Breeding drought tolerant cowpea: constraints,accomplishments, and future prospects |
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Authors: | E M Agbicodo C A Fatokun S Muranaka R G F Visser C G Linden van der |
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Institution: | (1) International Institute of Tropical Agriculture (IITA), Oyo Road, PMB 5320, Ibadan, Nigeria;(2) Wageningen UR Plant Breeding, Wageningen University and Research Center, Wageningen, The Netherlands;(3) The Graduate School Experimental Plant Sciences, Wageningen University, Wageningen, The Netherlands;(4) Sabo Bakin Zuwo Road, PMB 3112, Kano, Nigeria |
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Abstract: | This review presents an overview of accomplishments on different aspects of cowpea breeding for drought tolerance. Furthermore
it provides options to enhance the genetic potential of the crop by minimizing yield loss due to drought stress. Recent efforts
have focused on the genetic dissection of drought tolerance through identification of markers defining quantitative trait
loci (QTL) with effects on specific traits related to drought tolerance. Others have studied the relationship of the drought
response and yield components, morphological traits and physiological parameters. To our knowledge, QTLs with effects on drought
tolerance have not yet been identified in cowpea. The main reason is that very few researchers are working on drought tolerance
in cowpea. Some other reasons might be related to the complex nature of the drought stress response, and partly to the difficulties
associated with reliable and reproducible measurements of a single trait linked to specific molecular markers to be used for
marker assisted breeding. Despite the fact that extensive research has been conducted on the screening aspects for drought
tolerance in cowpea only very few—like the ‘wooden box’ technique—have been successfully used to select parental genotypes
exhibiting different mechanisms of drought tolerance. Field and pot testing of these genotypes demonstrated a close correspondence
between drought tolerance at seedling and reproductive stages. Some researchers selected a variety of candidate genes and
used differential screening methods to identify cDNAs from genes that may underlie different drought tolerance pathways in
cowpea. Reverse genetic analysis still needs to be done to confirm the functions of these genes in cowpea. Understanding the
genetics of drought tolerance and identification of DNA markers linked to QTLs, with a clear path towards localizing chromosomal
regions or candidate genes involved in drought tolerance will help cowpea breeders to develop improved varieties that combine
drought tolerance with other desired traits using marker assisted selection.
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Keywords: | Vigna unguiculata L Drought tolerance QTL mapping Comparative genomics Candidate genes Marker Assisted Selection (MAS) |
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