Fruit calcium content and lipoxygenase activity in relation to albinism disorder in strawberry

Nutrient elements and lipoxygenase (LOX) activity were determined in strawberry fruit to establish a relationship, if it exists, between nutrient ratios (N/Ca and K/Ca), and lipoxygenase activity with albinism disorder. About 33% strawberry fruit were affected by albinism. Etna had highest incidence of albinism (48.6%) and Sweet Charlie the lowest (16.2%). Dry matter content (%) was lower in albino fruit (5.23%) than normal fruit (7.36%). The concentration of N, P, and Mg did not differ significantly, but that of K (1.87 mg g⁻¹ fresh weight) was notably higher and of Ca (0.105 mg g⁻¹ fresh weight) was lower in albino fruit than normal fruit. Consequently, the nutrient ratios, N/Ca (9.78) and K/Ca (16.96) were higher in albino fruit than normal fruit. Cultivars differed widely in respect to dry matter (%), mineral content and nutrient ratios. LOX activity determined on dry weight or fresh weight basis was significantly higher in albino fruit than normal fruit, with significant differences among cultivars. Positive correlations existed between nutrient ratios and albinism incidence (r = +0.338), LOX activity and albinism incidence (r = +0.412), and LOX and nutrient ratios (r = +0.448). Thus, it appears from the study that calcium and LOX activity may not the basic cause of albinism in strawberry, but these may be involved in senescence or fruit ripening process, as LOX activity was lower in albino than in normal fruit.     

Nutrient shift in Parthenocissus tricuspidata seedling in response to soil water stress

A climate-controlled greenhouse experiment was conducted to determine the influence of soil water stress on the nutrient status of a climbing plant, Parthenocissus tricuspidata (Sieb.et Zucc) Planch. The results showed that water stress constrained N uptake more than P and K uptake in P. tricuspidata. Soil water supply significantly affected N efficiency ratio, but had no effect on P and K efficiency ratios. P. tricuspidata had low K concentration (<10 mg g⁻¹) in all its plant tissues, which allowed the plant to limit its stomatal opening and reduce its water loss. The study revealed that P. tricuspidata is able to adjust biomass distribution, nutrient uptake and nutrient use efficiency in response to soil water stress and that nutrient management for this plant under water stress should focus on N more than on P and K.     

Effects of high electrical conductivity of nutrient solution and its application timing on lycopene,chlorophyll and sugar concentrations of hydroponic tomatoes during ripening

Tomato (cv. Durinta) plants were grown hydroponically under two electrical conductivities (EC, 2.3 and 4.5 dS m⁻¹) of nutrient solution inside a greenhouse. The high EC treatment was initiated either immediately after anthesis (high EC treatment) or 4 weeks after anthesis (delayed high EC treatment). Fruits were harvested weekly beginning 2 weeks after anthesis, until all fruits reached the red stage (8 weeks after anthesis). Lycopene, chlorophyll, sugar and total soluble solid (TSS) concentrations of fruits were measured every week for all harvested tomatoes from the different ripeness stages. The results showed that lycopene concentration, fructose and glucose concentrations and TSS of red ripe tomato fruits were enhanced by both high EC and delayed high EC treatments compared to those in the low EC treatment. The lycopene concentration of red ripe tomato fruits in the high EC and the delayed high EC treatments showed an increase of 30–40% (1.29–1.39 mg g⁻¹ dry matter) compared to those in the low EC treatment (0.99 mg g⁻¹); however, there was no significant difference in the lycopene concentration between the high EC and delayed high EC treatments. TSS of red ripe tomato fruits grown in the high EC treatment was 6.1%, significantly greater than those grown in the delayed high EC treatment (5.7%). Weekly change in lycopene concentration indicated that lycopene synthesis was enhanced by the high EC treatment, regardless of the application timing. Regardless of EC treatment, chlorophyll concentration in fruit declined linearly during fruit development and ripening and reached non-detectable levels 7 weeks after anthesis. Our results indicated that: (1) accumulation of sugars and TSS in fruit was due to reduced water flux to the fruit under high EC as previously reported, and (2) lycopene synthesis was promoted by, but chlorophyll degradation was independent from, the osmotic and/or salt stress caused by the high EC.     

