Adaption of temperate climate horticultural plants in tropical and subtropical developing countries (Review Article)

In the small demonstration orchard of the College Faculty of Horticulture at Kecskemét the blooming time, the flower density and the honeybee activity was observed at a number of cultivars of 20 flower species during four consecutive years.

Fruit crop species were in flower during 3-4 months altogether. The blooming period of them was classified into five groups as early (almond, apricot, gooseberry), middle early (sweet cherry, red currant, currant-gooseberry, black currant, white currant, peach, plum, sour cherry), middle late (pear, strawberry, apple), late (black elder, quince, medlar, raspberry, blackberry-raspberry) and very late blooming period (blackberry). The blooming period of the members of the groups of early and medium early blooming often coincided partly and the same happened between the medium and the medium late as well as between fruits of late and very late flowering.

The flower density of some fruit species is extremely variable (currant-gooseberry, medlar), while at others it is fairly stable and evenly dense in consecutive years (sour cherry, sweet cherry, strawberry). At other fruit species it is moderately changeable. Some fruit species tended to attract more honeybees than others (plum, apple, quince, medlar) and some of them tended to attract much less (black elder, pear) but most species can be regarded as of medium attractivity.

On the flowers of some fruit species (pear, strawberry, quince) honeybees gathered pollen predominantly. At most fruit species however pollen and nectar gathering behaviour seemed to be gradually changing during the season. Namely most honeybees tended to gather pollen at the flowers of the early blooming fruit species, but on the other hand typical foraging behaviour gradually shifted to nectar gathering at the flowers of fruit species of moderate and late blooming periods.

Experiments were conducted with four sour cherry cultivars three of that were self-fertile and one was self-sterile. Different levels of fruit set were obtained by limiting, the bee pollination period. The limitation of the duration of the effective bee pollination period definitely affected the fruit set of all the four cvs. The mass of individual fruits seemed to be related to the final set but this relationship has not find to be definitely expressed statistically at that moderate level of maximum fruit sets (10-14 per cent at the maximum) we obtained in the experiments. For this reason, further research is needed to explore that level of fruit set that can notably reduce the fruit size (mass) to an undesirable extent.

'Fuji' apples from five different growing regions in Korea were analyzed for internal and external quality attributes which included fruit shape, color and sugar. Significant relationships were observed between final fruit color (a*) and air temperature in August. Red color was poorly developed where the average temperature in August was over 25 ^oC. The sugar composition was significantly different depending on region. The sucrose content decreased with increasing temperature above 16 ^oC during the harvest season. The fruit shape was not affected by agro-climatic conditions in this study.

In Hungary, fruit growers are increasingly interested in environmentally oriented growing methods, such as organic and integrated systems. The main factor in creating such systems is the establishment of a system of cultivar-pruning-plant protection based on production technology. Therefore, our aim was to examine the susceptibility of apple cultivars to diseases and pests and the effect of pruning technique on diseases and pests in organic and integrated growing systems.

Two pathogens (Venturia inaequalis, Podosphaera leucotricha) and two pests (Leueoptera malifoliella, Pannonychus ulmi) were observed in organic and integrated systems under "strong" and "weak" pruning techniques. Our results showed that, compared to integrated production, the pathogens and pests infected the trees more in the organic system. The pruning technique affected mainly the cultivars susceptible to diseases and pests. In general, the "weak" pruning technique correlated with a higher level of damage caused by diseases and pests than the "strong" pruning technique, especially in the organic growing system. The reason that techniques should be carefully chosen is that shoots grow faster and more vigorously after employing the "strong" pruning technique. This supports a better preservation of the trees, as a result of reduced susceptibility of plant tissues to diseases and pests.

Growth vigour of 36 apricot cultivars and new hybrids grafted on apricot seedling rootstock (Prunus armeniaca L.) was evaluated on the base of measurements of stem girth from the 4¹¹' to the 10th year after planting. There were differences in growth vigour of genotypes under study. In the evaluated set of genotypes the control cultivar 'Veecor may be classified as a genotype with below-average growth vigour. Only four genotypes (^-Reale d'Imola^-, Sanagian ^-Moldavskii krupnoplodnyl and 'LE-2385') were found with significantly higher growth vigour than that of control cultivar 'Veecot' in years of the end of experimental period. Two genotypes (Farmingdale', ^-LE-SE0-24') were found with significantly higher growth vigour only at the beginning of experimental period and one cultivar ('Vivagold^-) with significantly lower growth vigour in the first four years. Genotypes with different growth vigour can be used in further breeding programmes and/or as components inhibiting or supporting the growth in indirect vegetative propagation. Within the whole experimental period, the rank of growth vigour of genotypes practically did not change. This was demonstrated by highly significant or significant coefficients of correlation existing between individual pairs of years (r=0.32+ to r=0.96++). As far as the time difference between years in individual pairs of years was higher, the correlation coefficients were lower. In individual years, variability of growth vigour was relatively low and ranged from 9.83 to 13.64%.

