INFLUENCE OF HAND THINNING OF FLOWERS AND FRUITS ON YIELDING AND FRUIT QUALITY OF APPLES CULTIVAR SZAMPION Stanis ł

The thinning of fl owers and fruit sets did not change the strength of tree growth in a signifi cant way. Szampion cv. trees on rootstock A 2 grew better than on M.7. The trees of Szampion RENO cv. grew signifi cantly worst. The thinning of fl owers and fruit sets decreased the yield from a tree and the total yield from 1 ha of the studied biological material. Flower thinning slightly increased the mean commercial yield as compared to the control trees. Thinning of 50% of fl owers at the stage of the pink bud and sets after the June fall decreased the number of fruits on the trees of Szampion cv. grafted on M.7. It was only in 2004 that the fl ower thinning treatment signifi cantly increased the fruit weight. Flower thinning increased the percentage of fruits with a diameter of over 7 cm in the case of Szampion cv. trees grafted on M.7. This treatment considerably (in 2006 signifi cantly) improved fruit colouring. A positive reaction to fl ower thinning was also observed in Szampion RENO trees. In the case of Szampion cv., which shows a tendency to excessive fruit setting and small fruits, it is better to apply fl ower thinning eliminating the excess of sets in the period of cell division in growing fruits than do it later, after the June fall. The infl orescence removal treatment requires much more time than thinning of fruit sets.


INTRODUCTION
In the conditions when the European Union market is saturated with apple fruits, the quality of apples offered becomes a very important issue (M a k o s z , 2007).The most commonly applied methods of improving the quality of fruit is to use manual or chemical thinning of fl owers of fruit sets (B a s a k , 1993; J o n e s e t a l .1997; L i n k a n d B l a k e , 1998; B a s a k a n d J a d c z u k , 1999; K r z e w i ń s k a e t a l .1999; W i e n i a r s k a e t a l .2000; B a s a k e t a l .2002; Ty b u r s k i e t a l .2006).A common view dominates in scientifi c literature and in practice that chemical thinning is largely unreliabile, while manual thinning is very time-consuming.

MATERIALS AND METHODS
The experiment was established in 2004 on a production quarter of Szampion cv.planted on grey brown podzolic soil in 2000.The trees of this cultivar grafted on semi-dwarf M 7 rootstock were planted at a spacing of 3.8 x 1.7 m (about 1,550 trees per 1 ha) and on strongly growing A 2 rootstock at a spacing of 4 x 2 m (1,250 trees).In 2005 cv.Szampion RENO trees were included in the studies, grafted on M.7 rootstock and planted at a spacing of 4 x 2 m at the same time as the above mentioned plants.
The experiment was set up in a scheme of random blocks in 5 repetitions.The repetitions were the plots where 3 trees grew on each.The following set of combinations was used for the studied material: 1. Szampion on M.7 -control 2. Szampion on M.7 -manually thinned every second fl uorescence at the pink bud stage 3. Szampion on M.7 -manually thinned after the June fall -distorted and small sets were left, leaving the petioles 4. Szampion RENO on M.7 -control 5. Szampion RENO on M.7 -50% fl owers removed like in combination 2 6.Szampion on A 2 -control 7. Szampion on A 2 -thinned after the June fall like in combination 3.
The tree diameter at a height of 30 cm was measured in the experiment.The yield from each tree was weighed.Fruits picked up from particular trees were counted in combinations 1-3.During the harvest, 1 box of fruits from a repetition was taken for each combination.Those fruits were sorted out, estimating the proportion of fruits with a diameter of over 7 cm in the yield and the quantity of fruits with a pink blush covering more than 75% of the peel surface.
Based on these measurements, the cross-section area of the trunks was calculated as well as total and commercial yields from 1 ha of the orchard, the mean weight of fruits and the percentage of fruits with a diameter of over 7 cm and the colouring of over 75% of the peel area.Besides, measurements were made of the time of thinning and fruit gathering.
The results were statistically analyzed using variance analysis and Tukey's confi dence intervals at the level of signifi cance of 5%.

RESULTS AND DISCUSSION
No signifi cant effect of the thinning treatments was shown on the growth of Szampion cv.trees on two rootstocks and of cv.Szampion RENO.
Table 1 Infl uence of type of thinning and rootstock on the growth of apple trees cv. Szampion in 2004cv. Szampion in -2006. .Means followed by the same letters do not differ signifi cantly for p=0.05 The trees grew worse on M.7 as compared to A 2 rootstock.In 2004 signifi cant differences were shown between these rootstocks.The trees of cv.'Szampion RENO' were characterized by the poorest growth as compared to the other combinations.
The thinning of one tree on a semi-dwarf rootstock M.7 lasted from 12 to 25 minutes.Less intensive thinning of sets after the June fall required less time.The thinning treatments required 362-542 man-hours per 1 ha.

