A novel in vitro hydroponic culture system for potato (Solanum tuberosum L.) microtuber production

An innovative in vitro hydroponic culture system used in potato (Solanum tuberosum L.) microtuber production is described in this paper. In vitro potato plantlets, 6–8 cm in height, derived from meristems of potato tubers cultured on 1/2 Murashige and Skoog (MS) nutrient medium after 30 days culture were cut into 1.5 cm stem node segments and used as explants. These stem nodes were cultured in a novel system called in vitro hydroponic culture system containing 1/2 MS medium supplemented with 0.5 μM naphthaleneacetic acid (NAA), 0.3 μM gibberellic acid (GA₃), 3.7 μM adenine sulfate, 10% coconut water, 0.5 g/l activated charcoal, 80 g/l sucrose with or without 8 g l⁻¹ agar. Liquid medium was distributed to the carrier substrates in each storey of the system with the aid of capillary robes. In the present paper, the effects of porous material used as substrate carrier and the number of storeys involved in the culture system on microtuber formation and their morphological characteristics are reported. Cotton layer substrate is more stable for organogenesis of potato microtubers. Microtubers, 3.19 mm in diameter and 49.82 mg in weight, could be harvested from a one-storey in vitro hydroponic culture system containing filter paper as substrate. However, microtubers cropped from three-storey in vitro hydroponic culture system with cotton layer were bigger and weightier than those from three-storey system containing filter paper. The above results of the in vitro hydroponic system examined in this study might open up a new approach in producing potato and other hygrophilous microtuber.     

Closed cycle subirrigation with low concentration nutrient solution can be used for soilless tomato production in saline conditions

Closed cycle soilless techniques can be adopted to minimize water and fertilizer losses in greenhouse cultivation. There is a general lack of information regarding the soilless cultivation of vegetables with closed cycle subirrigation techniques, specifically when using saline water. In this study, a trough bench subirrigation system (SUB), with two fertilizer concentrations (“100%”, containing 9.8 mol m⁻³ N-NO₃, 1.6 mol m⁻³ P-H₂PO₄, 8.7 mol m⁻³ K⁺, 2.8 mol m⁻³ Ca⁺, 1.8 mol m⁻³ Mg⁺, 4 mol m⁻³ S-SO₄, and “70%”, containing 70% of the macronutrient concentration) in the nutrient solution (NS), was compared with open cycle drip-irrigation (DRIP with “100%” NS). For all the three treatments, NS was prepared using rain water (0.05 dS m⁻¹) and adding NaCl (1 g L⁻¹), in order to simulate moderate saline irrigation water. The effect of the treatments on tomato (Solanum lycopersicum L.) plant growth, yield, fruit quality, water use efficiency (WUE) and fertilizer consumption was evaluated. Substrate and recirculating NS composition were also studied. Subirrigation, regardless of NS concentration, reduced plant height (by 30 cm), leaf area (by 1411 cm²), total fresh and dry weight (by 429 and 48.5 g plant⁻¹, respectively) but not dry matter percentage of the whole plant, with respect to DRIP. Yield was reduced when plants were subirrigated with the higher concentrated NS, but no differences with open cycle DRIP were recorded when the lower NS concentration was used in SUB. Fruit quality was not affected by irrigation system or NS concentration. The higher WUE was obtained with subirrigation. NaCl accumulated similarly over the crop cycle in recirculating NS of both SUB treatments and in growing substrates of all the three treatments. Higher salt concentration was found in subirrigated substrates, in particular in the upper part of the substrate profile. Fertilizers accumulated in the subirrigated substrates when the higher NS concentration was used, but not when the NS concentration was reduced by 30%. The results of this study indicate that tomato can be grown successfully in a closed cycle subirrigation system, using saline water, by reducing the fertilizer NS concentration normally used with traditional open cycle systems.     

