Relation Between Apple-Tree Yield Self-Regulation and Meteorological Conditions During Fruit Set

Abstract

Apple has a tendency to bear huge amount of flowers or inflorescences. Plants have ability to eliminate excess number of fruitlets. Frequently fruit trees eliminate insufficient number of fruitlets to grow good quality fruits. Most processes related to yield self-regulation varies significantly between different apples varieties. Also meteorological conditions influenced flower buds differentiation and fruit growth during blooming and other development stages. The investigations were carried out in 2015 – 2016 at the Institute of Horticulture. The main aim was to evaluate yield self-regulation peculiarity in various apple varieties in different meteorological conditions. In our experiment we made fruit self – thinning evaluation of 15 different varieties. Meteorological conditions were varying. In 2015 there was lack of rainfall, while 2016 year was rainy. After each fruit-drop period the number of developed and undeveloped seeds were counted of self-sheded and normally growing fruits. Amount of developed seeds as auxins source is one of the most important factor for yield self-regulation. Varieties of apple which are blooming abundantly and eliminate high amount of fruitlets, grows fruits until maturity with stabile amount of developed seeds and produces permanent harvest annually, independently from meteorological conditions during vegetation. Such apple varieties need higher amount of developed seeds to inhibit abscission. Apple varieties tended to bloom abundantly and eliminate small amount of fruitlets depending on meteorological conditions. Demand of auxins to carry fruits depends on meteorological conditions therefore these apple-trees develop different amount of seeds, when weather conditions changes. We may presume, that different apple varieties need different amount of phytohormones or their ratio to hold fruitlets on the apple. Therefore apple trees with smaller amount of seeds in fruits grow more fruits to its normal size.