Symptoms resembling phytoplasma disease have been observed on peach trees in a seed-source plantation of stone fruits in south Hungary quite recently. In this publication we report on the results of woody indexing of symptomatic peach trees on GF 305 indicator in the field and under greenhouse conditions as well as on molecular studies. Phytoplasma infection detected on GF 305 indicators in greenhouse and field indexing was confirmed by PCR. Nested PCR was conducted using universal primer pairs followed by group and subgroup specific primers for the second amplification. RFLP analysis of nested PCR products was performed using Rsal restriction enzyme. Based on the results of molecular studies it can be concluded that phytoplasmas, belonging to the European stone fruit yellows subgroup (16SrX-B) were identified in peach trees. Further studies on symptomatic peach trees originating from different parts of Hungary are in progress.

The process of in vitro rooting and the anatomical characters of in vitro and ex vitro leaves and roots of Prunus x davidopersica 'Piroska' were studied. Best rooting percentage (50%) and highest root number (5.0) was achieved in spring on a medium containing 0.1 mg/I NAA + 30 g/1 glucose. At the end of rooting the parenchyma of the in vitro leaves was more loose and spongy, than during the proliferation period. In the first newly developed leaf of an acclimatised plant, the parenchyma was much more developed, contained less row of cells and less air space too, compared to the leaves developed in the field. The in vitro developed root had a broad cortex and narrow vascular cylinder with less developed xylem elements, but at the end of the acclimatisation the vascular system became dominant in the root.

The effects of the ethylene precursor ACC and two inhibitors, AgNO₃ and AVG, on root formation were tested in in vitro shoots of passion fruit (Passiflora Midis f.flavicalpa Deg.). The organogenic response was assessed on the basis of percentage of shoot-forming. roots, root number and length. The time course of ethylene production was also monitored. ACC inhibited root formation by delaying root emergence and increasine, callus formation at the basis of the shoots. In addition, ACC caused a marked increase in ethylene production, coupled to leaf chlorosis and senescence with lower rooting frequencies, number and length of roots. IAA supplementation increased ethylene production. Both ethylene inhibitors, AgNO₃ and AVG, at appropriate concentrations reduced callus formation at the basis of shoots. AVG increased the number of roots per shoot, but drastically reduced length of differentiated roots. Regarding to leaf pigments, ACC promoted a marked reduction on carotenoids and total chlorophyll, whereas AVG and AgNO₃ delayed explant senescence and pigments degradation, not differing from IAA supplemented and non-supplemented control treatments. The results confirm previous reports on the beneficial effects of ethylene inhibitors on in vitro rooting and suggest its reliability to be used as an alternative approach to evaluate sensitivity of Passiflora species to ethylene.

The 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.

Intensive research has been implemented on different aspects of the bee pollination of pear in Hungary in the past decade, extending to the following topics: the effect of the opening sequence of the flowers within the inflorescence of pear cultivars on the effectiveness of bee pollination; the nectar production of flowers of pear cultivars; intensity of honeybee visitation and their foraging behaviour at the flowers of pear cultivars; flower constancy of honeybees to pear plantations; competition by weeds in bloom for bee pollination in flowering pear orchards; and some aspects to the bee pollination strategies of pear plantations (the effect of the limitation of bee pollination period on the set and the yield, possible compensation of frost damage of flowers by bee pollination in pear orchards, the optimal size of single cultivar block in pear plantations). The results of these studies are reviewed in this paper and some important aspects that need further studies are outlined.

It has been established, that thiamin content added in 3 mg/I concentration to musts before fermentation resulted in the enhanced storability of sparkling wine base at lower SO2 levels. Fermentation rate is not increased by this concentration and it causes no "thiamine taste" in organoleptic evaluation.