Growth and nutrient partitioning of containerized Cercis siliquastrum L. under two fertilizer regimes

Lebanon's native flora is threatened by loss of natural habitat to rural and urban development and the increased demand of plant materials for landscaping. Despite Lebanon's floristic richness, most taxa used for landscaping are non-native. This study was done to determine if Cercis siliquastrum (L.) is amenable to container production. Therefore, six open pollinated seeds sources native to Lebanon were grown under two fertilizer rates to study growth, N, P, K uptake efficiency, and partitioning. Two-year-old seedlings were planted in 11 L containers in a 3:1 pine bark:compost substrate. Seedlings within each seed source or mother tree were grown at either 25 or 100 mg N L⁻¹ from 21N–3.1P–5.9K water-soluble fertilizer. Seedlings of all sources grown under 25 mg N L⁻¹ had greater dry weight than those grown at 100 mg. Nutrient loading occurred in plants under the high fertilizer rate, although total plant N, P, and K content were not affected by fertilizer rate. There were significant differences in mineral nutrient uptake and nutrient use efficiencies among the seed sources. The results show that C. siliquastrum is amenable to container production. The great variation in growth rate and nutrient use efficiency among the limited number of seed sources studied suggest that significant improvement can be made through mother tree selection and/or clonal propagation of superior individual plants within a source.     

Physiological and biochemical changes with special reference to mangiferin and oxidative enzymes level in malformation resistant and susceptible cultivars of mango (Mangifera indica L.)

Changes in biophysical attributes, mangiferin and polyphenol oxidase (PPO), catalase and peroxidase activities in malformation resistant mango cultivar Elaichi were studied at various stages of flower development and compared with susceptible cvs. Amrapali, Beauty Mc-lin and Dashehari. Accumulation of mangiferin was maximum (96.0 and 108.0 mg g⁻¹ FW) in Elaichi prior to flower bud differentiation (September) and at full bloom (February), while these were minimum (59.0 and 74.0 mg g⁻¹ FW) in susceptible cv. Beauty Mc-lin. Mangiferin promoted vegetative growth and exhibited inhibitory role on the occurrence of malformation. It was also found that the resistant cultivar had highest activity of PPO as compared to susceptible ones. There was no significant difference in the enzymes catalase and peroxidase activity at early stage of flower differentiation but at flower bud burst stage the catalase activity was enhanced significantly in cv. Elaichi (25.28 unit min⁻¹ g⁻¹ FW) in comparison to Amrapali (16.20 unit min⁻¹ g⁻¹ FW), Beauty Mc-lin (18.39 unit min⁻¹ g⁻¹ FW) and Dashehari (17.50 unit min⁻¹ g⁻¹ FW). The resistant cultivar had high leaf temperature (30.30 °C) and diffusion resistance (476.14 m mol m⁻² s⁻¹) during the flowering but the rate of transpiration and relative humidity (RH) were high in susceptible cultivars. Results of the present study clearly indicate that level of mangiferin could be considered as a potential biochemical indicator for screening mango genotypes to malformation.     

Nutritional quality of greenhouse lettuce at harvest and after storage in relation to N application and cultivation season

The effect of five levels of nitrogen fertilization on the growth and nutritional quality of Cos lettuce (Lactuca sativa L. cv. Parris Island) at harvest and after storage was studied during autumn and winter in South-West Greece. Plants were cultivated hydroponically in a greenhouse and the nitrate, chlorophyll and ascorbic acid (vitamin C) concentrations within the plant tissues were measured at harvest and following storage at 5 or 10 °C for 10 days. Nitrate accumulated in the leaves with increasing amounts of N within the nutrient solution and was higher in the winter than in the autumn. At the lowest N level (20 mg L⁻¹), the inner leaves accumulated more nitrate than the outer leaves, whereas at higher N levels (140, 200 or 260 mg L⁻¹) nitrate accumulation was higher in the outer leaves. Overall, the highest nitrate concentrations were detected in the petiole and the proximal end of the leaf, but at the lowest N application rate (20 mg L⁻¹) nitrate accumulated in the distal region of the leaf too. Although the nitrate concentrations within the leaves did not change significantly during 10 days storage at 5 or 10 °C, the chlorophyll and vitamin C concentrations decreased. Chlorophyll loss was higher in lettuce that was grown under low N levels and was higher at 10 °C than at 5 °C, but was reduced by enclosure of the lettuce in polyethylene film. It is concluded that the optimum N application rate for Cos lettuce grown hydroponically under cover during autumn and winter in South-West Greece, and in other areas with a similar climate, is 200 mg N L⁻¹ because at this N rate yield is satisfactory and leaf nitrate concentrations are below the maximum acceptable level for human consumption. Nutritional value (vitamin C concentration) and market quality (chlorophyll content) are highest at harvest and decrease during storage, but quality in terms of nitrate concentration does not change.     

