Apple Fruit Growth and Quality Depend on the Position in Tree Canopy.

Darius Kviklys,Mindaugas Liaudanskas,Valdimaras Janulis,Juozas Lanauskas,Kristina Laužikė,Nobertas Uselis,Jonas Viškelis,Giedrė Samuolienė

doi:10.3390/plants11020196

Abstract

Modern apple orchard systems should guarantee homogeneity of fruit internal and external qualities and fruit maturity parameters. However, when orchards reach productive age, a variation of these parameters takes place and mostly it is related to uneven light distribution within the tree canopy. The aim of the study was to evaluate the canopy position’s effect on fruit internal and external quality parameters. This is the first study where all the main fruit quality and maturation parameters were evaluated on the same trees and were related to the light conditions and photosynthetic parameters. Four fruit positions were tested: top of the apple tree, lower inside part of the canopy, and east and west sides of the apple tree. Fruit quality variability was significant for fruit size, blush, colour indices, total sugar content, dry matter concentration, accumulation of secondary metabolites and radical scavenging activity. Fruit position in the canopy did not affect flesh firmness and fruit maturity parameters such as the starch index, Streif index and respiration rate. At the Lithuanian geographical location (55°60′ N), significantly, the highest fruit quality was achieved at the top of the apple tree. The tendency was established that apple fruits from the west side of the canopy have better fruit quality than from the east side and it could be related to better light conditions at the west side of the tree. Inside the canopy, fruits were distinguished only by the higher accumulation of triterpenic compounds and higher content of malic acid. Light is a main factor of fruit quality variation, thus all orchard management practices, including narrow two-dimensional tree canopies and reflecting ground covers which improve light penetration through the tree canopy, should be applied.

Highlights

Facing overproduction of apples in world markets, fruit quality is becoming a main issue to enlarge the consumption of apples and increase benefits to growers
Absolute photosynthetically active radiation (PAR) values varied between 700 and up to 2200 μmol m−2 s−1 depending on the time of the year and on the time of the day when the light records were taken
During all the measurement dates the highest percentage, significantly, of photosynthetically active radiation (PAR) was recorded at the top of the canopy where it varied from 53% in July to 34% in October (Figure 1)

Summary

Introduction

Facing overproduction of apples in world markets, fruit quality is becoming a main issue to enlarge the consumption of apples and increase benefits to growers. Our previous studies demonstrated the significant impact of rootstock [1], planting distances [2], tree crown management and tree growth control [3,4], fertilization [5], crop load management [6], orchard location [7], etc., on external and internal fruit quality parameters. Most of these practices could be attributed to the improvement of light conditions and to the increase of light interception in modern orchards. Higher light interception could be achieved by high density planting systems [11]

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Results