Optimisation of thinning of apple fruitlets cv. 'Braeburn Mariri Red'

Apple blossom or fruitlet thinning is currently the basic care treatment in the production of apples for dessert fruit. It determines the regularity, levels and quality of yields. The fastest method of fruitlet thinning is chemical thinning performed by means of registered purpose-developed preparations. The response of apple trees to chemical thinning is largely dependent on the genetic traits and on the physiological status of the tree, and on the climatic conditions in a given season. Braeburn, and especially its coloured mutations, e.g. Braeburn Mariri Red, is a prospective cultivar for cultivation in Poland, as it stores well without loss of firmness. In addition it is characterised by more sour flesh taste compared to popular apples of cultivars ‘Golden Delicious’, ‘Gala’ or ‘Jonagold’, due to which it can be in demand in periods when apples of cv. ‘Antonówka’ are no longer available. The study analysed the effect of the Polish-registered preparations Brevis 150 SG and MaxCel on the level and quality of yield of cultivar ‘Braeburn Mariri Red’. Each of the methods of thinning caused a significant improvement of fruit size relative to the control. Only the application of MaxCel at the lower dose of 5l ha–1 proved to be completely ineffective in both seasons of the experiment due to the lack of any improvement in yield structure, in fruit weight, and also in fruit diameter and height. The application of Brevis at 1.1 kg ha–1 and of MaxCel at 7.5 l ha–1 produced similar effects on the level and structure of yield, but apples from trees treated with Brevis at 1.1 kg ha–1 were characterised by notably higher fresh firmness. The best effects of thinning were noted after the combined application of the preparations MaxCel/Brevis, as the yield was notably lower than in the control treatment, and the fruits were characterised by the highest values of the analysed quality parameters, i.e. fruit weight, diameter, height, and content of extract and dry matter.