Corm induction and multiplication of Amorphophallus albus in vitro

Summary

Amorphophallus albus, belonging to the family Araceae, has attracted widespread attention due to its considerable economic and medicinal importance. The natural propagation coefficient of A. albus is very low, which limits application of this crop. In vitro corms can be used for propagation of A. albus and have been proved to be superior over in vitro plantlets. To optimise procedures for in vitro corm production and multiplication, the effects of phytohormones, sucrose concentrations and incubation conditions with desirable phytohormone combinations for callus induction, corm formation and corm growth of A. albus were investigated. The results showed that calli were induced at high frequency from petiole segments on Murashige and Skoog medium supplemented with 1.0 mg l^–1 naphthaleneacetic acid (NAA) and 1.0 mg l^–1 6-benzyladenine (BA). Compact nodular calli were desirable for corm formation, and optimum corm formation was obtained in the presence of 0.5 mg l^–1 NAA and 2.0 mg l^–1 BA. With this auxin and cytokinin combination, an increase in sucrose concentration from 2% to 6% (w/v) significantly increased the corm formation rate and favoured corm growth, but negative effects occurred at higher sucrose concentrations. By incubating over a range of temperatures from 19°C – 28°C, 22°C produced the largest numbers of corms and highest mean fresh weight of each corm. Short-day (8 h) or long-day (16 h) photoperiods did not affect corm formation and growth significantly, except that corm weight fell under long-day conditions. The multiplication rate of in vitro corms was enhanced by apical meristem wounding. It was possible to store in vitro produced corms at 4°C for as long as 90 d to overcome apical dormancy and accelerate sprouting after planting into soil. This work has established an efficient protocol for multiplication of A. albus through an in vitro corm system.     

Effect of ethylene on breaking dormancy of freesia corms

Ethylene (C₂H₄) applied before chilling stimulated rooting and sprouting, and increased root number and length per corm. Only when corms experienced high temperature for a certain period before or after C₂H₄ treatment was a promotive effect on sprouting observed. When C₂H₄ was applied at the beginning of the high-temperature storage, the effect was greatest and all treated corms sprouted within 2 weeks of planting. Effects of ethephon on sprouting were slight.Shortening the dormant period with C₂H₄ could be useful for practical freesia forcing, since C₂H₄ has no adverse effects on the development of the root and the shoot.     

Prediction of saffron crocus corm mass by geometrical attributes

Saffron (Crocus sativus L.) is the most precious spice plant in the world. The only method for the reproduction of saffron is cultivation of corm. It is necessary to know relationships between mass and size of saffron corms in order to design and develop of planting, harvesting, grading and handling equipments. The objective of this research was to determine the most accurate models to predict saffron corm mass based on geometrical attributes. Models for predicting the mass of corms were classified as follows: (1) single or multiple variable regressions of saffron corm mass and dimensional characteristics, (2) single or multiple variable regressions of saffron corm mass and projected areas and (3) single regression of saffron corm mass based on its actual volume and calculated volume assuming the saffron corm shapes of sphere, oblate spheroid and ellipsoid. Three sets of corms were considered from Torbat-e-Heydareyeh, Kashmar, and Gonabad fields in Khorasan province of Iran. Some physical characteristics that were needed for the saffron corm mass modelling were determined for the three regions corms. The results showed that there were not significant differences between mean values of mass, height, major diameter, geometric mean diameter and projected areas of saffron corms for the three regions. However, there were significant differences between saffron corm minor diameter, volumes, corm density, bulk density and porosity for the three regions. Therefore, the mass of the corms was modelled based on the height, major diameter and projected areas irrespective to the regions, whereas in the third classification models, the mass of the corms was modelled for each region. The statistically significant fitted models were selected based on the higher coefficient of determination (r²) and lower regression standard error (RSE). The results of mass modelling showed that the prediction of saffron corm mass based on the major diameter (M = 0.0017a^2.5168, r² = 0.94, p < 0.05) and the first projected area (M = 0.0019 (PA₁)^1.2916, r² = 0.96, p < 0.05) were the most appropriate models. The model that predicted the mass of saffron corm based on the estimated volume of an ellipsoid shape was found to be the most appropriate. The developed models and data of physical characteristics of saffron corms could be used for designing and developing the saffron corm grader and other cultivation equipments.     

