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\hypersetup{pdftitle={Field Validation of a Newly Developed Multivariate Drought Stress Severity Index},pdfauthor={Julia Auber, M. Awais Khan, Leah Kuppinger, Evelyn Farfan, Merideth Bonierbale, Folkard Asch},pdfsubject={Tropentag 2016: Abstract},pdfkeywords={Drought tolerance, modelling, solanum tuberosum, stress intensity},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 18-21, 2016, Vienna, Austria}}\\[1ex] \Large{``Solidarity in a competing world ---\\fair use of resources''\\[2ex]}}
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\begin{center}
\Large{\textbf{Field Validation of a Newly Developed Multivariate Drought Stress Severity Index\footnote{\textbf{Contact Address:} Julia Auber, University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), Garbenstraße 13, Stuttgart, Germany, \mbox{e-mail}: \email{julia.auber@uni-hohenheim.de}}\\[0.8ex]}}
\normalsize{\textsc{Julia Auber$^{1}$, M. Awais Khan$^{2}$, Leah Kuppinger$^{1}$, Evelyn Farfan$^{2}$, Merideth Bonierbale$^{2}$, Folkard Asch$^{1}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), Germany}}}
\item[]{\small{\textit{$^{2}$International Potato Center (CIP), Peru}}}
\end{itemize*}
\index[author]{Auber, Julia}
\index[author]{Khan, M. Awais}
\index[author]{Kuppinger, Leah}
\index[author]{Farfan, Evelyn}
\index[author]{Bonierbale, Merideth}
\index[author]{Asch, Folkard}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Water shortage will be one of the main constrains in future crop production. The identification and development of crop varieties with low water demand is crucial for yield stability. Potato is one of the main world's staple food plants in and several varieties are known to have the potential to perform well under water limited conditions. However, current drought tolerance indices for potato are often based on yield and aboveground biomass and often over- or underestimating the plant's capacity to adapt drought. Therefore, the development of new stress severity indices (SSI) combining variety traits and environmental parameters should be considered as an approach to improve the drought tolerance indices for potato.



In a field experiment conducted in the costal arid region in South Peru, thirteen potato genotypes were subjected to different water treatments: full irrigation, early drought (terminal drought started at 55 days after planting (DAP)), intermediate (65 DAP) and late drought treatment (75 DAP). To validate the stress severity, destructive samplings (yield, biomass, and root architecture) were conducted in 10 days intervals. Simultaneously we monitored crop surface reflection, soil moisture (SM), evapotranspiration (ET), single crop evapotranspiration (ETc), water vapour deficit (VPD) and wind speed (WS) . The stress severity index was modeled based on soil moisture, stepwise including, evapotranspiration, ETc, VPD and WS to find best fitting SSI model to describe drought tolerance. 



In late drought stress treatment SSI increased from 0 up to 4 after severe drought for 30 days, whereas, in the early drought treatment a maximum of 1.6 was calculated. The SSI models with best goodness of fit, in combination with best fitting wavelength specific ratio derived by crop surface reflectance measurements will be presented and discussed.  Combining multiple environmental parameters and plant physiological responses to drought in models to calculate stress severity indices is a promising tool to adapt crop production under water limitation, however, more in"=depth analysis are needed especially with regard to variable environments. 















}

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\end{abstract}
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\noindent \textbf{Keywords:} Drought tolerance, modelling, solanum tuberosum, stress intensity
\index[key]{Drought tolerance}
\index[key]{Modeling}
\index[key]{Solanum tuberosum}
\index[key]{Stress intensity}
\end{document}
