Field Evaluations of Four Dry Bean Populations for White Mold Resistance
April 06, 2006
Progress report for the research project entitled Field Evaluations of Four Dry Bean Populations For White Mold Resistance funded by a Northarvest grant to Jack Rasmussen, Dept. of Plant Pathology, Ken Grafton, Dept. of Plant Sciences, and Bob Henson, Carrington (ND) Research and Extension Center, North Dakota State University.
Report prepared and submitted by Jack Rasmussen
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.
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, so are highly desirable for experimental purposes. This stability permits the increase of large amounts of seed of each population that can be used in multiple, replicated experiments in the field and greenhouse. 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.
Each line from each cross (nearly 500 lines in total) were previously 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 replicated field plots for reaction to white mold. The field trials were performed at Carrington, ND. Plants were inoculated at flowering, then were misted to ensure high disease pressure. In all, 125 lines were tested, including 10 controls. Othello, the susceptible check, was killed by white mold throughout the plot. However, several lines showed good levels of resistance in replicated plots and may be of value for breeding purposes.
Carrington Research Plot
White Mold in Field