Studies on The Effects of Light Quality on The Growth and Development of Plants: II. Formative Effects in Lycopersicon Esculentum and Pisum Sativum

Diffuse and surface-growing bacteria are the two main types of non-pathogenic contaminants in the carnation cultured-cutting test. Wiping the base of the cutting with 10 % Stergene before sterilization decreased fungal contaminants. A medium containing o.o1% crystal violet was used to isolate Verticillium cinerescens from infected plants. It allowed growth of fungi and pathogenic Gram-negative bacteria from stem sections, but prevented growth of Gram-positive contaminants. This medium decreased bacterial contamination in the cutting test, especially from surface bacteria.     

Molecular identification and antibiotic control of bacterial contamination in cultures of ginger (Zingiber officinale)

Zingiber officinale, Rosc., one of the major tropical spices in the world, belongs to the family Zingiberaceae. Bacterial contamination is a major constraint on the cryopreservation of in vitro shoot tip explants. The main objective of this study was to identify the nature of this bacterial contamination and its response to various antimicrobial agents (e.g. the antibiotics cephotaxime and streptomycin sulphate, or copper sulphate) for more effective control. The bacteria isolated from ginger plantlets were identified by amplification and sequencing of their 16S ribosomal DNA, followed by partial sequence analysis. Luteibacter yeojuensis was found in all contaminated cultures. L. yeojuensis is found mainly in soil and as a human pathogen. We believe this is the first report of L. yeojuensis contaminating in vitro cultures of ginger. Among the antimicrobial agents tested in the shoot multiplication medium [i.e. 1.0× Murashige and Skoog salts + 2.5 mg l^–l 6-benzylaminopurine + 3% (w/v) sucrose + 0.45% (w/v) Clarigar^TM], 100 mg l^–1 cephotaxime was most effective at reducing bacterial growth. It also gave the maximum number of shoots per shoot bud explant compared to the same medium supplemented with streptomycin sulphate, or CuSO₄, or control medium. No further bacterial contamination was observed when 8-week-old cultures were then subcultured on the same medium without added antibiotic or CuSO₄.     

Vascular blockage in cut roses in a suspension of Pseudomonas fluorescens

Summary

To analyse quantitatively the relationships between cut rose (Rosa hybrida L. ‘Pascha’) vase-life, the onset of cavitation, plant water potential, and bacterial concentrations in the vase water, rose stems were placed in water containing different concentrations of Pseudomonas fluorescens 2892 tet^r rif ^r. There was a significant correlation (P = 0.0009) between cut rose vase-life and the concentration of bacteria in the vase water. As the number of bacteria in the vase water increased, the rate of senescence also increased. The water potential for roses in the bacterial suspension (at 8.50 log₁₀ CFU ml^–1) proceeded to drop constantly after 5.17 h in the vase solution, with the water potential falling to as low as -2.35 MPa by the end of the experiment (at 117 h). In contrast, the water potential of roses in deionised water dropped from -0.419 MPa at 5.17 h, to only –0.663 MPa after 117 h. When roses were stood in a bacterial suspension (at 8.5 log₁₀ CFU ml^–1) for 30 h, 63.8% of the total cumulative cavitation events were seen, while roses stood in deionised water exhibited only 26.8% of the total cavitation events. Uptake of acid fuchsin and the movement of tagged P. fluorescens 2892 in the xylem indicated that bacteria did not travel beyond the open-ended xylem vessels and were generally restricted to the first 50 mm from the cut end of the stem.     

