WASHINGTON (AP) _ Agriculture Department scientists are working to create bean strains that resist rust and bean common mosaic virus _ an achievement that has so far proved elusive.

Currently, there are snap and dry bean cultivars that resist types of the leaf diseases, but they are still vulnerable to some strains of bean rust fungus or BCMV.

However, USDA's Agricultural Research magazine says researchers 2,000 miles apart in Maryland and Washington state may be nearing a line of beans that will fight off all of its leaf-destroying foes.

``We hope to have some resistant navy bean lines ready for release within the near future,'' said plant pathologist J. Rennie Stavely, who heads the cooperative bean improvement program in Beltsville, Md.

Both the rust and bean virus have been known to reduce crop yields by nearly one-third and, in extreme cases, wipe out an entire field of non-resistant beans.

Farmers for years have relied on a combination of fungicides and limited-resistance bean strains.

But Stavely's group has created 75 germ plasm lines of snap and dry beans that are resistant to all 65 known strains of rust.

Building on that achievement, Stavely and plant pathologist Matt Silbernagel edged toward the additional resistance to BCMV last year by developing a technique that simultaneously screens individual bean plants for susceptibility to both rust and BCMV.

The added resistance to BCMV is becoming particularly important with the appearance of a new strain in Idaho, the largest exporter of bean seeds.

This latest incarnation of the disease appears to have been imported from Africa about five years ago, and researchers fear it could spread to other states, including North Dakota, Michigan, Nebraska and Colorado.

Unlike other strains, the African version uses the very gene that provides resistance to BCMV _ the I gene _ against the bean plant to trigger a deadly response called black root.

Stavely and Silbernagel are trying to fight the African strain of BCMV by screening for plants that combine the I gene with two other genes that keep the virus at bay.

``Now our technique offers a way to screen bean populations for these gene combinations during early stages of plant development,'' Stavely said.

Their technique involves inoculating individual bean plants with the eight key races of rust fungus and two key strains of bean virus.

After determining resistance, the beans are crossed with other lines and eventually planted for field tests.