Evaluation and correction of nutrient availability to Gerbera jamesonii H. Bolus in various compost-based growing media

Nutrient deficiencies usually constrain the use of some composted materials as peat-substitute growing media even if some fertilizer is applied to the media. In this work, we assessed the suitability of various composted materials as such or mixed with peat for potted plant production, with special emphasis on their effects on nutrient availability to plants. Further, we examined the effect of vivianite [Fe₃(PO₄)₂·8H₂O] as a fertilizer and its mixture with humic substances (HS) on these growing media (particularly their effectiveness in preventing Fe deficiency chlorosis in alkaline substrates). A completely randomized experiment design was developed involving the growth of gerber (Gerbera jamesonii H. Bolus) and two factors, namely (i) the growing medium, specifically composted cork residue (C), compost obtained from a mixture of olive husk and cotton gin trash mixed with rice hulls and peat in a 1:1:1 volume proportion (OH), composted grape marc (GM), Sphagnum peat mixed with spent mushroom compost (M), coconut fibre (CF), and Sphagnum peat; and (ii) the Fe source (control without Fe, Fe-EDDHA, vivianite and vivianite + HS in a weight ratio of 10:1).     

Effects of plant growth promoting bacteria (PGPB) on yield,growth and nutrient contents of organically grown strawberry

The effects of plant growth promoting bacteria (PGPB) on the fruit yield, growth and nutrient element content of strawberry cv. Fern were investigated under organic growing conditions between 2006 and 2008. The experimental plot was a completely randomized design with 3 replicates. Three PGPB strains (Pseudomonas BA-8, Bacillus OSU-142 and Bacillus M-3) were used alone or in combination as bio-fertilizer agent in the experiment. Data through 3 years showed that the use of PGPB significantly increased fruit yield, plant growth and leaf P and Zn contents. Root inoculation of M3 and floral and foliar spraying of OSU-142 and BA-8 bacteria stimulated plant growth resulting in significant yield increases. M3 + BA-8, BA-8 + OSU-142, M3, M3 + OSU-142 and BA-8 applications increased cumulative yield by 33.2%, 18.4%, 18.2%, 15.3% and 10.5%, respectively. Number of fruits per plant significantly increased by the applications of M3 + BA-8 (91.73) and M3 (81.58) compared with the control (68.66). In addition, P and Zn contents of strawberry leaves with bacterial inoculation significantly increased under organic growing conditions. Available P contents in soil were increased from 0.35 kg P₂O₅/da at the beginning of the study to 2.00, 1.97 and 1.82 kg P₂O₅/da by M3 + OSU-142, M3 + BA-8 and M3 + BA-8 + OSU-142 applications, respectively. Overall, the results of this study suggest that root inoculation of Bacillus M3 alone or in combination with spraying Bacillus OSU-142 or Pseudomonas BA-8 have the potential to increase the yield, growth and nutrition content of strawberry plant under organic growing conditions.     

Hydraulic characteristics of composted pig manure,perlite, and mixtures of them,and their impact on cucumber grown on bags

Composted pig manure (CPM), unmixed or in mixture with perlite, was evaluated as growing medium based on both physical characteristics and agronomic performance. The physical properties were determined in CPM, perlite (0.5–2.5 mm), and their 75:25, 50:50 and 25:75 mixtures by volume. It was found that unmixed CPM has a higher bulk density (BD) than perlite, a slightly lower air space at a suction of 10 cm, and a markedly higher content in easily available water (EAW), although the water content at a suction of 10 cm is the same in the two media. Mixing CPM with perlite by 50:50 seems to increase the actual water content and decrease the actual air content at container capacity, while the BD and the EAW score intermediate to those in the unmixed constituents. Simulation of the relative hydraulic conductivity (K_r) indicates a sharp decrease in the unsaturated hydraulic conductivity (K) of CPM, perlite and their mixtures as the media suction increases. The differences in the decrease rate of K_r between the tested substrates are rather small, with the most and least steep decrease being observed in perlite and the mixture by 50:50, respectively. The agronomic performance of CPM was assessed by growing greenhouse cucumber in bags filled with perlite up to 20 cm in height, CPM up to 10 or 20 cm in height, and their mixture by 50:50 up to the same heights as CPM. A media height of 10 cm in the bag resulted in appreciably higher yields than a height of 20 cm, regardless of the type of the substrate, while the latter had no significant effect on yield. This effect of media height was ascribed to the steep decrease in K, which was minimized in all media at higher suction levels than 10 cm, thereby severely restricting water availability in their upper layers (10–20 cm) when their height in the bag was 20 cm.     

