Sequence analysis of Rice tungro spherical virus, engineering viral resistance and development of a self replicating vector for rice
Sequence analysis of Rice tungro spherical virus, engineering viral resistance and development of a self replicating vector for rice
Tungro disease is an important constraint for the cultivation of rice in India. Tungro is caused by simultaneous infection of rice with two viruses, Rice tungro spherical virus (RTSV) and Rice tungro bacilliform virus, which interact synergistically both in the plant as well as in the vector. Two full length viral genome (12174 nt) representing field isolates from Orissa and West Bengal were cloned. Indian isolates of RTSV are homologous to South East Asian isolates as assessed by nucleotide sequence analysis and thus RTSV population is stable geographically. Majority of the genes of the Indian isolates cluster together with the virulent isolate of RTSV. Rice transgenics were developed containing genes derived from RTSV. RNAi based construct expressing the sense and antisense genes in the same plant proved to be promising strategies to improve resistance against RTSV. Moderate levels of transgenic resistance probably can reduce the disease under field conditions. Virus induced gene silencing vector has been developed using self-replicating molecules of RTBV in rice for rice functional genomics. The findings are expected to be of major importance in the control of tungro disease in India.