Floral biology of hazelnut (Review article)

Apricot yields are highly variable according to the season. The variation is caused mainly by the adversities during the critical processes of floral biology, i.e. blooming and fertilisation. On the basis of information concerning blooming time and mutual compatibility relations of apricot varieties a system of securing regular and adequate yields has been developed.

Winter frosts of the continental type are well tolerated by most of the apricots, however, after the end of rest period, flower buds are loosing frost tolerance, 'rapidly.

Being one of the fruit species blooming earliest during the early spring, apricot start to bloom in Hungary around the end of March or early April as a mean of many years, but it also happened, exceptionally that apricot started to bloom at February 20 (at Letenye South Hungary). The early season, exposes the floral organs to frost injuries. As a consequence, apricot orchards on the Great Plain produce low yields in 3 years, intermediate yields in other 3 years out of a ten-year-period.

Moreover, weather conditions during the blooming period are often unfavourable for pollination. Cool, windy and rainy weather prevents the flight of insects and on the other hand, warm spells shorten the blooming process, nectarines and stigmata get dry and the female gametes loose viability before effective pollination occurres.

The fertility of individual cultivars are meeting different obstacles. Apricot cultivars differ greatly in the rate of flowers bearing underdeveloped pistils, which may attain even 60% (e.g. Orangered). New commercial cultivars are often self-incompatible. Local varieties of that type in Hungary are the „óriás" varieties (e.g. Ceglédi óriás, Szegedi mammut), and the new hybrid Ceglédi Piroska. Many of the cultivars are variable in their self-fertility (partially self-fertile): Budapest, Harmat, Korai piros, Mandulakajszi.

Inter-incompatibility is also known in apricots. The „óriás " varieties do not fertilise each other. During the growth of fruits, cool spells (2-4 ^°C) caused severe fruit shed in Ceglédi óriás.

Apricot flowers produce pollen and nectar at average rates related to other fruit species, thus bees are attracted sufficiently. Bee visits are very variable according to growing site and season. Most of the bees are pollen gatherers but sometimes nectar suckers are in majority. Bee pollination is necessary not only for the self-incompatible varieties but also to enhance the yield of self-fertile varieties.

Taking the blooming and fertility relations of the cultivars into account, plantations should not exceed two rows to a particular self-incompatible varieties, and possibly two different polliniser varieties are suggested to be planted as flanking the block in question.

In commercial plantations 2 to 4 bee colonies per hectare are proposed to move for the whole blooming period.

In the Carpathian Basin Kövidinka and White Riesling are promising wine grape varieties. As in the region continental climate dominates and dry years are not uncommon it was natural to study the water requirement and consumption of the two varieties. Morphological characters affecting transpiration were observed including leaf area, hairiness, number and type of stomata. The amount of water transpired per unit leaf area and time and rate of water consumption were measured in a model trial in cuttings with known water supply.

The water consumption of vine cuttings depends on varieties and is determined by the genotype but it is also affected by environment. Kövidinka requires little water and uses it to its advantage White Riesling requires more water and uses it rather lavishly. The results of our model trial could be introduced directly into viticulture practice.

In our country the maindenhair tree (Ginkgo biloba L.) is raised mainly from seeds, so the aim of our experiments was to determine the most useful generative propagation method. However, some experiments have been conducted earlier connected to the germination of the species, but the comparative control of physical seed treatment was done first time by the authors.

After the statistical evaluation of the results it can be stated that the percentage of germination has significantly increased if the seeds received physical treatment (scalding, mechanical scouring). Hereby the pericarp is getting soft or growing thinner, so the germination of the seed is easier. These treatments are extraordinarily simple, easy to carry out and their effect is very favourable, that is why their use is strongly advised.

Comparing the seeds collected at different times was found that the ability of germination is decreasing proportionally with the time spent in the open field. On the basis of our experiments and of earlier practice in Hungarian tree nurseries, our opinion is that the stratification of seeds is not necessary.

Pot experiments were conducted in order to investigate the effects of the controlled-release characteristic, nitrogen form and application method of polyolefin-coated fertilizers on the nitrate content and yield of lettuce (Lactuca sativa L.). Comparing broadcast application of polyolefin-coated urea (POCU) and urea at four fertilization levels, it was found that application of POCU decreased the nitrate content and increased the yield, due solely to its controlled-release characteristic. Comparing band applications of POCU or polyolefin-coated diammonium-phosphate (POC-DAP) to broadcast application of ammonium nitrate, it was found that a band application of both urea and ammonium containing polyolefin-coated fertilizers can decrease nitrate content in lettuce, without causing any significant yield decrease. This was a combined effect of the controlled-release characteristic and realized ammonium nutrition. Comparing effects of broadcast, band and spot applications of POC-DAP, it was found that nitrate content, was the lowest in the spot application treatment. However, considering both nitrate content and yield, band application was found to be the most effective application method.

