and lifted but uneaten corms. From the data collected, it was estimated that an individual bird can extract and eat about 200 plants per hour and that even a small flock can consume several thousand plants in a feeding session. Corms were typically within 20 mm of the soil surface and were removed primarily by the cockatoo with its beak, but the left foot was sometimes used to excavate the corm from the soil. Flock feeding sessions lasted from about 0.5 to 2.5 hours, but feeding by individual or pairs of birds was often shorter. Plants that had been removed from the soil appeared to have intact corms, but all that was left were the outer scales. Of the plants removed from the soil, only 6% had intact corms attached. The removal of large numbers of Onion Grass plants could impact on their population numbers over time if there was repeated annual harvesting.     

Effect of fungicides on mycorrhizal colonization and growth of onion

Summary Effect of five fungicidesviz Agrosan. Benlate, Captan, Ceresan and Plantavax on VA mycorrhizal symbiosis in onion was studied in a phosphorus deficient, sandy loam soil. Two levels of fungicides (2.5 g and 25 g/g soil) were applied to the soil. Agrosan, Benlate and Plantavax applied at 25 g/g soil reduced the mycorrhizal colonization significantly. All the fungicides, except Captan, applied at lower concentration reduced plant growth and P uptake. Captan applied at the lower concentration had no effect on mycorrhizal colonization, plant growth and P uptake, and when applied at higher concentration had least effect on plant growth compared to other fungicides.Contribution of U.A.S. Research project DR/AMB-1.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the change of rhythmicity

When pupae of Delia antiqua were transferred to constant darkness (DD) from light-dark (LD) cycles or constant light (LL), the sensitivity to light of the circadian clock controlling eclosion increased with age. The daily rhythm of eclosion appeared in both non-diapause and diapause pupae only when this transfer was made during late pharate adult development. When transferred from LL to DD in the early pupal stage, the adult eclosion was weakly rhythmic in non-diapause pupae but arrhythmic in diapause pupae. However, the sensitivity of the circadian clock to temperature cycles or steps was higher in diapause pupae than in non-diapause pupae; in the transfer to a constant 20 degrees C from a thermoperiod of 25 degrees C (12 h)/20 degrees C (12 h) on day 10 after pupation or from chilling (7.5 degrees C) in DD, the adult eclosion from diapause pupae was rhythmic but that from non-diapause pupae arrhythmic. In a transfer to 20 degrees C from the thermoperiod after the initiation of eclosion, rhythmicity was observed in both types of pupae. The larval stage was insensitive to the effect of LD cycle initiating the eclosion rhythm. In D. antiqua pupae in the soil under natural conditions, therefore, the thermoperiod in the late pupal stage would be the most important 'Zeitgeber' for the determination of eclosion timing.     

洋葱细胞质雄性不育系70及其保持系71基因组DNA的RAPD分析

采用RAPD技术,对洋葱细胞质雄性不育系70及其保持系71的基因组DNA的多态性进行分析。结果表明,在被检测的100条随机引物中,46条引物具有扩增产物,5条引物扩增出多态性条带。对这5条引物进行重复筛选和单株验证,只有G02扩增出的多态性片段,且表现稳定。推测该标记与育性有关。     

激光辐照洋葱L1代的生理效应研究

采用ＣＯ２和Ｈｅ－Ｎｅ两种激光的三种剂量,分别辐照两个洋葱品种的湿种子,采用生理生化的方法,从过氧化氢酶、叶绿素、总糖总量等三个方面考查研究洋葱Ｌ１各处理的生物学效应。结果表明：Ｈｅ－Ｎｅ激光辐照洋葱Ｌ１代的过氧化氢酶、叶绿素、总糖含量的变异大于ＣＯ２激光辐照,可作为激光诱导变洋葱育种参考。     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua

The influence of pupal diapause on adult eclosion rhythm of Delia antiqua was investigated. When non-diapause and diapause pupae were exposed to various photoperiods at 15, 20 and 25 °C, both of them emerged as adults close to the light-on time, but the phase of eclosion varied with photoperiod and temperature. Moreover, there was a significant difference in the eclosion time between non-diapause and diapause pupae; the eclosion peak of diapause pupae was earlier than that of non-diapause pupae. When non-diapause and diapause pupae were transferred to constant darkness (DD) after having experienced LD 12:12 at 15, 20 and 25 °C, both showed circadian rhythmicity in eclosion. Although the free-running period (τ) decreased slightly as temperature increased in both non-diapause and diapause pupae, the latter tended to show shorter τ than the former. This observation suggests that the observed difference in eclosion time in LD cycles between non-diapause and diapause pupae is due to differences in τ.     

