Expression of Meloidogyne incognita PolA1 hairpin RNA reduced nematode multiplication in transgenic tomato

Controlling root-knot nematodes ( Meloidogyne spp .) using RNA interference (RNAi)-based molecular strategy is currently gaining consideration as a safer alternative to the use of chemical nematicides. However, identifying target genes whose knockdown in the parasites can effectively protect host plants is critical to success of this strategy. In this study, we transformed tomato plants to express hairpin RNA of Meloidogyne incognita -specific sequence ( MiPA ) of PolA1 , an essential single-copy nuclear gene encoding the largest subunit of RNA polymerase I enzyme. We then evaluated nematode resistance in T 1 transgenic lines for efficacy of host plant-mediated silencing of PolA1 gene in invading nematodes. We observed a significant reduction in nematode egg masses per plant root, eggs per egg mass and overall parasite multiplication in the transgenic plants compared to the wild type. Transgenic plants also had a reduced number of nematode galls per plant root than wild type but not significant. Although agronomic traits evaluated at the early growth stage were comparable in transgenics and wild types of tomato plants, production of MiPA -specific siRNAs in transgenic plants as well as the significant reduction of nematode PolA1 gene expression in feeding nematodes isolated from roots of transgenic plants provided evidence of host-induced gene silencing. Put together, our results are an indication that silencing of PolA1 gene is useful for reducing propagation of root-knot nematodes in tomato hosts. Its application to other crops may be possible and useful in improving agricultural productivity.