Development of Mirafiori Lettuce big-Vein Virus-Resistant Lettuce

Lettuce big-vein disease caused by Mirafiori lettuce big-vein virus (MLBVV) is found in lettuce (Lactuca sativa) production areas worldwide. To produce MLBVV-resistant marker-free transgenic lettuce, the team of Yoichi Kawazu of the National Agriculture and Bio-oriented Research Organization in Japan constructed a vector which contained inverted repeats of the coat protein (CP) gene of MLBVV.

This vector was introduced into lettuce cultivars ‘Watson' and ‘Fuyuhikari' by Agrobacterium-mediated transformation. Regenerated plants were self-pollinated, and 312 T₁ lines were analyzed for resistance to MLBVV. Virus-negative plants were checked for the CP gene and the marker gene, and nine lines were obtained which were marker-free and resistant to MLBVV.

Analysis showed that three had two copies of the gene, while six lines had a single copy and were used for further analysis. Small interfering RNAs, which are indicative of RNA silencing, were detected in all six lines and MLBVV infection was inhibited in all of them. The transgenic lines produced could be used as resistant cultivars or parental lines for breeding.

For more information on the study, read the article on Transgenic Research.