激光辐照洋葱种子的生物学效应初探

采用Ｈｅ－Ｎｅ激光和ＣＯ２激光辐照洋葱两个品种的湿种子,采用随机区组设计,重复３次,利用生物统计学的方法,从个体水平上初步考查诱变Ｌ１代的生物学效应。结果表明：在出苗率、苗高、叶数、须根长、须根数、苗重、须根重等性状表现出不同处理所引起的生物学效应差异,激光种类不同,引起须根长的变异达到５％的显著差异,激光剂量不同引起须根数变异显著,苗高和苗重的变异达到极显著。     

Interacting effect of thermoperiod and photoperiod on the eclosion rhythm in the onion fly, Delia antiqua supports the two-oscillator model

Daily light and temperature cycles entrain adult eclosion rhythms in many insect species, but little is known about their interaction. We studied this problem in the onion fly, Delia antiqua. Pupae were subjected to various combinations of a photoperiod of 12L:12D and thermoperiods. The thermoperiods consisted of 12 h warm phase (W) and 12 h cool phase (C), giving a mean temperature of 25 °C with different temperature steps of 8, 4 and 1 °C. As the phase relation of the two Zeitgebers was varied, the phase of eclosion rhythm was shifted, depending on the phase angle with the light cycle and the amplitude of the temperature cycle. When the temperature step in the thermoperiod was 8 °C (WC 29:21 °C), the eclosion rhythm was entrained mainly to thermoperiod rather than photoperiod. In the regime with a 4 °C temperature step (WC 27:23 °C), both thermoperiod and photoperiod affected eclosion rhythm, and a phase jump of the eclosion rhythm occurred when the warm phase of thermoperiod was delayed 15-18 h from light-on. In regimes with a 1 °C temperature step (WC 25.5:24.5 °C), the eclosion rhythm was completely entrained to photoperiod. The observed interacting effect of light and temperature cycle on the eclosion rhythm in D. antiqua can be explained by the two-oscillator model proposed by Pittendrigh and Bruce (1959).     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua: the effect of thermoperiod

When non-diapause and diapause pupae of Deliaantiqua were exposed to various thermoperiods where thermophase (T) was 25 °C and the cryophase (C) was 15 or 20 °C (TC₁₅ or TC₂₀) in constant darkness (DD), the majority of both types of flies emerged before the rise in temperature. Eclosion time was delayed at the lower cryophase temperature. Moreover, there was a significant difference in the time of adult eclosion between non-diapause and diapause pupae; diapause pupae eclosed earlier than non-diapause pupae. When the two types of pupae were transferred to a constant low temperature (15 or 20 °C) after having experienced TC₁₅ or TC₂₀ 12:12 h, they showed circadian rhythmicity in eclosion. The free-running period (τ) of the eclosion rhythm changed after transfer to constant low temperatures in both non-diapause and diapause pupae, suggesting that this change represents a transient cycle until the temperature-sensitive oscillator is coupled again to the temperature-insensitive pacemaker. However, diapause pupae tended to show a shorter τ than non-diapause pupae. This observation suggests that the difference in adult eclosion time under thermoperiodic conditions between non-diapause and diapause pupae is related to their different τ s.     

Isozyme analysis of progeny derived from (Allium fistulosum ×Allium cepa) ×Allium cepa

Summary Relatively large quantities of seed were obtained from the interspecific backcross (A. fistulosum xA. cepa) ×A. cepa allowing, for the first time, an extensive study of the heritable traits exhibited by backcross progeny. Two backcross populations, BC1034 and BC1040, distinguished by differentA. fistulosum parents, were characterized for the isozyme markersIdh-1, Adh-1, andPgi-1. Statistical methods are described to calculate cell probabilities for a mixed population of F₂ and BC₁ progeny, using an estimate of the fraction of F₂ progeny in the population derived from the isozyme data. Cell probability distributions were calculated for a mixed population with independent pairs of loci and a mixed population with nonindependent pairs of loci. The isozyme lociIdh-1 andPgi-1 appear to be linked, with a map distance estimated at 33 centimorgans (cM) in BC1034 and 42 cM in BC1040. The probability distribution model for linked loci did not account for all of the distorted segregation ratios inIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The cytological literature does not support linkage betweenIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The distorted segregation ratios for these pairs of loci are likely the result of genetic incompatibilities between the two species.Journal Article No. 1578, Agricultural Experiment Station, New Mexico State University, Las Cruces, NM, USA     

