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Study of genetic resources for Powdery mildew resistance by biochemical and physiological parameters on peaches and nectarines in Romania
57-61.Views:245During 1997-2002, studies on the physiological and biochemical changes due to powdery mildew attack in peach and nectarine cultivars and hybrids belonging to different classes of resistance had been performed at the Research Station for Fruit Tree Growing (RSFTG) Baneasa Bucharest, located in the southern part of Romania. The study was based on disease assessments in the field and on other diagnosis criteria.
The southern part of Romania has favourable ecological conditions for growing peach and nectarine but trees have been attacked by various pathogens such as Sphaerotheca pannosa (Wallr.: Fr.) Lev. var. persicae Woronichin fungus for a long time. The presence of the pathogen causes important changes in the quantity and quality of fruits and affects the metabolism of trees.
This study was focused on several physiological and biochemical parameters such as photosynthesis and respiration intensity along with catalase activity; and changes in some biochemical compounds such as free, total and linked water content, dry matter, nitrogen and protein content, tannin levels. The aim was to find possible correlation among the above parameters and the biotic stress induced by the powdery mildew fungus calculated as attack degree (AD%).
Results showed that photosynthesis diminished significantly in the case of the attacked phenotypes, the respiration was more intense in the infected cultivars and catalase proved to be less intense in the affected plants. The total water content significantly increased in contrast to the dry matter and tannin contents, which greatly reduced in the case of resistant cultivars such as 'Victoria', Vectared 7', 'KB 11-40'. The total nitrogen and protein levels showed less influence on resistance to powdery mildew on all cultivars. All genetic material found resistant to powdery mildew is currently used in peach and nectarine breeding programs in Romania.
Further studies focused on isolation and characterization of resistance genes for powdery mildew resistance will be done in the future based on data collected during several years.
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Challenges of the vegetable and fruit market
83-89.Views:510The situation of the horticulture sectors have been in the limelight of the professional and economic decision makers all over Europe. This article analyses the situation of the sector from economic point of view and reveals the main reasons of its low income and high risk. It concludes that one of the biggest problems is the trading uncertainty in the vegetable and fruit sector that is caused by the asymmetric market structure of the post-regime era. Since sizes of vegetable and fruit plantations do not allow producers to supply individually the extremely concentrated food retail trade or the processing trade they must find alternative ways for trading their products. The study introduces two alternative solutions. One alternative is foundation of modern multi-level producer co-operatives with the help of EU subsidies. Secondary and tertiary co-operatives may achieve better market position and lower trading price risk with managing production, professional marketing, and improving the information flow. The other alternative is searching for new trading channels such as local provision, restructuring of local markets, and direct trade (home delivery and pick-it-yourself programmes). The shorter producer-consumer distance means better quality at lower price for customers and income in the case of smaller amount of products for producers. It is concluded that both solutions together or separately may help individual producers in their trading problems. However, whichever way they choose, producers must co-operate.
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The impact of location, row direction, plant density and rootstock on the sunburn damage of apple cultivars
19-30.Views:1132The effect of row direction (N-S, E-W), plant density (conventional and intensive) and rootstock (M9, MM106 and crab apple) on the sensitivity of 41 apple cultivars to sunburn injury was studied at 6 locations (Derecske, Kálmánáaza, Nagykutas, Nagylapos, Siófok, Tornyospálca).
During the observations the cultivars had rootstock-specific properties in respect of sunburn-susceptibility. Accordingly, the injury was decreased in the order: M9, MM106 and seedling rootstocks. The differences in sensitivity depend on the canopy of trees, caused finally by the growing vigour of rootstocks. Accordingly, the highest value of sunburn injury was observed on M9 rootstock, because this rootstock has a dwarfing effect upon the scion cultivars. Thus, vegetative area of these trees grow very slowly and the foliage is not enough compact to protect the fruit from solar radiation. The size and density of the foliage increased in the order: M9, MM 106 and crab apple seedling as rootstock. Moreover, relationships were demonstrated between the diameter of upper part of the crown, the leaf area, the number of fruits per tree and the injury of sunburn.
Authors categorized the cultivars in respect of values of sunburn incidence: 1. „Not sensitive", II. „Moderately sensitive" and HI. „Strongly sensitive" categories were constituted. Generally, Topaz and Gala cultivars showed low damage (or were free from symptoms), in contrast to this, Golden mutants suffered relatively much. The most sensitive cultivar was Jonica on all the three rootstocks. We searched for relationship between the fruit quality parameters and the frequency of sunburn. Significant correlation was found in the cases of fruit size and the extent of cover-colour. The latter is interpreted with the fact that the best coloured fruits are found on the periphery of crown as a consequence of more intense irradiation.
