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Plant function and evolutionary biology
RESEARCH ARTICLE

Quantitative trait locus mapping of the transpiration ratio related to preflowering drought tolerance in sorghum (Sorghum bicolor)

Mohankumar H. Kapanigowda A E , William A. Payne A B , William L. Rooney A , John E. Mullet C and Maria Balota D
+ Author Affiliations
- Author Affiliations

A Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843-2474, USA.

B International Center for Agriculture Research in Dry Areas, P.O. Box 5689, Addis Ababa, Ethiopia.

C Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, TX 77843, USA.

D Virginia Tech Tidewater Agricultural Research and Extension Center, 6321 Holland Road, Suffolk, VA 23437, USA.

E Corresponding author. Email: mohan.gowda@monsanto.com

This paper originates from a presentation at the Interdrought IV Conference, Perth, Australia, 26 September 2013.

Functional Plant Biology 41(11) 1049-1065 https://doi.org/10.1071/FP13363
Submitted: 18 December 2013  Accepted: 1 May 2014   Published: 27 June 2014

Abstract

To meet future food needs, grain production must increase despite reduced water availability, so waterproductivity must rise. One way to do this is to raise the ratio of biomass produced to water transpired, which is controlled by the ratio of CO2 assimilation (A) to transpiration (E) (i.e. the transpiration ratio, A : E divided by vapour pressure deficit) or anything affecting stomatal movement.. We describe the genetic variation and basis of A, E and A : E among 70 recombinant inbred lines (RILs) of sorghum (Sorghum bicolor (L.) Moench), using greenhouse experiments. Experiment 1 used 40% and 80% of field capacity (FC) as water regimes; Experiment 2 used 80% FC. Genotype had a significant effect on A, E and A : E. In Experiment 1, mean values for A : E were 1.2–4.4 mmol CO2 mol–1 H2O kPa–1 and 1.6–3.1 mmol CO2 mol–1 H2O kPa–1 under 40% and 80% FC, respectively. In Experiment 2, values were 5.6–9.8 mmol CO2 mol–1 H2O kPa–1. Pooled data for A : E and A : E VPD–1 from Experiment 1 indicate that A : E fell quickly at temperatures >32.3°C. A : E distributions were skewed. Mean heritabilities for A : E were 0.9 (40% FC) and 0.8 (80% FC). Three significant quantitative trait loci (QTLs) associated with A:E, two on SBI-09 and one on SBI-10, accounted for 17–21% of the phenotypic variation. Subsequent experiments identified 38 QTLs controlling variation in height, flowering, biomass, leaf area, greenness and stomatal density. Colocalisation of A : E QTLs with agronomic traits indicated that these QTLs can be used for improving sorghum performance through marker assisted selection (MAS) under preflowering drought stress.

Additional keywords: CO2 assimilation, marker-assisted selection, recombinant inbred lines, water use efficiency.


References

Balota M, Payne WA, Rooney WL, Rosenow DT (2008) Gas exchange and transpiration ratio in sorghum. Crop Science 48, 2361–2371.
Gas exchange and transpiration ratio in sorghum.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXmt1ygtg%3D%3D&md5=82fd1abb2e0c3373c4d13ff5c5f7ec38CAS |

Bhargava S, Paranjpe S (2004) Genotypic variation in the photosynthetic competence of Sorghum bicolor seedlings subjected to polyethylene glycol-mediated drought stress. Journal of Plant Physiology 161, 125–129.
Genotypic variation in the photosynthetic competence of Sorghum bicolor seedlings subjected to polyethylene glycol-mediated drought stress.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXis1eiu7Y%3D&md5=78fafe528f0b5541ecc0060ac25c0f60CAS | 15002674PubMed |

Bierhuizen JF, Slatyer RO (1965) Effect of atmospheric concentration of water vapor and CO2 in determining transpiration–photosynthesis relationships of cotton leaves. Agricultural Meteorology 2, 259–270.
Effect of atmospheric concentration of water vapor and CO2 in determining transpiration–photosynthesis relationships of cotton leaves.Crossref | GoogleScholarGoogle Scholar |

Blum A (1989) The temperature response of gas exchange in sorghum leaves and the effect of heterosis. Journal of Experimental Botany 40, 453–460.
The temperature response of gas exchange in sorghum leaves and the effect of heterosis.Crossref | GoogleScholarGoogle Scholar |

