Allelochemicals identified from Jerusalem artichoke (Helianthus tuberosus L.) residues and their potential inhibitory activity in the field and laboratory

Weed management systems often seek biological solutions to minimize the environmental impacts related to the use of herbicides in agricultural systems. The suppressive effects of allelochemicals can sometimes be used effectively to provide biological pest and weed control. Jerusalem artichoke (Helianthus tuberosus L.) has been reported to be a highly invasive weed in European cropping systems, but this plant is also gaining interest as a cultivated crop in Italy. The aim of this study was to investigate the impact of Jerusalem artichoke and its extracts upon the germination and growth of seedling weeds and crops. HPLC coupled to MS was used for identification of the compounds associated with the observed growth inhibition. The weed suppressive activity of local biotypes of Jerusalem artichoke on weed growth and establishment was also evaluated in a field experiment. Shoot extracts of the cultivar Fuseau were consistently most inhibitory to germination and seedling growth of lettuce, particularly the diethyl ether extract. Solvent partitioning of the aqueous extracts of dried artichoke shoots resulted in greater inhibition in comparison to the aqueous extract itself. The diethyl ether extract provided 2-fold greater growth inhibition, in comparison to the aqueous extract, at concentrations of less than 0.5 mg extract per Petri dish. HPLC MS evaluation of the diethyl ether extract led to the identification of salicylic acid (o-hydroxybenzoic acid), and the closely related compound p-hydroxybenzaldehyde, as well as minor quantities of o-coumarinic acid and coumarin in the active fraction inhibiting lettuce seedling growth. Field observations provided further evidence for the allelopathic potential of H. tuberosus residues, as significant weed growth inhibition was observed in Jerusalem artichoke-infested plots with soil-incorporated residues in comparison to non-infested field sites, both in terms of weed seedling emergence and growth. The allelopathic potential of H. tuberosus may be of interest in the implementation of integrated weed management programmes by considering the suppressive ability of this plant and its residues for weed management in the field.     

生姜浸提液对西瓜和苦瓜的化感作用

以不同浓度的生姜根茎浸提液为供体,以早佳8424西瓜和大白苦瓜为受体,采用培养皿滤纸法,初步研究了不同浓度生姜根茎浸提液对西瓜和苦瓜的化感作用。试验结果表明,当生姜根茎浸提液在2.5~20 g/L的浓度范围内,对西瓜和苦瓜的种子萌发和幼苗生长均具有促进作用,在低浓度时促进作用较为明显,随着浓度的升高促进作用减弱。当生姜浸提液浓度为2.5 g/L时,西瓜幼苗生长最好;浸提液浓度为5~10 g/L时,苦瓜幼苗生长最好。     

Potent herbicidal activity of Inula crithmoïdes L.

Aqueous (10, 20, 30 and 40 g/L) and organic (hexane, chloroform and methanol, at 3000 and 6000 ppm) extracts of Inula crithmoïdes L. (roots, stems, leaves and flowers) were evaluated for their allelopathic activities on radish, lettuce, peganum and thistle. Pot cultures were conducted by incorporation of I. crithmoïdes leaves and flowers powder (1.25 and 2.5 g/kg) in soil and by irrigation with their aqueous extracts at 40 g/L. PEG (polyethylene glycol) solutions, with similar osmotic potentials of aqueous extracts, at the highest concentration, were without effect on target species, this eliminates the extracts osmotic effect. Germination index was not affected by root and stem extracts and significantly decreased by the two other ones. For growth, leaf and flower extracts had the most significant toxicity at 40 g/L, inducing up to a total inhibition. For organic extracts, a strong toxicity was recorded for the three fractions at 6000 ppm, thistle seedling growth was more sensitive, especially to chloroform fractions. Soil incorporation of residues (at 2.5 g/kg) significantly decreased root (35–100%) and shoot (0–100%) length of target species. Irrigation soil with leaves and flower aqueous extracts was harmful for peganum and thistle, respective inhibition percentages were 100% and 66.5%. I. crithmoïdes may be favorably used for incorporating in agricultural systems for sustainable weed management.     