Yield and quality response of drip irrigated green beans under full and deficit irrigation

The effects of different irrigation regimes on yield and quality of green beans (Phaselous vulgaris L.) irrigated with a drip irrigation system under field conditions in the Mediterranean region of Turkey were evaluated along two years. Irrigation regimes consisted of four irrigation intervals based on four levels of cumulative pan evaporation (Epan) values (I₁: 15; I₂: 30; I₃: 45 and I₄: 60 mm); irrigations occurred on the respective treatments when Epan reached target values, and three plant–pan coefficients as for irrigation levels (Kcp₁ = 0.50, Kcp₂ = 0.75 and Kcp₃ = 1.00). Irrigation intervals varied from 2 to 4 days in I₁, 5 to 7 days in I₂, 8 to 10 days in I₃ and 10 to 12 days in I₄ treatments in 2004 and 2005 growing seasons Both irrigation levels and intervals significantly affected the green bean yields. Maximum and minimum yields were obtained from the I₁Kcp₃ and I₄Kcp₁ treatments as 24,320 and 14,200 kg ha⁻¹ in the first, and 23,850 and 13,210 kg ha⁻¹ in the second experimental year, respectively. As the Kcp value decreased the total yields in each irrigation interval also decreased. However, with the longer irrigation interval (I₄), lower yields were obtained with all Kcp coefficients. Seasonal water use (ET) values in the treatments varied from 276 mm in I₄Kcp₁ to 400 mm in I₁Kcp₃ in the first experimental year, and from 365 mm in I₄Kcp₁ to 472 mm in I₁Kcp₃ in the second experimental year. Significant linear relations were found between green bean yield and seasonal ET for each experimental year. Irrigation intervals resulted in similar water use in the treatments with the same Kcp value. Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values were significantly influenced by the irrigation intervals and plant–pan coefficients. WUE ranged from 4.33 kg m⁻³ in I₄Kcp₃ to 6.08 kg m⁻³ in I₁Kcp₃ in 2004, and varied from 3.62 kg m⁻³ in I₄Kcp₁ to 5.43 kg m⁻³ in I₂Kcp₂ in the 2005 growing season. Maximum IWUE was observed in I₂Kcp₁ (6.16 kg m⁻³), and minimum IWUE was in I₄Kcp₃ treatment (3.83 kg m⁻³) in the experimental years. Both irrigation levels and irrigation frequencies had significantly different effects on quality parameters such as fresh bean length, width, number of seed per pod and 100 fresh bean weights. In conclusion, I₁Kcp₃ irrigation regime is recommended for field grown green beans under the Mediterranean conditions in order to attain higher yields with improved quality.     

Inoculation of growing media with the rhizobacterium Variovorax paradoxus 5C-2 reduces unwanted stress responses in hardy ornamental species

