The segregation pattern of insect resistance genes in the progenies and crosses of transgenic rojolele rice

Abstract

Successful application of genetic transformation technique, especially in developing rice variety resistant to brown plant hopper and stem borer, will depend on fransgene being expressed and the gene inherited in a stable and predictable manner. This study aimed to analyse transgene segregation pattern of the progenies and the crosses of transgenic rice cv. Rojolele harboring crylAb and gnu genes. The third generation (T,) of five transgenic Rojolele events containing gnu and/or cry1 Ab were evaluated for two generations to identify the homozygous lines and to study their inheritance. The homozygous lines were selected based on the result of PCR technique. The segregation patterns of gnu and crylAb were studied in eight F, populations derived from Rojolele x transgenic Rojolele homozygous for crylAb and or gnu and their reciprocal crosses. Data resulted from PCR of F, populatibn were analysed using a Chi Square test. The study obtained six homozygous lines for gnu, namely A22- 1-32, A22-1-37, C72-1-9, Fll-1-48, K21-1-39, K21-1-48, and two homozygous lines for cry1 Ab, namely K21-1-39 and K21- 1-48. Both crylAb and gnu transgenes had been inherited through selfing and crossing with their wild type as indicated from the F, containing gnu and crylAb as many as 48.4% and 47.4%, respectively. In six of the eight crosses, gnu was inherited in a 3:l ratio consistent with Mendelian inheritance of a single dominant locus, while in the remaining two crosses, gnu was segregated in a 1:l ratio. The presence of crylAb in F, populations also showed a 3:l segregation ratio in all crosses. In the F, population derived from F, plant containing crylAb and gnu, both transgenes segregated in a 9:3:3:1 dihybrid segregation ratio. This study will add to the diversity of genetic sources for insect resistance and allow further use of these transgenic lines for pyramiding resistance to brown plant hopper and stem borer or separately in rice breeding programs whenever the efficacy tests and biosafety requirements have been completed.