Antioxidant properties of blackberry and blueberry fruits grown in the Black Sea Region of Turkey

Seven wild and ten cultivated blackberries (Arapaho, Bartin, Black Satin, Bursa 1, Bursa 2, Cherokee, Chester, Jumbo, Navaho, and Ness), and six lowbush (Vaccinium arctostaphylos) and four highbush (Vaccinium corymbosum) blueberries fruits (Ivanhoe, Jersey, Northland, and Rekord) were analyzed for total anthocyanins, total phenolics, and antioxidant activity as ferric reducing antioxidant power (FRAP) in this study. The respective ranges of total anthocyanin and total phenolic contents of the tested samples were: blackberries, 0.95–1.97 and 1.73–3.79 mg g⁻¹ and blueberries, 0.18–2.94 and 0.77–5.42 mg g⁻¹. FRAP values varied from 35.05 to 70.41 μmol g⁻¹ for blackberries, 7.41 to 57.92 μmol g⁻¹ for blueberries. Wild blackberries had the highest FRAP values while wild blueberries had the highest total phenolic and total anthocyanin contents. A linear relationship was observed between FRAP values and total phenolics for blueberries (r = 0.981). The anthocyanin pigments in samples were isolated and characterized by high-performance liquid chromatography (HPLC) with UV–visible detection. Cyn-3-glu was the predominant anthocyanin in all blackberry fruits.     

Fruit nutrient content and lipoxygenase activity in relation to the production of malformed and button berries in strawberry (Fragaria × ananassa Duch.)

Fruit nutrient content and lipoxygenase (LOX) activity were determined in strawberry fruit to establish a relationship, if it exists, between nutrients, and LOX activity with the fruit malformation and nubbins or button berry disorders. Nearly 17% fruit were affected by malformation and 10% by nubbins in open-field-grown strawberries. ‘Etna’ produced higher proportion of malformed (22.7%) as well as button berries (16.9%) and ‘Sweet Charlie’ the lowest (8.9% and 3.3%, respectively). Dry matter content (%) was lower in malformed (5.2%) and button berries (3.23%) than normal berries (7.41%). The concentration of P and Mg did not differ significantly, but that of N and K was notably higher and of Ca and B was lower in malformed and button berries than normal berries. Consequently, the N/Ca and K/Ca ratios were higher in malformed and button berries. LOX activity was significantly higher in malformed as well as button berries than normal berries, with significant differences among cultivars. The correlations between N, K and malformed and button berries were positive and between Ca and B, and malformed and button berries were negative. Similarly, the correlation between LOX activity and malformed, and button berries were also positive, indicating that excess of N and K, and deficiency of Ca and B are related to the production of malformed and buttons or nubbins in strawberry.     

Callus induction and plant regeneration from embryonic axes of Kosteletzkya virginica

Kosteletzkya virginica, a perennial dicot halophytic species of the Malvaceae, is native to American salt marsh. It was introduced into China as a potential species to improve coastal wetlands and to develop ecologically sound saline agriculture. K. virginica adapts excellently to the tidal-flat habitats in China's east coast, with multiple eco-benefits; in particular, its seed oil could be used to produce biodiesel. The purpose of this study was thus to develop a standardized protocol to induce a high frequency of callus and subsequent plantlet regeneration system for a K. virginica breeding program with the final objective of applying transgenic techniques to improve seed oil yield. The embryonic axes of K. virginica were used as explants for callus induction, shoot induction from the callus and then adventitious root induction from the shoots on nine culture media with different hormone combinations. The best results were achieved on the following media: (1) 93.94% callus induction on MS medium supplemented with 1.0 mg L⁻¹ indole-3-acetic acid (IAA), 0.3 mg L⁻¹ kinetin, 30 g L⁻¹ sucrose and 8 g L⁻¹ agar; (2) 65.83% shoot induction on 1/2MS medium supplemented with 0.1 mg L⁻¹ IAA, 0.5 mg L⁻¹ zeatin, 30 g L⁻¹ sucrose and 8 g L⁻¹ agar; (3) 96.67% rooting on MS medium containing 30 g L⁻¹ sucrose and 8 g L⁻¹ agar. The survival rate of plantlets by organogenic regeneration was 85% after being transplanted into potting soil in flowerpots and placed in the greenhouse. This experiment indicates that we established successful callus induction and plant regeneration protocols for K. virginica.     