In vitro propagation of ‘Arka Ravi’ chrysanthemum on growth regulator-free medium harbouring endophytic bacteria

Summary

To develop a micropropagation protocol for the elite chrysanthemum cultivar, ‘Arka Ravi’, in vitro cultures were established using surface-sterilised nodal microcuttings (1.0 – 1.2 cm) on semi-solid MS medium. Microbial contamination was observed in 22% of cultures during the initiation phase. Cultures that were devoid of obvious contamination were transferred to culture bottles containing MS medium supplemented with 30 g l^–1 sucrose, 2.5 g l^–1 Phytagel^® and either benzyl adenine (BA) or kinetin (KIN) supplied at 0, 1, 5, 10, or 20 µM, and were monitored, over eight in vitro passages, for their growth and microbial association. Shoot-tip and nodal microcuttings yielded a single shoot, coupled with rooting, in medium devoid of BA or KIN which was the best medium for continuous micropropagation. Rooting was inhibited with increasing concentrations of BA or KIN, and one or more shorter shoots with condensed internodes were induced, resulting in low rates of propagation. Culture indexing (i.e., testing the medium and tissue from visibly clean cultures using enriched bacteriological media) revealed quiescent endophytic bacteria associated with 80 – 100% of such cultures. Three distinct colony morphotypes were isolated and were identified as Ralstonia, Enterobacter, and Methylobacterium spp., based on their 16S rRNA gene sequences. These endophytes did not interfere with normal micropropagation, but tended to grow actively and outgrow older cultures, especially at higher cytokinin concentrations. Stable micropropagation of ‘Arka Ravi’ chrysanthemum for ≥ 2 years, with their resident endophytic bacteria in a covert form, was achieved on basal MS medium with > 90% shoot growth and rooting, a four-to-five-fold propagation rate at each 2 – 3 week sub-culture cycle, and with > 90% establishment of rooted plantlets ex vitro. These results suggest that in vitro cultures of chrysanthemum often harbour endophytes with no obvious indications of their presence or with possible hidden effects during micropropagation.     

Silicon promotes seedling growth and alters endogenous IAA,GA3 and ABA concentrations in Glycyrrhiza uralensis under 100 mM NaCl stress

A sand culture experiment was conducted to determine the effects of Si on the growth and endogenous hormone concentrations (indole-3-acetic acid [IAA], gibberellic acid [GA₃], and abscisic acid [ABA]) in Glycyrrhiza uralensis seedlings under 100 mM NaCl stress. Si time-dependently improved the growth and increased the biomass of seedlings, and the effect was greater at 20 days than that at 10 days after Si treatment. The effects of Si on the growth parameters and biomass were dependent on Si concentration, that is, these parameters increased with increasing Si concentration. Si also increased the levels of endogenous hormones in G. uralensis seedlings in a concentration-dependent manner. The effects on IAA and GA₃ increased with increasing Si concentrations, and the effect on ABA was higher at 2 mM Si than that at the other Si concentrations. Furthermore, the effects of Si on IAA and GA₃ were greater at 10 days than those at 20 days after the treatment, whereas the effect on ABA was greater at 20 days than that at 10 days after the treatment. Hence, Si can regulate the concentrations of endogenous hormones and correspondingly improve the growth of G. uralensis seedlings under salt stress condition.     

8种常见芽菜致病微生物的分离鉴定

对目前产业化程度较高的黄豆、黑豆、豇豆、萝卜、蕹菜、花生、黄秋葵、向日葵等8种芽菜患病植株上的致病微生物进行分离、纯化,共得到24株细菌菌株和8株真菌菌株;利用真菌ITS和细菌16Sr DNA通用引物,分别对分离得到的细菌和真菌基因组进行分子生物学鉴定。结果表明:24株细菌分属8个属,分别为克雷伯氏菌属(Klebsiella)、肠杆菌属(Enterobacter)、假单胞菌属(Pseudomonas)、不动杆菌属(Acinetobacter)、果胶杆菌属(Pectobacterium)、短稳杆菌属(Empedobacter)、戴尔福特菌属(Delftia)、从毛单孢菌属(Comamonas);24株细菌均为革兰氏阴性菌,除果胶杆菌属外,其余都不是典型的植物病原菌;其中不动杆菌属、肠杆菌属、克雷伯氏菌属和假单胞菌属的细菌出现在2种或2种以上芽菜上;另外4个属的细菌则只出现在1种芽菜上,呈现出寄主的专化性。8株真菌分属3个属,分别为镰刀菌属(Fusarium)、链格孢属(Alternaria)和根霉属(Rhizopus);其中根霉属和链格孢属的真菌分别只出现在萝卜芽菜和蕹菜芽菜上,其他6种芽菜上分离得到的真菌菌株均属于镰刀菌属。分离菌株回接试验结果表明,所有菌株均能对芽菜造成不同程度的腐烂症状,生产过程中环境微生物污染同样能致芽菜腐烂病发生。     