Inoculation of growing media with plant growth promoting rhizobacteria (PGPR) has a number of potential benefits for the production of ornamental plants. Certain rhizobacteria synthesise the enzyme ACC deaminase, which cleaves ACC, the precursor of the plant hormone ethylene. Bacterial metabolism is now known to lead to a reduction in [ACC] in the plant transpiration stream and bacteria are hypothesised to act on ACC exuded from roots. This in turn reduces the ethylene generated in plants growing in growing media inoculated with these bacteria. Here we tested if applications of the ACC deaminase containing rhizobacteria Variovorax paradoxus⁵C–²could be of benefit to ornamental growers by reducing ethylene generation in stressed plants. Ethylene is produced at levels that are inhibitory to growth and development under a number of abiotic stresses. The propagation and production of hardy ornamentals is deleteriously affected by abiotic stresses that involve ethylene signalling, including drought and physical wounding. Inoculation of growing media with V. paradoxus 5C-2 lowered ethylene emission from mature leaves of Cytisus × praecox experiencing drought stress. In addition, bacterial inoculation of the growing media resulted in significantly reduced abscission of the mature leaves under drought treatment. Beneficial effects of inoculation where also found in the wounding response of Fargesia murielae following divisional propagation and late season senescence in Aquilegia × hybrida in response to drought stress. Together these results demonstrate that V. paradoxus⁵C–²has real potential for use on ornamental nurseries in situations where plant stresses are unavoidable.     

A comparison of potato seed tuber yields in beds,pots and hydroponic systems

The objective of this study was to compare potato seed tuber production of cvs. Monalisa and Agata growing in beds, pots or hydroponics, with either single or staggered harvests. All culture systems were established in plastic sheeting-covered greenhouses protected with an anti-aphid network. The beds and 3 L pots were filled with Plantmax^® substrate and placed in suspended beds. The hydroponic system utilized NFT (Nutrient film technique) and 4 m × 15 cm × 7 cm PVC tubes with a 4% slope and the fertilizers were a commercial formula. Each experiment was 4 treatments in factorial Scheme 2 × 2 with 2 cultivars (Monalisa and Agata) and 2 harvest methods (single and staggered). All three experiments were carried out in randomized design with 6 replicates and 7 plants per replicate.     

High-frequency embryogenesis,regeneration of broccoli (Brassica oleracea var. italica) and analysis of genetic stability by RAPD

High-frequency somatic embryogenesis and shoot regeneration of broccoli (Brassica oleracea var. italica) were achieved. Cotyledon and hypocotyl explants from four varieties of broccoli were cultured on MS and modified MS media (mMS, supplemented with PG-96 organic components) with different combinations of growth regulator. The effects of genotypes, different explants, growth regulator combinations, organic components and AgNO₃ on induction of calli and shoots were evaluated. The optimal media for inducting calli/shoots and roots were mMS medium containing 3% (w/v) sucrose and 0.8% (w/v) agar supplemented with NAA at 0.5 mg l⁻¹, 6-BA at 3.0 mg l⁻¹, AgNO₃ at 4.0 mg l⁻¹ and MS medium containing 3% sucrose and 0.8% (w/v) agar supplemented with NAA at 0.2 mg l⁻¹, respectively. The callus induction percentages were over 90% in all four varieties; shoot induction percentage was 92.5% and the average number of shoot per explant was 4.1 from cotyledon explant in variety Bishan. In this study, we established high-efficient embryogenesis and shoot regeneration system of broccoli and analyzed genetic stability of regenerants at DNA level using RAPD molecular marker. Out of 62 arbitrary primers screened using PCR amplification, 79 polymorphic bands were amplified from 20 primers. The results demonstrated the genetic stability of regenerants from the same variety.     

Effect of nutrient sources on cucumber production in different substrates

The research was conducted in two successive seasons to compare the effect of nutrient sources, organic manure and inorganic conventional nutrient solution, in cucumber production performed with different local substrates. In fall, the experiment was designed to test three factors, namely cultivar [(a) Armada, (b) Gordion], nutrient source [(a) inorganic nutrient solution, (b) solid organic manure] and substrate [(a) 3 + 1 perlite + clinoptilolite, (b) 1 + 1 perlite + clinoptilolite, (c) 3 + 1 tuff + clinoptilolite, (d) 1 + 1 tuff + clinoptilolite, v/v]. Results showed that organic manuring decrease the total yield by 22.4% in comparison to inorganic nutrient solution. In organic manure treatment, vigorous variety (Armada) gave higher yield than less vigorous variety (Gordion). In the spring season, the tested factors were decreased to two and tested as nutrient source [(a) inorganic nutrient solution, (b) solid organic manure, (c) organic nutrient solution] and substrate. Armada was the only cultivar. Compared to that of the inorganic nutrient solution, total yield was reduced by 10.9% in the organic nutrient solution system and 31.3% in solid organic manure treatment.     

