Investigation of the physiological, biochemical and molecular responses of rice (Oryza sativa L.) to drought stress

Olaoye, O.A.

Investigation of the physiological, biochemical and molecular responses of rice (Oryza sativa L.) to drought stress

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Descripción

Rice is an important staple food crop for over half of the world's population, including Nigeria. Globally, climate change has been predicted to influence the magnitude of hydrological fluctuations, reportedly leading to an increase in drought intensity which is the major abiotic constraint to rice production. This study aimed to investigate the physiological, biochemical, and molecular responses of rice to drought stress with a view to developing an improved variety. Two mapping populations comprising 930 and 740 lines were derived by crossing a drought tolerant variety with low yield (TOG7400) as donor with susceptible and high yield (FARO44 and FARO57) as recipients, respectively. The populations were screened using randomized complete block design (RCBD) for all field experiments under drought and irrigated conditions. The progeny with the highest yield from each population was selected for physiological and biochemical evaluation using pot experiment. They were grouped into a well irrigated control and drought conditions which include mild (10-days water deficit (WD) and severe (15-days WD). Physiological traits such as days-to-flowering (FD), plant height (PH), tiller number (TN), panicle number (PN) and grain yield (GY), among others were recorded. Also, biochemical parameters for phytoprotectants (peroxidase (POX), catalase (CAT) and proline) and oxidative stress markers (malondialdehyde (MDA), and hydrogen peroxide (H2O2)) were determined. The populations were genotyped-by-sequencing using ultra high-throughput diversity array technology single nucleotide polymorphism (DArT-SNP) markers. Subsequently, linkage map was constructed by Kosambi function, and quantitative trait loci (QTL) were detected across the genome by inclusive composite interval mapping. QTL regions with phenotypic variance explained (PVE>5%) were scanned in-silico to identify putative and candidate genes in the rice genome annotation project database. The results show a strong direct correlation between PN and TN in drought and control populations (r = 0.99, 0.57), GY in the drought populations was directly correlated with TN and PN (r = 0.19; p<0.001). The biochemical evaluation revealed a higher accumulation of phytoprotectants (proline, CAT and POX) in the progenies and TOG7400 than the susceptible parents. However, the susceptible parents have a higher level of oxidative stress markers (MDA and H2O2). Some of the physiological traits such as FD, PH, TN, PN, among others observed for the pot experiment were statistically (p<0.05) significant in at least one level of observation (genotype, drought, and genotype-drought). In addition, the linkage mapping revealed 264 and 446 significant DArT-SNP markers across the genome in both populations. A total of five QTL regions with PVE > 5% detected across populations revealed important genes that have been established to confer tolerance to plants under stress. This study revealed that the cultivars and QTL regions detected are potential targets for improvement programs and marker-assisted selection/breeding of rice.