Field Evaluations of Four Dry Bean Populations for White Mold Resistance
April 18, 2005
Jack Rasmussen , Professor of Plant Pathology, NDSU
Ken Grafton, Professor, Department of Plant Sciences
Dean, College of Agriculture
Director, North Dakota Agricultural Experiment Stations, NDSU
Bob Henson, Assistant Agronomist
Carrington, N.D., Research and Extension Center, NDSU
Identify white mold resistance in four new dry bean populations.
Benefits to North Dakota and Minnesota dry bean producers
White mold is a persistent and economically damaging disease of dry beans in the Northarvest production area. Disease susceptibility is common in accepted cultivars, so the potential for serious economic damage in the future is high. Genetic resistance is the most efficient way to control any disease. The objective of this research is to identify new sources of genetic resistance to white mold in dry bean and to move that resistance into germplasm adapted to the Northarvest region that can be used by the breeding program for future cultivar development.
This project was initiated with greenhouse experiments that identified dry bean lines from Mexico, Central America and South America with potentially new and useable white mold resistance. These dry bean lines, collected, maintained, and obtained from the USDA, are genetically different from our varieties. Collectively, they may contain valuable sources of genetic resistance for the Northarvest production area. Included in this genetic variability may be new sources of resistance to white mold. Four of the best lines identified from these screens were crossed with Othello, a disease-susceptible Pinto bean cultivar adapted to this region.
White mold is a persistent and economically damaging disease of dry beans in the Northarvest production area.
A population of approximately 100 to 125 lines was developed in the greenhouse from each of the four lines by crossing them to Othello pinto bean. Each population was advanced to the F6 generation. F6 lines are genetically stable, like a cultivar. This stability will permit the increase of large amounts of seed of each population that can be used in multiple replicated tests in the field and greenhouse as we screen the populations for resistance to white mold. Also, since they are genetically stable, F6 lines that show promise for white mold resistance can be expected to contribute genetic resistance to the breeding program in a predictable fashion.
To our surprise, CNC/Othello progeny exhibited a high level of white mold resistance in addition to rust resistance.
Each line from each cross (nearly 500 lines in total) were evaluated in the greenhouse for white mold resistance. Last summer, the best 20 to 30 lines from each population, as determined by the greenhouse tests, were evaluated in the field for reaction to white mold. The field trials were performed at Carrington, ND in inoculated plots that were misted. Disease pressure was extremely high in these plots.
A fifth population was evaluated for resistance to white mold in the greenhouse. This population had the dry bean line CNC as a parent. CNC, a black bean from Central America, was originally of interest to us because it is resistant to all North American races of bean rust. We had previously crossed CNC to the Othello (because it is also rust susceptible) and developed the progeny into 100 F6 lines to analyze rust resistance in CNC.
Several lines developed from the crossing South American lines with Othello showed good levels of resistance in replicated plots and may be of value for breeding purposes. Additional experiments are needed to confirm this.
To our surprise, CNC/Othello progeny exhibited a high level of white mold resistance in addition to rust resistance. This resistance segregated in the population, as determined by greenhouse tests. We are now in the process of identifying individual lines from the CNC/Othello population that may have novel white mold resistance and novel rust resistance for the breeding program.