Genetic characterization of glufosinate-ammonium tolerant summer rape lines

Weed control is an important factor for the successful production of canola [Brassica napus (L.) and B. rape (L.)] on the Canadian prairies. Traditionally, various pre- and post-emergent herbicides have been used to achieve the required level of weed control. Recently, B. napus has been genetically engineered to express tolerance to the broad-spectrum, post-emergent herbicide, glufosinate-ammonium [2-amino-4-(hydroxymethylphosphinyl)butanoic acid]. This study was conducted to determine the genetics of glufosinate-ammonium tolerance in a series of Agrobacterium-mediated transgenic lines of B. napus carrying the phosphinothricin-acetyl transferase (pat) gene from Streptomyces viridochromogens (Krainsky) Waksman and Henrici. Twenty R-1:F-2 and 19 R-1:BCF1 populations derived from 20 R-1 transformants were analyzed for the number of transgenic inserts on the basis of their segregation pattern for herbicide tolerance. Fifteen of the 20 transgenic lines had a single insertion of the pat gene which behaved in a Mendelian manner and five had insertions at two independent loci. Ten transgenics with single gene inserts crossed in a half-diallel fashion were used to establish allelic relationships of transformants. The results indicated that the insertions had occurred at different loci within the plant genome with a possibility of an association between inserts in one case. It was concluded that transformants should be analyzed for number of transgene inserts and for genetic stability before they may be used in breeding programs for the development of glufosinate-ammonium tolerant B. napus cultivars.