Sawhney: Regulation of Male Sterility in Canola for Use in Hybrid Seed Production

Date: June 2011
Term: 8 years
Status: Completed
Researcher(s): Dr. Vipen Sawhney, Department of Biology, University of Saskatchewan
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a

Project Summary

Researchers at the University of Saskatchewan initiated a study in 2000 to develop a non-transgenic, GMS system in canola (Brassica napus) using chemicals to restore fertility. Using a previously isolated line (3-8) in canola, various lines were developed and selected for further breeding during the trials from 2000 to 2008. However, because of the variability of sterility expression in field conditions, researchers were unable to recommend this system for large-scale hybrid seed production in canola.

The development of hybrid canola varieties is important, because they exhibit hybrid vigor and are produced for desirable traits, such as early flowering, disease and abiotic stress resistance, and increases in crop yield. In many crops, hybrids are produced by hand crossing selected lines, which is labour-intensive and significantly increases the costs of hybrid seed production. Hybrids produced by this method are also not guaranteed with 100% hybridity.

Alternative plant breeding methods include the use of male sterile systems and fertility restorer lines. The male sterile hybrids can be obtained from natural or genic (GMS) sources, or cytoplasmic (CMS) sources, by using chemicals to induce male sterility, or by genetic engineering of crops to induce male sterility. Each of these approaches has merit as well as limitations.

Researchers at the University of Saskatchewan initiated a study in 2000 to develop a non-transgenic, GMS system in canola (Brassica napus) and to use chemicals to restore fertility. Researchers had isolated a line (3-8) in canola that was responsive to some plant growth substances (PGSs) for fertility restoration in greenhouse conditions, but there was no information on the performance of the line in field conditions as well as its expression in subsequent generations.

The objectives of the project were to: 1. develop a GMS system using line 3-8 in canola in which fertility can be restored by PGSs and, 2. to generate 100% pure male-sterile (ms) seed for crossing with other elite lines to produce F1 hybrids. Researchers also wanted to test the female fertility of the GMS line in terms of seed and pod development; to determine the performance of the GMS line 3-8 in field conditions in terms of fertility/sterility expression and to examine pollen development and germination; and to analyze the male sterility expression in the GMS line in subsequent generations from the pure ms seed produced by the PGS treatment in greenhouse and field conditions.

The first field trials were conducted in the summer of 2000 and continued through 2008. Various lines were developed and selected for further breeding during the trials. In 2007 and 2008, one line that showed the least variability in the phenotype and the best response for fertility restoration was selected for further field trials. However, the next generation showed variability in phenotype characteristics and the expression of male sterility was not stable in all plants.

Therefore, researchers were unable to identify a GMS line in canola that is stable under field conditions, i.e., which would show 100% male sterility. Because of the variability of phenotype expression, researchers were unable to recommend this system for large-scale hybrid seed production in canola. Researchers hope that future research focusing on plants with a selected phenotype may lead to isolation of a line that is stable in field conditions.

Figure 1. and Figure 2. Canola male-sterile flowers and plant. Source: V. Sawhney.

Full Report PDF: Regulation of Male Sterility in Canola for Use in Hybrid Seed Production