Evaluation of Salinity Tolerance of Canola Germination

Abstract

Canola (Brassica napus L., B. rapa L., Brassicaceae) is a genetically altered form of rapeseed with low erucic acid, a 22-carbon chain fatty acid that is used in a variety of polymer and lubricant products. Interest in canola is increasing steadily among health-conscious consumers due to its lowest content of saturated fatty acids (<70 g/kg) among major oil seeds. Domestic production of canola would reduce the import costs, enhance the productivity of American farms, and diversify agriculture (Starner et al. 1995). Canola oil is now the third largest source of edible oil following soybean and palm oil (Nowlin 1991). This increased demand, and the need for crop diversification, will undoubtedly promote increased acreage of canola in the western US, where some soils are prone to become saline (Francois 1994). Sims et al. (1993) reported that canola yields in Montana increased greatly with increased availability of water under normal conditions with lowered mean oil content. The average yield of 2.2 to 2.7 t/ha with oil content of 32% to 49% has been reported in Virginia during 1992 to 1995 (Virginia Agricultural Statistics 1995). The traditional approach to the cropping of arid lands has been to use conventional cultivars and modify the soil and water to meet the needs of the crop, or to make genetic selections from established cultivars for improved performance under arid conditions. Saline soils and saline irrigation waters present potential hazards to canola production. Germination is one of the most critical periods for a crop subjected to salinity. Germination failures on saline soils are often the results of high salt concentrations in the seed planting zone because of upward movement of soil solution and subsequent evaporation at the soil surface (Bernstein 1974). These salts interfere with seed germination and crop establishment (Fowler 1991). In an effort to develop the low erucic acid cultivars, the plant breeders are at the same time attempting to look for seedlings, which are tolerant to salinity. The two species of canola B. napus and B. campestris are classified as tolerant to salinity as per Maas and Hoffman (1977) salt tolerance classification table. Maas (1990) reported that even though both the species exhibit high salinity thresholds, the rate of yield decline above the thresholds was much greater than most other crops in the tolerant category. Shafii et al. (1992) reported that winter canola cultivars grown Pacific northwest had significantly higher oil content than the same ones grown in the Southeastern US. The tolerance of canola to salinity during germination however has not been reported. The objective of this study was to evaluate the germination response of canola to a wide range of cultivars, salinity levels, temperatures, and to determine their interactions.