- Agronomic: flax, sunflower
- Crop Production: application rate management, continuous cropping, double cropping, multiple cropping
- Education and Training: participatory research
- Natural Resources/Environment: soil stabilization
- Pest Management: genetic resistance, integrated pest management
- Production Systems: permaculture
- Soil Management: soil quality/health
This project is part of a long-term program that will bring perennial sunflower and perennial flax into agricultural systems to allow farmers to diversify their operations, improve profits, improve environmental quality, and reduce inputs of labor and supplies. In the last year and a half, we developed perennial flax breeding populations that will be evaluated in several organic and conventional field sites in Minnesota and North Dakota this year. A major breakthrough was achieved in our perennial sunflower populations, in which we retained perennial habit after back crossing with an elite annual inbred, an accomplishment never before recorded.
Perennial crops provide a combination of benefits to farmers and agriculture that cannot be conferred by annual crops. Existing perennial crops, such as alfalfa, protect against soil erosion and nutrient loss and improve water use efficiency. Fall tillage is not necessary during the multi-year lifetime of the crop stand. Cover cropping or polyculture may also be used successfully with perennials to reduce the need for summer tillage and herbicides. Perennial crops provide living ground cover for longer periods during the growing year because the plants can emerge from dormancy early in the growing season. These plants take up soil moisture, decreasing year-round tile line flow and concurrent leaching of nitrogen from the soil (Randall et al., 1997). Nitrogen from tile lines contributes to the contamination of surface waters in Minnesota and elsewhere (Randall and Iragavarapu, 1995).
Sunflower and flax have valuable seed oils that make them profitable for farmers to grow. In particular, sunflower has high-oleic and mid-oleic (also known as NuSun®) oil profiles, which are important seed oil profiles for the production of no-trans-fat vegetable oil. For the last several years, demand for NuSun® oil has exceeded supply. This demand is mostly from processed food manufacturers such as Frito Lay. Flax oil is also in demand as a health supplement, and has one of the highest concentrations of Omega-3 oils found in plants. Consumption of Omega-3 oils has been linked to improved heart health. Additionally, the black-and-white seeded (confectionary) sunflowers are grown for the production of snack-type sunflower seeds. This is a particularly high-value market.
The combination of environmental and economic benefits from perennial crops is important for producers who are looking for ways to reduce inputs and environmental harm while increasing profits. We believe that sunflower and flax are ideal candidates for perennialization because both the sunflower and flax genus contains perennial species that are similar to, or can intermate with, the crop-type species.
This project is a seminal study into the feasibility of using perennial relatives of existing annual crops to develop perennial varieties with the agronomic and seed characteristics similar to the domesticated relative. Surveys of germplasm and progeny of interspecific crosses indicate that variability exists for yield components, which will allow us to select for high yield in populations with perennial habit. Piper (1992) showed no significant correlation between vegetative vigor and yield in the perennial species Cassia marilandica in 3 out of 4 years. Thus, we expect that there will be little or no negative association between perennial habit and yield in perennial varieties.
Perennialization of domesticated sunflower was first proposed by Ščibria (1936), who noted that populations of H. tuberosus X H. annuus could be candidates for development of a perennial sunflower. While hybrid populations have been formed for disease resistance breeding in the past, no one has published specifically on the mode of inheritance of perennial habit in such populations. There has been casual mention of rhizome/tuber production in some F1 populations, while in other populations there was no production of rhizomes or tubers (Cedeno et al., 1985; Kräuter et al.,1991). The populations with noted tuber production tend to have H. tuberosus as the female, indicating that perennial habit may have at least partial cytoplasmic inheritance. Previous investigators have found that the F1 hybrid plants are tetraploid (2n=4x=68) and the BC1F1 plants are triploid (2n=3x=51) (Cedeno et al., 1985). Low fertility was found in the BC1F1 plants, which was likely due to the triploid condition of the genome. Further backcrossing gives rise to progeny with greater meiotic stability through progressive loss of chromosomes, and this has led to fertile, diploid populations after several backcrosses (Cedeno et al., 1985; Hulke and Wyse, 2008; C.C. Jan, personal communication, 2008). The development of resistance to white mold, downy mildew, and phomopsis diseases has been derived from wild perennial species in this way (Pustovoit et al., 1976; Skoric, 1985).
Breeding of perennial flax species was recently proposed by our research group and researchers at The Land Institute, Salina, KS. Many perennial relatives of flax exist that have omega-3 fatty acid profiles similar to that of annual flax (Yermanos and Beard, 1964). These species are split into two ploidy groups, 2n=2x=18 and 2n=2x=30. The latter group includes both the annual domestic flax and perennial relatives. Considerable cross-fertility has been noted between many of the 2n=18 species and between some 2n=30 species (Gill, 1987). Crossing between the two genomic groups is not likely to be possible because of the large genomic differences.
Our group initiated breeding of perennial sunflower and perennial flax prior to the start of this SARE project. The perennial sunflower breeding program was initiated in 2003 from crosses between 16 wild H. tuberosus accessions collected near Rosemount, MN, and RHA 265, a H. annuus fertility restorer line with high oil content. The resulting F1 plants were used as parents in a traditional backcross program using HA 434, an annual, high-oleic acid inbred line, as a recurrent parent. The BC1F1 plants produced very few seeds when backcrossed, resulting in a population bottleneck. None of the BC1F1 plants produced regrowth after the winter of 2005-2006, indicating that perennial habit was not retained through a backcross. New populations were formed for this SARE project to attempt to get around this problem, as described below. The perennial flax breeding program began in 2001, with observation plots of 13 perennial Linum species. Those that overwintered well were used as parents in crosses during the summer of 2004. Crosses were successful among 2n=18 perennial species, but no progeny were obtained in crosses between 2n=18 and 2n=30 species or among 2n=30 species. Because it appeared that interspecies crosses between the crop-type annual and perennial species of either group were impossible, we planned to directly improve populations of 2n=18 species in this SARE project.
Objectives of current research:
1. To produce and improve interspecific populations of sunflower to begin the process of moving the perennial habit genes from H. tuberosus into the crop-type annual genome of H. annuus.
2. To begin the process of improving the perennial species of flax (Linum spp.) for agronomic characteristics using recurrent selection.
Short term outcomes:
1. Determine the inheritance of perennial habit in annual x perennial sunflower populations while developing additional populations, as needed.
2. Develop perennial flax populations for line evaluation at multiple locations.
Intermediate term outcomes:
1. Develop perennial sunflower inbred lines.
2. Develop perennial flax open-pollinated varieties (OPVs).