In our laboratory for special determinations BOERINGER-MANNHEIM's enzyme-test combinations have been used for 10 years. Our present work deals with the practical aspects of the enzymatic determination of so important wine components like L-malic, L-lactic and citric acid, glycerol, D-gluconic acid, D-sorbitol, acetic aldehyde and D-glucose to D-fructose (G/F) ratio. Whenever possible, the results arc compared to the results of other methods (spectrophotometry, gas chromatography, polarimetry) used at our department.

Resistance of the Hungarian pepper (Capsicum annuum L.) cultivar "Gre_.ygo" to Tohamoviruses has been investigated. All plants of the population of Greygo proved to be resistant to tobacco mosaic and tomato mosaic viruses (TMV, ToMV), both represent the pepper pathotypes P_o of Tohamoviruses. Individuals of Greygo, however, were found to be susceptible to pathotypes P₁₂ and P₁₂₃ of pepper mild mottle virus (PMMV). When inoculated with the XM isolate of dulcamara yellow fleck virus (DYFV, pathotype P1) the population of Greygo segregated in resistant and susceptible plants. These results as well as inoculations of the progenies of three TMV resistant plants clearly showed, that besides the resistance allele Li the cultivar Greygo possesses also an another allele. This allele, provisionally marked by L²g behaves like to the allele L² characteristic to Capsicum frutescens cv. . Tabasco. Determination of the identity of the allele L²g to the allele L² needs further genetic and pathological informations. Relations between the Tohamoviruses pathogenic to pepper and the alleles of the resistance gene L are outlined for the discussion.

We have found that 50 mg/I kanamycin and 0.8 Mo1/1 mannitol concentration was sufficient to kill the control callus of bean (Phaseolus vulgaris L.) and differentiate transgenic from the non-transgenic cells. The GeneBooster particle delivery system was used for the bombardment of bean callus. The kanamycin resistance gene was used as a selectable marker. The test was made by transferring the healthy white callus, subcultured for three months on selective and non-selective medium. After selection on kanamycin containing media, several kanamycin resistant calli had been obtained, survived and grew. After selection on mannitol containing media no drought resistant calli had been obtained. Resistance of the selected calli were verified by their ability to grow repeatedly on selective medium containing 150 mg/I kanamycin. Selective pressure was maintained over a period of 8 months.

The goal of plant breeders is to improve the resistance of crops against virus, bacterium and fungus pathogens was easiest to achieve by selection for phenotypes displaying the hypersensitive reaction. The resistant plant of that type keeps its health by preventing or delaying the systemization of the pathogen by destruction of cells and tissues of variable size or amputation of the contaminated organs. The faster the reaction of the host plant is the more efficient and economical is the defense, since the extent of tissue destruction decreases proportionally with the speed of reaction.

During a breeding program for resistance carried out on several plant species, mainly vegetables over thirty years, also an alternative defense reaction has been experienced, which fundamentally differs from the hypersensitive reaction. In that reaction the cells and tissues of the host plant being exposed to the pathogen do not die, on the contrary they hinder systemization of the pathogen by tissue thickening. An additional significant difference is that on the contrary to hypersensitive reaction this reaction is less host- or pathogen-specific and works excellently even at high temperature (over 40 °C).

The chemical quality of the essential oils is determined by their composition as well as by the complex aroma features. For the evaluation of odour and aroma, sensory tests are practised, especially for applications such as aromatherapy, food industry or perfumery. In the recent studies we investigated eight Mentha origins (populations of Mentha iperita, M. spicata and M. arvensis) of our genebank collection using a new and effective instrumental sensory evaluation method parallelly with the usual GC analysis.

The results show that the examined mint clones possess different essential oil accumulation levels and special flavour characteristics, too. The GC analysis of the essential oil revealed characteristic differences at both inter- and intraspecific level in the proportion of mentol, menthon, carvon, limonene, menthyl acetate and in two not identified monoterpenes.

In the sensory tests the special complex aroma enables a reliable distinction with a single exception among the populations by the help of the "electronic nose" equipment. The distinction among the samples based on the sensor signals of the instrument — evaluated by multivariate methods — shows a close relation with the detected monoterpene components of the essential oil.

