Journal of Plant Pathology - Sipav.org

S1.34 Effects of prohexadione-calcium on grape cluster structure Journal of Plant Pathology (2011), 93 (1, Supplement), S1.33-S1.37
in the biosynthesis of anthocyanidins and other
flavonoids (Rademacher et al., 1992). Prohexadione is
structurally similar to 2-oxoglutaric acid, enabling the
compound to inhibit 2-oxoglutarate-dependent dioxygenases,
which are involved in the formation of growth
active gibberellins and in flavonoid metabolism
(Rademacher, 2000). Our objectives were to quantify
the response of grapes to prohexadione-calcium and to
determine whether reductions in berry size or crop yield
could be related to increased fruit and wine quality.
MATERIALS AND METHODS
Experimental design. The experiments were conducted
in the years 2009 and 2010 on field grown
grapevines (Vitis vinifera cv. Grüner Veltliner on Kober
5BB rootstock). The experimental vineyard was located
at the Federal Research Station Agneshof, Klosterneuburg,
(Austria). The vineyard was planted with a
vine-by-row spacing of 1.20 × 3 m in south orientation,
with a permanent green ground cover. The vines were
trained to espalier with two vertically positioned canes.
Soil and canopy management and grape protection
strategy for the year 2009 and 2010 [six applications of:
sulphur 0.3%, sulphur 0.3% and dithianon 0.05%,
azoxystrobin/folpet (combined product) 0.2%, proquinazid
0.025% and cymoxanil/dithianon (combined
product) 0.1%, metalaxyl-m/folpet (combined product)
0.2% and metrafenone 0.02%, cymoxanil/dithianon
(combined product) 0.1% and meptyldinocap 0.06%]
were carried out as in commercial vineyard. In the
evenings of the 9 June 2009 and 22 June 2010, respectively,
when sixty percent of the flowerhoods were fallen
(BBCH 66) (Lancashire et al., 1991), prohexadione-calcium
(1,8 kg/ha; 400 l water) with citric acid (0,1%) was
applied with a motorized backpack sprayer (STIHL SR
420). Two applications of botryticides (mepanipyrim
0.12%) were done at BBCH 73 – BBCH 75 (Table 1).
All experimental treatments were replicated in four randomized
plots consisting of 10 vines.
Weather data. Data were recorded on an ADCON
Weather Station located on the trial site.
Grape bunch length. Length was measured of two
bunches of the third shoot, counted from the basis of
Table 1. Nature of treatments and dates of application.
Number Treatment Application date
1 Control
2 Prohexadione-calcium 9 and 22 June 2010
3 Prohexadione-calcium
and Mepanipyrim
9 and 22 June 2010
14 and 19 July 2010
4 Mepanipyrim 14 and 19 July 2010
the cordon. If the third shoot was weak, then bunches
of the next shoot were considered.
Bending index. The bending index was developed to
assess the compactness of grape clusters. The index was
determined using the following scale: 1= firm, 2= flexible,
3= bending up to a maximum of 45°, 4= bending
up to a maximum of 90°, 5= bending above 90°. One
hundred grapes clusters were analyzed in each treatment
for grape bunch length and bending index.
Weight parameter. In 2009 and 2010 the weight of
the crop was measured with a laboratory scale on twelve
vines per treatment and replicates.
Berry diameter. The diameter of all berries from
three clusters per treatment was recorded. To this aim,
berries were cut with a scalpel through the middle and
measured with a ruler.
B. cinerea disease serverity. The severity of B. cinerea
attacks was assessed according to the EPPO Standards
[PP 1/17 (2)] on 100 bunches on 15 September 2009
and 13 September 2010.
Fourier transform infrared spectroscopy. Bunch
ripeness was determined on 100 berries per treatment
with Fourier transform infrared spectroscopy (FTIR),
which is used for routine quantification of wine and
grape parameters (for example sugar concentration). A
Foss instrument (WineScan FT 120, Type 77110 with
sampling 5027) was used to analyse the must samples
(Griffiths and de Hasseth, 2007).
Data analysis. SPSS Statistics 17.0 was used for data
analysis. Significance of main effects was determined by
analysis of variance (ANOVA) and Tukey.
RESULTS
There was no significant difference between the
treatments on cluster length (Fig. 1). Likewise, cluster
weight did not differ significantly in the variants (ANO-
VA, significance = 0.350) (Fig. 2).
When looking at the frequency with which a certain
berry diameter was observed, a significantly higher number
of berries with a diameter of 3 mm was found in the
variant prohexadione-calcium. Similarly, a higher number
of berries with a diameter of 8-10 mm was found in this
treatment as compared with the control (Fig. 3).
As for the density index, in the year 2009, the treatment
with prohexadione-calcium + botryticide differed
significantly α=0,000 (α>0.05) from the control and the
variant prohexadione-calcium and botryticide, which
was the treatment with the loosest grapes. In 2010,