EFFECTS OF DIFFERENT FRUIT THINNERS ON YIELD AND FRUIT QUALITY OF 'ROCHA' PEAR (PYRUS COMMUNIS L.)

Abstract

‘Rocha’ pear is a cultivar grown in Portugal, with high fruit quality and production when properly managed. Few products are available in Portugal for chemical thinning of ‘Rocha’ pear, and most of them show low efficacy. From 2011 to 2013, a trial was carried out to determine the right active ingredient, its concentration and application date in order to achieve the best yield and fruit quality results of chemical thinning in ‘Rocha’ pear. The trial was carried out in a commercial orchard in Bombarral, Portugal in the heart of ‘Rocha’ pear production. Trees were sprayed with benzyladenine (6-BA), naphtylacetic acid (NAA), prohexadione-calcium (ProCa), gibberellins (GA4+7) and forclorfenuron (CPPU). Two different thinning moments were established: chemical thinning when fruitlets’ diameter was between 11 and 13 mm; 24 mm for hand thinning. Unthinned control trees were used to compare the results obtained. Along the season fruit diameter was measured, and at harvest, fruit number and weight were evaluated, as well as fruit diameter, flesh firmness, total soluble solids (TSS), starch, and titratable acidity. Yield, fruit weight and fruit size were higher for the 6-BA 100 ppm + NAA 10 ppm combination. This mix proved to be effective in the decrease of fruit number during the three years’ trials (data not show). There was a slightly negative correlation between fruit weight and flesh firmness in treatments with NAA+6-BA but a positive correlation between fruit weight, TSS content, starch and acidity. In this trial no clear relationship was observed between the increase in the amount of the active ingredient and yield.