Effects of oxygen-enriched nutrient solution on greenhouse cucumber and pepper production

A series of experiments were conducted with greenhouse cucumber and pepper plants to determine the effects of oxygen enrichment of the irrigation water on yield and fruit shelf-life. The experiments were carried out in soilless culture in research greenhouses. Depending on the experiment, treatments included sub-ambient (2 mg L⁻¹), ambient (5–6 mg L⁻¹), medium (16 mg L⁻¹) and high (30–40 mg L⁻¹) levels of oxygen in the supply tank. Cucumber plants were grown in yellow cedar sawdust and pepper plants in either sawdust or perlite. Oxygen enrichment resulted in a promotion of cucumber yield in only one experiment; in two other experiments, none of the oxygen treatments, including those at sub-ambient levels, had an effect. There were no effects of oxygen enrichment on pepper yield. However, in both cucumber and pepper, fruit shelf-life was extended in oxygen-enriched treatments. In terms of system efficacy, oxygen levels in the irrigation water were measured at the dripper and found to decrease by 20–67% of initial values compared to the supply tank values, depending on the initial oxygen concentration and on the experiment. Oxygen concentrations decreased even further to virtually ambient levels when measured in the drain water or in the substrate reservoir. Cucumber plant growth was promoted under conditions which facilitated consistently high oxygen in the root zone, achieved through heavy irrigation (1 min in two) with oxygen-enriched nutrient solution of plants grown in saturated substrate (pumice). However, those extreme irrigation rates would not be practical for commercial cucumber or pepper production. Overall, this study demonstrates that oxygen enrichment of porous substrates under typical hydroponic conditions is difficult and possibly because of this, effects on yield are infrequent. However, fruit shelf-life may be improved.     

Effects of different organic apple production systems on seasonal nutrient variations of soil and leaf

An organic apple (Malus × domestica Borkh.) orchard was established to study the interaction effects of ground cover management systems (GMS) and nutrient sources (NS) on soil and tree nutrients in the Southern U.S.A. GMS mulches as follows: green compost (GC), wood chips (WC), shredded paper (SP), and mow-and-blow (MB). Across GMS, one of three NS treatments was applied: commercial organic fertilizer (CF), poultry litter (PL), and no fertilizer (NF). GC-treated plots had greater soil solution nitrate concentrations in year 3. GC plots also maintained greater seasonal soil organic matter and macronutrient concentrations during 3 years compared with the other GMS. Seasonal foliar nutrient concentrations grown under GMS in year 3 tended to follow nutrient concentration patterns similar to those observed in conventional apple orchards. GC and WC trees had overall greater leaf area, dry weight, and total foliar nutrient contents in year 3 than the SP and MB trees.     

Wetting agent effect on physical properties of new and reused rockwool and coconut coir waste

Wettability of growing medium in horticulture is an important practical factor of this industry. With a proper choice and a right application, wetting agent in the nutrient solution would improve wettability and some other physical properties of growing media. The aim of this study was to evaluate the effects on some physical properties of new and reused rockwool and coconut coir dust substrates with different doses of wetting agent (2, 10, 20, 100, 200, 1000, 2000, 10,000 and 20,000 mg L⁻¹) applied to the nutrient solution and their effects measured by using bioassays. The wetting agent was ether poly-ethylene-glycol nonil-phenol with 20% (w/v) as an active ingredient of a non-ionic surfactant. Bioassay results showed differences among species. For this, the method can be suggested as a good tool to be utilized through fertigation in soilless crops; however, other studies should be proposed for each species in particular. Except to the 2 mg L⁻¹ wetting agent content in reused coir waste, the total water-holding capacity increased with the wetting agent. With 2 mg L⁻¹ wetting agent content there was an important and significant increase the easily available water (over 600%) in both substrates (including the reused ones), while higher doses show no significant differences. The effect of adjuvants added through fertigation is directly dependant on the substrate type evaluated. The substrate reutilized after one crop, reduces the air capacity and increases the easily available water and total water-holding capacity. 2 mg L⁻¹ is the wetting agent concentration more adequate in coir waste and rockwool.     

