The influence of polleniser on biological properties and quality of apple (Malus domestica Borkh.) fruits

Abstract

The influence of pollenisers on biological properties of the newly introduced apple cultivars ‘Gala Must’, ‘Red Elstar’, ‘Rajka’ and ‘Topaz’ grown in the region of Cacak were investigated within the scope of this doctoral dissertation. Among the crosspollination, as well as in an open pollination variants within the cultivars abovementioned, the following parameters were studied: physiological properties (flowering phenophase, pollination and fertilisation phenophase, and fruit ripening phenophase), pomological properties (morphometric, chemical and organoleptic) and production properties (yield per tree and yield per unit land area). Flowering and fruit ripening phenophases were determined by using standard method. In vitro pollen germination rate of the studied apple cultivars, as well as quantitative efficacy of pollen tubes growth (number of pollen tubes and characteristics of their growth in particular regions of the style) monitored by fluorescent microscopy and the initial and final fruit set depending on polleniser, were analysed. Morphometric parameters of the fruit (weight, length, width, shape index, stalk length and seed number) along with chemical properties of the fruit (total and soluble solids content, total, inverted sugars and sucrose content, total acids, fruit juice pH value and total minerals content) were determined by standard methods. Organoleptic assessment of the fruit (over colour intensity, attractiveness, flavour, aroma and fruit consistency) involved grading based on UPOV instructions stated in cultivar release and apple cultivars protection procedures. Yield of the studied apple cultivars as influenced by polleniser was calculated manually. ‘Rajka’ belongs to the group of mid-early flowering cultivars, whereas the other assessed cultivars are classified as mid-late flowering. As regards harvest maturity, ‘Gala Must’ and ‘Red Elstar’ belong to the group of autumn cultivars, while ‘Rajka’ and ‘Topaz’ are winter cultivars. Quantitative parameters of pollen tubes growth in the style suggest not only the influence of polleniser genotype, but also point to temperature dependence of this influence. Six days after pollination pollen tubes were observed to penetrate the style base in all compatible pollination variants, except the cross ‘Rajka’ ‘Gala Must’ and open pollinated ‘Gala Must’ in the second year of the study. High initial and final fruit set were recorded in all pollination variants, and depended on polleniser and year of study. The influence of polleniser was observed almost in all morphometric, chemical and organoleptic properties of the studied apple cultivars (Metaxenia effect). The lowest fruit weight and size among the assessed cultivars was induced by ‘Red Elstar’ as polleniser; obtained fruits were flattened in shape and the number of seeds in the fruit was lowest. As regards chemical properties of fruits, polleniser had a significant effect on total and soluble solids contents in ‘Rajka’ and ‘Topaz’, and total dry matter content in ‘Gala Must’. As for sugars, acids and total…