西瓜化感作用及其化感物质成分分析

以早佳84-24为试材,研究了西瓜根、茎叶以及根系分泌物的化感效应,并对西瓜根、茎叶和根系分泌物中的化感物质进行了GC-MS检测。结果表明：西瓜根、茎叶水浸提液浓度为2.5 g?L-1时,促进西瓜种子发芽和幼苗生长|在浓度大于5.0 g?L-1时,表现为抑制作用,且随着浓度的增加,抑制作用增强|同一浓度时,西瓜茎叶水浸提液对西瓜种子发芽和幼苗生长的抑制作用大于根系水浸提液。西瓜根系分泌物浓度在2.5 μL?L-1时,促进西瓜种子发芽和幼苗生长|浓度为5.0 μL?L-1时,也开始表现为抑制作用。表明西瓜根、茎叶和根系分泌物对西瓜种子发芽和幼苗生长均呈现出低促高抑的规律。在西瓜根、茎叶和根系分泌物中共检测出32种化学物质,其中酯类化学物质最多,有14种|在西瓜根中检测到14种化学物质,茎叶中检测到19种,根系分泌物中检测到22种,其中一些曾被报道为化感物质,说明西瓜不同组织中化感物质的种类与含量不同,化感作用强度也不同。     

In vitro asymbiotic seed germination and seedling growth of Ansellia africana Lindl.

The effects of sodium hypochlorite treatment and growth medium on in vitro seed germination and seedling growth of the leopard orchid (Ansellia africana Lindl.) were investigated. Forty minutes treatment of seeds with 1.75% sodium hypochlorite stimulated germination (70.6%) and seedling development when measured at Stage 5 (emergence of first leaf) on P668 medium after 8 weeks of culture. The growth medium played a significant role in determining the germination response of A. africana seeds. Dark pretreatment of seed cultures significantly enhanced the germination percentage and the growth of rhizoids on the protocorms. Leaf growth in terms of length was substantially enhanced on P668 medium. It was significantly reduced in modified Knudson C medium after 16 weeks of culture. Seedlings developed on P668 medium showed a significantly better growth performance in relation to leaf length, leaf number, root length, fresh and dry weights per plant in vermiculite after 12 weeks of ex vitro growth in a mist house with 90% relative humidity. Further studies developing a suitable method for in vitro symbiotic germination could assist in reintroduction of this threatened orchid species into the wild.     

Influence of harvest time and after-ripening on the seed quality of eggplant

Eggplant cv. Emi and Tsakoniki were cultivated for seed in an unheated greenhouse and fruits were harvested at 25–65 days after anthesis (DAA) in order to determine the optimum harvest time. In addition, the effect of after-ripening on seed quality (i.e. seed size and germination) was examined by storing harvested fruit at 25 °C for 20 days prior to seed extraction. From the results, it was concluded that the optimum time of harvest for seed production is 55 DAA. Seeds extracted from fruits that were harvested at 25–35 DAA did not germinate, but when fruits harvested at the same age were stored for 20 days at 25 °C prior to seed extraction (i.e. seeds were after-ripened) germination was induced. Seeds extracted from fruits harvested at 45 DAA showed a high percent germination, which decreased after storage at 25 °C for 3 months. This decrease, however, was reduced by after-ripening prior to extraction. It is concluded that although eggplant is a non-climacteric species and fruit do not ripen after harvest, nevertheless seeds within the fruit continue to fill and mature after harvest; hence storage of prematurely harvested fruit prior to seed extraction permits the seeds of these fruits to after-ripen in situ and thereby increases seed size and germination. The implication of this result for eggplant seed production is discussed.     

西瓜化感作用及其机理研究

通过测定西瓜植株水浸液对其他蔬菜及其自身种子发芽和幼苗生长的影响,研究了西瓜的化感作用及其机理。结果表明:低浓度的西瓜水浸液对黄瓜、西瓜、辣椒、莴苣和番茄的种子发芽及根生长表现抑制效应,对黄瓜和西瓜的地上部生长表现促进作用;随着水浸液浓度的增加,对莴苣种子发芽和幼苗生长的抑制效应加大,莴苣体内保护酶和MDA的变化与西瓜植株水浸液浓度的增加有密切关系。     

Levels of physiological dormancy and methods for improving seed germination of four rose species