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Healthcare values and potential uses of the new Hungarian apple varieties on the basis on fruit analysis
25-28.Views:441Biological active compounds and valuable characteristics of some apple varieties and candidates were measured in our trials. Fruits of ’Rosmerta’, ’Hesztia’, ’Cordelia’ and ’Artemisz’ are recommended to enrich the Hungarian assortments for fresh consumption and choice of new tastes. Based on examined parameters it can be assumed that novel Hungarian resistant varieties are suitable for juice and fruit concentrate production, and due to high pectin content of their remaining pomace these varieties can be raw material of pectin production as well as they are also suitable for jam production mixed with other fruit species. Furthermore, functional food industrial product having high quality can be produced by using novel resistant varieties because of their high pectin and polyphenol content. Beside of their high market value their suitability for growing among orchard conditions is confi rmed by lower costs of production because of less plant protection treatments.
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Role of nutrient supply in yield increase and quality improvement of spice pepper
83-86.Views:217Hungarian spice pepper powder is a unique product, a real hungaricum with its flavour and aroma compounds and seasoning effect. Its competitiveness with foreign spice peppers is ensured by its high biological value deriving from the specially Hungarian production and processing technology. Besides the traditional and highly manual labour intensive processing technology, there are some modern industrial technologies as well, where high quality can be guaranteed only by producing excellent base material (raw pepper pods). This is the reason which necessitates the rational development of the elements of the production technology, such as nutrient supply. Our objective was to offer a contribution to this aim by our trials in plant nutrition.
Experiments on the nutrient supply of spice pepper were set up in the 2003 growing season in order to decide whether yields and fruit composition parameters of pepper could be increased by means of increased K fertiliser doses with lower N:K ratios. Several forms of potassium were used, as well as applying microelement top dressings in the single treatments. It was found that the increase of N:K ratio from I:1 to 1:6 did not increase yields, but resulted in higher pigment and dry matter content. Microelement top dressing had a yield increasing effect at each N:K ratio. Higher potassium doses did not accelerate ripening.
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Post-storage sensory quality of apple varieties
54-57.Views:228The changing situation of apple production in Hungary has given rise to a great demand for new varieties. Besides bearing capacity, fruit quality and suitability for new training systems, consumer preference is one of the grower's main considerations. Growers need reliable information in order to choose the appropriate variety, so consumer tests have become essential. Altogether, 1 I traditional and new varieties were involved in this project. In the first part of the experiment, panelists ranked the coded samples according to their appearance. In the second part, apples were cut into unpeeled slices and the samples were also coded. The assessors were asked to taste them and rank them again. The sensory tests were held after three different storage periods.
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Organoleptic evaluation of sweet cherry varieties
7-13.Views:20793The extraordinary abundance of precipitation in 2010 (somewhere around 1000 mm) influenced highly the development of taste and flavour in cherry fruits. As stated, only a few varieties out of 27 were acceptable as for commercial quality. Under the given climatic conditions, actually ‘Bigarreau Burlat’ earned 965.11 points and proved to be the best in the early ripening group. In the mid season group, three varieties earned more than 1000 points (‘Giant Red’, ‘Carmen’ and ‘Vera’ grown at Nagykutas and Pallag), whereas in the late ripening group ‘Germesdorfi’ sent from Csenger (1084), ‘Linda’ (1070.07) and ‘Lapins’ (1052) received recognition. Correlation has been tested on the basis of 27 varieties between the individual properties. We sated that the most important attributes, which influenced the general impression of decision makers are the following: form and size of the fruit (r=0.835 and 0.797), furthermore juiciness (r=0.776), taste (r=0.876) and sweetness (0.875). Crispness was considered to be typical to cherry (r=0.743). Relation between acidity and sweetness was also essential to determine the acceptance of the cherry character.
