Male Sterility

It takes a lot of work in the lab to make a difference where it counts: in productive capacity of the rice plant and ultimately in growers' pocketbooks.

One of the most useful genetic tools they've been exploring is photosensitive genetic male sterility, which would provide a short-cut in the plant breeding process. The researchers had previously discovered te gene that controls sterility in a Calrose cross at the Rice Experiment Station's winter nursery in Hawaii, but the gene literally "disappeared" in progeny grown at the Davis nursery during the summer of 1989.

Since the male sterile gene had already manifested itself in a natural cross, there still may be other combinations in which it will be transmissible. More controlled crosses are needed to determine the usefulness of this male sterile.

Tissue Culture

The second area of research is tissue culture selection fro herbicide resistance. During 1989 the researchers tested in the greenhouse three previously identified rice mutants with pre-emergent and foliar applications of the herbicide PursuitŪ. The selection with the greatest tolerance will be backcrossed into the normal .parent (M-102) to determine whether this tolerance can be genetically transmitted or enhanced.

Anther culture

Another approach with great potential to reduce the length of time needed to develop new varieties is anther culture. Essentially this labor-intensive technique entails growing rice plants in a petri dish. The resulting "instant" pure lines could shorten variety development by two to three years.

Rice plant characteristics passed along most readily in the anther culture process include callus induction, total shoot regeneration and green shoot regeneration. Three lines that may lend themselves well to the anther culture process are M-101, 78:18347 and S-201. Use of these lines will allow geneticists to work with otherwise nonregenerable materials.

An economic analysis of anther culture showed that while the technique is expensive, it offers a tremendous time savings and can be economical even at low regeneration rates. Costs decreased dramatically as regeneration rates improved.

Other studies

An analysis of 485 rice cultivars from 10 geographical regions and 31 countries resulted in the identification of a new cultivar group, genetically distinct from the two existing indica and japonica groups.