Volume 26 (2014): Issue 2 (December 2014)

Grafting of vegetable seedlings is a unique horticultural technology, practised for more than 50 years, to overcome problems associated with intensive cultivation on limited arable land. Grafting vegetables can protect against soil-borne diseases and nematodes, against abiotic stresses such as high/low temperatures, salinity, drought or excessive soil-water content, and against elevated soil concentrations of heavy metals and organic pollutants. In addition, the grafted plant takes up water and nutrients from the soil more efficiently and retains its vitality for longer periods during the growing season. However, rootstock/scion combinations may affect and alter the final size, yield, and quality of fruits from grafted plants, both immediately postharvest and during prolonged storage. These alterations may be attributed in part to differing production environments and methods, the type of rootstock/scion combinations used, and harvest date. The aim of this paper is to review the most recent literature on the effects of grafting on postharvest quality of fruits/vegetables: tomato, watermelon, melon, eggplant, cucumber and pepper. The review will conclude by identifying several prospects for future research aimed at improving the quality of grafted fruit/vegetable products.

By improving the thermal and moisture conditions in the immediate vicinity of plants, plastic covers influenced the growth and development and increased the yield of vegetables. Soil mulching with organic material is one method of soil water protection and also helps maintain a constant soil temperature within the root system of crops. This study investigated the effect of plant covering and the type of straw applied to soil mulching (rye, corn, rape or buckwheat) on the soil temperature, development of the plant and the yield of ‘Polfast’ F1 tomato. The effect of the straw was compared to a control plot without mulch. Soil temperature at a depth of 10 cm was higher in covered plots than in the plot without covers. The increase in soil temperature as a result of covering amounted to 1.3°C at 8:00 a.m. and 1.7°C at 2:00 p.m. Both in the morning and in the afternoon, the soil temperature in the plots without straw and without covers and under polypropylene fibre was higher than in the plots with straw. The application of covers resulted in higher aboveground parts of plants and higher leaf area compared to cultivation without covers. Irrespective of whether a covering was used, all of the types of straw investigated in the experiment caused the acceleration of growth and development of tomato plants. Simultaneous plant covering and soil mulching increased the total yield of fruits but did not have an influence on the share of marketable yield of the total yield.

The damage to pear and plum buds was investigated in Mashhad, after a period of unusually warm weather for a few days in March 2013 followed by a sudden drop in temperature to -12°C. Frost damages of vegetative and reproductive buds and spur-part below the buds of pear and plum cultivars were investigated based on visual observations. The following pear (Pyrus communis L.) cultivars were investigated: William’s, Bell de june, Ida, Spadona, Koshia, Domkaj, Dare Gazi, Mohamad Ali, Boheme, Shekari, Ghodumi and one Asian pear (Pyrus serotina Rehd.). Japanese plum (P. salicina L.) included ’Shiro’, ’Shams’, ’Computi’ and European plum (Prunus domestica L.) included ’Stanley’, ‘Early Santa Rosa’, ’Late Santa Rosa’, ’Shablon’ and ’Black Diamond’. Electrical conductivity (EC) and proline content were measured in reproductive buds. It was discovered that visual damages were different between cultivars, as the vegetative pear bud of ‘Ghodumi’ suffered the most damage and all parts of ‘Late Santa Rosa’ were the most susceptible in plum cultivars. On the other hand, ‘Computi’ had the most resistant reproductive bud and no damage was observed in the other parts. The EC and proline content of ‘Dare Gazi’ were the highest despite the fact that high proline content did not show high resistance, which was related to the phenological stage of ‘Dare Gazi’.

The aim of the present study was to improve the chilling tolerance of cucumber seedlings. The conditioned seeds in solutions of salicylic or jasmonic acid in concentrations of 10-2, 10-3 or 10-4 M or brassinolide in concentrations of 10-6, 10-8 or 10-10 M were subjected to temperature shock of 0, 2.5, 5, 35, 40 or 45°C for 1, 2 or 4 hours. Seedlings with 3 mm roots were chilled at 0°C for three days. The chilling susceptibility was evaluated by measurements of roots lengths, electrolyte leakage and total dehydrogenase activity.

