A survey of the World Genetic Stock of rice and the collection from Jeypore tract in Orissa State shows that (i) the percentage of awned varieties under cultivation is as low as 4.3 and (ii) the mutation for awnless condition is likely to have occurred very early in the evolutionary history of rice.
Awning appears to be mostly associated with hardiness, drought resistance, salt resistance, non-lodging habit etc. The predominance of tipped types in the cultivated rices is taken to indicate that, in these types, a physiological balance has been reached between general hardiness and the other advantages associated with awning on the one hand and certain desirable characters possessed by the awnless types on the other.
It is suggested that awning is governed by the action of major gene or genes and a polygenic system, thus explaining the continuous variation so commonly observed in any population segregating for awning.