Low seed germination is a major problem in commercial rose propagation and breeding and is species-dependent. The present work selected four rose species previously un-examined to explore effective methods for improving seed germination and the relevant dormancy mechanism and its levels in seven experiments. The results showed that both pulp and achenes from the four rose shrubs had chemical substances that significantly inhibited seed germination with the inhibitory effect was more pronounced in pulp extract than of achenes. Single treatments of H₂SO₄ scarification, short-term cold stratification (<16 weeks) or warm stratification were less effective in breaking dormancy as indicated by lower germination index than their combinations. Comprehensive comparisons showed that among the six treatments the most effective for breaking dormancy was H₂SO₄ scarification followed by warm plus cold stratification, then H₂SO₄ scarification followed by cold stratification and finally warm plus cold stratification. Scarification with H₂SO₄ for 2–4 h ordinal followed by warm stratification at 20 °C for 4 weeks and cold stratification at 5 °C for 8 weeks was the best pretreatment for increasing seed germination percentage for Rosa multibracteata (81.4 ± 2.9%), Rosa hugonis (13.1 ± 6.0%), and Rosa filipes (62.7 ± 5.7%); and H₂SO₄ scarification for 4 h followed by cold stratification at 5 °C for 12 weeks was the best pretreatment for Rosa sericea (46.7 ± 8.7%). Our results suggest that these four species have only physiological dormancy caused by integrative roles of pulp, pericarp and embryo. The level of physiological dormancy was ranked as R. hugonis > R. sericea > R. filipes > R. multibracteata.     

Amelioration of chilling stress by paclobutrazol in watermelon seedlings

Paclobutrazol (PBZ) is a member of the triazole plant-growth inhibitor group that is responsible for inducing tolerance to number of biotic and abiotic stresses. An experiment was, therefore, conducted to test whether PBZ application at various concentrations (0, 25, 50 and 75 mg L⁻¹) through seed soaking or foliar spray would protect watermelon (Citrullus lanatus) seedlings, subjected to chilling stress. Thirty-five-day old plants were exposed to chilling 5 h/day at 4 °C for 5 days. PBZ improved growth rate of watermelon seedling subjected to chilling stress and increased relative leaf chlorophyll content (RLCC) and chlorophyll fluorescence ratio (Fv/Fm) compared with the control at the end of chilling stress. PBZ ameliorated the injury caused by chilling stress by inhibiting increases in proline and leaf electrolyte leakage, which suggested that PBZ ameliorated the negative effect of chilling stress. PBZ was most effective in increased chilling tolerance of watermelon seedling when applied using the seed soak method than as a foliar spray. The best protection appeared to be obtained from seedlings seed soaked with PBZ at 50 and 75 mg L⁻¹.     

Chitosan specificity for the in vitro seed germination of two Dendrobium orchids (Asparagales: Orchidaceae)

The effects of different types of chitosan on seed germination and protocorm development were determined for two orchid species, Dendrobium bigibbum var. compactum and Dendrobium formosum. Six chitosan types derived from polymer or oligomer chitosan each with 70, 80 or 90% levels of deacetylation (P70, P80, P90, O70, O80 and O90, respectively), were evaluated as direct medium supplements at 0, 10, 20, 40 or 80 mg/L in modified VW medium by following seed germination and protocorm growth for 12 weeks. Chitosan of all six tested types and four concentrations were found to significantly enhance the proportion of D. formosum seeds that germinated, when compared to these germinated without chitosan. In contrast, chitosan caused no enhanced germination rate was noted for D. bigibbum var. compactum with all tested chitosans and doses tested. However, almost all types of chitosan at 10 mg/L, except O90, were able to significantly improve the growth of D. bigibbum var. compactum protocorms, whilst 10 or 20 mg/L of P70 chitosan was the best formula to enhance the growth of D. formosum protocorms. It is concluded that chitosan responses in seed germination and protocorm development were somewhat species and developmental stage dependent. Therefore, the appropriate chitosan application for each plant species should be evaluated first before use.     

