Indian Agricultural Research Institute, New Delhi
*Part III of Studies of Problems in Producing Hybrid Rice. Part II appeared in Indian J. Genet., 39.
In search of ideal attributes of male and female floral characteristics, that would improve cross-pollination, in all 5669 cultivated varieties, 1145 F1 hybrids and 94 forms of 9 wild allies of O. sativa were extensively screened. The study revealed a wide variation for length and breadth of anther and stigma, extent of elongation of filaments and style and the degree of protrusion of anthers and stigma. There were types with ideal floral features both among cultivated and wild species. For instance, types such as IARI 5824, IARI 5823, IARI 10536, IARI 10537, IARI 10668, IARI 11567, IARI 5821, IARI 5819, IARI 6193-G, IARI 11427, IARI 7253-A, and IARI 11226 have been found to have relatively long and broad anthers with distinct filament elongation while types like IARI 6637, IARI 7332, IARI 10979-A, IARI 10255-A, IARI 10255, IARI 10662, IARI 11143, IARI 11205, IARI 10212, IARI 10449, IARI 10574, IARI 10758 and IARI 10871 were having larger stigma and longer style with well-protruded stigma for longer periods. A numerical index, the ratio of anther size to stigma surface, has been found to be negateively related to the percentage of stigmatic exsertion. Based on the extent of usable variability available in the cultivated and closely related species for various floral characterstics, the possibilities of restructuring rice flower so as to facilitate increased cross pollination have been discussed.
