Geneticists Phil Miklas (left) and George
Vandemark analyze results of quantitative polymerase chain reaction assays used
to rapidly genotype bean plants for disease resistance. Click the image for
more information about it.
New Pinto Beans Resist White Mold
By Jan Suszkiw
July 24, 2006
Two pinto bean germplasm lines are now
available for breeding varieties of the crop that will resist white mold.
Caused by the fungus Sclerotinia sclerotiorum, white mold is an
endemic disease affecting pinto and other dry edible bean crops throughout the
United States. Crop losses can be minimized with fungicides, careful
irrigation, widely spaced rows and other measures. But the cornerstone defense
is to plant a disease-resistant crop, according to
Miklas, an Agricultural Research Service (ARS) plant geneticist who led in the
development of the new pinto bean lines, USPT-WM-1 and USPT-WM-2.
Under favorable conditions, the fungus mushroom stage will eject
millions of infectious spores into the air, infecting nearby bean plants or
riding the wind to wreak havoc elsewhere. Infected plants typically sport
white, cottony tufts on their stems, leaves and pods. At the crop level, severe
outbreaks can reduce yield and quality of the seed, notes Miklas, at the ARS
and Forage Crops Production Research Unit in Prosser, Wash.
The new pinto lines owe their resistance to such assaults to crosses made
between Aztec, a semiupright pinto bean, and ND88-106-4, an upright navy bean
breeding line. Miklas developed, tested and evaluated the new pintos together
with James Kelly at Michigan State University
in East Lansing, and Ken Grafton and Darrin Hauf, both with
North Dakota State University in Fargo.
Besides white mold resistance, the new pintos offer high yield. For example,
in field trials at a white-mold nursery in Michigan, USPT-WM-1 and USPT-WM-2
produced the second- and third-highest yields of 64 pinto beans tested.
However, they fell prey to race 53 of bean rust at a North Dakota site, and
were mildly susceptible to beet curly top virus.
The United States is the sixth-largest producer of dry edible beans,
generating farm sales of $451 million during 2001-03, according to the U.S.
Department of Agriculture's (USDA) Economic
Research Service. North Dakota is Americas top bean-growing state.
ARS is USDAs chief scientific