Shoot tip culture in mango: Influence of medium,genotype, explant factors,season and decontamination treatments on phenolic exudation,explant survival and axenic culture establishment

Summary

Attempts to establish shoot tip culture in mango (Mangifera indica L.) genotypes ‘Alphonso’, ‘Totapuri’, ‘Banganapalli’ and ‘Arka Anmol’ indicated that the problems of phenolic exudation, medium discoloration and explant browning were interrelated and influenced by a number of factors including medium, genotype, explant, season and decontamination treatments. Less phenolic exudation and better explant survival were observed in ½MS medium than full MS and in semi-solid than in liquid medium. Among explant factors, age and shading of shoots, length, thickness and scaling injuries on explant and lower cut petioles coming in contact with medium were important, but not the age of tree and the number of leaves on the shoot. Use of charcoal was beneficial but other adsorbents, antioxidants, dark incubation and submerged culture were not advantageous. The effect of season was prominent with least phenolics, minimum microbial contamination, best explant survival and genotype dependent growth response in current season’s semimature shoots collected during June-August. Deep seated microbial contaminants could not be checked completely. A scheme for establishing in vitro culture is suggested.     

Manurial Experiments With Fruit: I. The Effect of Long-Term Manurial Treatments on Soil Fertility and on the Growth,Yield and Leaf Nutrient Status of Strawberry,Var. Climax.

After planting, tulip bulbs can be infected by Botrytis tulipae present in the soil or by its spores on the bulb surface. The tunic around healthy bulbs may give partial protection to the scales. In contaminated soil infection does not occur when the distance between bulb and inoculum is 4 cm or more. The percentage of infected bulbs is considerably lower in the second year after soil contamination.     

滑菇子实体组织分离母种比较试验

进行了滑菇子实体不同部位的组织分离母种试验研究。结果表明：滑菇子实体分离母种，含水量较低的子实体的菌盖边缘组织是最佳选择。     

Characterization of bud-burst potential in Rhododendron catawbiense ‘Album’ plants from in vitro culture by measuring the manganese contents in the distal buds

Summary

It had been established that photoperiodic conditions influence morphogenesis in Rhododendron catawbiense ‘Album’ (Ericaceae). Plants developed from cuttings obtained by in vitro culture were grown in a greenhouse for one or two years, under different photoperiodic treatments. Under long days, the upper buds followed a rhythmic development. Under short days, the inhibition of the growth of the distal buds allowed the development of shoots from the plant base. When plants were placed under long days after six weeks under short days, the distal buds recovered their capacity to form a new growth unit. To find a method to characterize growth potential of vegetative buds, measurements of their mineral content were made. A relationship between the changes in manganese level of the distal buds and their growth potential during the formation of the vegetative system has been established. Under short-day conditions, manganese increased to reach more than 500 mg kg^-1 dry matter in several weeks. Under long days, the manganese level in the upper buds gradually decreased before burst. These results may not provide an explanation for the role of manganese in relation to the buds physiological activity. On the other hand, manganese measurements may be a useful test to estimate growth potential in Rhododendron buds.     