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Changing of inert content values of apricot varieties
39-41.Views:478The consumers have been exigent increasingly about excellent quality. The speci fie flavour and fragrance of apricot evolve during ripening. We need to be acquainted with changing of inert content during ripening to the choosing of optimal harvest time. The Regional University Knowled ge Centre -Research and Development in Foodstuff Chain project had presented an opportun ity to study the inner content of apricot. Our aim was to study evaluation of health care attributes of apricot fruit. We investigated different ripeness samples of four apricot varieties ('Mandulakajszi', 'Pann 6nia', 'Gonci magyar kajszi'. 'Harcot') in our study of 2007-2009. Samples were taken the orchard of Sóskútfruct Ltd. Hungary. We had measured the water soluble antioxidant capacity, polyphenol-, f3-carotene content and the dissimilar sugar and acid-fractions during ripening. We had experienced significant different in inert content between varieties.
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Nutritional values of traditional open-pollinated melon (Cucumis melo L.) and watermelon (Citrullus lanatus [Thumb]) varieties
29-31.Views:537The aim of our experiments was to investigate the internal quality parameters of some old melon and watermelon landraces or varieties whether they have any desirable characteristics. Measurements were carried out using 8 different types of melon (Cucumis melo L.) and 8 accessions of watermelon (Citrullus lanatus [Thumb]), which were self pollinated under greenhouse conditions. Besides the determination of dry matter content; soluble solids, titratable acidity of the fruit juices, investigation of carbohydrates, total phenol content was measured by spectrophotometer. Total antioxidant capacities were determined spectrophotometrically using the FRAP method. We found some accesions both among melon and watermelon varieties, which could be characterized by outstanding inner content.
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Influence of environment in electro-chemical quality of tomato
17-20.Views:309The aim of the research was to investigate the impact of different cultivation environments of tomato cultivars, the electro-chemical and the qualitative traits of the tomato fruits. The quality of tomato fruit harvesting was evaluated at the Laboratory of Institute of Horticulture and Viticulture University of Natural Resources and Applied Life Sciences, Vienna. Two hybrids of tomatoes were tested Belle-F1 and AmaF1, in two locations and two different treatments (open field and plastic tunnels). Model of experimental fields was based on random method and included three replications. Following parameters were analyzed and tested: pH, Rh, P-Value, Nitrates and the content of vitamin C. The values of pH for treatment in the open field and indoor production system were not significant (4.47 to 5.05). For P-Value derived from the two treatments the maximal values were without significant differences, while minimal values were significant. Study has shown also that the highest values of nitrate content (16.34 mg, open field) compared to average value differences were + 0.384 mg or 43.83% higher. In indoor production the nitrate content was lower in compared with plants cultivated in open fields, so these differences were +3.81 mg or 26.4 0%, and highly significant for both levels. In relation to vitamin C content, the highest value was identified in the indoor systemof 298.6mg, with variations from the overall average of 16.43% or + 42.15 mg. The coefficient of variation values for both levels was of 29.96 respectively 27.31%.
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Conditions of rentability in the apricot industry of Hungary
127-129.Views:458Total investment costs of an up to date apricot plantation requires about 5000 thousand HUF/ha. Modern
plantations yield under normal conditions 15–20 t/ha with 80% quality for fresh consumption. Consequently, taking the life span of a plantation (15 years), the internal rate of return of 15–17% per year (IRR), that means that the costs of investment will be regained in the 9–10th year, which is considered to be satisfactory. However, weather hazards (frost, hail) may occur at a probability of 20–25%, therefore, maintaining the quality (80% for fresh consumption) and yields (15–20 t/ha) are badly needed to speak about rentability. This level of yields maintains the option of feasibility up to 20–25% losses. -
Comparison of light yellow fleshed pepper varieties grown on rockwool under unheated forcing conditions
108-110.Views:222Experiments are going on all over the world assisting the joint effort of researchers and practicing specialists to identify the methods which can help either in the reduction of production costs or in the increase of yields.
The task of the growers is to make profitable use of the forcing facilities and to satisfy market demands at an acceptable price by means of improving production technology and applying new scientific, technological and technical information.
For the last few years, rockwool based forcing has been gaining in importance. The subject of our scientific work was the analysis of an important question of this technological variant, the selection of the variety. Besides, we also tried to identify the most suitable pruning technology for the varieties studied.
In Hungary, the highest demand is commonly known to be for the light yellow fleshed varieties which are suitable for stuffed dishes. In the future, due to their special quality and appearance, as well as to the Hungaricum character, they could become important export goods on the European Union market. It was within this variety type that comparison between varieties already common in production (HO F1, HRF F1, Danubia F1) was carried out, trying to get an answer to the question which of the three varieties could be produced with the greatest success. Considering the quantitative and qualitative indicators, it was H6 F1 that proved the best out of the three varieties tested under unheated forcing on rockwool. It excelled the other two varieties both in quality and in average fruit weight, preserving this advantage until the end of the growing period.