Rapid seedlings regeneration from seeds and vegetative propagation with sucker and rhizome of Eremospatha macrocarpa (Mann & Wendl.) Wendl and Laccosperma secundiflorum (P. Beauv.) Kuntze

To develop efficient seedling production methods for Laccosperma secundiflorum and Eremospatha macrocarpa, a study was conducted to examine regeneration using offsets combined with several physical and chemical treatments of seeds. Offsets categorized into small, medium and large diameters, were planted in three conditions: shaded and open nursery, and greenhouse. We tested sucker from E. macrocarpa, and sucker and rhizome from L. secundiflorum. For both species, high viability percentage (ranging from 55% to 100%) were observed for small and medium suckers planted in shaded nursery and greenhouse, against less than 49% for sucker planted in open nursery. The mean seedling emergence times were estimated to 84, 77 and 75 days after planting (DAP) for small, medium and large sucker of L. secundiflorum, respectively under open nursery condition, and 76, 75, 95 DAP for small, medium and large suckers of the same species, respectively in shaded condition. Greenhouse has a significant positive effect on E. macrocarpa seedlings emergence time. For this species, the mean seedling emergence times were estimated to 43 DAP for small sucker and 76, 93 DAP for medium and large suckers. No seedling was obtained from rhizome planted in all the growing conditions tested. Concerning seed dormancy breaking, germination percentages and rates were determined for 13 treatments. The best treatments were pre-soaking unscarified seeds for 4 days in 1.01 g l⁻¹ and 0.10 g l⁻¹ KNO₃, with 79% and 68% of germination, respectively and in 3.46 × 10⁻³ g l⁻¹ GA₃ for 68% of germination. These methods are suggested to improve germination of L. secundiflorum seeds. Successful and recommended methods for E. macrocarpa are pre-soaking scarified seeds in 3.46 × 10⁻³ g l⁻¹ and 3.46 × 10⁻⁴ g l⁻¹ GA₃, 96% and 94% of germination, respectively. Dormancy, probably a combination of mechanical and chemical dormancy, is present in the two species.     

The influence of desiccation and rehydration on the survival of polyembryonic seed of Citrus suhuiensis cv. limau madu

A study was carried out to investigate the influence of desiccation and freezing followed by various presowing rehydration procedures on the desiccation sensitivity of the seed of Citrus suhuiensis cv. limau madu. The freshly harvested seeds of limau madu were desiccated under a broad range of relative humidity (RH) to various equilibrium water contents (g H₂O g⁻¹ dw). The desiccated and desiccated–frozen seeds were either directly sown under germination conditions or subjected to presowing rehydration procedures: seed preheating, prehumidification and osmoconditioning. The hydrated and desiccated seeds were sown in controlled germination conditions and the survival was evaluated 4–6 weeks after sowing. The results showed that desiccation progressively reduced the percentage of normal seedling of the seeds of limau madu and the viability is almost lost at water contents below 0.08 g H₂O g⁻¹ dw. The estimated desiccation sensitivity was substantially high (WC₅₀ = 0.143 g H₂O g⁻¹ dw) when the desiccated seeds were rapidly rehydrated (uncontrolled rehydration). In contrast, seed prehumidification, preheating and osmoconditioning (controlled rehydration procedures) markedly enhanced normal seedling percentages decreasing the estimated values of WC₅₀ (between 0.08 and 0.127 g H₂O g⁻¹ dw). While the rapidly rehydrated desiccated–frozen seeds were almost killed at water content of 0.15 g H₂O g⁻¹ dw, prehumidification and preheating have noticeably increased percentage of frozen seeds survival at the same water content. However, at water content of 0.21 g H₂O g⁻¹ dw preheating significantly (P < 0.05) increased percentage of normal seedling of the frozen seeds. Seed desiccation markedly reduced the percentages of germinated seeds with multiple seedlings. Seed controlled rehydration remarkably increased the survival of polyembryos. The beneficial effect of seed controlled rehydration on the survival of the desiccated seeds was pronounced at medium water contents (0.08–0.25 g H₂O g⁻¹ dw).     

Growth,yield and essential oil content of three cultivars of basil grown under different levels of nitrogen in the field