Effects of conventional and organic fertilization on spinach (Spinacea oleracea L.) growth,yield, vitamin C and nitrate concentration during two successive seasons

Current experiment was laid out in order to compare different kinds of organic manure and chemical fertilizer application in growing spinach under the open-field conditions in two successive seasons. Matador type spinach (Spinacea oleracea L.) was cultivated organically and conventionally and spinach growth, yield, vitamin C and nitrate concentrations were checked throughout two successive seasons (autumn and winter). Commercial chemical fertilizer was used as conventional application, and chicken manure (CM), farmyard manure (FM) and blood meal (BM) were used as organic manure applications as a single and as mixtures at different quantities by aiming to receive 150 kg N ha⁻¹ for each, totally 19 applications. In general, autumn season gave the better results in terms of spinach growth, yield and resulted in lower nitrate concentration, whereas the vitamin C concentration was found to be higher in winter season. Reasonable applications to be recommended should be as follows with regard to the seasons; 3.5 ton ha⁻¹ CM and 0.6 ton ha⁻¹ BM + 0.85 ton ha⁻¹ CM + 4.0 ton ha⁻¹ FM for spinach growth; 3.5 ton ha⁻¹ CM and 5.0 FM + 1.2 CM + 0.4 BM applications for spinach yield; 5.0 ton ha⁻¹ FM + 2.5 ton ha⁻¹ CM and 15.0 ton ha⁻¹ FM for vitamin C and nitrate concentration in the autumn and the winter season, respectively. In conclusion, FM and CM can be used effectively in growing organic spinach especially in the autumn season and can be transferred successfully into an asset.     

Spatial and temporal oxygen distribution measured with oxygen microsensors in growing media with different levels of compaction

Oxygen microsensors were used to determine oxygen profiles in situ from the top to the bottom layer of the growing medium for potted plants of Rosa sp. ‘Dior’. The growing medium was peat- based and compacted uniformly to 3 different bulk densities of 0.14, 0.18 and 0.23 g cm⁻³ (0, 20 and 40% compacted, respectively). The water distribution in the pot was determined as water content (g cm⁻³) in the top, middle and bottom layers of the peat. Oxygen content was also determined after a standard subirrigation cycle and after excessive irrigation where the bottom of the pots were left waterlogged for 24 h. Measurements were carried out at 5.5 weeks during the production phase and at 12 weeks at the end of the production. The results showed that with increasing compaction and density, more water was transported to the upper layers of the pot. After a standard irrigation cycle there was no effect of the level of medium compaction on the oxygen distribution, whereas after excessive irrigation, the oxygen contents at the bottom of the pots were strongly reduced and the level of compaction significantly affected oxygen availability. The most compacted medium had the lowest oxygen content at 5.5 weeks, with anoxic conditions in the bottom 30 mm. Plant quality measured as fresh weight, dry weight, height and number of shoots with flowers and buds was not affected by the different levels of compaction. The use of oxygen microsensors provided a new insight into the spatial and temporal distribution of oxygen in growing media and how this was affected by the physical characteristics of the growing media.     

