|DINH, PHUONG - Washington State University|
|ZHANG, LINHAI - Washington State University|
|ELLING, AXEL - Washington State University|
Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2014
Publication Date: 5/7/2014
Citation: Dinh, P., Zhang, L., Brown, C.R., Elling, A. 2014. Plant-mediated RNA interference of effector gene Mc16D10L confers resistance against Meloidogyne chitwoodi in diverse genetic backgrounds of potato and reduces pathogenicity of nematode offspring. Nematology. 6:669-682.
Interpretive Summary: Root knot nematodes parasitize plants by physically entering the root. They establish a close relationship by inducing the root cells to specifically nourish the nematode during the rest of its life cycle. The nematode secretes proteins, called effectors that stimulate a susceptible plant to develop a giant cell that is like a big kitchen for the nematode. If the plant, however, reacts to the effector by unleashing a cascade of resistance reactions parasitism will fail and there will be no damage to the plant. In this study a transgene that interferes with the expression of an effector was inserted and expressed in the plant. We found significant reductions in infection sites and numbers of eggs produced in transgenic plants when inoculated. This technique could provide a host reaction that obviates the need for control by chemical fumigation saving 20 million dollars for the Washington industry.
Technical Abstract: Meloidogyne chitwoodi is a major problem for potato production in the Pacific Northwest of the USA. In spite of long-term breeding efforts no commercial potato cultivars with resistance to M. chitwoodi exist to date. The RMc1 resistance gene against M. chitwoodi has been introgressed from Solanum bulbocastanum into cultivated potato (S. tuberosum), but M. chitwoodi pathotypes are able to overcome this resistance. In this study, an RNA interference (RNAi) transgene targeting the M. chitwoodi effector gene Mc16D10L was introduced into potato cvs. Russet Burbank and Désirée, and the advanced breeding line PA99N82-4, which carries the RMc1 gene. Stable transgenic lines were generated for glasshouse infection assays. At 35 days after inoculation (DAI) with M. chitwoodi race 1 the number of egg masses per gram root formed on RNAi lines of cvs. Russet Burbank and Désirée was reduced significantly by up to 68% compared to empty vector control plants. At 55 DAI, the number of eggs was reduced significantly by up to 65%. In addition, RNAi of Mc16D10L significantly reduced the development of egg masses and eggs formed by the RMc1 resistance-breaking M. chitwoodi pathotype Roza on PA99N82-4 up to 47 and 44%,respectively. Importantly, the plant-mediated silencing effect of Mc16D10L was transmitted to M. chitwoodi offspring and significantly reduced pathogenicity in the absence of selection pressure on empty vector control plants. This finding suggests that the RNAi effect is stable and nematode infection decreases regardless of the genotype of the host once the RNAi process has been initiated in the nematode through a transgenic plant. In summary, plant-mediated downregulation of effector gene Mc16D10L provides a promising new tool for molecular breeding against M. chitwoodi.