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. Tradition ally, various pre- and post-emergent herbicides have been used to achieve t he required level of weed control. Recently, B. napus has been genetically engineered to express tolerance to the broad-spectrum, post-emergent herbic ide, glufosinate-ammonium [2-amino-4-(hydroxymethylphosphinyl)butanoic acid ]. This study was conducted to determine the genetics of glufosinate-ammoni um tolerance in a series of Agrobacterium-mediated transgenic lines of B. n apus carrying the phosphinothricin-acetyl transferase (pat) gene from Strep tomyces viridochromogens (Krainsky) Waksman and Henrici. Twenty R-1:F-2 and 19 R-1:BCF1 populations derived from 20 R-1 transformants were analyzed fo r the number of transgenic inserts on the basis of their segregation patter n 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 insert s crossed in a half-diallel fashion were used to establish allelic relation ships of transformants. The results indicated that the insertions had occur red at different loci within the plant genome with a possibility of an asso ciation between inserts in one case. It was concluded that transformants sh ould be analyzed for number of transgene inserts and for genetic stability before they may be used in breeding programs for the development of glufosi nate-ammonium tolerant B. napus cultivars.