魔芋组培快繁的影响因素

以万源花魔芋顶芽、球茎为外植体,比较不同激素浓度配比对外植体培养的影响,并进一步诱导试管微型芋。结果表明：顶芽是魔芋组培快繁的最佳外植体,腋芽产生频率高、速度快,较球茎分化不定芽的时间提早60 d左右|腋芽分化适宜培养基是MS + BA 2.4 mg?L-1 + NAA 0.1 mg?L-1,腋芽分化率90%|在增殖培养基中腋芽增殖系数达3.58|腋芽在MS + BA 0.5 mg?L-1 + NAA 0.01 mg?L-1 + 蔗糖50 g?L-1培养基中诱导形成微型芋,培养60 d的诱导率达90.9%。     

Cloning,characterization and expression analysis of a 9-lipoxygenase gene in Gladiolus hybridus

Plant lipoxygenases (LOXs) is a functionally diverse class of dioxygenases involved in multiple physiological processes such as growth, senescence, and stress-related responses. Previously, based on the analysis of LOX1 activity and corm formation, it was depicted that LOX1 increased jasmonic acid (JA) synthesis and induced enlargement at top of stolon branches, forming cormels in Gladiolus hybridus. Here, LOX gene (GhLOX1) in full length was isolated from developing corms in G. hybridus. Sequence analysis showed that GhLOX1 was a novel LOX1 gene encoding 9-LOX. Transient expression analysis determined GhLOX1 to be a cytoplasm protein. Real time RT-PCR showed that the mRNA level of GhLOX1 gene correlated positively with LOX activity and was highest in cormels. GhLOX1 mRNA level, LOX activity and endogenous methyl jasmonate (MJ) content in corms increased steadily with a MJ gradient from 0.1 mmol/L to 0.5 mmol/L. Conversely, GhLOX1 mRNA level, LOX activity, and endogenous MJ content in corms steadily decreased with the increasing concentration of Salicylhydroxamic acid (SHAM). At the same time, we observed that MJ and SHAM treatments effected both LOX1 mRNA level and LOX activity, leading to promotion and inhibition of corm formation and enlargement, respectively. These data reveal that GhLOX1 is a novel LOX1 gene encoding a cytoplasm 9-LOX protein and its expression would contribute to LOX activity which plays an important role in corm formation and enlargement. In general, GhLOX1 is an ideal candidate for the promotion of corm formation and enlargement by gene manipulation in G. hybridus.     

In vitro propagation of Gladiolus by precocious axillary shoot formation

Axillary buds excised from corms of 3 cultivars of hybrid Gladiolus were cultured on nutrient medium containing various levels of 6-benzylaminopurine (BAP). BAP prevented dormancy, promoted shoot growth and inhibited root development. These effects were accompanied by precocious outgrowth of axillary shoots which developed into detachable, independent in vitro plantlets which could be serially sub-cultured for further proliferation. The level of BAP required to promote a steady rate of axillary branching was inversely related to its natural propagation rate. Plantlets not sub-cultured on to fresh medium eventually became dormant with the formation of small corms which could be planted in compost.     

The Relation in the Apple Between the Development of Young Shoots and the Thickening of Older Stems.

Summary

As a crop new to the western world, opportunities for production of Chinese water chestnut have barely been exploited. In China, over the latitude range 21º to 34ºN it is planted in spring and harvested in autumn. Opportunitiesexist to extend its cultivation to new climates, where growth throughout the year is not constrained by low temperature, but may be constrained by photoperiod. To study the response of Chinese water chestnut to photoperiod, six experiments wereconducted intropical central Queensland. One set focussed on planting early in spring, with long-day treatments superimposed. Anotherset investigated autumn and winter plantings, also with superimposed long-days, and the third compared the performance ofChinese water chestnut under constant or decreasing photoperiods, ranging from 8.h to 20.h, in light-out chambers. Corm formation was strongly retarded by long days but promoted by the photoperiods which were shorter than a criticalmaximum. Thecritical photoperiod was between 12.0±12.5.h, below which corm formation was rapid, and above which it was non-existent, or minimal if combined with cool (<21º mean) temperature. Under short days, to the detriment of stem growth, significantly more dry matter was allocated to corms and rhizomes. The latter provided potential corm sites. The response of corm formation and rhizome production to photoperiods shorter than the critical was more pronounced the moreextended the treatment period. The data provide evidence for the ability to manipulate timing of harvest at the field scale to extend availability of fresh produce on the market.     

