Rice is one of the most important food crops in the world. Abiotic stresses directly or indirectly affect the physiological status of rice and negatively alter its overall metabolism. Drought in rain-fed, lowland ecosystems is particularly harmful to growth and yield. As with many other food crops, drought tolerance in rice is a polygenic trait in which many genes localized in various quantitative trait loci (QTL) have additive effects on resistance to desiccation. For these reasons, breeding drought-tolerant rice is complex, time-consuming, and cost-intensive. Marker-assisted breeding (MAB) is a more efficient approach but requires comprehensive molecular linkage maps. Increased trehalose accumulation in various tissues correlates with exposure of the plant to drought. Elevated trehalose levels probably play roles in osmo-protection and the stabilization of various essential functions. Here, we document trehalose accumulation, the activity of the enzyme trehalase, and plant growth in three Mexican rice genotypes: two drought-tolerant accessions (Temporalero A95 and Sabanero A95) and one drought-sensitive variety (Morelos A98). Our data show that similar trehalose contents were found in roots of all three accessions under irrigated conditions, but that drought enhanced the synthesis of trehalose only in drought-tolerant varieties. Changes in the levels of non-structural sugars accompanied the accumulation of trehalose. Increased trehalase activities and photosynthetic capacities in drought-tolerant varieties was observed under stress conditions, which was accompanied by lower stomatal resistance and better water-holding capacity. We conclude that DNA markers built around trehalose metabolism can be used during MAB to study drought tolerance in rice and other crops.
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