Cucumber fruit quality at harvest affected by soilless system,crop age and preharvest climatic conditions during two consecutive seasons

Cucumber fruits (Cucumis sativus L., cv. Trópico F1) grown on perlite substrate and NFT (Nutrient Film Technique) were harvested during two seasons (winter and spring) to monitor the effects of climatic conditions and hydroponic growth systems on fruit quality at harvest. The best fruit quality at harvest, as measured by lightness and hue angle parameters, was obtained during the 3 weeks following the first winter picking. When values of a parameter of preharvest climate value called G^* were lower than 0.4 MJ m⁻² °C day⁻¹ interval⁻¹, the cucumber achieved its optimum quality at harvest, as measured by the dark green color of the skin. NFT-grown fruits showed darker and greener skin color (higher hue angle and lower lightness) compared with perlite-grown fruit, irrespective of the season considered. During the winter season, the plant transpiration rate was 30% higher in perlite than in NFT culture, which correlates with higher differences in G^* and 40% additional yield in perlite. However, in spring G^* was not sensitive enough to discriminate between the two hydroponic systems. In general, fruit quality at harvest in spring was lower than during the winter, due to flesh whitening, higher longitudinal and equatorial calibers, and slightly higher pH, as well as worse epidermal color coordinates (ranging from the dark and dull green color typical of winter fruit to light and a vivid green-yellow color). During the spring season, NFT-grown fruit were less acid than perlite-grown fruit with no apparent correlation with the climatic conditions or fruit nutrition.     

An integrated method for irrigation scheduling of potted plants

Hourly meteorological and soil water potential data collected during the summer season on a container crop of 2-year-old plants of Hypericum hidcote were used to develop a methodology that integrates climate-based (AET = ETo × K_c) and soil-based methods (soil water potential measurements by tensiometers) for the automatic control of the irrigation of plants growing in pots. Hourly ETo values were calculated by the CIMIS equation, derived from the Penman formula. Tensiometric data, by a soil-specific tensiometric curve, were transformed into pot water weight and used to estimate actual hourly evapotranspiration (AETt).     

Improved protocol for Agrobacterium mediated transformation of tomato and production of transgenic plants containing carotenoid biosynthetic gene CsZCD

Improved protocol for Agrobacterium mediated transformation of tomato (Lycopersicon esculentum) Micro-Tom was developed to use in corporation of the carotenoid biosynthetic genes CsZCD (Crocus zeaxanthin 7,8-cleavage dioxygenase). From these experiment, a transformation methodology using explants from cotyledons cultured for 1 day on the medium with zeatin 2 mg/L, IAA 0.1 mg/L, carefully submerged in the Agrobacterium inoculum for 20 min, then concultured with the agrobacterium for 3 days on the same medium, followed by a transfer to the same medium with 500 mg/L cefotaxin for 3 days and then by a transfer to the same medium with 100 mg/L kanamycin and 500 mg/L carabenillin for 6–8 weeks and resulted in a greater than 20% transformation efficiency in the concentration of Agrobacterium OD600 = 0.2 tested. In this transformation method, no feeder layers were used and the subculture media was minimal. Among the Agrobacterium concentrations of OD600 = 0.2, 0.5 and 1.0, the best transformation efficiency, 20.87%, was obtained by using OD600 = 0.2, which was significantly higher than that of OD600 = 1.0. The presence of the inserted target genes was checked using a rapid and efficient PCR test. The protocol was successfully employed in the production of transgenic Micro-Tom tomato containing the carotenoid biosynthesis CsZCD under constructive promoter. This procedure represents a simple, efficient and general means of transforming tomato.     

Estimated nitrogen use efficiency,surplus, and partitioning in young apple trees grown in varied organic production systems

A certified organic apple (Malus × domestica Borkh.) orchard was established to study the interaction of ground cover management systems (GMS) and nutrient sources (NS) on nitrogen (N) use efficiency and N surplus in the Southern U.S. for three years. Trees treated with green compost (GC) and wood chips (WC), regardless of the NS, had greater N accumulation and leaf N use efficiency compared to the shredded paper or mow-and-blow treated trees. The WC-treated trees had comparably low N surplus relative to the GC trees that induced more [NO₃⁻] in soil or soil solution in the rooting zone in September in year 3. GC trees had the highest [NO₃⁻] mineralization in the soil during winter. GMS had greater overall effects on the tree response variables than did the NS.