2012 Annual Report
1a.Objectives (from AD-416):
To produce, with the aid of traditional breeding approaches, a sunflower with improved tolerance or resistance (hereafter referred to as ‘resistance’) to the herbicide atrazine of the triazine herbicide family (triazine), and to determine the mode of inheritance of such resistance.
1b.Approach (from AD-416):
Kansas State University (KSU) and the USDA, Agricultural Research Service (ARS), corresponded regarding the 2005 Sunflower Status Report reference to discovery of triazine resistance in sunflower germplasm. This correspondence resulted in transfer of bulked seed of mutagen-treated HA 821, HA 382, RHA 274 and RHA 801 (Miller and Vick, 1999. Crop Sci. 39:364-367), from ARS to KSU. These seeds were produced for the purpose of gene discovery for reduced saturated fatty acid seed composition, but could also be used for other gene discovery purposes. KSU received the bulked population of fourth generation seed on April 29, 2005, and proceeded to conduct field and greenhouse screens for atrazine resistance. Following field exposure to atrazine, heads of surviving plants were bagged to ensure self pollination. Resulting seed was bulked within source population, and subjected to greenhouse trials to confirm atrazine resistance. Seed bulked within populations was subjected to field and greenhouse atrazine challenges again in 2006 and 2007, with greenhouse trials conducted at KSU in 2006 and 2007. At the suggestion of Croplan Genetics, seed collected from individual heads in 2007 were kept separate, subjected to greenhouse challenge, and planted as individual lines in 2008 and subsequent field and greenhouse trials. Under guidance of USDA-ARS, testcrosses were made with promising lines in 2008 to investigate transmissibility of the resistance trait; the resulting hybrid seed was subjected to controlled environment challenge in 2008.
The traditional breeding with chemical mutagenesis, described above, was used to produce lines derived from HA 821, HA 382, RHA 274 and RHA 801 with point mutations scattered throughout the genome. The field and greenhouse screening trials described above resulted in discovery that one or more of these point mutants provide resistance to atrazine and possibly other herbicides of the triazine family. Research is ongoing to determine the mode of resistance of each of the potential sources, and also to determine transmittance of the resistance to hybrids. After the mode of resistance is determined, purification of resistant lines and or transfer of the resistance trait to alternative lines will continue until a pure line is available for joint release by USDA-ARS and Kansas State University.
Sunflower growers in the central plains are sometimes faced with failed corn or small grain crops and would like the option to plant sunflower after the failed crop. On some of these fields, there is residue of atrazine from previous weed control efforts, which would normally kill sunflower and most broadleaf (non-grass) crops. The purpose of this work is to develop lines of sunflower with genetic resistance to atrazine and other herbicides in the triazine family, so that sunflower can be grown on atrazine treated land. This year we continued physiological trials with putative herbicide-resistant lines and their testcrosses to see if the gene action of the resistance is additive or dominant in hybrids. This is an important facet of the research in that it will tell us if we need to have the resistance genes on both the male and female sides of the hybrid, or just in one of the parents, when this trait is commercialized. Preliminary results indicate that there is good resistance in hybrids formed with RHA 373. A second year of observations will be obtained in the summer of 2012 from laboratory and greenhouse screening of hybrids and the experimental inbred lines. The results of this work will benefit the sunflower seed industry by allowing another niche market in which to sell sunflower seed, as well as provide more options to farmers/producers.