Fruit Set of Several Sour Cherry Cultivars in Latvia Influenced by Weather Conditions Before and During Flowering

Fruit set is a crucial stage in the process of yield formation, which is influenced by environmental factors, growing technologies and peculiarities of genotype. The aim of the study was to evaluate the quality of pollen (viability and germination capacity) and the effect of weather before and during flowering on fruit set in sour cherry cultivars ‘Latvijas Zemais’, ‘Zentenes’, ‘Bulatnikovskaya’, and ‘Orlica’. The research was carried out in Institute of Horticulture (Latvia University of Agriculture) in 2009-2016. Good pollen viability and germination was found for cultivars ‘Latvijas Zemais’ and ‘Bulatnikovskaya’. Negative effects of increasing air temperature (in the range of 7.7 to 17.5 °C) and relative humidity (in the range of 51.4 to 88.5%) was observed for all cultivars during flowering. The effects of diurnal temperature fluctuations, wind and the amount of days with precipitation differed depending on sour cherry cultivar.