Breeding Sorghum for Resistance to Grass Targeting Herbicides.

Abstract Competition by grass weeds is one of the greatest challenges of sorghum production under mechanized agriculture. A recent national survey of sorghum growers ranked weed infestation as the major problem undermining sorghum production in the United States. The problem is exacerbated by the lack of effective post emergence weed management option. Cognizant of this, the weed science and sorghum breeding programs at Kansas State University initiated new effort to develop sorghum parent lines and germplasm that are resistant to Acetolactate synthase (ALS) and Acetyl Co-enzyme-A Carboxylase (ACCase) inhibitor herbicides. The new approach offers a rare post emergence grass weed control option for sorghum and is expected to reduce losses incurred to grass weed competition. Resistance sources to both herbicide families were identified among local and exotic wild sorghum populations. Segregation analysis indicated that the resistance to both herbicide families is conditioned by single co-dominant gene with two or more modifier genes affecting resistance expression to the ALS. Efforts in the past few years identified series of sorghum germplasm sources with homozygous resistance to both ALS and ACCase inhibitor herbicides and additional materials in to which both traits are incorporated. Performance of hybrids between public seed parent lines and the initial ALS and ACCase resistance R-line selections gave yields that are 90 to 115% of standard hybrid checks.