A field experiment was conducted in Southern Italy to investigate the effect of different nitrogen (N) rates (0, 100 or 300 kg ha⁻¹) on the number of branchings and leaves per plant, plant height, yield of above-ground fresh biomass, total leaf area, dry weight, leaf-to-stem ratio, leaf essential oil content and the essential oil quality at commercial harvest (full bloom) of the three cultivars of basil (Ocimum basilicum L.): (i) “Mostruoso mammouth” (MM); (ii) “Genovese profumatissimo” (GP); (iii) “Napoletano a foglia di lattuga” (NFL). Nitrogen fertilization up to 300 kg ha⁻¹ increased yield of above-ground and leaf fresh biomass, leaf essential oil yield, but it did not affect leaf-to-stem ratio, plant height and the number of branchings per plant. The increase in essential oil yield induced by N fertilization depended on an increase in both leaf essential oil concentration and leaf biomass. The increase in LAI with increasing N fertilization was due to an increase in leaf number per plant rather than in individual leaf expansion. The cultivar GP was different in morphology from MM and NFL, since it had greater leaf number and plant height, but lower leaf-to-stem ratio and LAI. The physiological efficiency of N use (PE) in producing above-ground biomass was not related to N application whereas PE in producing essential oil (PE-oil) tended to increase with increasing levels of N applied. With regard to the effect of the cultivar, GP was less efficient in N use for oil production than MM and NFL since PE-oil of GP was lower while leaf N and PE-biomass were higher than the other cultivars. NFL was the richest in methyl chavicol but the lowest in linalool, whereas MM and GP contained linalool and eugenol.     

Bio-efficiency of compost extracts on the wet rot incidence,morphological and physiological growth of okra (Abelmoschus esculentus [(L.) Moench])

An experiment was carried out to investigate the efficacy of rice straw and empty fruit bunch (EFB) of oil palm compost extracts either fortified or unfortified with Trichoderma harzianum on morpho-physiological growth and occurrence of Choanephora wet rot of okra. Treatments tested were water (control) (T1), rice straw (RST) compost extract (T2), Trichoderma-enriched RST compost extract (T3), empty fruit bunch of oil palm compost extract (T4), Trichoderma-enriched EFB compost extract (T5), aqueous suspension of Trichoderma (T6), and a fungicide Dithane M-45^® (2 g l⁻¹ of water) (T7). The experimental results revealed significant variations amongst the treatments in respect of morphological characters, e.g. shoot length, tap root length, number of leaves per plant, and leaf area. The shoot and tap root length, number of leaves per plant, leaf area were significantly (P ≤ 0.05) higher in Trichoderma-enriched RST compost extracts (T3) followed by Dithane M-45^® (T7), Trichoderma-enriched EFB extracts (T5), RST (T2), EFB (T4) and aqueous suspension of T. harzianum (T6) in both Choanephora inoculated and uninoculated (control) plots. Similarly, net photosynthetic rate and chlorophyll content were higher in plants receiving Trichoderma-enriched RST compost extracts (T3) with 76.2% reduction in Choanephora wet rot incidence when compared with rest of the treatments. These experimental results revealed that morpho-physiological characters of okra could be modified by the application of Trichoderma-enriched compost extracts. This suggests that use of Trichoderma-enriched compost extracts would be more beneficial in environmentally friendly okra cultivation and may be used as an alternative to inorganic fertilizers/fungicides to enhance plant growth and reduce disease incidence subsequently, resulting in higher yield.     

喜马拉雅紫茉莉种子化感作用初探

研究喜马拉雅紫茉莉种子水浸提液对绿豆、小麦种子萌发和幼苗生长的影响,分别用浓度为0.0125、0.025、0.05、0.1g/ml的喜马拉雅紫茉莉种子水浸提液处理绿豆、小麦种子,测定其种子萌发及幼苗生长状况。结果表明,不同浓度的喜马拉雅紫茉莉种子水浸提液对绿豆和小麦种子萌发和幼苗生长均存在不同程度的抑制作用。其中,对绿豆发芽率的平均化感效应(RI)为-4.45,发芽势的为-7.23;对小麦发芽率的平均RI值为-8.05,发芽势的为-9.12;对绿豆苗高的平均RI值为-49.9,根长的为-71,根数的为-50;对小麦苗高的平均RI值为-34.7,根长的为-49.1,根数的为-52.7。可见,喜马拉雅紫茉莉种子水浸提液对不同作物的化感作用不同,对同一作物的不同发育时期化感作用也不同,对幼苗期的影响显著大于种子萌发期。     

