CSU Fusarium Wilt Resistance Research

Project identifies a major locus for resistance to this destructive fungal disease in the common bean.

Fusarium wilt is a fungal disease of common bean that causes plant yellowing, wilting, stunting and early maturity. These symptoms are caused mostly by inhibition of water transport in the plant due to the growth of the fungus in the water conducting vessels. This disease problem is increasing in the high plains region of the U.S. where yield losses greater than 10% have been reported (Salgado et al., 1995). This disease is difficult to control using chemical or cultural methods because the fungus produces spores that persist in soil for long periods, and can survive and increase in non-host plants without causing disease. Currently, the best method to control Fusarium wilt is through the use of resistant cultivars. Genetic resistance to this fungus has been identified in a variety of common bean germplasm.

Recently, a study was undertaken to identify regions of the common bean genome (loci) that are responsible for resistance to Fusarium wilt. This was accomplished using a technique called quantitative trait locus (QTL) analysis on individuals of a population developed from a cross between a resistant and susceptible bean cultivar. Briefly, this technique identifies statistical associations between differences in the DNA of individuals and the level of disease severity in those individuals. Using this method, a single locus was found to be responsible for nearly 70% of Fusarium wilt resistance in this population. This means that there is likely to be a major gene at this locus that confers resistance to the pathogen. This study also showed indications that additional loci with smaller effects may be involved in resistance.

This resistance locus is a good candidate for use in Marker-Assisted Selection (MAS) during variety development. Marker-assisted selection is a tool that can be used by breeders to select resistant individuals based on molecular markers. This type of screening is theoretically more efficient and reliable than disease severity assays, which are lengthy and can be greatly influenced by environmental factors. In MAS, DNA is extracted from an individual and screened using a molecular marker that targets the locus or gene of interest. Each individual can then be saved or discarded based on its actual genotype rather than on its disease phenotype. Such a marker is currently under development for the Fusarium wilt resistance locus found in this study.
This study focused predominantly on resistance to a highly virulent strain of the fungus that was isolated from a bean field in Colorado (Salgado and Schwartz, 1993). However, preliminary experiments indicate that this locus also confers resistance to strains of the pathogen from Colombia and Spain. This is especially exciting because it means that this region of the bean genome may provide horizontal resistance to many strains of the pathogen, which will greatly simplify the process of breeding Fusarium wilt resistant cultivars. In addition to MAS breeding, traditional breeding methods are also being explored to transfer this resistance locus from the resistant bean parent into desirable bean varieties.

by Amy Fall and Patrick Byrne
Graduate Student and Assistant Professor
Colorado State University

Colorado Bean Industry - Can it survive in the 21st Century?

Dry edible beans, especially pintos, have been an important crop in Colorado agriculture since production statistics were first compiled in 1909 for dry beans. At that time, 5000 acres averaged 580 lb/A with a price of $ 3.60/cwt. The industry enjoyed steady growth throughout the 20s and saw a record high in 1943 with 460000 harvested acres, with an average yield of 525 lb/A and a price of $ 5.70/cwt. Since 1970, acreage has fluctuated between 120,000 to 225,000 acres, yields have steadily increased to more than 1800 lb/A, and price has varied from $ 8.60 to $ 31.20/cwt (please see figures).

Economic Reality
Average gross income/acre has fluctuated from $ 87 in 1971 to $ 514 in 1988. The past 5-yr average is $ 325/A with declining returns noted each year from $ 405 in 1996 down to $ 298 in 1999. In 1999, northeastern Colorado irrigated pinto bean crop production estimates were $ 285 for pre-harvest operating costs (more than 35% related to irrigation expenses), with an additional $ 70/A penciled in for property and ownership costs at a total of $ 358/A. CSU Agr. Economist Dennis Kaan estimated that a pinto grower needed to yield at least 30 cwt/A @ $ 15/cwt or 25 cwt/A @ $ 18/cwt to break even. Therefore, using 1999 statistics a Colorado grower with an average yield of 18.5 cwt/A and a price of $ 15/cwt grew pinto beans at a net loss of - $ 7/A with NO return for property and other ownership costs.

