RESUMO: A disponibilidade de um protocolo eficiente de regeneração in vitro é imperativa para a transformação genética de plantas. O uso de material genético adaptado à região alvo como plataforma de transgenia permite acelerar o desenvolvimento de uma cultivar. Portanto, o objetivo deste estudo foi adaptar um protocolo de regeneração in vitro para genótipos brasileiros de trigo. Para esta finalidade, a capacidade de regeneração in vitro de embriões imaturos de seis genótipos brasileiros de trigo, utilizando dois protocolos de regeneração de embriões somáticos, foi analisada. Além disso, combinações de 2,4-D e picloram no meio de indução de calos foram analisadas buscando aumentar a eficiência de regeneração. Os genótipos com maior eficiência de regeneração foram BR18-Terena e PF020037, produzindo 0,42 e 1,13 brotações por explante usando os protocolos Hu e Wu, respectivamente. A adição de 1mgL-1 de 2,4-D no meio de indução de calos foi o mais favorável, produzindo 3,73 e 3,07 brotações por explante para PF020037 e BR18-Terena, respectivamente. Concluindo, foi adaptado um protocolo de regeneração para dois genótipos brasileiros recomendados e desenvolvidos para o cultivo no Cerrado.

ABSTRACT: The availability of an efficient protocol for in vitro regeneration is imperative for genetic transformation. Using genotypes adapted to the target region as a transgenic platform accelerates the development of cultivars. Therefore, this study aimed to adapt an in vitro regeneration protocol for Brazilian wheat genotypes. For this purpose, the in vitro regeneration capacity of immature embryos from six Brazilian wheat genotypes using two protocols of regeneration of somatic embryos was analysed. Furthermore, combinations of 2,4-D and picloram in the callus induction medium were tested in order to improve regeneration efficiency. Genotypes with higher regeneration efficiency were BR18-Terena and PF020037, yielding 0.42 and 1.13 shoots per explant using the Hu and the Wu protocol, respectively. Adding 1mgL-1 2,4-D in the callus induction medium was the most favourable, producing 3.73 and 3.07 shoots per explant for PF020037 and BR18-Terena, respectively. In conclusion, a protocol for regeneration for two Brazilian wheat genotypes recommended and developed to be cultivated at the Cerrado region has been adapted.

Abstract Low transformation efficiency is one of the main limiting factors in the establishment of genetic transformation of wheat via Agrobacterium tumefaciens. To determine more favorable conditions for T-DNA delivery and explant regeneration after infection, this study investigated combinations of acetosyringone concentration and pH variation in the inoculation and co-cultivation media and co-culture temperatures using immature embryos from two Brazilian genotypes (BR 18 Terena and PF 020037). Based on transient expression of uidA, the most favorable conditions for T-DNA delivery were culture media with pH 5.0 and 5.4 combined with co-culture temperatures of 22 °C and 25 °C, and a 400 μM acetosyringone supplement. These conditions resulted in blue foci in 81% of the embryos. Media with more acidic pH also presented reduced A. tumefaciens overgrowth during co-culture, and improved regeneration frequency of the inoculated explants. BR 18 Terena was more susceptible to infection by A. tumefaciens than PF 020037. We found that it is possible to improve T-DNA delivery and explant regeneration by adjusting factors involved in the early stages of A. tumefaciens infection. This can contribute to establishing a stable transformation procedure in the future.