Mass propagation of 5 newly introduced Hosta varieties was carried out by the method of micropropagation. Our aim was to determine exact variety specificity after the micropropagation period in the pattern of peroxidase isoenzymes by isoelectric focusing in pH 3-9 range and to determine that phenological phase of mother plant in which the isoenzyme pattern of mother plant can safely be comparable to the isoenzyme pattern of micropropagated descendants. The isoenzyme patterns of descendants were similar to the mother plants of the same hybrid lines. The older leaves seemed to be not so suitable for examination than newly developed ones despite of the higher activity of peroxidase enzymes. There were big differences in isoenzyme patterns of leaves in different phenological phases. With this quick and easy method Hosta varieties could be selected already in the very early stage of micropropagation.

The toxicity of spinosad to adult female bees tended to be least to the honey bee (Apis mellifera L.) (LD₅₀ = 0.078 pg/bee), intermediate to the alkali bee (Nomia melanderi) (0.065 pg/bee), and greatest to the alfalfa leafcutter bee (Megachile rotundata (F.)) (0.058 pg/bee), both in topical drop tests and in tests involving spinosad residues on alfalfa (Medicago sativa) foliage. For the calculated LD₅₀ pg/g, the honey bee (LD₅₀ = 0.612 pg/g) was the most susceptible followed by the alkali bee (0.773 pg/g) and the leafcutter bee (1.908 pg/g). The honey bee oral LD50 was 0.063 pg/bee and the calculated LD₅₀ 0.492 pg/g. Adding an adjuvant to spinosad sprays did not change the toxicity of spinosad to bees in residue bioassay studies. Spinosad at as high as 500 ppm in feeders containing a sucrose/honey syrup caused no significant reduction in honey bee visitation or total syrup consumed.

Rooting of in vitro 'Royal Gala' shoots was studied under different conditions of root induction and root elongation phase. The rooting capacity was affected by both rooting phases. Very high rooting percentage could be reached with both liquid and solid root induction media. Raising the temperature from 22 °C to 26 °C during root induction phase increased the rooting percentage. Presence of activated charcoal in root elongation media can affect the number of roots per rooted shoots and can increase the rooting percentage, the length of roots and the rate of survival depending also on other conditions during rooting. Presence of NAA in root elongation media reduced the number and the length of roots considerably. Favourable effect of activated charcoal on rooting was mainly due to adsorption of NAA.

Sambucus nigra is a very common elder species in Europe. Due to its excellent composition, natural dye content and healing power it can be considered as a biological active plant. In Hungary the cultivation of Sambucus nigra started in the nineties and since that time there is a growing demand for this plant. Sambucus nigra is a special fruit due to its sole.-application for processing industry. Partly fruit products are made of it, partly it is used as a natural dye. In both cases the first step is the knowledge and evaluation of the composition of the various elder varieties and candidates. For that reason composition studies of different elder types were performed in several years at the Department of the Canning Technology of the Szent Istvan University.

The most important sample was the Haschberg variety, which is the sole elder type accepted and allowed for propagation by the government. This plant is grown in the Pilot Plant of the Szent István University in Szigetcsép. Among the studied samples there were some varieties cultivated in the Fertőd Research Station. They were the following types: No. 33, 480 and 481. Besides elder collected wild in Szigetcsep and the very promising early-ripened SZ-CS 21-23 variety originated also from Szigetcsép were investigated. One year it was possible to study the Sambu variety, too. Department of the Fruit Culture of the Szent István University helped to obtain the various elder types and candidates. Along our experimental activities, the following components and parameters were studied: the content of pectin, organic acid, carbohydrate, mineral, vitamin C, total acid, aquesoluble dry material, anthocyanin and the pH.

After having obtained a juice, a concentrate from the species has been made and — after freezing — the aquesoluble dry substance and the acid content, as well as the colour parameters were monitored. Studies were performed in two years (1997-98). On the basis of these results classes were established for all compounds, from which an overall ranking was derived.

It was found that in both years the Haschberg variety proved to have the best composition. Therefore regarding to the overall series of order the experiments performed in the second year supported the results obtained in the previous year. Results have shown that Sambucus nigra has excellent composition beside its curative effect. Its mineral content has surpassed that of the other fruits and it had advantageous acid-and carbohydrate composition. The ascorbic acid content of the Haschberg variety is striking. It can be concluded from the experiments that the Haschberg type has the most advantageous composition, therefore it is suitable for making special curative and exclusive products.