Production Challenges

Our region's bean industry continues to face increasing production costs (energy, chemicals, equipment, labor) and stiff competition from other production regions such as MinDak, Canada, and even China for limited international markets for pintos and other market classes including great northern and light red kidney. These new areas have exploded in recent years and have brought literally millions of "new" production acres (mostly rainfed) into the picture as their growers also struggle to improve their economic fortunes which were based primarily upon low input crops such as wheat. The Canadian provinces (e.g., Alberta, Saskatchewan, Ontario) are committed to an aggressive program and long-term investment in the development of adapted, productive and high quality pulse crops such as dry bean, field pea, and lentils for their growers. They are focusing upon reduced inputs (fertility, pesticides, irrigation) to give their growers an economic advantage so they can net a few more dollars per acre from large acreages. This competition from Canada has the MinDak and Michigan bean industries worried, and Canadian trade and transportation advantages (e.g., provided by NAFTA) allow their industry to ship quality beans from Canada through the United States to U.S. domestic and Mexican markets at the disadvantage of U.S. and certainly the High Plains bean industries. And the Mexican government and industry have even sent experts to China to help them improve bean quality and secure future markets for export to demanding consumers in Mexico.

What is Our Future?
So, where does this leave us in Colorado and the High Plains? Based on production trends outside Colorado during the last 10 years, it is unlikely that bean prices (especially for pintos) will exceed $ 20/cwt very often. We know that we can count on increasing production costs (especially energy, equipment, labor) and expanding competition for limited export and even domestic markets, as cheap Canadian beans continue to stream into the U.S. for packaging and marketing even at the local scene. So with this bleak outlook, do we throw in the towel and watch our Colorado bean industry dwindle down to a non-functional level in the next few years? Or do we accept the challenges ahead and invest our collective energies and resources to emerge even stronger after overcoming these challenges?

• Can we improve net economic returns to our bean growers and industry by reducing inputs and costs, while maintaining acceptable yield and seed quality?
• Can we improve access to a larger share of existing or new pinto markets willing to pay for high quality beans?
• Can we pursue new bean classes with domestic and/or international market opportunities?

(a) Production Input Responses - investigate and quantify agronomic and pest management issues that respond to varying levels (low to high) or types of inputs;
(b) Varietal Improvement Responses - increase resources for ongoing breeding efforts to improve traditional varieties of pinto, great northern, light red kidney, and black for key production and marketing traits.

Challenge - Improve Access to Pinto Markets
Identify and prioritize means to market Colorado and High Plains pinto beans in domestic and international markets during the next 1 - 3 years. For example, the following issues could be addressed with private (growers, dealers and their organizations) and public (state and federal agencies involved with promotion and marketing of agricultural commodities) sector resources:

(a) Reduce Marketing Costs;
(b) Improve Cooperation Between Local Bean Industry Personnel
( c ) Enhance Market Access

Challenge - Diversify Bean Types
Identify and prioritize other bean market types that could enhance and diversify Colorado and High Plains pinto and great northern bean production in the next 3 - 10 years. For example, the following issues could be addressed with university, USDA and private sector resources, especially bean processors that are willing to diversify and enhance their receiving and handling operations:

(a) Select within current germplasm and varietal releases, and/or breed new releases of diverse market types including light red kidney, black, and other niche-market bean types (cranberry, yellow, Flor de Mayo) that are adapted to growing conditions in Colorado and the surrounding region;
(b) Conduct wide-spread testing of promising entries at experiment stations and in grower fields, emphasize early-generation production of certified seed in western regions to support commercial production of priority market types / varieties as quickly as possible;
(c ) Develop a complete production / pest management package for each new release to provide growers with the most efficient and economical strategy fine-tuned for that unique market type

Get Involved Now!
The basic problem today is a lack of bean community concern for or articulation of this problem. Action is needed today, and any further delays will signal the demise (sooner than later) of the dry bean industry in Colorado and surrounding region.

Howard F. Schwartz
Professor
Colorado State University