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Traditionally grown domesticated apple varieties are known for their adaptability to different climates and a wide range of soil types, and some for resistance to the main diseases. Their evaluation and preservation are very important, not only for restoration of traditional orchards, but also as a source of genetic material for breeding new varieties. Micropropagation of the most valuable varieties could be a way to propagate plants for restoration of traditional orchards, or as a prerequisite for ex situ long-term conservation through cryopreservation. Fruit samples were taken from trees 50 or more years old, of 13 traditionally grown domesticated apple varieties in Bjelovar Bilogora County in Croatia. Morphological traits of the fruits were evaluated during 3 years, and chemical characteristics (soluble solids, reducing sugars, acids and total phenol content) were evaluated during one vegetation year. Tissue culture was established from shoot apices approximately 1 mm in size isolated from buds of 1-year-old scion woods. Axillary branching was induced from two types of explants on MS medium with the addition of 2% glucose, 1% sucrose, 0.1 g L−1 myo-inositol, 0.8% agar, 0.2 mg L−1 gibberelic acid (GA3), 0.1 mg L−1 indole-3-butyric acid (IBA) and 1.5 mg L−1 6-benzylaminopurine (BAP) in proliferation medium 1 (PM1) or 2 mg L−1 zeatin (ZEA) in proliferation medium 2 (PM2). The morphological characteristics of the traditionally grown domesticated apple varieties mentioned were not different from their standard values. Average fruit weight (AFW), average fruit height (AFH) and average fruit diameter (AFD) were less than standard values, which can be explained by the age of the fruit trees. Principal component analysis of these traditionally grown domesticated apple varieties showed that fruit traits very important in today’s breeding for new cultivars, like fruit weight, shape, skin color and flesh taste, stand out in explaining the variability. Despite the age of the fruit trees, the fruits still have surprisingly positive chemical characteristics, especially Canadian Reinette for which the highest concentration of total phenols was found. Of the five traditionally grown domesticated apple varieties used, tissue culture was successfully established for Jonathan and Canadian Reinette varieties. Higher multiplication efficiency was obtained for the Jonathan variety. Medium supplemented with 1.5 mg L−1 BAP produced a significantly higher number of shoots/explant in comparison with those supplemented with ZEA. Morphological features of shoots produced on medium supplemented with ZEA, however, were better. Both explant types, shoots placed in the medium vertically or two-nodal stem segments placed in the medium horizontally, gave similar results for axillary branching.

Pollination success and final fruit set of sweet cherry depends on self- and cross- (in)compatibility relations among cultivars in orchard. The objective of this study was to determine the compatibility relationships and to select pollenizers for the most important Croatian sweet cherry cultivars, ‘Gomilicka’ and ‘Stonska’. Phenological observations, pollen germination, pollen tube growth and fruit set were assessed following self- and cross-pollination treatments in two flowering seasons. In general, we found overlap of flowering periods of all cultivars included in the study, but low synchronization was observed for the full-bloom period among traditional cultivars, particularly ‘Stonska’ (early cultivar) and ‘Tugarka’ (late cultivar). There was a significant difference in fruit set among the type of pollinations and pollen donors. ‘Gomilicka’ and ‘Stonska’ are self-incompatible, and cross-pollination is necessary for good fruit set. According to the overlap in flowering time and fertilization level in ‘Gomilicka’, cross-pollination with ‘Garnet’, ‘Isabella’ and ‘Starking Hardy Giant’ was more effective than that of the traditionally grown cultivars ‘Stonska’ and ‘Tugarka’, and introduction of these cultivars as pollenizers is a good choice that can provide regular and abundant fruit set. Despite the different S-allele combinations of traditional cultivars, overlap in flowering time with some of the introduced cultivars, and favourable climatic conditions, we found also significant effects of pollen-pistil interactions in the style and ovary on the dynamics of pollen tube growth and final fruit set. Inter-incompatibility reactions between cultivars were not observed.

Sweet cherries express self-incompatibility, which affects the choice of parents and mating combination in a breeding program. Self-incompatibility is controlled by a multi-allelic single locus (S-locus). Here, the S-alleles were first time studied in 37 local sweet cherry genotypes native to Croatia by using polymerase chain reactions (PCR). Thirteen specific primers designed for the amplification of S1, S2, S3, S4, S5, S6, S7, S9, S10, S12, S13, S14 and S16 alleles were employed. Alleles S3 and S12 were found to have the highest frequencies (39 and 19%, respectively) while S1 and S4 were observed in the lowest frequency (3%) among the examined genotypes. The results obtained, together with information compiled from previous studies, allowed the extension of a total of 10 formerly described cross-incompatibility groups (CIG) determined among the 37 Croatian sweet cherry genotypes. S3S12 was the most frequent allelic combination (49%), which was observed in 18 Croatian sweet cherry genotypes. A combination of consensus and allelespecific PCR amplification was capable enough to identify all the S-alleles in the genotypes studied. The method also provided a rapid and efficient approach for identifying the S-genotypes of sweet cherry genotypes native to Croatia. The results are indicating possible genetic relationships between Croatian and Turkish sweet cherry cultivars as well.

The trial was conducted in a ‘Gala’/M9 orchard and the experiment was designed as a randomized block comprising four treatments (application of Prohexadione-Ca: 125 mg-l, 250 mg-l, 2 x 125 mg-l, and control - without growth regulator). Experiments have been carried out for 2 years (2003, 2004). Application of Regalis reduced trunk cross-sectional area increment, and cumulative extension shoot growth. The effect increasing with concentration, and a greater inhibition was obtained when the trees were sprayed two times. Compared to control, return bloom of Regalis-treated trees was not affected. No negative effects of treatment with Regalis on yield per tree were observed, but some reduction of average fruit weight was found.