Large-scale in vitro propagation of giant reed (Arundo donax L.), a promising biomass species

Summary

Giant reed (Arundo donax L.), a promising energy crop, is vegetatively-propagated from fragments of stems and rhizomes. This may limit large-scale cultivation, since it is time-consuming and involves considerable cost and effort. Tissue culture is an alternative to conventional methods of vegetative propagation and may represent a useful tool for large-scale propagation of plants for biomass production programmes. This report describes a protocol for the large-scale in vitro propagation of giant reed by adventitious bud formation. Stem nodes with dormant buds proved to be the most effective to initiate in vitro cultures giving the highest percentage of differentiated shoots (77%) compared to the other plant fractions tested. A sterilisation procedure using 5 g l^–1 HgCl₂ enabled the production of sterile explants. Moreover, early results indicated that late Autumn excision dates not only gave a higher percentage of well-developed shoots ( > 80%), but also a lower level of bacterial contamination (15 – 20%). 6-Benzylaminopurine (BAP) at 3.0 mg l^–1 was most effective in promoting shoot multiplication when added to a basal medium containing Murashige and Skoog (MS) macro- and micro-nutrients, Morel’s vitamins, 30 g l^–1 sucrose, and 7.0 g l^–1 bacteriological agar supplemented with 1.0 mg l^–1 indole-3-acetic acid (IAA) and 0.05 mg l^–1 gibberellic acid (GA₃). Rooting was successfully induced on the same basal medium used for proliferation, modified by halving the MS macro-nutrients and replacing BAP and the other growth regulators with 2.0 mg l^–1 1-naphthaleneacetic acid (NAA). Successful acclimatisation (> 95% survival) of plantlets was carried out, even in late Winter, in a cold greenhouse or under simpler facilities such as shade nets.     

The mode of action of ethephon in increasing health of gladiolus corms

Gladiolus corms and cormels were treated with various combinations of ethephon and the fungicides methylethyl mercury benzoate, benomyl, thiobendazole and methylmercury dicyandiamide either before or after storage at 10 °C and 30 °C for 6 weeks. The treated corms were examined for germination, splitting and rot symptoms caused by Fusarium oxysporum f. sp. gladioli.

Ethephon increased corm splitting in all treatments; it also increased germination in corms stored at 30 °C, and it increased the proportion of corms showing typical Fusarium rot symptoms by stimulating the growth of latent internal Fusarium. The effectiveness of the fungicides tested against F. oxysporum f. sp. gladioli was enhanced by the addition of ethephon. Permeability of corms to methylethyl mercury benzoate was increased by ethephon, and it is concluded that ethephon improves the efficiency of this fungicide, and probably of other fungicides as well, by increasing their penetration into gladiolus corms.     

Effect of 2-Chloroethanephosphonic Acid (Ethrel) on Health,Dormancy, and Flower and Corm Yield of Gladioli

2-Chloroethanephosphonic acid (Ethrel), an ethylene releasing compound, was used on gladiolus corms as a 30-minute dip treatment in various concentrations and at various times during storage.

The most important effect of Ethrel was the marked increase in health and survival of treated plants infected with latent Fusarium.

Ethrel at 1000 ppm enhanced sprouting when corms were stored at high temperatures or stored for a short period at 5 °C. Treatment of cold-stored corms at high concentrations delayed sprouting.

Ethrel increased corm splitting, delayed flowering and slightly shortened flower stems. The size of harvested corms was reduced, but the yield of cormels was greatly increased by Ethrel.     

Effects of bud scales and gibberellins on dormancy of in vitro cultured Japanese pear leaf buds

Leaf buds of Japanese pear were collected in early June and early November and regarded as summer and winter dormant buds, respectively. Bud explants with and without scales were prepared from each of them, and cultured in vitro for 75 days at 25°C with 14 h photoperiod, on a medium either without growth regulators, or supplied with BA and GAs (GA₃ and GA₄₊₇), singly or in combination.When either BA or GA₄₊₇ was contained in the medium, bud expansion occurred. Thereafter, summer dormant buds grew into shoots in the presence of BA, while winter dormant buds, although they swelled profusely, remained in a rosette. In the presence of BA, GA₄₊₇ markedly stimulated shoot elongation of summer dormant buds, but GA₃ did not. In winter dormant buds, GA₄₊₇ not only failed to stimulate shoot elongation, but also interfered with the BA-induced swelling described above.The presence of bud scales delayed expansion of summer dormant buds, while it had little effect on winter dormant buds. The delaying effect of scales on expansion of summer buds was effectively removed by application of GA₄₊₇ to the medium.     

