A Large‐Effect QTL for Grain Yield under Reproductive‐Stage Drought Stress in Upland Rice

Abstract

Genetic control of yield under reproductive‐stage drought stress was studied in a population of 436 random F3–derived lines from a cross between the upland rice (Oryza sativa L.) cultivars Vandana and Way Rarem. Screening was conducted under upland conditions at IRRI during the dry seasons of 2005 and 2006. Lines were evaluated in drought stress and nonstress trials in both years to identify QTL contributing to drought resistance. For QTL detection, a set of random lines and the highest and lowest‐yielding lines under both stress and nonstress conditions were genotyped by 126 SSR markers. A QTL (qtl12.1) with a large effect on grain yield under stress was detected on Chromosome 12 in both years. The whole population was genotyped for additional markers on Chromosome 12, allowing QTL localization to a 10.2 cM region between SSR markers RM28048 and RM511. Under stress conditions, the locus also increased harvest index, biomass yield, and plant height while reducing the number of days to flowering. Under nonstress conditions, qtl12.1 did not significantly affect any trait. The additive effect of this QTL on grain yield under stress was 172 kg ha−1 per year over the 2 yr of testing, representing 47% of the average yield under stress and explaining 51% of the genetic variance. The yield‐increasing allele was derived from the susceptible parent, Way Rarem, suggesting an epistatic effect. This is the first QTL reported in rice having a large and repeatable effect on grain yield under severe drought stress in the field.

Drought-tolerance QTLs commonly detected in two sets of reciprocal introgression lines in rice

“…However, very few QTLs are actively targeted in breeding programs because most QTLs have not been validated in different genetic backgrounds and environments (Price et al 2002b;Yue et al 2008), which may also have hampered the pace of DT breeding. Nevertheless, several major DT QTLs, such as qDTY 12.1 (Bernier et al 2007;Mishra et al 2013), qDTY 1.1 (Vikram et al 2011), qDTY 6.1 (Venuprasad et al 2012), and the QTL closely associated with the markers EM11-11 ) and RM410 (Gu et al 2012) have been identified and used for developing DT varieties via MAS. Through functional and comparative genomic studies, many stressresponsive transcription factors were recently shown to affect DT (Liu et al 2007;Lu et al 2009;Ye et al2009;Zhao et al 2010;Jeong et al 2013).…”

The effects of drought on rice cultivation in sub-Saharan Africa and its mitigation: A review

“…Bernier et al (2007) identified large-effect QTLs for grain yield under drought stress. If confirmed, these identified QTLs have to be fine mapped for use in breeding programs.…”

“…A recombinant inbred population obtained from a cross between high-yielding lowland rice IR64 and Cabacu was used to identify 10 QTLs for grain yield and component traits under reproductive-stage drought stress (Trijatmiko et al, 2014). The qDTY12.1 is the first reported large-effect QTL for grain yield under severe upland reproductivestage drought conditions and was identified in a population of 436 F3-derived lines from a cross between Vandana and Way Rarem (Bernier et al, 2007). Two other large-effect QTLs, qDTY2.1 and qDTY3.1, well known to affect grain yield under lowland reproductivestage drought, were identified in a back cross inbred line (BIL) population derived from a cross between Swarna and Apo.…”

“…African rice is one of the two independently domesticated Bernier et al (2007) rice species, with its distribution being limited to West Africa. Its genetic potential in terms of resistance to both biotic and abiotic stresses has been well documented and deployed in rice improvement (Wambugu et al, 2013).…”

Correlation among Agro-Morphological Variation and Genetic Diversity of Rice (<i>Oryza sativa </i>L.) under Drought Stress

“…Recent studies at the IRRI (International Rice Research Institute) found that there is moderate to high heritability of grain yield under drought stress [4,6,7]. Basically, the main objectives of a breeding program for drought tolerant rice are to determine standard tolerant varieties, to identify important traits, and to evaluate the tolerant levels at seedling and reproductive stages.…”