Allelopathic potential in lettuce (Lactuca sativa L.) plants

Lettuce (Lactuca sativa L.) is known to contain water-soluble substances that are allelopathic. Aqueous or methanol extracts and residues from leaves of lettuce cultivar “Cheongchima”, which showed the most inhibitory effects, were assayed to determine their allelopathic effects on seed germination and early seedling growth of several plant species. The aqueous extracts applied to filter paper significantly inhibited seed germination of alfalfa with increasing of extract concentration. Methanol extracts from hexane fraction of lettuce plants showed the most inhibition on alfalfa root growth and followed by ethylacetate, butanol and water fractions. Incorporation with leaf residues of 100 g kg ⁻¹ into soil significantly inhibited shoot and root fresh weights of barnyard grass by 79 and 88%, respectively. These results suggest that extracts or residues from lettuce plants had potent allelopathic activity and that the activity differed depending on cultivar, extract or fraction.     

Morphological,anatomical and physiological responses of Campylotropis polyantha (Franch.) Schindl. seedlings to progressive water stress

In this study we implemented a potted water supply experiment for 100 days by a completely random sole-factored design with five treatments: 100% (W₁₀₀), 80% (W₈₀), 60% (W₆₀), 40% (W₄₀) and 20% (W₂₀) of water holding capacity (WHC), corresponding to the soil volumetric water content (SVWC) maintained at 38.8 ± 0.3%, 31.6 ± 1.7%, 25.6 ± 1.3%, 16.5 ± 0.7%, and 8.1 ± 1.1%, respectively. The objective was to evaluate the ability of the 2-month-old Campylotropis polyantha (Franch.) Schindl. seedlings to tolerate drought and to explore the mechanism resisting drought. We monitored the growth process of seedling height and leaf number monthly and further investigated those changes in plant growth, dry mass accumulation and allocation, water-use efficiency (WUE), leaf functional traits, chlorophyll a fluorescence and pigment contents across the water deficit gradient. We found that the seedlings presented optimal growth, dry mass production, and physiological activity only at the W₁₀₀ and W₈₀ treatments and afterwards significantly decreased with progressive water deficit; the WUE was improved under moderate water stress (W₆₀ and W₄₀) but reduced under severe stress (W₂₀). The serious leaf shedding, growth stopping and seedling death under the W₂₀ condition revealed that the current-year shrub seedlings could not withstand severe drought. Water stress-induced decrease in total plant leaf area due to a combination of limited expansion of younger leaves and shedding of old leaves caused the leaf area ratio reduction under drought. The reduced mesophyll cell was a major anatomical response of leaves along the water stress gradient. The progressive water stress significantly damaged light harvesting complex and reduced photochemical processes and PSII activity. Our results clearly showed that the current-year shrub seedlings took the avoidance and tolerance mechanisms to withstand progressive drought stress and around 25.6% SVWC and around 12.3% SVWC separately are thresholds to limit the optimal growth and dry mass production and to last growing and surviving for the current-year shrub seedlings.     

Effect of nitrogen form and radiation on growth and mineral concentration of two Brassica species

Three greenhouse experiments were carried out to determine the growth, yield, nitrate, total N and S concentration in shoots, and water uptake of hydroponically grown Brassica rapa L. subsp. nipposinica var. chinoleifera and Brassica juncea L. In each experiment, daily photosynthetically active radiation (PAR) level was 5.0 mol m⁻² (low), 6.8 mol m⁻² (medium) or 9.0 mol m⁻² (high). Plants were supplied with nutrient solutions having equal N concentrations of 11 mM in different forms: 100% NH₄, 50% NH₄ + 50% NO₃, and 100% NO₃. Nitrogen supplied as 100% NH₄ reduced fresh and dry shoot biomass, leaf area, and leaf number in both Brassica species, especially at low and medium PAR levels. In both Brassica species, S concentrations were highest, while nitrate concentrations were lowest in leaves of plants grown at N supplied as 100% NH₄. No differences in leaf nitrate concentrations were observed between 50% NH₄ + 50% NO₃ and 100% NO₃ treatments. Low and high PAR levels increased the nitrate concentrations and decreased the N/S ratio in leaves of both crops compared to medium PAR level. Fresh shoot biomass was maximized in Brassica rapa when PAR level was above the medium value and nitrate was supplied in the nutrient solution as NO₃ or as a mixture of 50% NO₃ and 50% NH₄. The highest fresh shoot biomass of Brassica juncea was observed in all nutrient solution treatments at high PAR level.     