Investigations of the effect of foliar application of some nutrients and fertigation in comparison with broadcast nitrogen fertilization on mineral fruit composition of young apple 'Golden Delicious', grafted on M9 rootstock was conducted in years 2000-2001. Two orchard experiments were established, one with 2-year and the other with 3-year old trees, grown at a spacing of 3.2 x 0.7 m and trained to super spindle. In year 2000 fruits were hand thinned on 2-year and 3-year trees to 20 and 50 fruits/tree respectively. In 2001 fruits were not thinned because of low fruit set. The results showed no significant beneficial effect of applied treatments on fruit mineral content in both experiments. Ratios of N/Ca, K/Ca and (Mg + K)/Ca in fruits indicated good storage quality as related to normal crop load. On the contrary, when treatments were applied on trees with inadequate crop load, no beneficial effect occurred and fruits showed low storage life. This result illustrates the important balance between vegetative growth and fruit load that occurs during tree establishment.

SummaryThe Croatian olive (Olea europaea L.) cultivar, ‘Lastovka’ is mainly used for oil production. While fruit yields are high and regular, the growing area is limited due to its sensitivity to low temperatures, with production concentrated on the South Dalmatian island of Korcula. Different morphological types have been observed during production. In order to determine the extent of intra-cultivar diversity, 47 individual ‘Lastovka’ trees were analysed for 11 morphological traits and assessed using AFLP markers, and compared to ten trees each of the cultivars ‘Oblica’ and ‘Drobnica’. Clear differentiation among cultivars was detected, and the results showed that both the morphological and molecular data were equally reliable for discriminating between cultivars. The existence of intra-cultivar diversity in ‘Lastovka’ was therefore confirmed at both the morphological and molecular levels, providing an opportunity for the selection of potentially superior clones.

The trial was conducted in a `Elstar'/M9 orchard (2500 trees/ha) and the experiment was designed as a split-block comprising five treatments (fertigation with 45 kg·ha-1 N, 60 kg·ha-1 N, 120 kg·ha-1 N, irrigation without fertilizers, and control—without irrigation and without fertilizers), and two timing variants (treatments during vegetation period from 1 May to 20 June—variant A, and treatments from 1 May to 1 Aug.—variant B). The treatments were imposed beginning in the second year after planting and lasted five years. Fertigation with different amounts of nitrogen had no consistent effect on tree growth, cumulative yield and yield efficiency, however, treatments had a significant influence on regularity of bearing. The index of alternate bearing varied with treatment, but in both variant was significantly higher in control and in treatment with irrigation without application of fertilizer. These results demonstrated that the natural tendency of `Elstar' to alternate bearing could be broken by the different rates of nitrogen applied by fertigation.

An investigation on the growth and cropping of sweet cherry trees, which were cultivated on heavy soil, was conducted for five years after planting (1997- 2001). The experiment included the self compatible cultivar Lapins grafted on ten rootstocks of differing vigour, including: F 12/I, Ma x Ma 14, PiKu 4.20, Gisela 4, Gisela 5, Gisela 12, Weiroot 13, Weiroot 72, Weiroot 158 and Edabriz. In our growing conditions, the cultivar Lapins did not yield as expected. On the rootstocks PiKu 4, 20 and Gisela 4 the highest yields were achieved, while trees on the rootstock F 12/1 had the lowest yield. The rootstock Edabriz was of the lowest vigour, while PiKu 4.20 was of the highest vigour. Our results supported those of others indicating that Gisela 5 is, among dwarf cherry rootstocks, the most promising for modern, intensive sweet cherry growing. In addition, the results indicated that the rootstock Gisela 4 is also promising for intensive orchards because is amongst the most dwarfing, precocious and productive rootstocks. Edabriz was too weak for commercial use.

The ability of various treatments to induce sylleptic shoot development of nursery trees of the apple `Jonagold' and `Golden Delicious' on root-stock M.9 was investigated. The leader management techniques were: removal of sub-terminal leaves, removal of sub-terminal leaves with application of 0.25% Paturyl 10 WSC (6-benzyladenine), and treatment with 0.25% Paturyl 10 WSC (two times at 24 days interval); application of 20% Promalin (GA4+7) two times in 9 days interval; and control; starting when scion length was 75 cm. Removal of sub-terminal leaves increased total branch length, but not stimulated the lateral branching. Treatments with Paturyl resulted in the lower tree height, in the higher number of branches, and in the greater branch length. Removal of sub-terminal leaves in combination with Paturyl increased the lateral shoot number even more than treatment only with Paturyl. Promalin increased branching, but had little influence on the total branch length. In addition, Promalin decreased branch crotch angles.

SummaryThe most important olive (Olea europaea L.) cultivar in Croatia is ‘Oblica’, which is cultivated in all growing regions and makes up ≤ 75% of all olive trees. A total of 36 typical ‘Oblica’ trees were sampled from five growing regions in Croatia. An analysis of 12 morphological traits revealed high variability among the samples. Geographical latitude had the greatest influence (r = 0.276) on morphological characteristics, followed by longitude (r = 0.223), and altitude (r = 0.127). The correlation between all 12 morphological characteristics and geographical coordinates was 25.7%, which indicates a strong environmental influence on morphology. Molecular identification of the 36 samples, based on AFLP markers, suggested that intra-cultivar genetic variability was limited (4.82%). These results suggest that a few closely-related clones constitute the genetic structure of ‘Oblica’, while the observed morphological diversity is due to environmental factors.