Hatchery production provides some control of the broodstock but remains problematic because disease-resistant strains of this oyster have not yet been developed.

He searched the world to discover and preserve lost strains of wheat and other crops and helped breed them into stronger, more disease-resistant strains.

It was publicly released by the USDA in 1925, and was one of the first disease-resistant strains that also had a good resistance to Verticillium and Fusarium wilt.

Modern cultivars and hybrids, disease-resistant strains and dwarf species have become the norm and thus it is difficult to plant restored gardens accurately.

Mr. Johnson, the retired virologist, said the best hope lay in the search for a disease-resistant strain of rainbows to form the stock for repopulation.

Grain stress the urgency of preserving old varieties as both disease-resistant strains and ones that will thrive without high levels of pesticide or fertilizer application.

The integration of research and breeding allows faster development of new disease-resistant strains; information is more efficiently and creatively managed within an 'internal' market, especially given the advent of bio-technology.

More than 10,000 trees in five states are growing from irradiated nuts, but no disease-resistant strain has appeared so far.

Castine's streets are lined with Cape and other antique style houses, and shaded by large elms which are replaced with disease-resistant strains when they succumb.

Development of disease-resistant strains of cassava.