Blum A (2004) Sorghum physiology. In ‘Physiology and biotechnology integration for plant breeding’. (Eds HT Nguyen, A Blum) pp. 141–223. (Marcel Dekker: New York)

Blum A (2005) Drought resistance, water-use efficiency, and yield potential: are they compatible, dissonant, or mutually exclusive? Australian Journal of Agricultural Research 56, 1159–1168.
Drought resistance, water-use efficiency, and yield potential: are they compatible, dissonant, or mutually exclusive?Crossref | GoogleScholarGoogle Scholar |

Brown RH, Byrd GT (1997) Transpiration efficiency, specific leaf weight, and mineral concentration in peanut and pearl millet. Crop Science 37, 475–480.
Transpiration efficiency, specific leaf weight, and mineral concentration in peanut and pearl millet.Crossref | GoogleScholarGoogle Scholar |

Brück H, Payne WA, Sattelmacher B (2000) Effects of phosphorus and water supply on yield, transpirational water-use efficiency, and carbon isotope discrimination of pearl millet. Crop Science 40, 120–125.
Effects of phosphorus and water supply on yield, transpirational water-use efficiency, and carbon isotope discrimination of pearl millet.Crossref | GoogleScholarGoogle Scholar |

Cassady AJ (1965) Effect of single height (Dw) gene of sorghum on grain yield, grain yield components and test weight. Crop Science 5, 385–389.
Effect of single height (Dw) gene of sorghum on grain yield, grain yield components and test weight.Crossref | GoogleScholarGoogle Scholar |

Chen WF, Xu Z, Zhang L (1995) ‘Physiological bases of super high yield breeding in rice.’ (Liaoning Science and Technology Publishing Company: Shenyang, China)

Condon AG, Richards RA, Rebetzke GJ, Farquhar GD (2004) Breeding for high water-use efficiency. Journal of Experimental Botany 55, 2447–2460.
Breeding for high water-use efficiency.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXovVOisrk%3D&md5=90b38625e31cd7fa0534cc52af61a418CAS | 15475373PubMed |

Crafts-Brander SJ, Salvucci ME (2002) Sensitivity of photosynthesis in a C4 plant, maize, to heat stress. Plant Physiology 129, 1173–1180.

Crasta OR, Xu WW, Rosenow DT, Mullet JE, Nguyen HT (1999) Mapping of post-flowering drought resistance traits in grain sorghum: association between QTLs influencing premature senescence and maturity. Molecular Genetics 262, 579–588.

de Wit CT (1958) ‘Transpiration and crop yield.’ (Versl. Landbouwk. Onderz. 64.6 Institute of Biological and Chemical Research on Field Crops and Herbage: Wageningen: The Netherlands)

Donatelli M, Hammer GL, Vanderlip RL (1992) Genotype and water limitation effects on phenology, growth, and transpiration efficiency in grain sorghum. Crop Science 32, 781–786.

Eastin JD, Dickinson TE, Krieg DR, Maunder AB (1983) Crop physiology in dryland agriculture. In ‘Dryland agriculture. 1st edn’. (Eds HE Dregne, WO Willis). Agronomy monograph 23. pp. 334–364. (American Society of Agronomy, Crop Science Society of America and Soil Science Society of America: Madison, WI)

Food and Agricultural Organization (FAO) (2002) ‘Crops and drops: making the best use of water for agriculture.’ (FAO: Rome)

Food and Agriculture Organization (FAO) (2009a) ‘How to feed the world in 2050. World Summit on Food Security.’ (FAO: Rome). Available at http://www.fao.org/wsfs/wsfs-list-documents/en/. [Verified 24 May 2014]

Food and Agriculture Organization of the United Nations (FAO) (2009b) ‘Preliminary 2009 data on sorghum area, production and productivity.’ (FAO: Rome). Available at http://faostat.fao.org/site/567/default.aspx#ancor. [Verified 24 May 2014].

Faris JD, Haen KM, Gill BS (2000) Saturation mapping of a gene-rich recombination hot spot region in wheat. Genetics 154, 823–835.

Flynn DFB, Sudderth EA, Bazzaz FA (2006) Effects of aphid herbivory on biomass and leaf-level physiology of Solanum dulcamara under elevated temperature and CO2. Environmental and Experimental Botany 56, 10–18.
Effects of aphid herbivory on biomass and leaf-level physiology of Solanum dulcamara under elevated temperature and CO2.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28Xhtlaktrs%3D&md5=30bb8f3018fe51fd9b46b9e5b887fbd8CAS |

Gill KS, Gill BS, Endo TR, Taylor T (1996) Identification and high density mapping of gene-rich regions in chromosome group 1 of wheat. Genetics 144, 1883–1891.

