Quantitative trait loci influencing drought tolerance in grain sorghum (Sorghum bicolor L. Moench) |
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Authors: | H Kebede P K Subudhi D T Rosenow H T Nguyen |
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Institution: | (1) Plant Molecular Genetics Laboratory, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409-2122, USA e-mail: henry.nguyen@ttu.edu Fax: +1 806-742-2888, US;(2) Texas A&M University Agricultural Research and Extension Center, Route3, Box 219, Lubbock, TX 79401, USA, US |
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Abstract: | Drought is a major constraint in sorghum production worldwide. Drought-stress in sorghum has been characterized at both pre-flowering
and post-flowering stages resulting in a drastic reduction in grain yield. In the case of post-flowering drought stress, lodging
further aggravates the problem resulting in total loss of crop yield in mechanized agriculture. The present study was conducted
to identify quantitative trait loci (QTLs) controlling post-flowering drought tolerance (stay green), pre-flowering drought
tolerance and lodging tolerance in sorghum using an F7 recombinant inbred line (RIL) population derived from the cross SC56×Tx7000. The RIL lines, along with parents, were evaluated
for the above traits in multiple environments. With the help of a restriction fragment length polymorphism (RFLP) map, which
spans 1,355 cM and consists of 144 loci, nine QTLs, located over seven linkage groups were detected for stay green in several
environments using the method of composite interval mapping. Comparison of the QTL locations with the published results indicated
that three QTLs located on linkage groups A, G and J were consistent. This is considered significant since the stay green
line SC56 used in our investigation is from a different source compared to B35 that was used in all the earlier investigations.
Comparative mapping has shown that two stay green QTLs identified in this study corresponded to stay green QTL regions in
maize. These genomic regions were also reported to be congruent with other drought-related agronomic and physiological traits
in maize and rice, suggesting that these syntenic regions might be hosting a cluster of genes with pleiotropic effects implicated
in several drought tolerance mechanisms in these grass species. In addition, three and four major QTLs responsible for lodging
tolerance and pre-flowering drought tolerance, respectively, were detected. This investigation clearly revealed the important
and consistent stay green QTLs in a different stay green source that can logically be targeted for positional cloning. The
identification of QTLs and markers for pre-flowering drought tolerance and lodging tolerance will help plant breeders in manipulating
and pyramiding those traits along with stay green to improve drought tolerance in sorghum.
Received: 2 June 2000 / Accepted: 15 November 2000 |
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Keywords: | Pre-flowering drought tolerance Stay green Genetic mapping Comparative mapping |
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