Factors affecting mango (Mangifera indica L.) protoplast isolation and culture

The major factors influencing protoplast isolation and culture of mango (Mangifera indica L.) cv. Kensington Pride were investigated. The resultant protocol was used to compare plating efficiency among 4 mango cultivars. Most responses differed between proembryonic masses (PEMs) and leaf sources. Protoplast yields of 15.22 × 10⁶ g⁻¹ from PEMs and 8.68 × 10⁶ g⁻¹ from greenhouse-derived leaves were obtained in a solution of 0.7 M mannitol CPW plus 1.5% cellulase, 1% hemicellulase and 0.75% macerozyme for PEMs or 0.5 M mannitol CPW plus 1.5% cellulose, 1% hemicellulase and 1.5% macerozyme for leaves. Culture in Ca-alginate beads with initial plating densities (IPD) of 2.5 × 10⁴ Pp mL⁻¹ for PEMs and 2.5 × 10⁵ for leaves gave the highest plating efficiencies (FPE). For PEMs 1 mg L⁻¹ 2,4-d and 3.5 mg L⁻¹ kinetin gave an FPE of 2.85% whereas lower kinetin (2 mg L⁻¹) plus 0.5 mg L⁻¹ 6-BAP was most effective for leaves (FPE of 2.12%). Most protoplast mortality occurred during the first week of culture and was more severe in liquid culture. In Ca-alginate beads, protoplast survival at 14 days was higher for PEMs (30%) than leaf (21%) as was the frequency of cell division (17.6% compared to 13.6%). PEMs protoplasts continued development through embryogenesis to in vitro plantlet regeneration whereas leaf protoplasts underwent cell division up to 40-cell colonies but failed to proceed further. For PEMs, polyembryonic cvs. Kensington Pride and Keow Savoey produced higher FPE (1.95%) than monoembryonic cvs. Tommy Atkins and Keitt (1.75%). There was no effect of cultivar for leaf protoplasts.     

Molecular characterization and analysis of somaclonal variation in chrysanthemum cultivars using RAPD markers

Molecular characterization using RAPD analysis was carried out in eight cut flowers and two pot plant cultivars of chrysanthemum. Three of them (‘Refocus’, ‘Red Reagan’, and ‘Sheena Select’) were established in vitro and the occurrence of somaclonal variation was studied using the same molecular technique. Two induction media (MS + 0.1 mg l⁻¹ NAA + 0.1 mg l⁻¹ BA, and MS + 2.0 mg l⁻¹ IAA + 0.5 mg l⁻¹ Kinetin), and two proliferation media (MS + 0.1 mg l⁻¹ NAA + 0.2 mg l⁻¹ BA, and MS + 4.0 mg l⁻¹ IAA + 2.0 mg l⁻¹ Kinetin) were employed in order to evaluate the effect of the medium composition in the shoots’ stability. Likewise, the effect of the culture age was considered in assessing genetic stability. Monthly subcultures were carried out, identifying the origin and history of the shoots, throughout a nine-month proliferation period followed by acclimatization. Molecular markers were obtained in every subculture cycle and from the acclimatized plants. Only one shoot from the 7th subculture of the cultivar ‘Refocus’ showed a different band pattern. The use of RAPD for chrysanthemum cultivar characterization and somaclonal variation detection is discussed.     