Graham D, Lessman KJ (1966) Effect of height on yield and yield components of two isogenic lines of Sorghum vulgare. Crop Science 6, 372–374.
Effect of height on yield and yield components of two isogenic lines of Sorghum vulgare.Crossref | GoogleScholarGoogle Scholar |

Hammer GL, Farquhar GD, Broad IJ (1997) On the extent of genetic variation for transpiration efficiency in sorghum. Australian Journal of Agricultural Research 48, 649–655.
On the extent of genetic variation for transpiration efficiency in sorghum.Crossref | GoogleScholarGoogle Scholar |

Harris K, Subudhi PK, Borrell A, Jordan D, Rosenow DT, Nguyen HT, Klein PE, Klein R, Mullet JE (2007) Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence. Journal of Experimental Botany 58, 327–338.
Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXhtlOlt7c%3D&md5=62753958637fa0a1475d31dab7b0f0feCAS | 17175550PubMed |

Harrison SA, Boerma HR, Ashely DA (1981) Heritability of canopy apparent photosynthesis and its relationship to seed yield in soybean. Crop Science 21, 222–226.
Heritability of canopy apparent photosynthesis and its relationship to seed yield in soybean.Crossref | GoogleScholarGoogle Scholar |

Havaux M (1996) Short-term responses of Photosystem I to heat stress. Photosynthesis Research 47, 85–97.
Short-term responses of Photosystem I to heat stress.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK28Xit1aksLw%3D&md5=6f1d6868d26e406eaae007911f7d8f36CAS | 24301710PubMed |

Henderson SA, Von Caemmerer S, Farquhar GD, Wade LJ, Hammer GL (1998) Correlation between carbon isotope discrimination and transpiration efficiency in lines of the C4 species Sorghum bicolor in the glasshouse and the field. Australian Journal of Plant Physiology 25, 111–123.
Correlation between carbon isotope discrimination and transpiration efficiency in lines of the C4 species Sorghum bicolor in the glasshouse and the field.Crossref | GoogleScholarGoogle Scholar |

Hirota O, Oka M, Takeda T (1990) Sink activity estimation by sink size and dry matter increase during the ripening stage of barley (Hordeum vulgare) and rice (Oryza sativa). Annals of Botany 65, 349–354.

Howell TA (2001) Enhancing water use efficiency in irrigated agriculture. Agronomy Journal 93, 281–289.
Enhancing water use efficiency in irrigated agriculture.Crossref | GoogleScholarGoogle Scholar |

Kebede H, Subudhi PK, Rosenow DT, Nguyen HT (2001) Quantitative trait loci influencing drought tolerance in grain sorghum (Sorghum bicolor L. Moench). Theoretical and Applied Genetics 103, 266–276.
Quantitative trait loci influencing drought tolerance in grain sorghum (Sorghum bicolor L. Moench).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXmvVeks7c%3D&md5=31818d2578e9f6527aee9b4c49f51232CAS |

Kidambi SP, Krieg DR, Rosenow DT (1990a) Genetic variation for gas exchange rates in grain sorghum. Plant Physiology 92, 1211–1214.
Genetic variation for gas exchange rates in grain sorghum.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BC3cnhvFGnsw%3D%3D&md5=47c5655d4a2adcb4bf23bc706fd10a08CAS | 16667391PubMed |

Kidambi SP, Krieg DR, Nguyen HT (1990b) Parental influences on gas exchange rates in grain sorghum. Photosynthetica 50, 139–146.

Kim JS, Klein PE, Klein RR, Price HJ, Mullet JE, Stelly DM (2005) Chromosome identification and nomenclature of Sorghum bicolor. Genetics 169, 1169–1173.
Chromosome identification and nomenclature of Sorghum bicolor.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXjtVOls70%3D&md5=f306bb9787dca171fbdc92ca8cf39b9dCAS | 15489512PubMed |

Klute A (1986) Water retention: laboratory methods. In ‘Methods of soil analysis. Part 1’. 2nd edn. (Ed. A Klute) pp. 635–662. Agronomy Monograph 9. (ASA and SSSA: Madison, WI)

Knapp SJ, Stroup WW, Ross WM (1985) Exact confidence intervals for heritability on a progeny mean basis. Crop Science 25, 192–194.
Exact confidence intervals for heritability on a progeny mean basis.Crossref | GoogleScholarGoogle Scholar |

