Vector integration in triple R gene transformants and the clustered inheritance of resistance against potato late blight

Abstract

Genetic transformation with resistance (R) genes is expected to enhance resistance durability against pathogens, especially for potato, a vegetatively propagated crop with tetrasomic inheritance and a long-term breeding program. In this study, 128 potato transformants were analysed for the presence of vector T-DNA genes, borders and backbone sequences. They were harvested after transformation using a construct containing neomycin phosphotransferase II (nptII) and three R genes against potato late blight (Phytophthora infestans). Our analysis revealed that 45 % of the R gene-containing transformants possessed a low T-DNA copy number, without the integration of vector backbone and borders. The integration of vector backbone sequences was characterized using eight genes, and backbone gene tetA was selected for the early prediction of plants with backbone sequence integration. Three transformants, two plants harbouring one T-DNA copy and one plant harbouring three T-DNA copies, were crossed with susceptible cv. Katahdin. Based on our results, we conclude that all four T-DNA genes were inherited as one cluster and segregated in a Mendelian fashion. The three T-DNA inserts from the transformant harbouring three T-DNA copies were statistically proven to be un-linked and inherited into the offspring plants independently. All of the R genes were functionally expressed in the offspring plants as in their parental transformants. This functional gene stacking has important implications towards achieving more durable resistance against potato late blight.

Transformation of the potato variety Desiree with single or multiple resistance genes increases resistance to late blight under field conditions

“…No amplicons were produced using non-transformed Desiree DNA, showing that T-DNA sequences were specifically detected (Table A.4). Transformation events that showed partial integration of T-DNA were found at low frequencies, as described before (Zhu et al, 2013), and only events with complete T-DNA integrations were maintained. Next, the integration of vector backbone genes was tested.…”

The Ph-3 gene from Solanum pimpinellifolium encodes CC-NBS-LRR protein conferring resistance to Phytophthora infestans

“…For late blight, however, single R genes were quickly overcome in the field. Stacking of two or multiple Rpi genes can confer resistance to a broad and complementary set of isolates (Zhu et al 2012, 2013). For stacking strategy, the knowledge of interaction between P. infestans (effectors) and host ( R genes) is essential, which helps to evaluate the durability of R genes (Vleeshouwers et al 2008).…”

“…An alternative approach to introduce single or multiple R genes is genetic transformation (Halpin 2005). To achieve durable resistance, three potato Rpi genes were introduced into one genotype through a one-step transformation strategy, and the resulting plants showed an expected broadened resistance spectrum (Zhu et al 2012, 2013). This approach, however, requires prior knowledge of the gene(s), including mapping, cloning, and functional characterization.…”

Comparación de la resistencia horizontal y vertical contra el tizón tardío de la papa en Toluca

“…Sin embargo, en la actualidad se sabe que los genes R están involucrados en todos los tipos de resistencia por lo que se está tratando de generar variedades con una combinación de varios genes mayores y menores, a lo cual se le ha llamado construir pirámides de genes (Adillah et al, 2010;Kim et al, 2012;Zhu et al, 2013). Esta estrategia se desarrolla actualmente con la ayuda de la ingeniería genética, pero algunas variedades viejas que poseen una combinación de genes mayores y menores, las cuales fueron generadas por métodos tradicionales en México y otros países, han demostrado que tienen una resistencia duradera (Grünwald et al, 2002;Rietman et al, 2012).…”

“…However, at present it is known that the R genes are involved in all types of resistance so it is trying to develop varieties with a combination of several major and minor genes, to which has been called build pyramids of genes (Adillah et al, 2010;Kim et al, 2012;Zhu et al, 2013). This strategy is currently being developed with the help of genetic engineering, but some older varieties that have a combination of major and minor genes, which were generated by traditional methods in Mexico and other countries, have shown to have a lasting resistance (Grünwald et al, 2002;Rietman et al, 2012).…”