Plant Sciences Department,
NDSU, Fargo, ND
The longterm objective of the dry bean breeding program at North Dakota State University is to develop high yielding, high quality, adapted lines for production in the Northarvest region. In order to achieve this objective, we need to develop genetic variability by making controlled pollinations among selected parents. In 2000, we made about 700 unique hybridizations involving nine market classes and exotic seed types. Parental lines consist of adapted cultivars grown in the Northern Plains, breeding lines developed at NDSU, and germplasm possessing desirable traits from other breeding programs. Unadapted germplasm lines from other sources are evaluated for desirable traits and introgressed into adapted material (e.g., pre-breeding). Each year, the breeding program evaluates material from around the world as possible sources of resistance to white mold, rust, root rot, bean common mosaic virus, micronutrient deficiencies, and bacterial blights, in addition to selecting for yield, yield stability, and overall adaptation. Selection for these components allows the breeding program to develop material that will be productive across a range of Northern Plains environments with few inputs required.
The breeding scheme used in the breeding program is known as the pedigree breeding method. Because of the excellent support by the Northarvest Bean Growers Association, we are able to utilize an off-season nursery in Puerto Rico for generation advance. Once single plant selections have been made in North Dakota for easily identified traits, such as plant maturity, architecture, pod load, lack of diseases, and appropriate seed characteristics, the lines are grown in the off-season nursery. Selection of superior lines or plants continues until lines possessing desirable agronomic traits and appropriate levels of disease resistance are identified. The time required to develop and release a variety after the initial cross is made is usually 10-12 years, but can be reduced considerably if off-season nurseries are used.
Yield Tests, Breeding Nurseries, and Variety Trials
The breeding program has yield tests and/or breeding nurseries at nine locations in North Dakota and Minnesota (Erie, Hatton, Forest River, Johnstown, Casselton, Carrington, Oakes, Park Rapids, and Perham). In 2000, pinto (P) navy (N), and miscellaneous (M) bean class variety trials were grown near Erie (P, N, & M), Hatton (P, N, & M), Forest River (P & N), Crete (P & N), Perham (M), and Park Rapids (M); preliminary yield tests were grown at Erie, Hatton, Johnstown, and Perham (kidney and crans only). Approximately 1,500 variety trial plots were harvested, in spite of the fact that about 400 plots were abandoned because of severe flood damage. An additional 5,500 plots from yield trials and breeding nurseries were harvested in 2000.
Breeding nurseries were located at Erie, Hatton, Johnstown, and Perham (irrigated). Germplasm evaluation nurseries were at Erie and Perham; the Midwest Regional Performance Nursery (a four-state trial coordinated by NDSU) and the Cooperative Dry Bean Nursery (12 states and provinces, coordinated by the University of Idaho) also were at Erie. Disease nurseries were at Hatton (white mold and rust), Erie (common blight), and Perham (root rot). Breeding nurseries, yield trials, and other trials will total more than 10,000 plots planted on over 45 acres. Annual results of state-wide variety trials are published in the NDSU Extension Service Bulletin A-654 (revised).
Northarvest Greenhouse Facility
Thanks to a grant provided by the Northarvest Bean Growers Association, the bean breeding and pathology programs were able to construct a greenhouse facility that virtually doubles the assigned space to these projects. The total cost of the greenhouse project is near $55,000 with Northarvest providing approximately 50% of the funds. Now that adequate greenhouse space is available, these programs are able to evaluate thousands of lines for reaction to rust, white mold, bacterial blights, virus, and anthracnose while still maintaining a continual hybridization and seed grow-out program.
White Mold -- White mold continues to be a serious management problem for dry bean growers and is ranked as the disease of most concern to producers. The potential for improved genetic resistance as a control measure has been demonstrated. Two major mechanisms of genetic resistance to white mold exist: 1) Avoidance usually associated with improved plant architecture; and 2) Physiological associated with biochemical functions at the cellular level. Generally, greenhouse and laboratory methods screen solely for physiological resistance, whereas field plantings screen for both physiological and avoidance mechanisms. Thus, greenhouse and laboratory resistance may not correlate well to field resistance. The breeding project has relied on evaluating material in the field, and also evaluates material from other programs entered in the National White Mold Nursery. This national nursery is grown in Michigan, New York, Nebraska, Colorado, North Dakota, and Ontario, Canada. In the 1997-99 nursery, a navy line, ND 97-076-01, was one of the lines with reduced damage in North Dakota and Michigan. This line has since been released as the navy cultivar, ARTHUR. The breeding program continues to evaluate materials for resistance to white mold and is collaborating in evaluating materials from the USDA Plant Germplasm collection for reaction to white mold with the NDSU Plant Pathology Department and the University of Nebraska. Several lines showed promising levels of resistance in the greenhouse and we are currently verifying our results.
Rust -- Rust has, at times, been a severe disease problem, particularly for pinto bean producers. This fungal pathogen is composed of many races (at least 80 in the United States and over 200 worldwide) and has the capability to increase in variability, since it can complete its entire life cycle on the bean plant. Resistance usually is controlled in a single gene fashion, whereby one gene in the plant imparts resistance to one specific race of the pathogen. Often, this type of vertical resistance is short-lived, because the selection pressure placed on the rust race forces a change in the rust population. As a result, a new rust race is developed, and the former resistant variety becomes susceptible. This was observed in the pinto variety Olathe which, when first grown in North Dakota, was completely resistant, but is now susceptible to at least one component of the rust population.
The dry bean breeding program currently is involved (in cooperation with Dr. Jack Rasmussen, Plant Pathology Department, NDSU) in determining the inheritance of broad-based rust resistance genes that were found in tropical germplasm. This resistance may be the result of one gene conferring resistance to more than one race, or a tight (linked) cluster of genes. By understanding the mechanism of inheritance, we will be better able to develop an efficient breeding strategy to utilize this new source of resistance.
The breeding program has cooperated extensively with USDA-ARS and other state scientists to incorporate high levels of rust resistance into the major bean market classes. To date, this collaborative relationship has resulted in the release of 18 rust resistant pinto lines and 12 navy lines. These lines provide unique sources of resistance to both public and private bean breeders.
Root Rots -- A nursery composed of 170 entries was evaluated in a root rot infested field near Perham, MN. Lines were evaluated for root health by digging five random plants from a row and recording the amount of root damage using a rating scale of 1 = no damage to 9 = severe damage. As expected, the susceptible cultivar Montcalm had the highest average rankings, while some lines, such as FR 266, Wisc. RRR-36, Wisc. MDR 147, and G 122, continued to show little damage, in spite of severe conditions. We evaluated two tropical lines, VAX 3 and VAX 5, that possess high levels of resistance to common blight for reaction to root rot. The level of resistance was quite high and hybridizations were begun to transfer this resistance using backcross breeding. We also were able to evaluate some populations derived from these resistant sources and Montcalm, and were pleased to see that the level of resistance was good to very good. In addition to the root rot evaluation nursery, F2 populations were grown and root health was used as one of the traits as single plant selections were made.
Anthracnose -- In collaboration with Dr. Luis del Rio, Plant Pathology Dept., NDSU, we have begun evaluating breeding lines for resistance to anthracnose. This very serious disease of bean is in Manitoba and we can conclude that it is only a matter of time before it is reported in the Northarvest region. Anthracnose is most frequently spread by use of infected seed. We will evaluate material using both seedling inoculation and identify resistance genes using molecular markers associated with those genes.