Indian Agricultural Research Institute, New Delhi, 110 012, India
*Part IV on “Problems in producing rice hybrids” Part III appeared in Indian J. Genet: 39.
Based on screening of a large collection of varieties (5669), F1 hybrids (1145) and allied wild species (7), three sets of material were chosen to study their relative performance in respect of the expression of their floral characteristics under four different locations and seasons. The material included one set of 12 cultures with large male organs, a set of 13 cultures with large female organs and a set of 25 cultures with large female organs but decreased male organs.
The study revealed a negative relationship between the size of male and female organs. Using the ratio of anther size to stigma surface (male incompatibility index) the probable sources of cytoplasmic male sterility restorer systems have been inferred. Cultures IARI 5824, IARI 5823, IARI 10536, IARI 10537 and IARI 10668 had 70% larger anther size than population mean and they may be of use in developing ideal B and R lines. Similarly cultures IARI 10449, IARI 10255A, IARI 7332, IARI 10754, IARI 10255 and IARI 10212 were found to have the largest stigmatic surface among the lines studied. Besides their usefulness as donors of ideal female organs, the likelihood of their having male sterility factors has been indicated.
The study, in general, has brought out that all the ideal component features for enhanced cross pollination such as large anther size, well-protruded and voluminous stigma and desired level of male incompatibility index exist among cultivars and hence there is hardly any need to resort to wild species for such attributes.