Effects of cultural cycles and nutrient solutions on plant growth,yield and fruit quality of alpine strawberry (Fragaria vesca L.) grown in hydroponics

Alpine strawberry (Fragaria vesca L.) was grown in hydroponics with the nutrient film technique, in order to evaluate the effects of four buffer concentrations (1.3, 1.6, 1.9, 2.2 mS cm⁻¹) and two cultural cycles (summer-spring versus autumn-spring) in terms of growth, yield and fruit quality (dry and optical residues, sugars, acids, antioxidants, mineral composition). The longer summer-spring cycle gave a correspondingly higher yield than the autumn-spring one. The 1.3 mS cm⁻¹ nutrient solution was the most effective in terms of overall and spring production. However, the autumn and winter yields were not affected by the buffer EC. Fruit quality did not change with the cultural cycle, but the berries harvested in the spring had higher vitamin C and sucrose content and lower nitrate content compared with berries picked up in the winter. Fruit quality was also improved when the nutrient solution concentration increased. From the productive point of view, the cultural cycle choice should be made considering that 71% of the yield of the more productive summer-spring cycle derived from the spring harvest. Moreover, as regards the nutrient solution strength, 1.3 mS cm⁻¹ EC should be preferred during the spring season, whereas the 2.2 mS cm⁻¹ EC proved to be best in the winter in terms of fruit quality.     

Combined effects of leaf/fruit ratios and N and K fertigation levels on growth and distribution of nutrients in pot-grown persimmon trees

Responses of pot-grown persimmon trees (Diospyros kaki cv. ‘Fuyu’) with two different leaf/fruit (L/F) ratios and three different fertigation levels were studied. On July 2, the L/F ratios of 4-year-old trees were adjusted to 20 and 10 by fruit thinning. From July 4 to August 26, each pot was fertigated with a solution containing 0–0 g (none), 10–8 g (medium), or 20–16 g (high) of nitrogen (N) and potassium (K), respectively. The L/F ratio of 10 resulted in higher yields but smaller fruits containing lower soluble solids than the ratio of 20. The non-fertigated trees with the L/F ratio of 10 produced the smallest fruits, but the medium fertigation increased the size of the fruit at this ratio. The high fertigation level decreased fruit skin color at both ratios. Fruit dry weight increased the most among the tree components, accounting for 48–57% of the tree total dry weight at the L/F ratio of 20 and for 64–72% at the ratio of 10. The increase in tree total dry weight at the ratio of 10 was greater than that at the ratio of 20. The trees receiving medium fertigation had higher tree total dry weights than those receiving high fertigation, especially at the ratio of 10. As the L/F ratio changed to 10 from 20, the percentages of N and K partitioned to fruits in the non-fertigated trees increased from 38% to 51% and from 67% to 96%, respectively, of the tree total N and K increases; the percentage decreased with increasing fertigation level. Although fertigation significantly increased total N and K contents of the tree, the increase in K at the ratio of 10 was less in high fertigation rather than in the medium level. The results indicated that adjusting supplemental N and K was necessary to ensure fruit growth and N and K accumulation for trees with high fruit loads, but high levels of fertigation are not necessarily preferable.     

Response of four olive (Olea europaea L.) cultivars to six B concentrations: Growth performance,nutrient status and gas exchange parameters

A greenhouse experiment was conducted to study the effects of boron (B) on growth, nutrient status, B distribution and gas exchange parameters of olive plants (Olea europaea L.). One-year-old own-rooted olive plants of the Greek cultivars Megaritiki, Chondrolia Chalkidikis, Amfissis and Kalamon were grown in a sand–perlite medium and irrigated with nutrient solutions containing: 0.27, 0.5, 1, 2.5, 5 and 10 mg L⁻¹ B (0.27 and 10 mg L⁻¹ were considered as control and excess B treatment, respectively). After culturing for 185 days, leaves and stems (from basal and apical part of the shoots) and roots were separately sampled. Our results showed that the final number of leaves per plant was negatively correlated with B concentration in the nutrient solution. Furthermore, in B10.0 treatment, ‘Megaritiki’ had decreased length and number of lateral stems, ‘Chondrolia Chalkidikis’ and ‘Amfissis’ showed decreased length of lateral stems and ‘Kalamon’ decreased length of lateral stems and plant height. In general, dry weight of stems and leaves was not significantly correlated with B concentration in the nutrient solution. B concentration in leaves and stems was linearly correlated with B supply. A linear correlation existed between B concentration of the nutrient solution and that of leaves and stems. At the end of the experiment, B levels in the leaves and stems of B0.27 and B0.5 treatments did not differ significantly. In general, the increase of B concentration in the nutrient solution, negatively affected the nitrogen (N) concentration of leaves and stems while phosphorus (P) and iron (Fe) concentrations were not affected. Furthermore, potassium (K) and calcium (Ca) concentration in stems of plants supplied with 10 mg L⁻¹ B was decreased. In addition, high B supply resulted in increased magnesium (Mg) and manganese (Mn) concentrations in ‘Chondrolia Chalkidikis’ and ‘Amfissis’ and in the decrease of zinc (Zn) concentrations, in all plants. A significant decline in photosynthetic rate at the end of the experiment was observed in the B5.0 treatment regardless of cultivar.     