Dietary intake of large amounts of nitrates and oxalates presents a health hazard. In this study experiments were conducted with two oxalate accumulating vegetables rhubarb (Rheum rhabarbarum L.) and Swiss chard (Beta vulgaris L. var. cicla L.)) using POC-DAP in order to improve their nutritional quality. In the rhubarb experiment oxalate content was significantly reduced by band application of POC-DAP, while effects on ascorbate and nitrate contents were ambiguous. The improved nutritional quality in the POC-DAP treatment was rather a cause of ammonium nutrition than a cause of less amount of released fertilizer nitrogen. In the Swiss chard experiment oxalate and nitrate contents were reduced, while ascorbate content was increased by a band application of POC-DAP. The improved nutritional quality in the POC-DAP treatment was the cause of both the less amount of released nitrogen and the realised ammonium nutrition. It was also found that by using POC-DAP for Swiss chard cultivation, labour and energy costs of top-dressings could be eliminated without yield decrease. It was concluded that the nutritional quality of rhubarb and Swiss chard could be improved by using a band application of POC­DAP.

The influence of nitrogen-fertilizer applied in 0, 50, 100 and 150 kg/ha dosages, as well as the time of the harvest carried out in full flowering and early fruit set stages were studied on the herb and essential oil production of garden thyme (Thymus vulgaris L.). The small plot experiment was installed in the Experimental Field of Tarbiat Modarres University near Teheran, under sandy loam soil conditions. On the basis of the results the nitrogen-fertilizer had a significant effect on the dry-matter production of the species: the herb yield, calculated on one hectare, increased from 671.88 kg up to 1021.00 kg value as a result of 150 kg nitrogen dosage. The essential oil yield proved to have a similar tendency because neither the accumulation level of essential oil, nor the ratio of thymol were effected by the nutrient supply. Analyzing the effect of harvest time changes in both dry-mass production and essential oil accumulation were observed. The highest herb yield (1238.20 kg/hectare) was obtained in early fruit set, when about.50 per cent of fruits reached their full size in the inflorescence. The accumulation level of essential oil also reached its maximum at the sane development stage, showing 0.75 per cent value, which is about two fold higher comparing to the accumulation level was measured at the time of full flowering (0.41 %).

Over 10 years of field trials show reductions of most of the pests in Brassicas undersown by clover. The pest-reducing effects are due to the 'appropriate / inappropriate landings' hypothesis (Finch, 1996), and the 'host plant quality' hypothesis (Theunissen, 1994). To find out the mechanisms within the 'host plant quality' hypothesis in the most promising intercropping (collards undersown by clover) glasshouse experiments were conducted to see whether intercropping influences the mean relative growth rate, fecundity and time of maturity of Myzus persicae (Sulzer) (Homoptera: Aphididae) a common pest of Brassicas.

The treatment modelling intercropping showed the smallest mean relative growth rate, delayed the maturity and slowed down the growth of cabbages. The treatment modelling monocropping showed the highest mean relative growth rate and the maturity was reached earlier. These results may indicate that intercropping delays the growth of settled aphid populations, giving another proof that in the case of clover undersown cabbages the 'host plant quality' hypothesis is likely to be acting. The differences between treatments where the roots of clover and cabbages were separated and allowed to grow together suggest that the effect is via the roots by competition.

A useful method was improved to test and to evaluate the susceptibility of plants to fire blight and the virulence of E. amylovora strains. Six Hungarian strains from different host plants were tested on in vitro cultured apple rootstocks. Disease rating was used for the characterization of the process of disease development. The different strains had different capacity to cause disease, mainly in the first period of incubation. There were significant differences between the virulence of the strains.

Progression of apple scab epidemic in six apple cultivars, including two current and susceptible (Gala Must, Elstar), two old (Egri Piros, Darusóvári), and two resistant cultivars (Relinda, Releika), were described and analysed in a two-year-study, in two environmental-friendly growing systems (organic and integrated). Curves of disease progress, linear regression analysis of transformed disease incidence data and Area Under Disease Progress Curves (AUDPC) were used to characterise the epidemic processes of the selected cultivars. Cumulative disease progress curves showed continuous but asymmetrical scab development on the moderate or highly susceptible cultivars Gala Must, Elstar and Egri Piros, and on the tolerant or resistant cultivar Darusóvári and Relinda, in both systems. The cultivar Releika showed no symptoms either on fruit or leaf. In linear regression analysis, the best linearisation was given by logistic transformation. Adequate parameters leaf disease incidence rate, of obtained from a regression equation, were higher in the organic system than in the integrated system. Values of AUDPC showed great differences in leaf disease incidences among cultivars and between growing systems. AUDPC gave more differences for comparison of progresses of disease epidemic than growth rate of disease in different systems of disease control. Moreover, the obtained results were compared with similar studies on different pathosystems, and biological interpretations of the analyses are discussed below.