不同类型魔芋种芋的生长分析

通过对不同类型魔芋脱毒种芋的萌芽出苗特性、田间长势、分苗数、田间发病情况、产量、球茎膨大倍数、繁殖系数、生长周期等进行研究。研究结果表明,一级包衣种、二级种、三级种比原原种提前8～18天出苗;一级包衣种、二级种的分苗数较多;一级包衣种、二级种、三级种的田间发病率低于原原种,其中一级包衣种发病率最低,仅为7.4％。二级种、三级种综合性状较好,生产力水平高,膨大倍数高,可通过规模化生产得到大量种芋,解决生产中种芋缺乏的问题。     

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.     

The influence of photoperiod and plant density on yield of winter-grown gladioli in Queensland

The yields of inflorescences, corms and cormlets, and the inflorescence quality of winter-grown gladioli in south-east Queensland, were studied under 2 daylength regimes, 3 plant densities (150 000, 300 000 and 450 000 corms ha^?1) and 3 plant arrangements (bed, double row and single row). The daylength treatments were the natural daylength (12.3–14.5 hours) and a 24-hour photoperiod treatment in which natural daylengths were extended using incandescent light of an intensity of 150 lux. Two cultivars were used.Extending the photoperiod to 24 hours delayed flowering by approximately 15 days, and increased the number of inflorescences harvested from low, medium and high density treatments by 20, 91 and 169%, respectively, when compared to the inflorescence yield from these density treatments under natural daylengths. The quality of the inflorescences from the high-density treatment receiving the 24-hour photoperiod was similar or superior in all quality characteristics to that of inflorescences grown under the most favourable density treatment under natural daylengths (150 000 corm ha^?1). Plant arrangement had little effect on the number of days to flowering or inflorescence yield but inflorescence quality was improved when plants were grown in a double-row arrangement compared to those from the bed or single-row arrangements. Extension of the photoperiod had no effect on the number of new corms per plot. However, the average weight of new corms and the weight of cormlets per plot and per corm were reduced by approximately 32, 71 and 63%, respectively, when compared to the results obtained from plants grown under natural daylengths. These results suggest that flowers compete for available photosynthates with corms and cormlet development.The economic feasibility of extending photoperiod for the commercial production of winter-grown gladioli in south-east Queensland is discussed.     

Effect of low temperature on breaking dormancy and flowering of Arisaema sikokianum (Araceae)

Arisaema sikokianum (Araceae) native to Japan is classified as a vulnerable species in the Red Data Book of Japan. Control of dormancy is essential for efficient corm production and forcing culture. Sprouting of both vegetative and reproductive corms was enhanced by exposure to low temperature. Vegetative corms exposed to low temperatures at 5 °C longer sprouted faster when grown at 20 °C. Effective temperatures for breaking dormancy was 5 °C. Reproductive corms treated at 5 °C longer showed shorter days to flower. Successful forcing culture was achieved; corms treated at 5 °C from November for 30 days flowered on 5th February.     

Plum Rootstock Trials at East Malling

Summary

Dormant axillary buds excised from crowns of pineapple (Ananas comosus L., Merr.) cultured on growth regulator free Nitsch medium sprouted after 8–10 d. Sprouted buds produced multiple shoots (7–10 shoots per bud) upon transfer to solidified Murashige and Skoog medium supplemented with 9.67 μM NAA, 9.84 μM IBA and 9.29 μM KIN. Each isolated shoot upon subculture to liquid medium of the same composition further proliferated to form more multiple shoots (60–65 shoots) and were maintained on a gyratory shaker (90–100 rpm). In vitro grown shoots were rooted on White medium supplemented with 0.54 μM NAA and 1.97 μM IBA. In vitro plantlets were established in cups with soilrite and hardened for four weeks. Phenotypic variants such as albinos, white streaked shoots and shoots with elongated internodes were observed in in vitro cultures. Approximately 520 in vitro produced plantlets were established in the field and these plants exhibit somaclonal variation. Thirty-eight plants were found to be yellowish, spineless with anthocyanin streaks and three were anthocyanin rich, spined plants.     

