Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence

Abstract

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.

Genetic diversity among sorghum landraces and polymorphism assessment of local improved varieties for stay-green trait

“…Overall, six stay-green QTLs for postflowering drought tolerance have been identified and four (labeled as Stg1, Stg2, Stg3 and Stg4) are considered as major stay green QdTLs while two (StgA and StgB) are considered as minor QTLs. These have been consistently identified in a range of environments (Subudhi et al, 2000;Harris et al, 2007) and in different genetic backgrounds (Subudhi et al, 2000). Many studies have been conducted to assess sorghum diversity in Burkina Faso but they were focused on agro-morphological characterization (Sawadogo et al, 2014;Nebie et al, 2013;Barro-Kodombo et al, 2008) and enzymatic characterization (Zongo, 2005).…”

“…The most common source of the stay-green trait has been BTx642, formerly named B35. Several markers linked to the stay-green QTLs have been identified in B35 (Harris et al, 2007;Kassahun et al, 2009). Overall, six stay-green QTLs for postflowering drought tolerance have been identified and four (labeled as Stg1, Stg2, Stg3 and Stg4) are considered as major stay green QdTLs while two (StgA and StgB) are considered as minor QTLs.…”

Mapping QTL for stay-green and agronomic traits in wheat under diverse water regimes

“…Although chlorophyll retention behaves as a good indicator of photosynthetic capacity and senescence (Lopes and Reynolds 2012;Harris et al 2007;Verma et al 2004;Haussmann et al 2002;Borrell et al 2000a, b), both NDVI and CC were highly sensitive to water regime differences (Fig. 1), and water deficiency decreased CC and increased NDVI (Table 2).…”

“…Identification of common chromosome regions shared by NDVI and biomass and yield should be helpful in understanding the genetic basis of the relationship between these traits, and should allow breeders to utilize the trait as an indirect selection criterion for grain yield improvement. Chlorophyll content (SPAD value) was used for assessment of staygreen in sorghum, and four stay-green QTL were identified (Harris et al 2007). It was reported that individual alleles for stay-green enhanced grain yield in sorghum under drought by modifying canopy development and water uptake patterns (Borrell et al 2014).…”

Stay-green expression in early generation sorghum [Sorghum bicolor (L.) Moench] QTL introgression lines

“…The trait is likely to be more easily manipulated using a marker-assisted breeding approach, using as selection criteria speciWc alleles at molecular loci linked to genomic regions contributing to the stay-green trait (i.e., quantitative trait loci = QTLs), identiWed in carefully managed, replicated, multi-environment tests. The work of diVerent groups has led to a better understanding of the inheritance of stay-green (Walulu et al 1994;van Oosterom et al 1996;Tuinstra et al 1997), to the mapping of QTLs associated with postXowering drought tolerance in sorghum (Tuinstra et al 1996(Tuinstra et al , 1998Crasta et al 1999;Tao et al 2000;Xu et al 2000b;Subudhi et al 2000;Kebede et al 2001;Sanchez et al 2002;Haussmann et al 2002) and identiWcation of markers linked to these QTLs (Hash et al 2003;Harris et al 2007).…”