In this study, the rate of scab infection and quality parameters (content of vitamin-C, dry matter, sugar, total acids, specific weight, quality index and flesh firmness) of some apple cultivars are given, moreover, the relation between those characters was examined in two environmental systems (organic and integrated) in a rainy season. In the organic fruit production, scab infection of leaves was significantly higher than in the integrated system, in case of the same cultivars, which means that the rate of decrease in leaf area was heavier in the organic production. Cultivars did not differ statistically in parameters of inner content when the integrated system was compared to the organic one. Results did not show statistical difference between loss of leaf area caused by apple scab and the parameters of inner content, which is attributed to the regeneration of leaf area due to favourable weather conditions. Data on apple scab and inner content of the fruit justify essentially the environmental systems of apple production.

The aim of our study was to examine susceptibility or resistance of 18 pepper varieties to four viruses [tobacco mosaic

tobamovirus (TMV), sowbane mosaic sobemovirus (SoMV), NTN strain of potato Y potyvirus  (PVYNTN) and cucumber mosaic cucumovirus (CMV). Out of the 18 varieties, 13 were resistant to CMV infection. Thirteen varieties were susceptible to TMV, while five ones (Dabora Fl, Brill Fl, Feherozon Synthetic, Ciklon Fl, Cecil Fl) showed only local hypersensitive reaction. All of the tested pepper varieties showed resistance to SoMV. Eight varieties (Tuba, Fehérözön Synthetic, Boni, Alba Regia, Korona, Édesalma, Cecil Fl, Star) were found to be resistant to PVY^NTN. Out of the examined varieties five (Boni, Alba Regia, Korona, Édesalma, Star) were resistant to three viruses (SoMV, CMV and PVYNTN). Only one (Cecil F1) displayed complex, extreme resistance to SoMV, PVYNTN, CMV and hypersensitive reaction to TMV, therefore this hybrid is very important in pepper breeding and growing for virus resistance.

The ashy stern blight of pepper (Capsicum annuum) is often caused by Macrophomina phaseolina. Serious wilt disease occurred between 1994 and 1996 of pepper plants in Hungary. In 1996-98 screening experiments were made on many pepper cultivars. Culture (Knopp) solution experiments, pot experiments, greenhouse and field trials were carried out. We determined the incidence of disease by visual examinations, testing on PDA culture, and light microscope. There were significant differences in susceptibility of cultivars and breeding materials.

Shoot multiplication responses of three apple scions to different concentrations of BA and BAR as single source of cytokinins and in combination with two concentrations of KIN were studied. The effects of hormones depended on genotype, type and interactions of different cytokinins. Use of BAR significantly enhanced the shoot multiplication of cv. Jonagold (6.5 shoots per explant). The multiplication rate of cv. Jonagold could not be improved by using the combination of BAR and KIN. The best proliferation was achieved by 1.0 mg 1^-1 BA combined with 1.0 mg 1^-1 KIN of cv. Prima..(8.1) and of cv. Galaxy (10.4).The effect of 0.5 mg 1^-1 BA along with 1.5 mg 1^-1 KIN was similar on multiplication rate (10.9) of cv. Galaxy.

The requirements for in vitro micrografting in apple are described. In vitro multiplicated shoots of cv. Royal Gala were the sources of rootstocks and scions after different pre-treatment, respectively. Oxidative browning of cut surfaces could be inhibited by the use of antioxidant mixture during grafting process. Scion base cut in v-shape was stuck by 1% agar-agar solution into the vertical slit of rootstock. There was no any displacement and the rate of fused and further developed grafts was 95 percent. Agar-agar between the rootstock and scion made the transport of different materials possible and hold the graft units together until the fusion took place. Fusion was proved also by histological studies. Some of in vitro micrografts were planted and acclimatisated and the survival was 100 percent.

Different aromatic cytokinins (BA, BAR, TOP and KIN) were tested alone or in combination for the shoot proliferation response of ‘Húsvéti rozmaring' apple scion. The best multiplication rate was achieved by dual cytokinin application (1 mg 1-¹ BA + 1.5 mg 1^-1 KIN). The rooting capacity was affected considerably by the position of shoots: transfer of the three-week-old shoots to the same or other proliferation medium in vertical position inhibited the following rooting totally. Post-effects of different cytokinins (BA and TOP) on subsequent rooting could be detected: BA increased the number of roots markedly, while TOP resulted in significantly longer roots.