Direct regeneration of plants derived from in vitro cultured shoot tips and leaves of three Lysimachia species

The regenerability of three ornamental species—Lysimachia christinae, Lysimachia rubinervis and Lysimachia nummularia ‘Aurea’, were investigated using in vitro leaves and shoot tips. 6-Benzylaminopurine (BAP) and α-naphthalene acetic acid (NAA) added to Murashige and Skoog (MS) medium were tested for their effect on organogenesis. On the medium, shoot regeneration occurred directly without callus formation. In these species, L. christinae developed the highest regeneration rate and numbers of shoots/explant from shoot tips (100%, 12.25) and leaf bases (100%, 13.01) on the MS medium containing 3.0 mg l⁻¹ BAP and 0.1 mg l⁻¹ NAA. For L. rubinervis, the highest shoot induction rate and number of shoots/explant were obtained from shoot tip (100%, 16.87–17.20) on the MS medium with 0.1 mg l⁻¹ NAA and 3.0–5.0 mg l⁻¹ BAP. L. nummularia ‘Aurea’, however, showed the highest regeneration rate and number of shoots/explant (100%, 12.73) from leaf bases on MS medium supplemented with 1.0 mg l⁻¹ BAP and 0.1 mg l⁻¹ NAA. All in vitro shoots rooted well on half macronutrient MS medium containing 0.1 mg l⁻¹ NAA. After acclimatization, transplanted plantlets grew normally and flowered in the field.     

Production gradients in smallholder banana (cv. Giant Cavendish) farms in Central Kenya

Banana is an increasingly demanded food and cash crop in sub-Saharan Africa. Reported yields in smallholder farms vary substantially. The importance and spread of yield constraints have not been properly quantified. A study was carried out in Central Kenya to (i) quantify the yield levels, the primary yield constraints, and the spatial production gradients in such systems (ii) explore how soil fertility gradients relate to gradients in soil fertility management, and whether this is a function of farmer resource availability. Data was collected on crop management aspects, pests and diseases, and soil and plant tissue samples analyzed for nutrient contents. Bunch yields were higher near homesteads (29.8 t ha⁻¹ yr⁻¹) than at mid-distance (26.8 t ha⁻¹ yr⁻¹), or far away 20.2 t ha⁻¹ yr⁻¹. Yields were much higher than previously reported (11–14 t ha⁻¹ yr⁻¹) in Kenya. Both soil and tissue K levels were higher near and mid-distance, than far from the homestead. Gradients of soil pH, total N, available P and Organic carbon were found, being higher near the homestead, while Mg and Ca were lowest near the homesteads. K was the most deficient nutrient, with tissue K index (I_K) decreasing when moving away from the homesteads. P and Ca deficiencies were also observed. Resource-poor farmers’ soils were higher in exchangeable K and Mg, pH, and total N, and supported higher mat densities compared to resource-endowed farmers’ farms. Soil quality problems were the biggest yield loss factors and not pests and diseases.     

In vitro germination of walnut (Juglans regia L.) embryos

The present studies were undertaken with a view to standardize the medium and culture conditions for embryo culture of five cultivars of walnut viz., ACO 38853, Netar Akhrot, Gobind, Solding Selection and Blackmore. Embryos from mature fruits were aseptically excised and cultured on MS medium supplemented with different combinations of BAP, kinetin and GA₃. Best performing medium was MS with 0.5 mg l⁻¹ kinetin, 0.5 mg l⁻¹ BAP and 2 mg l⁻¹ GA₃ yielding 66.6% germination in Netar Akhrot after 12 days of culturing. Percent germination of excised embryos was higher when GA₃ and cold treatments were simultaneously applied as compared to those when applied separately. Netar Akhrot was found to be the best responding cultivar, which had a range of 25–66.6% embryo germination under different culture conditions. Plantlets with shoots and roots have been obtained in Netar Akhrot and ACO38853 and are transferred to soil after hardening.     