Krieg DR, Hutmacher HB (1986) Photosynthetic rate control in sorghum: stomatal and nonstomatal factors. Crop Science 26, 112–117.
Photosynthetic rate control in sorghum: stomatal and nonstomatal factors.Crossref | GoogleScholarGoogle Scholar |

Krieg DR, Girma FS, Peng S (1992) No evidence of cytoplasmic male-sterility systems influencing gas exchange rate of sorghum leaves. Crop Science 32, 1342–1344.
No evidence of cytoplasmic male-sterility systems influencing gas exchange rate of sorghum leaves.Crossref | GoogleScholarGoogle Scholar |

Lambrides CJ, Chapman SC, Shorter R (2004) Genetic variation for carbon isotope discrimination in sunflower: Association with transpiration efficiency and evidence for cytoplasmic inheritance. Crop Science 44, 1642–1653.

Li Z, Pinson SRM, Stansel JW, Paterson AH (1998) Genetic dissection of the source–sink relationship affecting fecundity and yield in rice (Oryza satva L.,). Molecular Breeding 4, 419–426.
Genetic dissection of the source–sink relationship affecting fecundity and yield in rice (Oryza satva L.,).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1cXntlOmt7k%3D&md5=65b17aac23fc86e880185260c764c990CAS |

Li H, Payne WA, Michels GJ, Rush CM (2008) Reducing plant abiotic and biotic stress: drought and attacks of greenbugs, corn leaf aphids, and virus disease in dryland sorghum. Environmental and Experimental Botany 63, 305–316.
Reducing plant abiotic and biotic stress: drought and attacks of greenbugs, corn leaf aphids, and virus disease in dryland sorghum.Crossref | GoogleScholarGoogle Scholar |

Menz MA, Klein RR, Mullet JE, Obert JA, Unruh NC, Klein PE (2002) A high-density genetic map of Sorghum bicolor (L.) Moench based on 2926 AFLP, RFLP, and SSR markers. Plant Molecular Biology 48, 483–499.
A high-density genetic map of Sorghum bicolor (L.) Moench based on 2926 AFLP, RFLP, and SSR markers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XjsFWrsbY%3D&md5=7c9dc1159a904e3f8d3870c197099133CAS | 11999830PubMed |

Mortlock MY, Hammer GL (1999) Genotype and water limitation effects on transpiration efficiency in sorghum. Journal of Crop Production 2, 265–286.
Genotype and water limitation effects on transpiration efficiency in sorghum.Crossref | GoogleScholarGoogle Scholar |

Onken AB, Wendt CW (1989) Soil fertility management and water relationships. In ‘Soil, crop and water management systems in the Sudano-Sahelian zone: proceedings of the international workshop’, 7–11 January 1987, ICRISAT (International Crops Research Institute for the Semi-Arid Tropics) Sahelian Center, Niamey, Niger. pp. 99–106. (Patancheru, Andra Pradesh, India)

Passioura JB (1977) Grain yield, harvest index and water use of wheat. Journal of Australian Institute for Agricultural Science 43, 117–120.

Payne WA (1997) Managing yield and soil water use of pearl millet in the Sahel. Agronomy Journal 89, 481–490.
Managing yield and soil water use of pearl millet in the Sahel.Crossref | GoogleScholarGoogle Scholar |

Payne WA (2000a) Water relations of sparse canopied crops. Agronomy Journal 92, 807
Water relations of sparse canopied crops.Crossref | GoogleScholarGoogle Scholar |

Payne WA (2000b) Optimizing crop water use in sparse stands of pearl millet. Agronomy Journal 92, 808–814.
Optimizing crop water use in sparse stands of pearl millet.Crossref | GoogleScholarGoogle Scholar |

Payne WA, Drew MC, Hossner LR, Lascano RJ, Onken AB, Wendt CW (1992) Soil phosphorus availability and pearl millet water-use efficiency. Crop Science 32, 1010–1015.
Soil phosphorus availability and pearl millet water-use efficiency.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3sXotVShsA%3D%3D&md5=c6f1877d1e40b4edc6ce3190cc315b51CAS |

Peacock JM (1982) Response and tolerance of sorghum to temperature stress. In ‘ Sorghum in the eighties: proceedings of the International Symposium on Sorghum,’ 2–7 November 1981, Patancheru, Andra Pradesh., India. pp. 143–159. (International Crops Research Institute for the Semi-Arid Tropics: Patancheru, Andra Pradesh, India)

