Abschlussbericht Projekt: „Verminderung der ... - BLE

H. J. Dames GmbH & Co. KG, Rotenburg a. d. F., Germany) with three replications. Each
replication consisted of an amount of tubers (Σ tuber ) adequate to a volume of 6 L. Afterwards,
treated tubers were stored at room temperature for 48 hours. For BSI determination
they were cut into halves length-wise and a half tuber was evaluated visually using a scale
with four scores of discolouration: No discolouration indicated the lack of any melanin
development and therefore no blackspot susceptibility (Σ 1 ). Discolouration of up to one
quarter of length and less than 5 mm in depth denoted slight blackspot susceptibility (Σ 2 ).
Medium blackspot susceptibility corresponded to a discolouration of up to one quarter of
length and more that 5 mm in depth or one half of the length and a maximum of 5 mm in
depth (Σ 3 ). Serious blackspot susceptibility was indicated by any discolouration stronger
than that described before (Σ 4 ). The blackspot susceptibility, expressed as the percentage of
discoloured tubers was calculated as:
( ) ( 0.3∑ + 0.5∑ + ∑ )/
∑
BSI % 2 3 4
* 100
(1)
= tuber
BSI: blackspot index (%)
Σ: amount of analysed tubers
To determine the concentration of nutrients the ground samples were dissolved in 65 %
HNO 3 (Roth, Germany) (Kuennen et al. 1982) during a thermic decomposition at 175°C
for 12 hours, which was realized in pressurized Teflon vessels (Aysola et al. 1987). Dissolved
samples with a final concentration of 40 % HNO 3 were the basis for the following
analyses. The measurement of P followed the official method of §35 LMBG L 06.00/9
(Wilhelm et al. 1993) using an UV-Vis spectral system (HP 8453, Germany) were the extinctions
of samples were measured at 436 nm and the P concentration was determined
according KH 2 PO 4 -calibration solutions with P concentrations between 0 to 14 mg L -1 . The
concentrations of Se, B, Fe, Ca and Mg were detected with an inductively coupled plasma
mass spectrometer (ICP MS) using established methods of the Geo-scientific Research
Centre of the Faculty of Geoscience and Geography at the Georg-August-University of
Goettingen. Therefore, multiple calibration solutions for Se, B and Fe and for Ca and Mg
were prepared. Characteristic isotopes of the minerals were chosen to avoid possible interferences
with other isobaric masses and to obtain the highest peak to background ratio
(Makishima et al. 1997; Müller et al. 2003). The concentration of K was measured using an
atomic absorption spectrometer (Unicam Solaar M Series) applying appropriate dilutions
(Westermann et al.1994; McNabnay et al. 1999).
Much of evidence showed nutrient concentrations of tubers as a function of dry matter (e.g.
Locascio et al. 1992; Bergmann 1993; Bamberg et al. 1998; Putz 1998; Seppänen et al.
2003; Turakainen et al. 2004, 2006; Nitsch 2005; Rogozińska et al. 2005; Sulaiman 2005;
Dilworth et al. 2007). In this study, nutrient concentrations are presented in tuber fresh
weight because dry matter itself has a strong relationship towards blackspot susceptibility
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