Burkholderia semiarida sp. nov. and Burkholderia sola sp. nov., two novel B. cepacia complex species causing onion sour skin

Two putative novel Burkholderia cenocepacia lineages found in the semi-arid region of north-east Brazil causing onion sour skin were studied using genomic approaches to determine their taxonomic position. Four strains belonging to one novel lineage (CCRMBC16, CCRMBC33, CCRMBC74, and CCRMBC171) and one strain (CCRMBC51) belonging to another novel lineage had their whole genome sequenced to carry out taxogenomic analyses. The phylogenomic tree built using the type (strain) genome server (TYGS) clustered the strains CCRMBC16, CCRMBC33, CCRMBC74, and CCRMBC171 into the same clade, while grouped the strain CCRMBC51 separately. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) analysis showed values above 99.21 % and 93.2 %, respectively, among the strains CCRMBC16, CCRMBC33, CCRMBC74, and CCRMBC171, while ANI and dDDH values between these strains and the strain CCRMBC51 were below 94.49 % and 56.6 %, respectively. All these strains showed ANI and dDDH values below 94.78 % and 58.8 % concerning type strains of the B. cepacia complex (Bcc) species. The phylogenetic maximum likelihood tree constructed based on the multilocus sequence analysis of core genes (cMLSA) clustered the strains CCRMBC16, CCRMBC33, CCRMBC74, and CCRMBC171 and the strain CCRMBC51 in two exclusive clades, which did not cluster with any known species of the Bcc. Therefore, combined data from TYGS, ANI, dDDH, and cMLSA demonstrated that the strains represent two novel species of the Bcc, which we classified as Burkholderia semiarida sp. nov. and Burkholderia sola sp. nov., and proposed the strains CCRMBC74^T (=IBSBF 3371 ^T = CBAS 905 ^T) and CCRMBC51^T (=IBSBF3370^T = CBAS 904 ^T) as type strains, respectively.     

The biology and host specificity of the onion weed rust, Puccinia barbeyi, a potentially useful agent for biological control in Australia

Onion weed, Asphodelus fistulosus L., (Liliaceae) a weed of Mediterranean and Middle Eastern origin is widespread in southern Australia where it invades pastures making them unsuitable for grazing. A program of research is underway to discover natural enemies of this plant and to study their possible role in the biological control of onion weed. A rust fungus Puccinia barbeyi (Roum.) Magnus has been found to severely attack A. fistulosus . Observations on the biology of the rust confirmed that it is monoecious and microcyclic and multiplied essentially by aecial and telial stages, although occasionally urediniospores also appeared among teliospores. Several members of the Liliaceae exposed to the aeciospores of the rust remained unattacked indicating that it is most probably specific to Asphodelus spp. and thus its potential for the biological control of A. fistulosus in Australia should be studied further.     

Analytical study of phenotypic and biochemical attributes of onion cultivars in relation to infestation of onion thrips,Thrips tabaci

Onion thrips is a major threat to onion crop throughout the world. It is a potential vector of Iris yellow spot virus and causes significant economic damage to bulb production. Phenotypic and biochemical traits of onion cultivars were assessed against Thrips tabaci. Onion Gawran LR-241 (OG) cultivar was tolerant against the infestation of T. tabaci whereas Onion White (OW) was susceptible. Number and size of stomata, cuticle thickness, cell wall thickness and surface wax of onion leaves were studied with the help of scanning electron microscope and quantitative and qualitative analysis was carried out to estimate epicuticular wax and other bio-chemical components through GC/MS. Onion Gawran has thick cell wall, sharp and dense wax crystals, wider central angle and small sized stomata compared to other cultivars. Epicuticular wax components of OG cultivar were heptacosane (5.2%), octacosanol-1 (9.2%), 2-methyl octacosane (4.2%), heptadecanol-1 (5.2%), hexacosanol-1 (4.2%), azulene, 1,4-dimethyl-7-(1-methylethyl) (36.9%), hexadecanoic acid (1.95%), heptadecane (4.2%), triacontanol-1 (5.8%) and hentriacontanone-16 (23.40%). Azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) was only found 36.9% in OG but absent in other three cultivars. 2-methyl octacosane was absent in Poona Red Desi and OW cultivars. Hentriacontanone-16, 2-methyl octacosane, fatty alcohols (Octacosanol-1 and Triacontanol-1) and azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) were effective in the formation of epicuticular wax in onion cultivars. It implies that phenotypic and biochemical characteristics of OG cultivar proved as resisting features to T. tabaci.