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\hypersetup{pdftitle={Survival and Electrolyte Leakage are Indices to Evaluation of Freezing Tolerance in Flixweed (\textit{Descurainia sophia})},pdfauthor={Ahmad Nezami, Ebrahim Izadi Darbandi, Hassan Baigi Roohollah},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Descurainia sophia, freezing stress, electrolyte leakage, flixweed, LT50 },pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\begin{center}
\Large{\textbf{Survival and Electrolyte Leakage are Indices to Evaluation of Freezing Tolerance in Flixweed (\textit{Descurainia sophia})\footnote{\textbf{Contact Address:} Ahmad Nezami, Ferdowsi University of Mashhad, College of Agriculture, Department of Agronomy and plant breeding, Mashhad, Iran, \mbox{e-mail}: \email{nezamiahmad@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Ahmad Nezami$^{1}$, Ebrahim Izadi Darbandi$^{2}$, Hassan Baigi Roohollah$^{3}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$Ferdowsi University of Mashhad, College of Agriculture, Department of Agronomy and plant breeding, Iran}}}
\item[]{\small{\textit{$^{2}$Ferdowsi University of Mashhad, Department of Agronomy, Iran}}}
\item[]{\small{\textit{$^{3}$, }}}
\end{itemize*}
\index[author]{Nezami, Ahmad}
\index[author]{Izadi Darbandi, Ebrahim}
\index[author]{Roohollah, Hassan Baigi}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Flixweed (\textit{Descurainia sophia }(L.)) is one of the most important weeds in Iranian winter wheat farms. In order to evaluate freezing tolerance of different flixweed ecotypes, an experiment was carried out under controlled conditions in 2008 at the College of Agriculture, Ferdowsi University of Mashhad. In this study 5 flixweed ecotypes (Eghlid, Sabzevar, Hamedan, Neishaboor and Torbatejam), across 10 temperatures (between 0, and -18 °C, with two"=degree intervals) were evaluated as a completely randomised design in a factorial arrangement with three replications. Plants were kept until 4--6 leaf stage in natural environment to acclimation, then transferred to the thermogradient freezer. After freezing the cell membrane integrity was measured through electrolyte leakage (EL) and the lethal temperature (LT50) of samples was measured. Samples after freezing were transferred to the greenhouse and their survival percentage, plant height, and dry weight were determined after 3 weeks.  Results showed that the effect of different freezing temperatures were significant ($p < 0.05$) on all plant characteristics. As temperature decreased, electrolyte leakage increased on all flixweed ecotypes.  Electrolyte leakage increased on all flixweed ecotypes with decreasing  temperature lower than -4\textdegree{}C. Minimum and maximum EL \% were observed at 0\textdegree{}C (\mbox{37\,\%}) and -16\textdegree{}C (\mbox{63.1\,\%}) and minimum and maximum survival were observed at 0\textdegree{}C (\mbox{98.6\,\%}) and -16\textdegree{}C (\mbox{0\,\%}). The Sabzevar ecotype showed the highest EL \% (56.2\,\%)  and lowest survival (\mbox{54.1\,\%}), while the Hamedan  ecotype showed the lowest EL \% (40.5\,\%) and highest survival (\mbox{64.4\,\%}). Highest and lowest LT50 was observed for Hamedan (11.7\textdegree{}C) and Zabzevar (8\textdegree{}C) ecotypes, respectively. According to these results, Sabzevar and Hamedan flixweed ecotypes had the lowest and highest cold tolerance. It seems, that Hamedan ecotype's tolerance to cold stress maybe caused by acclimation in native moderate condition.







}

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\end{abstract}
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\noindent \textbf{Keywords:} \textit{Descurainia sophia}, freezing stress, electrolyte leakage, flixweed, LT50 
\index[key]{Descurainia sophia@\textit{Descurainia sophia}}
\index[key]{freezing stress}
\index[key]{Electrolyte leakage}
\index[key]{Flixweed}
\index[key]{LT50 }
\end{document}