Responses of non-primed or primed seeds of ‘Marketmore 76’ cucumber (Cucumis sativus L.) slurry coated with Trichoderma species to planting in growth media infested with Pythium aphanidermatum

Aqueous slurries of commercial preparations of Trichoderma harzianum Rifai strain KRL-AG2 G41 (Th), T. virens Strain G-41 (Tv), or their combination (ThTv, at half rates each of the single application rate) were applied to ‘Marktetmore 76’ cucumber seeds (Cucumis sativus L.) that were non-primed or primed for 3 days at 25 °C either osmotically (−2.5 MPa from 0.337 molal Ca(NO₃)₂) or osmomatrically (−1.0 MPa from 0.135 molal Ca(NO₃)₂ plus −1.5 MPa from 50% water in exfoliated grade 5 vermiculite). Slurries were applied to seeds (1 mg per seed) either before or after priming. Seeds were sown in soilless, peat-based media with or without inoculation with Pythium aphanidermatum (Pa). Protection against damping-off caused by high pressures of Pa (16% emergence in non-coated, non-primed seeds) was increased by slurry coating Th on non-primed (76.4% emergence) or on osmotically primed seeds, with coating either before or after priming having no effect on efficacy (average 62.6% emergence). Slurry coating Th on osmomatrically primed seeds failed to increase final emergence percentage (FEP). Colony forming units per three seeds (CFU, all 10³) was 2.8 for non-primed seeds, and 3.2 and 2.6, respectively, when osmotically and osmomatrically primed seeds were coated after priming. In a second study with lower disease pressure (58.1 FEP from non-coated, non-primed seeds), slurry coating of non-primed or osmotically primed seeds with Th, Tv or ThTv reduced percentage damping-off and increased FEP. The combination coating eliminated damping-off only in non-primed seeds, and tended to reduce percentage damping-off in osmotically or osmomatrically primed seeds compared to coating with Th or Tv alone. In a third study using only non-primed seeds, slurry coatings with mefenoxam fungicide, Th, Tv, or ThTv decreased total damping-off to 2.6%, 7.4%, 2.0%, and 0%, respectively, from the 30.1% occurring in non-coated seeds. Th, Tv or ThTv applied to growth media at the same rate as the seed coating (1 mg per seed) were generally as effective as the seed coatings, and only the ThTv growth medium application eliminated damping-off. A fourth experiment revealed that Th, Tv or ThTv remained viable on non-primed seeds for up to 4 weeks (the longest storage duration) at 21 or 4 °C, but 21 °C storage resulted in faster seed germination by week 3 and higher CFU per three seeds by week 4. In summary, coating of non-primed seeds with Th, Tv or ThTv was more effective than coating primed seeds in reducing percentage damping-off. While priming treatments generally led to faster seedling emergence and greater seedling shoot fresh weight than was achieved with non-primed seeds, only for non-primed seeds was damping-off eliminated by the ThTv seed coating or growth medium application.     

Asymbiotic seed germination,mass propagation and seedling development of Vanda coerulea Griff ex.Lindl. (Blue Vanda): An in vitro protocol for an endangered orchid

The application of modern biotechnology for conservation of any endangered species requires an efficient in vitro regeneration protocol. In this study a reliable protocol was developed for in vitro seed germination, protocorm multiplication and subsequent plantlet regeneration of Vanda coerulea, an endangered orchid species. Among the four basal media evaluated for asymbiotic seed germination, Phytamax was found to be the best followed by Murashige and Skoog (MS). Phytamax was also found good for protocorm development. For protocorm like body (PLB) regeneration, protocorms were then further cultured on Phytamax media fortified with different phytohormones either individually or in combinations. The frequency of protocorm like body (PLB) regeneration significantly relied on kinds and concentrations of plant growth regulators used. A combination of 1-naphthaleneacetic acid (NAA) (5.36 μM) and 6-benzyle amino purine (BAP) (3.80 μM) was found to be suitable for maximum PLB regeneration. Healthy plantlets were induced from PLBs when cultured on same basal medium supplemented with activated charcoal (AC – 3.0 g/l). Plantlets with well developed leaves and roots were transplanted to pots filled with a mixture of charcoal, brick pieces and sphagnum moss and transferred to the greenhouse. This protocol will enable mass propagation and conservation of this exquisite orchid.