Microdroplet Application of GA4+7 + BA: Sites of Absorption and Effect on Fruit Set, Size, and Shape of ‘Delicious’ Apples

Abstract

The greatest increase in length to diameter (L/D) ratio of apple (Malus domestica Borkh.) following microdroplet application of gibberellins A4+7 plus 6-benzylamino purine (GA4+7 + BA) occurred when this mixture was applied in the calyx or on the receptacle surface. Movement of GA4+7 + BA to the receptacle from surrounding flower parts or spur leaves was limited. No GA4+7 + BA treatment of 25-600 ppm (0.625-15 μg GA4+7 + BA/flower) influenced fruit set or increased fruit weight. Increased L/D ratio was due to a combination of increased fruit length and decreased fruit diameter. Reduced fruit diameter and weight were attributed to a lower seed number.

Commercial-Scale Use and Influence of 1-aminocyclopropane-1-Carboxylic Acid as a Rescue Thinner on Fruit Set and Early Fruit Growth in Apples

“…Although some of these bloom thinners effectively reduce fruit sets in certain apple cultivars, other apple cultivars have shown ineffective thinning results [3,4]. Post bloom thinners such as naphthalene acetic acid (NAA), gibberelin (GA4+7), 6-benzylamino purine and 1-naphthyl-N-methylcarbamate (carbaryl) have been used for reducing fruit set in apples [5][6][7][8]. Carbaryl showed synergistic effect when used in conjunction with a commercial 6-BA formulation (MaxCel, Valent BioSciences LLC) [5,6].…”

“…Post bloom thinners such as naphthalene acetic acid (NAA), gibberelin (GA4+7), 6-benzylamino purine and 1-naphthyl-N-methylcarbamate (carbaryl) have been used for reducing fruit set in apples [5][6][7][8]. Carbaryl showed synergistic effect when used in conjunction with a commercial 6-BA formulation (MaxCel, Valent BioSciences LLC) [5,6]. However, the use of carbaryl faces regulatory concerns in the USA and is banned in certain areas in Europe.…”

Effects of GA4+7+BA and CPPU on russeting and fruit quality in apple (Malus × domestica)

“…Plant growth regulators have become the major contributors in the improvement of apple production owing to their desirable effects on shape and quality of fruit. many commercial formulations of gibberellins and cytokinin such as GA 4+7 and BA have been reported in developed countries to increase the size and improve shape of apple fruit through elongation and development of more prominent calyx lobes (Greene 1984). A synthetic cytokinin, CPPu (n-(2 chloro-4-pyridyl)-n phenylurea) has been found effective in stimulating fruit growth in apples, grapes and cranberry (Devlin and Kiszanski 1988).…”