Dragan Milatović

Multivariate analysis of vineyard peach [Prunus persica (L.) Batsch.] germplasm collection

Thirty vineyard peach [Prunus persica (L.) Batsch.] genotypes were studied to determine the overall degree of polymorphism and to detect similarities among genotypes. The variation was observed for traits related to phenology, morphology, yield and fruit quality. Many fruit characteristics that are important to breeders are present in this collection. The majority of important correlations were determined between the characteristics representing fruit size (fruit width, fruit height, fruit weight and stone weight) and between those ones representing fruit quality (fruit attractiveness, taste, flavour and soluble solids content). Cluster and principal component analysis showed a considerable phenotypical diversity in the vineyard peach germplasm. Clustering of genotypes was in accordance with its purpose (fresh consumption or rootstocks production). Parameters with high discriminating values were those related to fruit size and fruit quality.

Evaluation of different methods for determining growing degree-day thresholds in apricot cultivars

The aim of this study was to examine different methods for determining growing degree-day (GDD) threshold temperatures for two phenological stages (full bloom and harvest) and select the optimal thresholds for a greater number of apricot (Prunus armeniaca L.) cultivars grown in the Belgrade region. A 10-year data series were used to conduct the study. Several commonly used methods to determine the threshold temperatures from field observation were evaluated: (1) the least standard deviation in GDD; (2) the least standard deviation in days; (3) the least coefficient of variation in GDD; (4) regression coefficient; (5) the least standard deviation in days with a mean temperature above the threshold; (6) the least coefficient of variation in days with a mean temperature above the threshold; and (7) the smallest root mean square error between the observed and predicted number of days. In addition, two methods for calculating daily GDD, and two methods for calculating daily mean air temperatures were tested to emphasize the differences that can arise by different interpretations of basic GDD equation. The best agreement with observations was attained by method (7). The lower threshold temperature obtained by this method differed among cultivars from −5.6 to −1.7°C for full bloom, and from −0.5 to 6.6°C for harvest. However, the “Null” method (lower threshold set to 0°C) and “Fixed Value” method (lower threshold set to −2°C for full bloom and to 3°C for harvest) gave very good results. The limitations of the widely used method (1) and methods (5) and (6), which generally performed worst, are discussed in the paper.

Cross-(in)compatibility in apricot (Prunus armeniaca L.).

Summary Eight apricot (Prunus armeniaca L.) cultivars and selections were self- and cross-pollinated in order to determine their pollen and stylar compatibility. Overall, 40 pollination combinations were examined. Pollen-tube growth in pistils pollinated in the laboratory was analysed using fluorescence microscopy. Three inter-incompatiblity groups of cultivars were found, of which two had not been described previously, while an existing group was expanded with one additional cultivar. The first group consisted of three Hungarian cultivars (‘Ligeti Orias’, ‘Cegledi Orias’, and ‘Szegedi Mammut’) and a Moldavian cultivar (‘Kostjuzhenskyi’). The second group consisted of two American cultivars (‘Stark Early Orange’ and ‘Nugget’). The third group consisted of two Serbian selections (‘Novi Sad Early’ and ‘Frushka Gora Early’). In the incompatible cultivar combinations, pollen-tube growth stopped in the style with the formation of the characteristic swelling. In the compatible combinations, the pollen tubes reached the ovary in the majority of the pistils examined.

Susceptibility of Sweet Cherry Cultivars to Rain Induced Fruit Cracking in the Region of Sarajevo

Susceptibility of 5 sweet cherry cultivars, grafted on Gisela 5, to rain induced fruit cracking was studied in the region of Sarajevo, during a two – year period (2010 – 2011). Testing of fruit cracking was done using index by Christensen. During the testing period, significant differences in susceptibility to fruit cracking among both the cultivars and the years of testing were found. All the cultivars had the highest fruit cracking index in 2010 year. The highest susceptibility to rain induced fruit cracking was evidenced in cultivar ‘Burlat’ during both years. Cultivars ‘Kordia’, ‘Regina’, ‘Karina’ and ‘Schneiders Spӓte Knorpelkirsche’ were moderately susceptible to fruit cracking.

Relationship between ripening time and sugar content of apricot (Prunus armeniaca L.) kernels

Apricot seeds could be obtained as a byproduct in different juice or conserve producing industries. Disposal of large amount of apricot seeds is wasting of potentially precious sources of phytochemicals. This study encompassed apricot cultivars that have different origin and flowering time with the aim of providing valuable information about the sugar content in its kernels. High-performance anion-exchange chromatography with pulsed amperometric detection was used for the determination of 22 sugars in the kernels of 70 apricot cultivars. The most common sugars in the apricot kernels are sucrose, fructose, and glucose whose ratio proved to be ripening time dependent (1:1:1 in the early, 1:2:3 in medium and 1:3:3 in the late cultivars). The kernels of the apricot with shorter vegetation period had the highest sum of glucose and fructose compared to other groups. Other sugar components were present in different levels as minor constituents depending on the ripening time. Also, most common sugars and some low-level sugars were strongly correlated to each other, indicating the normal metabolic carbohydrate pathway. To understand the distribution modes of sugars, a principal component analysis was performed.

Investigation of pollen morphological characteristics in some quince (Cydonia oblonga Mill.) cultivars

Morphological characterization of pollen grains is very important in the identification of individual species and cultivars of fruit trees, including quince. As material for these studies, the pollen of eight quince cultivars, Leskovacka, Vranjska, Morava, Pazardzijska, Hemus, Asenica, Portugal, and Triumph was used. During the 3-year study period (2010-2012), using scanning electron microscopy (SEM), the following characteristics were investigated: the size and shape of pollen grains (length, width, and length-to-width ratio), colpus length, colpus width, mesocolpium width, and characteristics of exine pattern [number of ridges per area (100 μm2) at the equatorial region of exine, ridge width, and furrow width]. The tested quince cultivars differed significantly in terms of morphological characteristics of pollen. The exceptions were colpus and mesocolpium width, as well as the ridge and furrow width on the exine, which showed no statistically significant difference. Pollen grains of quince are characterized by great length (over 53 μm). The shape of pollen grains varied from prolate (Leskovacka, Vranjska, Morava, Hemus, Asenica, and Triumph) to perprolate (Pazardzijska and Portugal). The exine pattern of all cultivars was striate with longitudinal ridges, which were more parallel in cultivars Vranjska, Hemus, Portugal, and Triumph and less parallel in cultivars Leskovacka, Morava, Pazardzijska, and Asenica. Three groups of similar cultivars are separated on the basis of hierarchical cluster analysis results. Some pollen morphological characteristics, such as the size and shape of pollen grains and colpus length, can be used in the identification of quince cultivars.