Genetic characterization and field evaluation to recover parental phenotype in transgenic sugarcane: a step toward commercial release

Abstract

Sugarcane commercial variety RA 87-3 was transformed with a genetic construct harboring the epsps gene from Agrobacterium strain CP4 conferring tolerance to glyphosate and nptII gene for kanamycin selection. Transformed lines were multiplied in greenhouse, and herbicide tolerance was evaluated using different concentrations (3, 4, 8 and 16 l/ha) of glyphosate (Helm 48 % p/v). All herbicidetolerant (HT) lines were field tested to confirm glyphosate tolerance and perform preliminary evaluations of phenotypic resemblance to parental cultivar. All transformed lines maintained herbicide tolerance, but many showed phenotypic changes and/or growth aberrations. Ten HT lines, showing close growth resemblance to RA 87-3, were analyzed using nine compulsory morphologic markers proposed by the International Union for the Protection of New Varieties of Plants (UPOV) and 339 molecular markers. Out of the ten HT lines tested, six showed minor morphologic and genetic variations and were selected for field testing over two vegetative crop cycles (plant cane and first ratoon) at two production areas in Argentina. The six field-tested HT lines were found to be almost indistinguishable when comparing agronomic and industrial characteristics and chemical composition. Stable heritance of the CP4 epsps gene and glyphosate tolerance throughout different clonal generations were confirmed by RT-qPCR and Southern blot. Taking into account all results, two out of the six lines tested were selected for a possible commercial release. Our study confirms the utility of genetic transformation as a complementary tool to classical breeding procedures and highlights the usefulness of UPOV traits together with molecular markers for early selections of transgenic events that closely resemble their parental genotype.

Expression patterns of cp4-epsps gene in diverse transgenic Saccharum officinarum L. genotypes

“…An efficient biolistic mediated transformation procedure with some variations was followed to transform all three different cultivars (US2003S-114, HSF-240, and US2003S-778) with good callus transformation efficiency, which is in accordance with previous reports by Vickers et al (2005) and Noguera et al (2015). The qRT-PCR analyses were carried out to examine transgene expression patterns in meristematic tissues in sugarcane genotypes HSF-240, S2003US-778, and S2003US-114 using qRT-PCR.…”

Plant growth-promoting bacteria isolated from sugarcane improve the survival of micropropagated plants during acclimatisation

“…Micropropagated sugarcane seedlings of the TUC 03-12 variety were obtained by in vitro cultivation of meristems, according to the EEAOC's high-quality seed cane production programme (Noguera et al, 2015). After the in vitro multiplication and rooting process, seedlings were transferred to ex vitro conditions in a nursery for acclimatisation.…”

Genetic engineering: an efficient approach to mitigating biotic and abiotic stresses in sugarcane cultivation

“…After two rounds of glyphosate application, only the transgenic events with higher expression levels of the GT gene-encoded protein survived applications with high glyphosate concentration. It is worth mentioning that the transgenic event expressing the CP4 epsps gene from A. tumefaciens developed in Argentina by Noguera et al 13 (2015) was the closest attempt to release herbicide-resistant sugarcane worldwide ( Figure 1 ). Exhaustive studies concerning health and environmental regulations were performed to assess their potential impact on agricultural systems and food safety necessary for commercial deregulation of any transgenic event in Argentina.…”