Evaluation of agronomic and industrial traits, genetic variation and transgene stability in glyphosate-tolerant sugarcane

NOGUERA A.S.; ENRIQUE, R.; OSTENGO, S.; PERERA, M. F; RACEDO, J.; COSTILLA, D,; CUENYA, M.I.; WELIN, B.; CASTAGNARO, A.P.

San Diego

Conferencia; XXII International Plant and Animal Genome Conference; 2014

Sugarcane (Saccharum hybrid) commercial variety RA87-3 was transformed through particle bombardment with a chimeric transgene constitutively expressing the gene epsps from Agrobacterium strain C4 conferring tolerance to the broad-spectrum herbicide glyphosate. Out of forty three (43) PCR-positive transformed lines, seventeen (17) showed high glyphosate-tolerance when tested in the greenhouse and were selected for further field studies and a possible commercial release. All greenhouse herbicide-tolerant lines were planted in a small?scale field trial to verify glyphosate tolerance and to evaluate phenotypic resemblance to parental line RA87-3. All lines maintained glyphosate tolerance but several events showed phenotypical growth differences leaving only six (6) lines (15, 18, 22, 27, 28 and 37) with a growth phenotype closely related to the parental line. To corroborate field test results, all six events, together with 4 lines showing growth differences, were genotypically analyzed using 15 TRAP markers which generated 339 fragments, out of which 212 were polymorphics. Interestingly, five out of the six lines with a growth phenotype closely related to RA87-3, showed 100% similarity, whilst the remaining line (27), only differed in two markers (over 99% similarity) when compared to the parental elite variety. In contrast, all four lines showing phenotypic growth alterations were found to harbour significant marker polymorphism compared to the parental line RA87-3 (>95%). The six genotypically and phenotypically closely related glyphosate-tolerant events were selected for field testing at two independent production areas in Argentina and evaluated for agronomic traits and biochemical parameters to ensure comparable production characteristics to their commercial parental elite variety. From these studies it was concluded that all six lines showed comparable agronomical and industrial traits as compared to parental line 87-3. However, lines 28 and 37 were found to be almost identical in all conducted studies as compared to parental origin, and subsequently these 2 events were selected for commercialization. These results show that even though, only a relatively low number of genetically transformed lines are produced in a sugarcane variety it is possible to recuperate a closely related copy of the parental line used for genetic transformation demonstrating the usefulness of molecular breeding for this genetically complex crop species