Molecular mapping of QTLs conferring stay-green in grain sorghum (<i>Sorghum bicolor</i> L. Moench)

Abstract

Drought resistance is of enormous importance in crop production. The identification of genetic factors involved in plant response to drought stress provides a strong foundation for improving drought tolerance. Stay-green is a drought resistance trait in sorghum (Sorghum bicolor L. Moench) that gives plants resistance to premature senescence under severe soil moisture stress during the post-flowering stage. The objective of this study was to map quantitative trait loci (QTLs) that control the stay-green and chlorophyll content in sorghum. By using a restriction fragment length polymorphism (RFLP) map, developed from a recombinant inbred line (RIL) population, we identified four stay-green QTLs, located on three linkage groups. The QTLs (Stg1 and Stg2) are on linkage group A, with the other two, Stg3 and Stg4, on linkage groups D and J, respectively. Two stay-green QTLs, Stg1 and Stg2, explaining 13-20% and 20-30% of the phenotypic variability, respectively, were consistently identified in all trials at different locations in two years. Three QTLs for chlorophyll content (Chl1, Chl2, and Chl3), explaining 25-30% of the phenotypic variability were also identified under post-flowering drought stress. All coincided with the three stay-green QTL regions (Stg1, Stg2, and Stg3) accounting for 46% of the phenotypic variation. The Stg1 and Stg2 regions also contain the genes for key photosynthetic enzymes, heat shock proteins, and an abscisic acid (ABA) responsive gene. Such spatial arrangement shows that linkage group A is important for drought- and heat-stress tolerance and yield production in sorghum. High-resolution mapping and cloning of the consistent stay-green QTLs may help to develop drought-resistant hybrids and to understand the mechanism of drought-induced senescence in plants.

Productivity of a doubled haploid winter wheat population under heat stress

“…The changes in chlorophyll content observed in the lines of the population after heat stress, and the frequency distribution of these changes, suggested that one or a small number of dominant major genes could be responsible for the development of the stay-green trait. As reported [23] that stay-green was associated with post-anthesis drought resistance, giving plants resistance to premature senescence at various levels of soil moisture stress. Stay-green plants produce higher, stable yields with a high chlorophyll content [24].…”

“…Three QTLs were found to affect the chlorophyll content under post-anthesis drought stress, the intervals of which completely overlapped the stay-green QTL intervals [23]. The leaf chlorophyll content exhibited a significant correlation with the stay-green rating, suggesting that the measurement of chlorophyll content using a chlorophyll meter and the manifestation of the staygreen trait could be useful in screening for drought and heat tolerance in wheat [2,23,25,26]. In the present work, the significant differences in the chlorophyll content of the flag-leaves confirmed the fact that some lines were more tolerant than others.…”

“…The relative water content in the leaves of stay-green lines is much higher than that of non-staygreen lines, indicating that a better stalk transportation system functions under stress conditions. Three QTLs were found to affect the chlorophyll content under post-anthesis drought stress, the intervals of which completely overlapped the stay-green QTL intervals [23]. The leaf chlorophyll content exhibited a significant correlation with the stay-green rating, suggesting that the measurement of chlorophyll content using a chlorophyll meter and the manifestation of the staygreen trait could be useful in screening for drought and heat tolerance in wheat [2,23,25,26].…”

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

“…It has a low grain yield under the conditions of this experiment, due to its short plant height, small panicle size, and low grain number. A number of stay-green QTLs have been identiWed by diVerent research groups based on RIL populations derived from crosses involving this line or its derivatives (Tuinstra et al 1996;Crasta et al 1999;Xu et al 2000b;Subudhi et al 2000;Sanchez et al 2002). The recurrent parent, R 16, is a released, high yielding but very senescent, post-rainy (rabi) season variety.…”

“…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).…”