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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 x
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.