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Sour cherry for fresh consumption in the retail sector A consumer aspect
81-84.Views:349The basic objective of our study is the promotion of fresh consumption of sour cherry and the enhancement of necessary knowledge. Primer collection of data was planned in three groups of retail shops, always sour cherry being the matter of study. The sampling dates were adapted to the sour cherry season weeks in Hungary. Three samples per week have been taken. Every time a short interview and purchase was planned. Every time, it was stated that the commodity was held for a longer period on the shelf, which trespasses the optimum of the fruit. At the same time there was no concordance between quality and price. From the point of view of the consumer this cannot be accepted.
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Effect of N, P, K and Mg fertilizers on some vegetative and generative parameters of a sweet cherry cultivar
27-30.Views:920This two-year-study was aimed to provide results on the effect of nitrogen, phosphorus, potassium and magnesium fertilizer treatments (control, NP, NPK, NPKMg) on vegetative and generative features of the sweet cherry cultivar ‘Carmen’. Examinations were performed in an orchard planted in 2012 on Prunus mahaleb rootstock with spacing of 5 x 2.5 m. All treatments improved the vegetative features of the sweet cherry trees in both years of 2016 and 2017. Fertilizer treated trees increased trunk cross section area (TCSA) with 51.3-63.1%, while control trees showed 48.3% trunk growth increase. Yields of control trees were lower in both years (5.9-7.2 kg/tree), than that of the fertilized trees (7.8-11.3 kg/tree). Treatments also increased the phosphorus (16-22%), magnesium (12-20%) and potassium content (3.5-18%) of the fruits compared to control treatments.
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Climatic indicator analysis of blooming time for sour cherries
11-16.Views:757County Szabolcs-Szatmár-Bereg produces more than the half of the total sour cherry grown in Hungary. Successful production, i.e. yield, depends largely on weather conditions. Most attention should be paid to the weather during the blooming period, being most decisive from the points of view of quality as well as quantity. In order to predict yields expected, the characterisation of the most important weather parameters is necessary. For that purpose, the database of the Institute of Research and Extension Service for Fruit Growing at Újfehértó Ltd. has been utilised. Records of weather conditions were collected throughout the period 1984-2005, i.e. daily minimum, maximum and mean temperatures (°C), precipitation (mm), and phonological diary of sour cherry varieties ’Újfehértói fürtös’, ’Kántorjánosi’ and ’Debreceni bôtermô’. Data of 7 indicators have been traced: number of frosty days, the absolute minimum temperatures, means of minimum temperatures, number of days when daily means were above 10°C, means of maximum temperatures, number of days without precipitation, and number of days when precipitation was more than 5 mm. On the one hand, we surveyed the changes; on the other hand, estimates have been attempted for the future changes expected during the following decades. The indicators being associated with certain risky events may serve for the prediction of the future recommendations to prevent damages.
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Evaluation of introduced plum varieties under extreme climatic conditions
7-10.Views:504In the gene bank variety collection, 15 plum varieties were examined based on morphogenetic and pomological traits. Most cultivars of self-fertilizing or pollinating partners were well-cultivated. In addition to Queston, Stanley, Valor and Verity, towards 11 new cultivars have been experienced in this paper.
From the observations, it seems that the growth and plantation of Valor, Presenta, Topfive and Bellamira can increase. However, the Top Sugar and Valor fruit sizes are best suited to market requirements. The role of Stanley may be reduced, but there is no reason to replace it. However, the questions of local varieties of domestic origin fall into a different category, and raw materials for quality products are difficult to replace with other varieties.
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Susceptibility of European pear genotypes in a gene bank to pear psylla damage and possible exploitation of resistant varieties in organic farming
95-101.Views:1065We evaluated 285 pear genotypes (commercial cultivars, ancient local varieties, unnamed local strains, seedlings, wild seedlings) in the largest gene bank of pear in Hungary from the point of view of psylla resistance to explore their possible exploitation in organic farming. We have found some 10 new resistant types (Bókoló körte, Bôtermô Kálmán, Füge alakú körte, Nagyasszony körte, Nyári Kálmán, Rozs nyári körte, Viki körte, Pb-242, Pb-299, 0-632) and 7 highly tolerant ones (Cure-6, Kései Kálmán, Kieffer, Kieffer Éd, Steiner, Téli Kálmán, II. B-3- 6/4, 96-16/5) (Table 1). These made up 3.5 + 2.8 per cent of the investigated genotypes, while 93.7 per cent of them were susceptible to pear psylla damage. Taking earlier and present results into account we can list more than 30 European pear cultivars being resistant or highly tolerant to pear psylla infestation and damage. In fact, the list of resistant and highly tolerant cultivars may serve as a basis selecting pear cultivars fitting to the specific requirements of the organic farming. By the end we can conclude that there is some real hope to exploit some resistant or highly tolerant ancient or local cultivars in organic farming but further investigations are needed to estimate their yield capacity and fruit quality.