Peng S, Krieg DR (1992) Gas exchange traits and their relationship to water use efficiency of grain sorghum. Crop Science 32, 386–391.
Gas exchange traits and their relationship to water use efficiency of grain sorghum.Crossref | GoogleScholarGoogle Scholar |

Peng S, Krieg DR, Girma FS (1991) Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines. Photosynthesis Research 28, 1–7.
Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3MXhs1Wqt7c%3D&md5=f3ded1c102daf2475b4f629ee9ffbb64CAS | 24414793PubMed |

Prasad PVV, Boote KJ, Allen LH (2006) Adverse high temperature effects on pollen viability, seed-set, seed yield, and harvest index of grain-sorghum (Sorghum bicolor (L.) Moench) are more severe at elevated carbon dioxide due to higher tissue temperatures. Agricultural and Forest Meteorology 139, 237–251.
Adverse high temperature effects on pollen viability, seed-set, seed yield, and harvest index of grain-sorghum (Sorghum bicolor (L.) Moench) are more severe at elevated carbon dioxide due to higher tissue temperatures.Crossref | GoogleScholarGoogle Scholar |

Rami JF, Dufour P, Trouche G, Fliedel G, Mestres C, Davrieux F, Blanchard P, Hamon P (1998) Quantitative trait loci for grain quality, productivity, morphological and agronomical traits in sorghum (Sorghum bicolor L. Moench). Theoretical and Applied Genetics 97, 605–616.
Quantitative trait loci for grain quality, productivity, morphological and agronomical traits in sorghum (Sorghum bicolor L. Moench).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1cXntFKlsL4%3D&md5=2c43ffd2a8f172d19cbebabdf49a014eCAS |

Rebetzke GJ, Richards RA, Condon AG, Farquhar GD (2006) Inheritance of carbon isotope discrimination in bread wheat (Triticum aestivum L.). Euphytica 150, 97–106.
Inheritance of carbon isotope discrimination in bread wheat (Triticum aestivum L.).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28Xpt1Onu74%3D&md5=35ee7f25038ad188d679dd7ab30148a7CAS |

Rooney WL (2004) Sorghum improvement – integrating traditional and new technology to produce improved genotypes. Advances in Agronomy 83, 37–109.
Sorghum improvement – integrating traditional and new technology to produce improved genotypes.Crossref | GoogleScholarGoogle Scholar |

Rosenow DT, Dahlberg JA (2000) Collection, conservation and utilization of sorghum. In ‘Sorghum: origin, history, technology, and production’. (Eds CW Smith, RA Frederiksen) pp. 305–328. (John Wiley & Sons: New York)

Rosenow DT, Ejeta G, Clark LE, Gilbert ML, Henzell RG, Borell AK, Muchow RC (1996) Breeding for pre- and post-flowering drought stress resistance in sorghum. In ‘Proceedings of the international conference on genetic improvement of sorghum and pearl millet’, 23–27 September, 1996, Lubbock, TX. pp. 400–411.

Sandhu D, Champoux JA, Bondareva SN, Gill KS (2001) Identification and physical localization of useful genes and markers to a major gene-rich region on wheat group 1S chromosomes. Genetics 157, 1735–1747.

Sharkey TD (2005) Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, Rubisco deactivation, reactive oxygen species, and thermotlerance provided by isoprene. Plant, Cell & Environment 28, 269–277.
Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, Rubisco deactivation, reactive oxygen species, and thermotlerance provided by isoprene.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXislKqs78%3D&md5=aed948d3d8a60d2b68bd3b7151a99983CAS |

Squire GR (1993) ‘The physiology of tropical crop production.’ (Commonwealth Agricultural Bureaux International: Wallingford, UK)

Srinivas G, Satish K, Madhusudhana R, Nagaraja Reddy R, Murali Mohan S, Seetharama N (2009) Identification of quantitative trait loci for agronomically important traits and their association with genic-microsatellite markers in sorghum. Theoretical and Applied Genetics 118, 1439–1454.
Identification of quantitative trait loci for agronomically important traits and their association with genic-microsatellite markers in sorghum.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXls1Oltrg%3D&md5=aaa01095b1d7eebef4fd435adb1094a4CAS | 19274449PubMed |

Stiller WN, Read JJ, Constable GA, Reid PE (2005) Selection for water use efficiency traits in a cotton breeding program. Crop Science 45, 1107–1113.
Selection for water use efficiency traits in a cotton breeding program.Crossref | GoogleScholarGoogle Scholar |

