Anuj Chiluwal1, Ramasamy Perumal2, Hari P Poudel3, Kebede Muleta1, Troy Ostmeyer1, Lauren Fedenia4, Meghnath Pokharel1, Scott R Bean5, David Sebela1, Raju Bheemanahalli1,6, Halilou Oumarou1, Patricia Klein4, William L Rooney7, S V Krishna Jagadish8. 1. Department of Agronomy, Kansas State University, 2004 Throckmorton Plant Sciences Center, 1712 Claflin Road, Manhattan, KS, 66506-5501, USA. 2. Agricultural Research Center, Kansas State University, Hays, KS, 67601, USA. 3. Agriculture and Agri-Food Canada, 5403 First Ave. South, Lethbridge, AB, T1J 4B1, Canada. 4. Department of Horticultural Sciences, Texas A&M University, College Station, TX, 77843, USA. 5. Grain Quality and Structure Research Unit, CGAHR, USDA-ARS, 1515 College Avenue, Manhattan, KS, 66502, USA. 6. Department of Plant and Soil Sciences, Mississippi State University, Mississippi State, MS, 39762, USA. 7. Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, 77843, USA. 8. Department of Agronomy, Kansas State University, 2004 Throckmorton Plant Sciences Center, 1712 Claflin Road, Manhattan, KS, 66506-5501, USA. kjagadish@ksu.edu.
Abstract
MAIN CONCLUSION: QTL hotspots identified for selected source-sink-related traits provide the opportunity for pyramiding favorable alleles for improving sorghum productivity under diverse environments. A sorghum bi-parental mapping population was evaluated under six different environments at Hays and Manhattan, Kansas, USA, in 2016 and 2017, to identify genomic regions controlling source-sink relationships. The population consisted of 210 recombinant inbred lines developed from US elite post-flowering drought susceptible (RTx430) and a known post-flowering drought tolerant cultivar (SC35). Selected physiological traits related to source (effective quantum yield of photosystem II and chlorophyll index), sink (grain yield per panicle) and panicle neck diameter were recorded during grain filling. The results showed strong phenotypic and genotypic association between panicle neck diameter and grain yield per panicle during mid-grain filling and at maturity. Multiple QTL model revealed 5-12 including 2-5 major QTL for each trait. Among them 3, 7 and 8 QTL for quantum yield, panicle neck diameter and chlorophyll index, respectively, have not been identified previously in sorghum. Phenotypic variation explained by QTL identified across target traits ranged between 5.5 and 25.4%. Panicle neck diameter and grain yield per panicle were positively associated, indicating the possibility of targeting common co-localized QTL to improve both traits simultaneously through marker-assisted selection. Three major QTL hotspots, controlling multiple traits were identified on chromosome 1 (52.23-61.18 Mb), 2 (2.52-11.43 Mb) and 3 (1.32-3.95 Mb). The identified genomic regions and underlying candidate genes can be utilized in pyramiding favorable alleles for improving source-sink relationships in sorghum under diverse environments.
MAIN CONCLUSION: QTL hotspots identified for selected source-sink-related traits provide the opportunity for pyramiding favorable alleles for improving sorghum productivity under diverse environments. A sorghum bi-parental mapping population was evaluated under six different environments at Hays and Manhattan, Kansas, USA, in 2016 and 2017, to identify genomic regions controlling source-sink relationships. The population consisted of 210 recombinant inbred lines developed from US elite post-flowering drought susceptible (RTx430) and a known post-flowering drought tolerant cultivar (SC35). Selected physiological traits related to source (effective quantum yield of photosystem II and chlorophyll index), sink (grain yield per panicle) and panicle neck diameter were recorded during grain filling. The results showed strong phenotypic and genotypic association between panicle neck diameter and grain yield per panicle during mid-grain filling and at maturity. Multiple QTL model revealed 5-12 including 2-5 major QTL for each trait. Among them 3, 7 and 8 QTL for quantum yield, panicle neck diameter and chlorophyll index, respectively, have not been identified previously in sorghum. Phenotypic variation explained by QTL identified across target traits ranged between 5.5 and 25.4%. Panicle neck diameter and grain yield per panicle were positively associated, indicating the possibility of targeting common co-localized QTL to improve both traits simultaneously through marker-assisted selection. Three major QTL hotspots, controlling multiple traits were identified on chromosome 1 (52.23-61.18 Mb), 2 (2.52-11.43 Mb) and 3 (1.32-3.95 Mb). The identified genomic regions and underlying candidate genes can be utilized in pyramiding favorable alleles for improving source-sink relationships in sorghum under diverse environments.
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