Quantification of phenolic acids and antioxidant activity in sweetpotato genotypes

Phenolic acid composition and antioxidant activity in roots of 14 commercially important sweetpotato genotypes were evaluated. Significant differences in total phenolics, individual phenolic acids, and antioxidant activity were found among the different sweetpotato genotypes. Total phenolic content, expressed in terms of chlorogenic acid equivalent, in different genotypes ranged from 1.4 to 4.7 mg g⁻¹ dry weight (DW). Antioxidant activity was evaluated as Trolox equivalent, ranging from 1.3 to 4.6 mg g⁻¹ DW. The highest total phenolic content and antioxidant activity were observed in a purple-fleshed genotype. Chlorogenic acid and 3,5-dicaffeoylquinic acid were the predominant phenolic acids, while caffeic acid was the least abundant in most genotypes. The highest content of chlorogenic acid (422.4 μg g⁻¹ DW) was present in a white-fleshed cultivar ‘Quarter Million’ imported from Jamaica. However, a purple-fleshed genotype had the highest amounts of 3,5-dicaffeoylquinic (485.6 μg g⁻¹ DW), 3,4-dicaffeoylquinic (125.6 μg g⁻¹ DW), 4,5-dicaffeoylquinic (284.4 μg g⁻¹ DW), and caffeic (20.5 μg g⁻¹ DW) acids.     

Ethychlozate reduces acidity of loquat (Eriobotrya japonica) fruit

Ethychlozate (ethyl 5-chloro-1H-3-indazolylacetate, Figaron) was applied to 12-year-old ‘Jiefangzhong’ (a high-acid cultivar) loquat (Eriobotrya japonica) trees at 0 (control), 75, 150 and 250 mg L⁻¹ on March 19th, 90 days after flowering. To determine pulp titratable acidity (TA), organic acid concentration and acid-metabolizing enzyme activity, fruits were collected at 0, 13, 25, 42 and 49 days after treatments (DAT), when fruits were ripe. Malate was the major organic acid determining loquat pulp acidity. Ethychlozate was very effective in reducing pulp malate concentration, thus decreasing pulp acidity. The best result for reducing acidity (malate) was obtained when ethychlozate was applied at 250 mg L⁻¹. The ethychlozate-treated pulp showed lower phosphoenolpyruvate carboxylase (PEPC) and NAD-malate dehydrogenase (NAD-MDH) activities through the experimental period, but higher or similar NADP-malic enzyme (NADP-ME) from 25 to 49 DAT compared to non-sprayed control. The reduction in malate concentration in the ethychlozate-treated pulp was probably caused by decreased malate biosynthesis and increased malate degradation.     

Effect of organic and inorganic fertilizers applied during successive crop seasons on growth and nitrate accumulation in lettuce

A romaine-type lettuce (Lactuca sativa L.) cv. Corsica was cultivated during three successive crop seasons (late-spring, late-autumn and late-winter) in the same soil of an experimental greenhouse in S.W. Peloponnese, Greece. Seven long-term fertilization treatments were tested for their effect on plant growth and nitrate concentration in the external lettuce leaves. Treatments included: three different doses of organic fertilization (composted sheep manure) applied at the start of each crop season, three different doses of inorganic N fertilization applied via fertigation during each crop season, and a control treatment in which no fertilizer was applied. A drip irrigation system was used to water all plants. The highest nitrate levels were observed in the medium and maximum inorganic fertilization treatments (572–664 mg kg⁻¹) in all crop seasons. They were significantly higher compared to the respective organic fertilization treatments (253–435 mg kg⁻¹) and all other fertilization treatments (148–435 mg kg⁻¹). Crop season affected lettuce growth more than nitrate accumulation in the lettuce leaves: lettuce biomass production was the smallest and most uniform in the late-autumn season and did not respond to the fertilization treatments tested (ranging from 409 to 439 g plant⁻¹), while in the late-spring season biomass production was the highest and most variable (561–841 g plant⁻¹), it correlated with nitrate concentration in the leaves and in the medium and maximum inorganic fertilizer doses it significantly exceeded production from all other fertilization treatments (827–841 g plant⁻¹). Following the three crop seasons the residual availability of N, P and K was clearly enhanced in the soil receiving the organic compared to the inorganic fertilization. Nitrate concentration in lettuce leaves was far below the upper limits set by the European Commission in all fertilization treatments throughout the three crop seasons, a result attributed mainly to the sufficient level of light intensity and duration throughout the year in Southern Greece.