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Preliminary results of renewal pruning an 18 years old sour cherry trees
41-42.Views:311Sour cherry is a light demanding fruit species. As most of the crop is developing from buds on one year old shoots and 2-yearold wood, the formation of bare wood can be seen apparently in a badly maintained canopy. The formation of „whip shoots” indicates the degree of bare wood. Unfortunately in many gardens and commercial orchards sour cherry trees resemble willow trees. Owners often decide to grub old orchards, although the useful cropping lifespan of the trees planted in a correct spacing can be 20-30 years on a move vigorous rootstock. Therefore renewal pruning can contribute to the full renewal of the orchard, but the length of its effect is depending on the growth characteristics and renewal capabilities of the cultivar. The growth characteristics of the cultivars are different. The regeneration capabilities of different aged wood are also different. These differences emphasize the need for cultivar specifi c pruning. Knowing the reactions to renewal pruning, we can ensure regular high crops with excellent quality by applying cultivar specifi c rotation pruning.
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Training systems of fruit trees in Hungary
123-127.Views:1104Growing sites and soil conditions of Hungary warrant profitable production of several temperate fruits at elevated levels of quality. The climate of the Carpathian basin is a mixtures of three main climatic zones the prevalence of which may change seasonally: Atlantic, continental and Mediterranean, therefore, growing sites are rather various. Temperature minima of the winter and late spring frosts are the main elements of risk. In choice of the system of cultivation, regularity of yields and intensity are to be observed equally. Regular yields are particularly aimed in stone fruit cultures.
For apple and pear plantations of high density required for intense production are promoted favourably. Accessories of intense orchards (irrigation, supporting system, rootstocks, phytotechniques, etc.) are important. In peach and plum trees are trained to funnel-shape crowns, in general, intense-types are possible in plum, only. In apricots, a Hungarian speciality, the "umbrella" type of crown is applied, almost exclusively, according to Papp. In sweet and sour cherry, the harvest technique, manual or mechanised, according to the intended utilisation, are determining the form of training.
Red and black currants as small fruits are grown mostly as bushes or hedgerows without any supporting system designed to facilitate mechanical harvest. Raspberries and blackberries are grown as hedges on trellis. Gooseberry is a special case, being a low, thorny bush difficult to be picked. Thus grafted small trees are attached to a wire-trellis which helps to solve problems of plant protection too.
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Comparative study of sour cherry samples for their anthocyanin content measured by tools of the laboratory and by portable equipments
29-31.Views:919The inner quality of fruits depends on many components. The analysis of pharmacologically important fruit species as the sour cherry consumed as a common food is an expensive task, mostly requiring an equipped laboratory. In sour cherry, one of its valuable components, the anthocyanin content deserves special attention. A portable analytical implement, which has been developed by our team measures the anthocyanin content on a scale of 1024 PharMgrades. The system is a member of the UVEX family of implements working with a microprocessor and performs the measurement quickly. The portable variant (UVEX-ML-1) does not require much training, the laboratory variant (UVEX UL-1) performs a large quantity of tests under modest laboratory conditions. Preparation of the samples is easily done, the necessary elements are available in the trade. The reagent is easily stored and dosed. The system was tested and proved to be of sufficient precision and the result showed acceptable variance according to the checks performed by a spectrophotometer in the laboratory.
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Experimental results of the effects of Hungarian climatic conditions to German disease-resistant industrial apple varieties
53-56.Views:206In the recent years, several disease-resistant apple varieties appeared through the modern breeding technologies. These varieties can be grown with low usage of pesticides, which mean not only environment friendly fruit growing, but the production costs are also lower. In Eastern-Hungary — it is one of the main apple growing regions — a new apple growing structure started to form by the investment of the German Wink Ltd. — several resistant apple varieties were brought from Germany. 'Resistant' refers genetic resistance that usually transferred from the genome of wild apple species. But the fruit of these apple species is not only resistant to diseases, but its quality is poorer, too. In Germany the Re-apples are grown only for the processing industry. Due to climatic circumstances in Eastern Hungary, the first experiences showed better parameters during laboratory measurement, the fruits have more beautiful view, shape and inner characters than usual industrial apples.
