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The study assessed the variations in morphologically, physiologically and anatomically distinct traits of wild rice species in Sri Lanka; O. nivara, O. rufipogon, O. eichingeri, O. rhizomatis and O. granulata, which could be useful in rice breeding. The wild rice species were grown in a common garden, and the morphological traits were measured soon after heading. The results showed qualitative parameters such as the panicle type, awning, stigma colour, lemma and palea pubescence, seed coat colour, blade pubescence and ligule shape, are distinctive among the five species and are promising characters in their field identification. ANOVA revealed that the quantitative traits, such as flag leaf length, flag leaf width, culm length, culm diameter, panicle length, 100 grain weight and plant height are useful for further confirmation of species. The highest net photosynthetic rate (5.86 µmol m-2 s-1), high cluster width of the base (61.4 µm), and trichome density (184.33 per 25 mm² area) were observed in O. rufipogon compared to the rest, and such desirable traits are effective in rice breeding. Moreover, transpiration rates, stomatal conductance and substomatal CO2 concentration are ideal physiological traits to be considered in super rice breeding. Significant correlations were observed between transpiration and photosynthesis processes. Thus, our study provides a clear picture on habitat preferences, life cycle, distinctive morphologies and diverse functional traits to be effectively used in field identification and future utilisation of wild relatives of rice in the plant breeding programmes. [ABSTRACT FROM AUTHOR]