Water stress is a serious challenge to rice production. Understanding water stress tolerance is essential for precise trait modification. We identified an EMS induced mutant showing enhanced tolerance to water deficit stress at the vegetative stage. Multiple alterations in physiological behaviour, root morphological and anatomical structure, stomatal response and gene expression in various signalling pathways were found to be responsible for increased tolerance in the mutant. The mutant will be useful for dissecting the water stress tolerance mechanism in rice.

Dwarf plant height and tillering ability are two of the most important agronomic traits that determine the plant architecture, and have profound influence on grain yield in rice. To understand the molecular mechanism controlling these two traits, an EMS-induced recessive dwarf and increased tillering1 (dit1) mutant was characterized. The mutant showed proportionate reduction in each internode as compared to wild type revealing that it belonged to the category of dn-type of dwarf mutants. Besides, exogenous application of GA3 and 24-epibrassinolide, did not have any effect on the phenotype of the mutant. The gene was mapped on the long arm of chromosome 4, identified through positional candidate approach and verified by cosegregation analysis. It was found to encode carotenoid cleavage dioxygenase7 (CCD7) and identified as an allele of htd1. The mutant carried substitution of two nucleotides CC to AA in the sixth exon of the gene that resulted in substitution of serine by a stop codon in the mutant, and thus formation of a truncated protein, unlike amino acid substitution event in htd1. The new allele will facilitate further functional characterization of this gene, which may lead to unfolding of newer signalling pathways involving plant development and architecture.

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