Transfer of transgenes for resistance to rice tungro disease into high-yielding rice cultivars through gene-based marker-assisted selection

Abstract

Rice tungro disease (RTD), caused by the simultaneous infection of rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV), is one of the major threats to sustainable rice production in South and Southeast Asia. Transgenic resistance against RTBV has been reported previously using an RNA interference (RNAi) construct (ORF IV of RTBV, placed both in sense and anti-sense orientation under CaMV 35S promoter), in the scented rice line Pusa Basmati-1 (PB-1). This construct was transferred to two high-yielding tungro-susceptible indica rice cultivars (IET4094 and IET4786) from the transgenic PB-1 rice line using back cross breeding till the BC₂F₃ stage. On challenge inoculation, the progenies (BC₂F₁) showed mild symptoms of tungro, in contrast to severe symptoms displayed by the recurrent parents. Segregation of the transgene indicated near homozygosity of the plants at the BC₂F₃ stage, implying that the lines can be used as a valuable resistance source for further breeding against RTD.