Explanations as in table 1
In the case of the control combinations, the highest yield from a tree was obtained from Szampion on A 2 only in 2005.The differences between the rootstocks and between Szampion RENO and Szampion proved to be signifi cant.Similar tendencies were observed in the other years of the study, but the differences between the studied biological material turned out to be insignifi cant.
The present observations confi rm the fact known in literature that the strength of tree growth and its yielding are mostly determined by biological elements: the rootstock and the cultivar (B i e l i c k i e t a l .1999; Wo c i ó r e t a l .2001).
Flower thinning signifi cantly decreased the yielding of cv.Szampion on M.7 in the fi rst two years of the study.A similar tendency was observed in Szampion in 2006 and in Szampion RENO in both study years, but the differences between the combinations were insignifi cant.
Set thinning in the years 2004 and 2005 significantly decreased the yield of cv.Szampion on both rootstocks.In 2006 the differences between the control trees and those on which sets were thinned were insignifi cant.
The present results confi rm those which were obtained in experiments of a number of authors (B a s a k , 1993; J o n e s e t a l .1997; L i n k a n d B l a n k e , 1998; W i e n i a r s k a e t a l .2000; K a p ł a n a n d Wo c i ó r , 2005; Ty b u r s k i e t a l .2006), pointing to the fact that fl ower set thinning decreases the total yield.The degree of yield reduction depended on thinning intensity as well as the manner and date of the treatment.
Flower thinning increased the commercial yield from 1 ha by about 1 ton for the cultivars of Szampion and Szampion RENO.Irrespective of the rootstock, fruit set thinning slightly decreased the commercial yield as compared to the control combination.
W i e n i a r s k a e t a l .(2000) and S z o t (2007) report that -depending on the manner and date of thinning -an increase of the commercial yield of Szampion cv. was obtained.Earlier thinning usually gave better results.A similar regularity was observed in the present studies.x On average, in the course of 3 years, the thinning of fl owers and fruit sets decreased the number of fruits of Szampion cv. on the trees grafted on M.7.The differences between the control combination and the thinned trees were signifi cant only in 2005.Flower thinning signifi cantly increased the fruit weight of Szampion cv.only in 2004.It deserves mentioning that in 2004, in the control combination and after thinning, fruits of much smaller weight were obtained as compared to the previous years.x In the case of the Szampion and Szampion RENO cultivars, the studies found out a positive effect of fl ower thinning on the percentage of fruits with a diameter of over 7 cm in the yield.Signifi cant differences, in comparison to the control combination, were observed only for Szampion cv. in 2004.
Removing distorted and small sets after the June fall did not improve the percentage of fruits with a diameter of over 7 cm.A similar effect was obtained in earlier studies (K a p ł a n a n d Wo c i ó r , 2005) conducted on Szampion cv.trees grafted on M.26 and P 60 when thinning was not intensive.
A small or no effect of set thinning after the June fall on the commercial yield of Szampion cv. was observed in the most recent studies by S z o t (2007).
Sets thinning did not signifi cantly affect the colouring of Szampion cv.fruits on either rootstock in the years 2004and 2006. In 2005 this treatment significantly decreased the percentage of very well coloured fruits of Szampion cv. on M.7, and it did not change this property in the trees grafted on A 2.
Flower thinning had a positive effect on the percentage of very well coloured fruits of 'Szampion' and Szampion RENO cultivars in each year of the study, and only in 2006 the differences were signifi cant compared to the control combination.
In 2005 much better fruit colouring was found out in all combinations than in the other years.The positive effect of early thinning on fruit colouring is also observed by other authors (W i e n i a r s k a e t a l .2000; K r z e w i ń s k a e t a l .2002).

CONCLUSIONS
1.The thinning of fl owers and fruit sets did not change the strength of tree growth in a signifi cant way.The Szampion cv.trees on rootstock A 2 grew better than on M.7.The trees of Szampion RENO cv.grew signifi cantly worst.2. The thinning of fl owers and fruit sets decreased the yield from a tree and the total yield from 1 ha of the studied biological material.Flower thinning slightly increased the mean commercial yield as compared to the control trees.3. Thinning of 50% of fl owers at the stage of the pink bud and sets after the June fall decreased the number of fruits on the trees of Szampion cv.grafted on M.7.It was only in 2004 that the fl ower thinning treatment signifi cantly increased the fruit weight.
Fruit set thinning after the June fall did not change the fruit weight in any signifi cant way as compared to the control combination.4. In the case of Szampion cv.trees grafted on M.7, fl ower thinning increased the percentage of fruits with a diameter of over 7 cm.This treatment con-siderably (in 2006 signifi cantly) improved fruit colouring.A positive reaction to fl ower thinning was also observed in the Szampion RENO trees. 5.The effect of fruit set thinning on fruit quality was related to the rootstock and it varied in particular years.The thinning of sets of Szampion cv. on M.7 after the June fall in the years 2004 and 2006 only slightly affected the percentage of fruits with a diameter of over 7 cm and fruit colouring.In 2005 the studies showed an incomprehensible fall in the percentage for both these features as compared to the control combination.The Szampion cv.trees grafted on A 2 increased the percentage of frutis with a diameter of over 7 cm after fruit set thinning, but did not improve the colouring.6. Considerable differences in colouring between the study years point out that the weather determined the quantity of very well coloured fruits to a greater degree that thinning treatments.

Table 2
Infl uence of type of thinning and rootstock on yielding of applescv.Szampion in 2004cv.Szampion in  -2006.   .

Table 3
Infl uence of thinning on the number of fruits and the fruit weight in applescv.Szampion in 2004cv.Szampion in  -2006.   .

Table 4
Infl uence of type of thinning and rootstock on fruit quality in applescv.Szampion in 2004cv.Szampion in  -2006..Numerous authors (K r z e w i ń s k a e t a l .1999; C z y n c z y k e t a l .2001; K a p ł a n a n d Wo c i ó r , 2005; S z o t , 2007) suggest leaving only a defi nite number of sets in the period of manual thinning so as to ensure a satisfactory yield of very good quality.The present studies point out that in the case of the Szampion cv.trees grafted on semi-dwarf rootstock M.7 this number should not exceed 200.This problem requires further studies.
Szampion'./ Infl uence of intensity of hand thinning of sets on fruit quality of cv.Szampion.Roczniki AR w Poznaniu, Ogrodnictwo, 41: 395-402.Ty b u r s k i M .S ., Wa ź b i ń s k a J ., P ł o s z a j B .2006.