The obtained results indicated that cucumber tolerance to chilling conditions depended on the plant growth regulators used during seed imbibition and its concentration as well as the temperature initiating thermal shock and its duration. The highest tolerance to chilling, expressed by the subsequent growth of roots, was observed after seed conditioning in salicylic acid solutions in a concentration of 10-4 M for 16 h at 25°C, then exposed for 4 h to a shock temperature of 5°C. The length of seedling roots after such treatment was over 12 times longer than the control (imbibed in distilled water and not subjected to short-term temperature impact). An increased chilling tolerance of cucumber seedlings may result from enhanced membrane integrity and total dehydrogenase activity. Further research is needed to explain the mechanism of the positive effects of salicylic acid, jasmonic acid or brassinolide application to reduce the injurious effects of chilling on cucumber seedlings.

The measurement of ethylene concentration in the apple core is considered a good method of determining OHD, but requires high accuracy and expensive equipment. The measurement of ethylene production seems to be a technologically easier method. During research conducted in the years 2003-2008, measurements of ethylene production were evaluated as a method for determining the harvest maturity of ‘Jonagored’ apples intended for storage. Measurements were carried out every 4-5 days starting a few weeks before the estimated harvest date. Apples were picked on four dates and after five months the loss of mass, firmness, TSS and TA was measured, the incidence of physiological disorders and fungal diseases was assessed and sensory tests were conducted to evaluate storability. Based on this evaluation it was determined which of those dates was OHD. After a period of low ethylene production, the production accelerated rapidly to reach an average level between 10.0 and 12.5 ppm kg-1 hr-1 on the OHD. Later, ethylene production rose still more sharply and quickly reached several dozens of ppm kg-1 hr-1. The accuracy of the new method was compared with other methods used to determine the maturity stage. The results obtained through the measurement of ethylene production showed the least deviation from the six-year average and only the results obtained using the Streif index method, which may be unreliable for some cultivars according to the literature, had a comparable margin of error.

In a four-year field experiment, fenhexamid, iprodione, pyrimethanil and thiram were applied in four different series as fungicides recommended for the control of grey mold (Botrytis cinerea) in strawberries. The plant protection products had no significant effect on the chemical composition of strawberry fruits of the Kent and Senga Sengana cultivars with the exception of an increase in the vitamin C level in ‘Kent’ strawberries. They also contributed to minor variations in the content of extract, total sugars, organic acids, polyphenols and anthocyanins. Dithiocarbamate residues were detected in all samples from the first harvest of strawberries that had been treated with the thiram fungicide

Experiments leading to the procurement of subsequent inbred generations were conducted in the years 2006- 2013. Seeds obtained from open pollination and after self-pollination of four strawberry cultivars (Teresa, Senga Sengana, Kent and Chandler) and clone 1387 were used. These genotypes were evaluated for their tolerance to strong inbreeding under in vitro culture conditions. The aims of this study were to estimate the inbreeding depression of each of the progenies. During the investigation, the germination percentage as well as seedling viability were evaluated. The highest seed germination was shown for populations derived from ‘Teresa’ × open pollination (82%) and ‘Kent’ (7) S₄ (78%). Seeds derived from self-pollination resulted in the lowest germination - an average of 16.8%. Generally, seed germination was significantly lower for the five S₁ offspring, whose depression was 0.62, in comparison with the S₄ seedlings, whose depression was 0.31. Inbred offspring showed a depression in relation to the average weight of a single seedling of 0.08 in the case of S₁ progeny, whereas in the case of S4 progeny it was 0.23. The highest germination energy was shown by ‘Kent’ (7) S₄ seeds (74%) and hybrids of ‘Teresa’ derived from open pollination (75%); whereas seeds obtained at the same time from self-pollination germinated 10.8% on average.

Red beet (Beta vulgaris L.) may be consumed at all stages of growth, both in the form of small early vegetable during spring and later, during winter, when stored. Therefore, knowledge of the dynamics of changes in the content of individual components in subsequent stages of growth is very important.

The experiment was conducted for two consecutive growing seasons. The study included four cultivars of red beet ‘Boro’ F₁, ‘Czerwona Kula’, ‘Nochowski’ and ‘Regulski Cylinder’. The aim of this study was to assess the dynamics of changes of selected components during the growing season. Particular attention was paid to the content of components having a positive impact on the quality of red beet, such as: antioxidant activity, the content of betalain pigments, soluble sugars and dry matter.

On the basis of the survey it was demonstrated that the optimal harvest date of red beet roots, with respect to the favorable nutrient and health-related content, falls in the 8^th and 11^th week of the growing season depending on the weather conditions in a given year. A significant increase in the anti-radical activity, soluble sugars as well as betanin and vulgaxanthin (2009) was observed between the 6^th and the 8^th and also in the 11^th week of the cultivation. A gradual drop in betanin to vulgaxanthin ratio was observed within the following weeks of the vegetation. On the basis of the research conducted we can conclude that the cultivar recommended for consumption is ‘Nochowski’.