In our paper we discuss the results of sensory (consumer) tests, carried out in Eastern Hungary and in the Budapest-region the data analysis of systematic storing experiments (refraction, flesh firmness, weight loss, etc.) and profile analysis of fresh and stored Re-apples. (In the profile analysis the ProfiSens software [4,5] has been used.)
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Sensorial appraisal of sour cherries grown by environmental technology
27-30.Views:972Sour cherry samples have been tested by a panel of potential consumers, and the judgments expressed by points given for each attribute. The correlation of individual traits with “general impression” has been explored. Primary raising of data was aimed to evaluate the effect of environmental growing technology upon sensorial impression of fruits for fresh consumption. Organoleptic tests consist of tasting and filling out of forms with numerical data as ratings them regarding taste, flavour and flesh firmness. The values of coefficients of correlation showed that a couple of other attributes as appearance, juiciness and sugar/acids perceived were irrelevant from the point of view of acceptance, i. e. the general impression.
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Comparative study of plum cultivars belonging to different taxons during 1980-1996
13-19.Views:307The program of the Research Institute of Cegléd, comprises the acclimation and selection of 7 Prunus-species and 39 cultivars grafted on Myrobalan C. 679 (P. cerasifera) seedling stocks. In addition two varieties have been investigated on three different rootstocks each: Myrobalan C. 174 (P. cerasifera), Bitter almond C. 449 (P. arnygdalus var. amara) and Sweet almond C. 471 (P. amygdalus var. dulcis). Fruits of commercial quality are produced maroly on some cultivars of P. salicina-, P. italica- and P. cerasifera character. Authors explain the three possible causes of low yields experienced in non-European plums:
1/ unfavorable environmental conditions
2/ lack of irrigation and
3/ superficial information concerning the variety, rootstock and adequate traditions as well as growing practices.
A rather tight correlation has been stated between blooming dates and the main ripening period. However, the early blooming time alone cannot be considered as the cause of low productivity. The decay of plum trees is attributed to special ecological requirements and phytosanitary problems of the foreign plum cultivars. The analysis of regression revealed stochastic relations involving several other characters too, which facilitate the planning of cross-combinations in the breeding program.
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Effect of maturity stage on content, color and quality of tomato (Lycopersicon lycopersicum (L.) Karsten) fruit
41-44.Views:761Soluble solids (Brix°), carbohydrate, organic acid, lycopene, polyphenols and HMF content of indeterminate round type tomato Lemance F1 fruits were measured in six ripeness stages from mature green to deep red stage. Color of fruits was determined by CIELab system. The L*, a*, b* values were received directly and used to calculate from which the a*/b* and the chroma were calculated. The Brix', carbohydrate, lycopene and HMF content were the highest in the 6111 stake (deep red). Carbohydrate contents constitute nearly 50% of the Brix°. The mature green stage had the lowest acid content but in subsequent stages it was fundamentally unchanged. Polyphenol content changed little during fruit ripening. Lycopene content changed significantly during maturation and accumulated mainly in the deep red stage. Analyses showed that a*/b* was closely correlated with lycopene and can be used to characterize stages of maturity in fresh tomatoes.
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Illumination-Independent Reflectance Information Acquirement for Leaf Water Potential Measurement on the Example of Satsuma Mandarin
75-79.Views:208Mandarin fruit sugar content can be increased when subjecting the satsuma mandarin tree (Citrus unshiu MARC. var. satsuma) to moderate water stress by mulching during the period of active sugar accumulation, thereby fruit quality improvement can be realized. In the frame of the precision agriculture production system, a non-destructive measuring method development became necessary based on remote sensing, field spectroscopy and image analysis, to be able to measure the degree of water stress. Large amount of visual information have been recorded at ground level, in near infrared, red and green channels by a false color digital camcorder designed specially for remote sensing applications. A method have been found to be able to calculate the absolute reflection of mandarin leaf surface by comparing leaf reflectance with known reference target reflectance, thereby established the basis of further studies in this topic. Leaf absolute reflection can be measured reliably, under variable natural illumination at field conditions. Functional correlation can be searched between visual information and leaf water potential measured by PMS pressure chamber.