马铃薯脱毒试管苗污染控制效果研究

通过在MS培养基中加入抗生素和杀菌剂进行逐步筛选,解决马铃薯脱毒试管苗快繁过程中的污染问题.结果表明:防止马铃薯脱毒试管苗污染的最佳抑茵剂组合MS+ 50 mg/L硫酸庆大霉素+50 mg/L氨苄青霉素+50 mg/L硫酸链霉素+0.4g/L多茵灵,该组合有效降低了马铃薯脱毒苗细菌和真菌污染,提高了快繁效率.     

Status of Macrophomina phaseolina on Strawberry in California and Preliminary Characterization of the Pathogen

ABSTRACT

Macrophomina crown and root rot has become a significant soil-borne disease issue in California. For many locations in the state, the disease is associated with fields that are no longer pre-plant, flat field fumigated with methyl bromide + chloropicrin. Inoculation experiments indicated that some differences in strawberry cultivar susceptibility to Macrophomina phaseolina were seen a short time after the inoculation, but as disease progressed such differences did not persist. Preliminary characterization studies of Macrophomina phaseolina isolates from strawberry indicated that such isolates may have a host preference for strawberry. Macrophomina phaseolina isolates from watermelon, thyme, and apple failed to cause disease in strawberry. Five cover crop species, which can be rotated with strawberry, did not develop disease when inoculated with strawberry isolates. In preliminary analysis using simple sequence repeat markers, isolates obtained from strawberry formed a separate group compared to isolates recovered from other known Macrophomina phaseolina hosts.     

In vitro development and germination of immature olive embryos

Summary

In vitro culture methods were used to germinate olive embryos prior to maturation. Fruit, seed and embryo development were established with consecutive sampling from 20 to 100 days after bloom. For that same period, embryo development and germination success were determined by in vitro culture trials using one-third strength MS medium with or without the addition of zeatin. For early developmental stages, when isolation of the embryo was difficult, a cut portion of the seed containing the embryo was used for culture. The embryos cultured within the cut seed portions germinated and formed normal plantlets. Histological observations indicated a close similarity between the natural and in vitro immature embryo differentiation pattern, progressing through preglobular, globular, heart-shaped and torpedo-shaped stages. In some cases, however, the in vitro immature embryos developed or germinated abnormally. The presence of zeatin (0.25 mg l^–1) in the culture medium and the use of a cut seed-portion containing the immature embryo allowed in vitro germination sooner after bloom than previously obtained. On the contrary, zeatin was a handicap for mature olive embryo in vitro germination, which reached 100% seedling formation when no plant growth regulators were used.     

青霉素和乳酸对西瓜组织培养中细菌污染的抑制作用

以细菌污染的西瓜组培苗为试材,通过在培养基中添加不同浓度的青霉素或乳酸进行处理,研究青霉素和乳酸对西瓜组培苗中细菌污染的抑制作用。结果表明,青霉素50mg/L或乳酸90mg/L对初代细菌有较好的抑制作用。在此基础上进行青霉素或乳酸连续处理和交替处理。结果表明,青霉素或乳酸连续处理9代,对西瓜组培苗的伸长与生根有明显的抑制作用。采用交替处理,对西瓜组培苗的伸长与生根影响较小。     

Rapid in vitro germination of zygotic embryos of fluted pumpkin (Telfairia occidentalis Hook. f.)

