Abstract
Rice provides about half of the calories consumed in Asian countries, but its productivity is often reduced by drought, especially when grown under rain-fed conditions. Cultivars with increased drought tolerance have been bred over centuries. Slow selection for drought tolerance on the basis of phenotypic traits may be accelerated by using molecular markers identified through expression and metabolic profiling. Previously, we identified 46 candidate genes with significant genotype × environment interaction in an expression profiling study on four cultivars with contrasting drought tolerance. These potential markers and in addition GC-MS quantified metabolites were tested in 21 cultivars from both indica and japonica background that varied in drought tolerance. Leaf blades were sampled from this population of cultivars grown under control or long-term drought condition and subjected to expression analysis by qRT-PCR and metabolite profiling. Under drought stress, metabolite levels correlated mainly negatively with performance parameters, but eight metabolites correlated positively. For 28 genes, a significant correlation between expression level and performance under drought was confirmed. Negative correlations were predominant. Among those with significant positive correlation was the gene coding for a cytosolic fructose-1,6-bisphosphatase. This enzyme catalyzes a highly regulated step in C-metabolism. The metabolic and transcript marker candidates for drought tolerance were identified in a highly diverse population of cultivars. Thus, these markers may be used to select for tolerance in a wide range of rice germplasms.
Highlights
Rice (Oryza sativa L.) is one of the world’s most important staple foods with 720 million tons harvested in 2011
In a previous microarray study, we have identified genes that were differentially expressed in four rice genotypes of contrasting drought tolerance [36] and could be marker candidates for drought tolerance
Drought tolerance has been assessed in field trials to measure either final yield or physiological parameters that are predictive for yield under stress
Summary
Rice (Oryza sativa L.) is one of the world’s most important staple foods with 720 million tons harvested in 2011 (www.fao.org 24.07.2012). In Asia, its main cultivation area, rice provides 35– 60% of the calories consumed [1]. Centuries of breeding yielded a wide range of cultivars adapted to different watering regimes from irrigated, deep-water cultures to rain-fed lowland and upland cultivars [3]. About 50% of the rice acreage is rain-fed and not irrigated [4]. In these areas, drought is the major environmental factor that reduces productivity by 13–35% [5,6]. Drought stress causes yield loss in rice, but in many other crops like potato, wheat and maize. More food will have to be produced with less water to provide for the increasing world population [7]
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