JXB Advance Access originally published online on December 14, 2006
Journal of Experimental Botany 2007 58(2):327-338; doi:10.1093/jxb/erl225
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RESEARCH PAPER |
Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence
1Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
2Molecular Genetics and Plant Genomics Laboratory, Department of Plant and Soil Science, Texas Tech University, Lubbock, Texas 79409-2122, USA
3Department of Primary Industries and Fisheries, Hermitage Research Station, Warwick, Queensland 4370, Australia
4Texas A&M University Agricultural Research and Extension Center, Lubbock, Texas 79401, USA
5Division of Plant Sciences and Center for Soybean Biotechnology, University of Missouri-Columbia, Columbia, Missouri 65211, USA
6Department of Horticultural Sciences and Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA
7USDA-ARS, Southern Plains Agricultural Research Center, College Station Texas 77845, USA
* To whom correspondence should be addressed. E-mail: andrew.borrell{at}dpi.qld.gov.au
Sorghum is an important source of food, feed, and biofuel, especially in the semi-arid tropics because this cereal is well adapted to harsh, drought-prone environments. Post-flowering drought adaptation in sorghum is associated with the stay-green phenotype. Alleles that contribute to this complex trait have been mapped to four major QTL, Stg1–Stg4, using a population derived from BTx642 and RTx7000. Near-isogenic RTx7000 lines containing BTx642 DNA spanning one or more of the four stay-green QTL were constructed. The size and location of BTx642 DNA regions in each RTx7000 NIL were analysed using 62 DNA markers spanning the four stay-green QTL. RTx7000 NILs were identified that contained BTx642 DNA completely or partially spanning Stg1, Stg2, Stg3, or Stg4. NILs were also identified that contained sub-portions of each QTL and various combinations of the four major stay-green QTL. Physiological analysis of four RTx7000 NILs containing only Stg1, Stg2, Stg3, or Stg4 showed that BTx642 alleles in each of these loci could contribute to the stay-green phenotype. RTx7000 NILs containing BTx642 DNA corresponding to Stg2 retained more green leaf area at maturity under terminal drought conditions than RTx7000 or the other RTx7000 NILs. Under post-anthesis water deficit, a trend for delayed onset of leaf senescence compared with RTx7000 was also exhibited by the Stg2, Stg3, and Stg4 NILs, while significantly lower rates of leaf senescence in relation to RTx7000 were displayed by all of the Stg NILs to varying degrees, but particularly by the Stg2 NIL. Greener leaves at anthesis relative to RTx7000, indicated by higher SPAD values, were exhibited by the Stg1 and Stg4 NILs. The RTx7000 NILs created in this study provide the starting point for in-depth analysis of stay-green physiology, interaction among stay-green QTL and map-based cloning of the genes that underlie this trait.
Key words: Drought adaptation, NIL, sorghum, stay-green QTL
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