Summary

Fluted pumpkin, Telfairia occidentalis, is becoming an important regional vegetable for its food and medicinal uses. The recalcitrant nature of its seed makes conservation difficult and in vitro techniques may be a viable option for conservation. A pilot study was conducted on the effects of different concentrations of a commercial bleach [3.85% (w/v) sodium hypochlorite] for surface sterilisation of T. occidentalis seed. The optimum concentration [25% (v/v)] was then used as a basis to investigate the responses of mature embryonic axes of T. occidentalis to different concentrations of kinetin (Kin; 0, 1.0, or 2.0 mg l^–1) and 1-naphthaleneacetic acid (NAA; 0, 0.5, or 1.0 mg l^–1) combined in a factorial design. The results of the first experiments indicated that commercial bleach at 25% (v/v) resulted in the lowest contamination of explants (10%), with no evident injury to the embryonic axes. The results revealed that root emergence started 3 d after initiation (DAI) only on Murashige and Skoog medium (MS) with no added plant growth regulator (PGR), and that, by 12 DAI, all media supported the rooting of explants. The highest rooting percentage (69%) was observed at 15 DAI on MS medium with 0.5 mg l^–1 NAA, without Kin. However, shoot emergence started at 9 DAI on PGR-free MS medium, on MS with 0.5 mg l^–1 NAA, or on MS plus 1.0 mg l^–1 Kin. The highest shooting percentage (91%) of explants was observed with 0.5 mg l^–1 NAA at 21 DAI. Considering all other growth parameters, MS medium supplemented with 0.5 mg l^–1 NAA was found to be best for the germination of embryonic axes of T. occidentalis.     

内蒙古野生银白离褶伞子实体组织分离试验

采用组织分离法对内蒙古野生银白离褶伞进行了子实体不同分离部位、菌丝体污染率,以及新鲜子实体和阴干3 d的子实体的对比分离试验。试验结果表明,菌褶和菌柄交界处是最佳的组织分离部位;菌丝体污染率以菌褶和菌柄交界处为最低;经过阴干3 d的子实体相对新鲜的子实体分离污染率较低,分离效果较好。     

季节因素和供体年龄对辣椒小孢子培养的影响

以N24为试验材料,在不同季节和植株开花时期进行小孢子培养,研究季节因素和供体年龄对辣椒小孢子培养的影响。结果表明,辣椒小孢子胚性化反应受供体季节因素的影响较大,夏季的胚状体产率是冬季的2.3倍,但褐化率和污染率均较高;供体年龄也是影响辣椒小孢子培养的重要因素,夏季的最佳培养时期为始花15～30d,最高胚状体产率为13.56%,冬季的最佳培养时期为始花45～60d,最高胚状体产率为5.14%。     

Biological control of the shoot disease of Amaranthus hybridus caused by Choanephora cucurbitarum with Bacillus subtilis

Summary

Isolates of Bacillus subtilis from soil and ogili (a local food condiment) controlled choanephora shoot disease of the vegetable crop plant, Amaranthus hybridus, in the greenhouse. Disease developed on plants inoculated simultaneously with the pathogen Choanephora cucurbitarum and the ‘ogili’ isolate, but not the soil isolate, of B. subtilis. Application of either bacterial strain to plants one day before a challenge with the pathogen prevented disease development. A single application of either strain prevented disease development from a subsequent challenge with the pathogen at any time over a thirty day period. Viable counts of the microflora on the shoot tips of the treated plants indicated strongly that the inoculated bacteria multiplied and colonized the extending shoot tip whether or not the shoots were covered with polythene bags. Both strains of Bacillus subtilis inhibited mycelial extension growth as well as conidial germination in vitro.     

Sewage sludge and refuse composts as peat alternatives for conditioning impoverished soils: Effects on the growth response and mineral status of Petunia grandiflora

A glasshouse pot experiment is described comparing the growth reponse, nutritional , status and heavy metal content of Petunia grandiflora in an impoverished acid sandy soil amended with peat or composted sewage sludges and refuse. The composts consistently out-performed peat as soil améliorants because of greater nutrient availability. However, results indicated that rates of application of composts to soil should be adjusted according to the conductivity of the applied material and the salt tolerance characteristics of the plant species to be grown to avoid detrimental effects on plant growth. There were no phytotoxic effects on plant growth due to contamination of the composts with heavy metals irrespective of the level of incorporation into soil, indicating that proposed lower metal limits for composts compared with sewage sludge would be unnecessarily restrictive to compost use. Composted sewage sludges and refuse are shown to have considerable potential for use in the amenity and landscape industry for improving impoverished soils.