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\hypersetup{pdftitle={Can Cowpea Genetic Diversity Stabilize and/or Increase Leaf and Seed Yields in Subsistence Agriculture?  },pdfauthor={Joshua Okonya},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Biodiversity, intercropping, mixture, monoculture, stability, variety},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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\Large{\textbf{Can Cowpea Genetic Diversity Stabilize and/or Increase Leaf and Seed Yields in Subsistence Agriculture?  \footnote{\textbf{Contact Address:} Joshua Okonya, Georg-August-Universität Göttingen, Department of Crop Sciences, Institute of Agronomy in the Tropics, Grisebachstraße 6, 37077~Göttingen, Germany, \mbox{e-mail}: \email{joshua.okonya@gmail.com}}\\[0.8ex]}}
\normalsize{\textsc{Joshua Okonya}}
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\begin{itemize*}
\item[]{\small{\textit{Georg-August-Universität Göttingen, Department of Crop Sciences, Institute of Agronomy in the Tropics, Germany}}}
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\index[author]{Okonya, Joshua}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Cowpea (\textit{Vigna unguiculata}) is an important leafy vegetable and grain legume in Uganda. It is usually grown with other crops like maize, sorghum or cassava mainly in northern and eastern districts.  Grain and leaf yields are low and mixture effects had never been assessed. Unlike in commercial agriculture, where variety mixtures in cereal crops are known to give higher and more stable yields, the performance of cowpea variety mixtures in subsistence agriculture is little known. 







Mixtures containing up to four determinate cowpea varieties UG-CP-9=A, Dakawa=B, Ex-Iseke=C and IT 93K-2045--29=D acquired from AVRDC were subjected to all possible 2-way (A+B, A+C, A+D, B+C, B+D and C+D); 3-way (A+B+C, A+B+D, A+C+D and B+C+D) and 4-way (A+B+C+D) combinations. These were grown in intercrop with maize in 2008 at three locations in Soroti and Kumi districts in eastern Uganda. Yield data for cowpea leaf and grain from three replicated plots in each environment was subjected to one way ANOVA using the GLM procedure of SYSTAT. The percentage mixture effect was calculated as follows: mixture effect (\%) = (mixture yield --- pure line component average)/ pure line component average $\times$ 100.  PLABSTAT was used to generate the ecovalence (Wi) values as a measure of stability with low ecovalence values indicating higher stability.







The total cowpea DM leaf yield and grain yield ranged from 3.7 (Variety A) to \unitfrac[6.7]{g}{m}2 (variety C and mixture B+C) and 12.1(variety D) to \unitfrac[36.7]{g}{m}2 (variety B) respectively. Mixture effects ranged from -9.3 (mixture A+C+D) to \mbox{14.0\,\%} (mixture C+D) for leaf yield and -30.3 (mixture A+B) to \mbox{21.9\,\%} (mixture C+D) for grain yield. None of the mixture effects was significantly different at $p < 0.05$. Stability of leaf and grain yields cross the three environments ranged from Wi = 0.06 (mixture B+D) to 5.30 (variety D) for leaf and Wi = 4.45 (mixture B+D) to 894.84 (variety A) for grain. 







The results suggested that the leaf and seed yields of cowpea variety mixtures grown in marginal environments were more stable than of single varieties but not all mixtures yielded more than single varieties.



}

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\noindent \textbf{Keywords:} Biodiversity, intercropping, mixture, monoculture, stability, variety
\index[key]{Biodiversity}
\index[key]{Intercropping}
\index[key]{Mixture}
\index[key]{Monoculture}
\index[key]{Stability}
\index[key]{Cowpea!varieties}
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