Abstract
A glasshouse experiment was conducted to compare the performance of a stay-green QTL introgression line (RSG 03123) and its parental lines (B35, a stay-green and R16, a high yielding cultivar with rapid senescence) after flowering, when water-limited (WL) or well-watered (WW). Flowering time and plant height were similar in RSG 03123 and the recurrent parent, R16. Under WW conditions, retention of green leaf area (GLA) and chlorophyll was similar in RSG 03123 and R16, whereas under WL conditions RSG 03123 retained significantly (P<0.05) more GLA. The rate of senescence was also lower in RSG 03123 as compared to R16 under WL conditions. B35 displayed a delayed onset of senescence under both WW and WL conditions while both R16 and RSG 01323 displayed an earlier onset of senescence under WL conditions. Photochemical efficiency of photosystem II (ΦPSII), gas exchange characteristics, and total soluble carbohydrates contents, in both leaf and stem, were higher in RSG 03123 than in R16 under WL conditions. These parameters were enhanced in RSG 03123 due to higher retention of chloroplast proteins, such as light-harvesting chlorophyll binding protein complex of PSII (LHCPII), oxygen-evolving complex 33 kDa (OEC33), phosphoenolpyruvate carboxylase (PEPC) and the large subunit of ribulose bisphosphate carboxylase-oxygenase (Rubisco). The stay-green characteristics of RSG 03123 were intermediate between R16 and B35; nonetheless, the results show that stay-green QTL are functional during senescence and improve tolerance to water limitation after flowering. Key words: Stay-green QTL, introgression, drought, photosynthesis.
Highlights
Feeding the increasing population is a challenge to all nations (Foley et al, 2011), especially those in the drought-prone agro-ecological regions
Compared to B35, both RSG 03123 and R16 were significantly (P
We have proved that the introgression of the 3 putative SG QTL (Stg1, Stg3 and Stg4) from B35 into the senescent R16 background (RSG 03123) resulted in enhanced retention of green leaf area (GLA), chlorophyll and chloroplast enzymes
Summary
Feeding the increasing population is a challenge to all nations (Foley et al, 2011), especially those in the drought-prone agro-ecological regions. Stay-green (SG) genotypes, on the other hand, do not display this drought-induced senescence and retain their green leaves longer resulting in improved grain yield under stress (Rosenow, 1994; Duvick et al, 2004; Jagadish et al, 2015; Badigannavar et al, 2018). Stay-green genotypes are either functional or cosmetic (Thomas and Howarth, 2000). Functional stay-green genotypes possess an increased duration of both green leaf area and of photosynthesis, whereas cosmetic stay-greens remain green due to defective chlorophyll breakdown but photosynthetic competence is lost (Thomas and Howarth, 2000)
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