Controlled atmosphere storage allows for the long-term and short-term storage of fruit without a significant decrease in quality, resulting in a longer shelflife of fresh fruit. The Department of Horticulture at the West Pomeranian University of Technology in Szczecin conducted research on the effects of post-harvest precooling (3-4°C within two hours) and storage conditions (conventional cold room and controlled atmosphere storage) on fruit firmness, chemical composition, colour and weight loss.

After six weeks of storage, it was found that the quality of fruit had declined. In comparison with fresh fruit, the harvest was found to have lost weight and darkened in colour. In addition, a decrease in firmness and the content of ascorbic acid and polyphenolic compounds was also observed. The fruits that were stored in a cold room with a controlled atmosphere and rapidly chilled immediately after harvest were the least affected. In addition, the research showed that there was a high correlation between the anthocyanin index and the polyphenol content in the fruits. To maintain the high quality of the fruit, the fruit must be very rapidly cooled soon after harvest and stored under optimal conditions - a cold room with a controlled atmosphere.

The in vitro propagation of chrysanthemum (Chrysanthemum × grandiflorum (Ramat.) Kitam.), one of the world’s most important ornamentals, is a very well-studied topic and shows numerous strides each year. This mini-review condenses the knowledge that has been published on chrysanthemum biotechnology, especially in vitro culture in the wider plant science literature. In 2013 and 2014, important strides were made in molecular breeding, particularly anti-viral strategies, including through transgenics, and our understanding of flower genetics and flowering regulation.

The mid- to long-term preservation of papaya (Carica papaya L.) would allow for the safeguarding of important germplasm. In this study, soft friable callus (SFC) and hard callus (HC) were induced from the first two true leaves of 10-day-old seedlings containing a midrib derived from the germinated seed of two cultivars (‘Rainbow’ and ‘Sunrise Solo’). Following germination on a Murashige and Skoog (MS) medium that contained 3% sucrose and was free of plant growth regulators (PGRs), sections of the first true leaves from 10-day-old seedlings were exposed to seven published callus or somatic embryogenesis protocols for zygotic embryos, leaves or hypocotyls. Optimal SFC and HC induction was carried out on a half-strength MS medium following the Fitch (1993) or the Ascêncio-Cabral et al. (2008) protocol, respectively. SFC formed shoots that could then convert to plants when transferred to a full-strength MS medium devoid of PGRs. Plantlets 10-cm tall were acclimatised in two steps: first by in vitro acclimatisation in aerated vessels, the Vitron, under CO2-enriched (3000 ppm CO₂), then by the transfer of individually rooted plantlets in Rockwool® blocks to a substrate of soil: pine bark : perlite (1:1:1, v/v/v). SFC and HC were then encapsulated in alginate beads, which were exposed to low temperature storage (LTS) at 10°C and 15°C, and also cryopreserved for 30 days. All encapsulated alginate beads that contained SFC, HC or leaf tissue that had been stored under LTS or cryopreserved were able to regenerate callus when placed on an optimal callus induction medium. Plants derived from the control, LTS and cryopreservation protocols, either from SFC or HC, were successfully acclimatised.

The results of two years (2010-2011) of field studies using two types of nonwoven mulches (one biodegradable, polylactic acid PLA 54 g m^-2, and traditional polypropylene PP 50 g m^-2) on the yield and quality of tomato are presented. Seeds of tomato (‘Mundi’ F1) were sown in a greenhouse, in containers filled with perlite and sand, and then the plants at the cotyledon stage were replanted in multipot trays filled with substrate for vegetable plants. In the last week of May, seedlings were planted on mulches in the field at a spacing of 50 × 100 cm. The mulch was maintained throughout the growing season. A plot that remained unmulched served as the control. Tomatoes were harvested once a week. The fruits were evaluated for L-ascorbic acid, dry matter, soluble sugars and nitrate content. In 2011, the analysis of the plant material showed that the concentration of L-ascorbic acid was about 23% higher in the tomato fruits harvested from plants grown on biodegradable PLA 61 g m^-2 mulch in comparison to the control. A similar effect was demonstrated for the soluble sugar concentration in 2011 for both types of nonwovens.