Subudhi PK, Nguyen HT (2000) Linkage group alignment of sorghum RFLP maps using a RIL mapping population. Genome 43, 240–249.
Linkage group alignment of sorghum RFLP maps using a RIL mapping population.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXjtVOqu7w%3D&md5=95098f753a223688720d0e96d55d2890CAS | 10791811PubMed |

Tanner CB, Sinclair TR (1983) Efficient water use in crop production: research or re-search? In ‘Limitations to efficient water use in production’. (Eds HM Taylor, WR, Jordan, TR Sinclair) pp. 1–27. (American Society of Agronomy, Crop Science Society of America and Soil Science Society of America: Madison, WI)

Tuinstra MR, Grote EM, Goldsbrough PB, Ejeta G (1996) Identification of quantitative trait loci associated with preflowering drought tolerance in sorghum. Crop Science 36, 1337–1344.
Identification of quantitative trait loci associated with preflowering drought tolerance in sorghum.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK28XmsFCkur0%3D&md5=5d1fd52d262d4629db027d01c3f06353CAS |

Tuinstra MR, Grote EM, Goldsbrough PB, Ejeta G (1997) Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench. Molecular Breeding 3, 439–448.
Genetic analysis of post-flowering drought tolerance and components of grain development in Sorghum bicolor (L.) Moench.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1cXit1Kit7c%3D&md5=1a19cc80cf05350c66a89b69529430bcCAS |

Unger PW, Payne WA, Peterson GA (2006) Water conservation and efficient use. In ‘Dryland agriculture’.2nd edn. Agronomy monograph. (Eds PW Unger, WA Payne, GA Peterson) pp. 39–85. (American Society of Agronomy, Crop Science Society of America and Soil Science Society of America: Madison, WI)

United States Department of Agriculture (USDA) (2012) ‘World agricultural production.’ (Foreign Agricultural Service, USDA Office of Global Analysis, National Technical Information Service: Washington, DC)

Vadez V, Krishnamurthy L, Hash CT, Upadhyaya HD, Borell AK (2011b) Yield, transpiration efficiency, and water-use variations and their interrelationships in sorghum reference collection. Crop and Pasture Science 62, 645–655.
Yield, transpiration efficiency, and water-use variations and their interrelationships in sorghum reference collection.Crossref | GoogleScholarGoogle Scholar |

Vadez V, Deshpande SP, Kholova J, Hammer GL, Borell AK, Talwar HS, Hash CT (2011a) Stay-green quantitative trait loci’s effects on water extraction, transpiration efficiency and seed yield depend on recipient parent background. Functional Plant Biology 38, 553–566.
Stay-green quantitative trait loci’s effects on water extraction, transpiration efficiency and seed yield depend on recipient parent background.Crossref | GoogleScholarGoogle Scholar |

Veldboom LR, Lee M, Woodman WL (1994) Molecular facilitated studies of morphological traits in an elite maize population. II. Determination of QTLs for grain yield and yield components. Theoretical and Applied Genetics 89, 451–458.
Molecular facilitated studies of morphological traits in an elite maize population. II. Determination of QTLs for grain yield and yield components.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2MXislOrsbs%3D&md5=abe4a7d6bdc15b17b53719ec3f048356CAS | 24177894PubMed |

Wright GC, Rao RCN, Farquar GD (1994) Water-use-efficiency and carbon isotope discrimination in peanuts under water deficit conditions. Crop Science 34, 92–97.
Water-use-efficiency and carbon isotope discrimination in peanuts under water deficit conditions.Crossref | GoogleScholarGoogle Scholar |

Xin Z, Aiken R, Burke J (2009) Genetic diversity of transpiration efficiency in sorghum. Field Crops Research 111, 74–80.
Genetic diversity of transpiration efficiency in sorghum.Crossref | GoogleScholarGoogle Scholar |

Xu W, Subudhi PK, Crasta OR, Rosenow DT, Mullet JE, Nguyen HT (2000) Molecular mapping of QTLs conferring stay green in sorghum. Genome 43, 461–469.
Molecular mapping of QTLs conferring stay green in sorghum.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXksVGgs7s%3D&md5=691460caa70692b55b133acee735b7a6CAS | 10902709PubMed |

Xu Z, Zhou G (2008) Responses of leaf stomatal density to water status and its relationship with photosynthesis in a grass. Journal of Experimental Botany 39, 3317–3325.