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 Phil 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 Vegetable 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 research agency.