The influence of increasing concentrations of naphthaleneacetic acid and the antibiotics cefotaxime, timentin, kanamycin, and hygromycin on eggplant (Solantun melongena L. cv. Embil) somatic embryogenesis was investigated. Cotyledon explants were excised from 16 to 20 days old in vitro grown seedlings. NAA promoted somatic embryogenesis, although its concentrations had no influence on the mean number of embryos. Callusing decreaSed significantly with increasing NAA concentrations. Morphogenesis was stopped with 50 to 100 mg L^-1 kanamycin and 7.5 to 15 mg L^-1 hygromycin. Although early globular embryos were observed up to 15 mg L^-1, further embryo development was inhibited at 10 mg L^-1. Interestingly, cefotaxime (250 and 500 mg L^-1) promoted a marked effect on enhancing fresh weight of calli, accompanied by decrease in embryo regeneration, whereas timentin concentrations (150 and 300 mg L^-1) did not affect embryo differentiation as compared to the control treatment.

Cotyledonary segments of five different genotypes of watermelon were used to induce organogenesis. Five different hormone combinations were applied to enhance the induction of shoot formation on the surface of the segments. The phases of organogenesis were followed with light and scanning electron microscope. Shoots were obtained after four weeks, then the shoots were transferred to hormone free medium for root induction.

This method of regeneration can be applied in transformation experiments. GUS histochemical assay was made to check the expected success of using Agrobacterium for the transformation.

We report the method for the establishment of rapidly growing callus cultures of Phaseolus vulgaris and the conditions required for efficient transformation using high velocity microprojectiles and high level of transient gene expression. Using hypocotyl explant and vertical culture on B5 medium with lmg/1 kinetin and 2 mg/1 2,4-D, we can recommend to get a rapidly growing callus from bean which is a good starting material to introduce foreign DNA into bean cells. The GeneBooster particle delivery system was used for the bombardment of bean callus and the Hgm resistance gene (Hgmr) was used as a selectable marker gene. 25mg/I hygromycin (Hgm) concentration was sufficient to kill the control callus. We used the standard physical factors, the appropriate pressure of N2 gas for the bombardment of the callus tissue, the shooting distance and the size of tungsten particles used as microprojectiles. Selective and nonselective tests were made by transferring the healthy green and white calluses, subcultured for 4 months on selective and nonselective medium. Several Hgm resistant calli had been obtained. Selective pressure was maintained over a period of 10 months.

Dianthus chinensis and Dianthus caryophyllus varieties were tested for shoot regeneration from leaf and petal explants and transformed with Agrobacterium tuniefaciens strains (EHA 105 and LBA 4404) harbouring an apple derived ACS cDNA in antisense orientation in order to reduce ethylene production and influence the ethylene dependant traits in carnation. After transformation regenerating shoots were selected on MS medium containing 50-75-100-125-150 mg/1 kanamycin and supplemented with 1 mg/1 BA, 0.2 mg/1 NAA. Transgene integration was proved by PCR analysis with npt II spcific primers followed by Southern hybridisation of DNA isolated from green shoots on medium containing 150 mg/1 kanamycin. Several putative transformants were subjected to RT-PCR in order to examine the npt 11 expression at mRNA level. Both the transformant and the non-transformant plants were potted into glasshouse to observe the effect of changed ethylene production on flowering time, petal senescence and vase life.

Tissue cultured Cymbidium PLBs (protocormlike body) were used as starting material to induce embryogenic callus which could serve as objects of genetic transformation. We obtained callus using two methods. The first method was culturing the PLB segments for one month in liquid MS medium in the presence of 0.5 mg/1 benzyladenine and 0.05 mg/1 naphtylacetic acid followed by cultivation on the same composition solid medium with 0.5 g/l activated charcoal for an additional month. Callus formation was observed on 30% of the explants. The second way was to propagate the PLB segments on solid MS medium supplemented with 1 mg/1 thidiazuron. In these cultures we also observed callus formation on 20% of the explants.

Callus cultures derived from young stems of two varieties of Taxus baccata cv. aureovariegata (genotype I) and Taxus baccata L. (genotype II, III) were induced. Gamborg's B5 medium was supplemented with different concentrations of auxin (2,4-D) in combination with cytokinins (kinetin or topolin) and with a phenolic-binding compound (PVP) to prevent callus darkening and growth inhibition. Stem explants displayed different responses to in vitro culture depending on plant genotype and on the season. Genetic variability was observed in the growth rate of calli initiated from all three genotypes of the same Taxus species. We found the best growth of callus cultures originated from the genotype ill in defined media. After the first subculture the majority of the cream-coloured primary callus turned brown and ceased its growth. However, the long-term culture was initiated.

In the semi-arid tropics viticulture was successful according to technologies developed by Hungarian expertise