The influence of illumination levels of daylength extension on yield of winter-grown gladioli in Queensland

The yields of inflorescences, corms and cormlets, and inflorescence quality of winter gladioli were studied under varying illumination levels of 12 hour daylength extension ranging from 0 to 333 lux. The illumination level of the daylength extension for each plot depended on its distance from 2 tungsten halogen light sources mounted at 6 m above ground on poles spaced 8 m apart. The lamps were adjusted for wide beam distribution and aimed at points on the ground 8 m from the base of the poles.Inflorescence yield was increased by increasing the illumination level of daylength extension. The relationship between horizontal illumination level in lux (x) and number of inflorescences (y) was described byy=27.3?10.9 exp(?0.02x)Ninety-seven % of maximum inflorescence yield was obtained at a daylength extension illuminance of 144 lux, while 97% of the maximum number of florets per spike and the other flower quality characteristics were obtained at a daylength extension illumination level of approximately 100 lux. Ninety-seven % of the maximum number of days to flowering was approached at a daylength extension illuminance of 45 lux.There was no clear relationship between the illumination level of daylength extension and number and weight of new corms, or the average weight of each new corm. However, the weights of cormlets per plot and per new corm were higher from plants which received no daylength extension.The commercial application of tungsten halogen lamps to provide daylength extension for winter gladioli production is discussed.     

Effects of various gaseous compounds and respiratory inhibitors on breaking dormancy of freesia corms

The exposure of freesia corms to an atmosphere containing 1 ml/l C₂H₄ strongly promoted sprouting of the corms when the treatment was applied at a high temperature (28–31°C), but the response was weak at temperatures below 20°C. Repeated treatments with C₂H₄ did not enhance sprouting, i.e. was not more effective than a single treatment. Exposure to an atmosphere containing CO of concentrations over 1 ml/l accelerated sprouting. The maximum effect of CO was obtained with 10 ml/l at 28–31°C.The effect of C₂H₄ combined with CO was similar to that of a single treatment with each separately. Soaking corms in solutions of 10^?1 M potassium cyanide and 30 g/l calcium cyanamide effectively promoted sprouting, but similar treatments with slaked lime and thiourea had no effect.Treatments with C₂H₄, CO, KCN and CaCN₂ did not stimulate C₂H₄-evolution in dormant corms. Respiration of the corms was increased by C₂H₄ and CO, and decreased by KCN and CaCN₂.     

Multiple plantlets in lateral bud and leaf explant in vitro cultures of pineapple

Plantlets were obtained from usually dormant axillary buds, excised from the crown of pineapple (Ananas comosus L. Merr.) and grown in culture. Multiple shoots arose from single buds grown on Murashige and Skoog medium supplemented with auxins and kinetin. Shaking culture-flasks during growth increased the number of multiple shoots formed, when compared with stationary liquid cultures. Leaf explants excised from in vitro plantlets developed into a callus capable of plantlet regeneration. Subjecting developing buds to surgical segmentation also resulted in multiple shoot formation. Such shoots, when excised and grown on Murashige and Skoog medium supplemented with auxins, developed roots and grew into complete plantlets capable of being grown in soil.     

Viability of excised embryos,shoot proliferation and in-vitro flowering in a species of rattan Calamus thwaitesii Becc.

Summary

92% of embryos excised from fresh mature unripe fruits of Calamus thwaitesii germinated in a modified Y3 medium with 0.05 mg l^±1 of 6-benzylaminopurine (BAP). This was higher than the 72% germination obtained with ripe seeds sown in soil. Stored seed lost viability within two weeks due to dehydration of embryos. Germination commenced with the differentiation of the haustorium and the cotyledonary sheath, observable in embryos germinating in vitro. This was followed by the development of the plumule. The first eophylls were simple and lanceloate. Decapitation of the in-vitro seedlings and transfer to a medium with higher levels of BAP at 5 or 8 mg l^±1 resulted in the production of multiple shoots after 4±5 months, initially from buds that developed around the collar region. Repeated subculture resulted in the development of a clustering habit similar to that of field clumps with a rhizome, axillary shoots and dormant buds. Two axillary meristems were induced to develop precociously into inflorescences. Incorporation of activated charcoal and alpha-naphthaleneacetic acid (NAA) with 5 or 8 mg l^±1 BAP reduced multiple shoot formation and brought about root development. Single shoots or clusters developed roots in a Y3 medium with reduced macro elements and supplemented with NAA (5.mg.l^±1) and activated charcoal. Nursery establishment with 65% survival of plantlets was possible. In-vitro culture of excised embryos could be recommended, as propagules could be made available whenever desired by rooting proliferated shoots. It also allowed the safe transport of germplasm.