Rpi-vnt1.1, a Tm-2² Homolog from Solanum venturii, Confers Resistance to Potato Late Blight

Abstract

Despite the efforts of breeders and the extensive use of fungicide control measures, late blight still remains a major threat to potato cultivation worldwide. The introduction of genetic resistance into cultivated potato is considered a valuable method to achieve durable resistance to late blight. Here, we report the identification and cloning of Rpi-vnt1.1, a previously uncharacterized late-blight resistance gene from Solanum venturii. The gene was identified by a classical genetic and physical mapping approach and encodes a coiled-coil nucleotide-binding leucine-rich repeat protein with high similarity to Tm-2(2) from S. lycopersicum which confers resistance against Tomato mosaic virus. Transgenic potato and tomato plants carrying Rpi-vnt1.1 were shown to be resistant to Phytophthora infestans. Of 11 P. infestans isolates tested, only isolate EC1 from Ecuador was able to overcome Rpi-vnt1.1 and cause disease on the inoculated plants. Alleles of Rpi-vnt1.1 (Rpi-vnt1.2 and Rpi-vnt1.3) that differed by only a few nucleotides were found in other late-blight-resistant accessions of S. venturii. The late blight resistance gene Rpi-phu1 from S. phureja is shown here to be identical to Rpi-vnt1.1, suggesting either that this strong resistance gene has been maintained since a common ancestor, due to selection pressure for blight resistance, or that genetic exchange between S. venturii and S. phureja has occurred at some time.

R/Avr gene expression study of Rpi-vnt1.1 transgenic potato resistant to the Phytophthora infestans clonal lineage EC-1

“…We selected five transgenic events with the Rpi-vnt1.1 gene from the potato variety 'Desiree' that are extremely resistant to two isolates of the EC-1 clonal lineage of P. C is the untransformed plant DNA from Desiree variety; numbers are each of the resistant transgenic events; and P is probe from nptII gene with a size of 597 bp infestans and investigated R and Avr gene expression to improve our understanding of the stability of the resistance conferred by the Rpi-vnt1.1 gene in transgenic potato. Our finding of EC-1 resistant transgenic events with Rpi-vnt1.1 gene was unexpected based on the R/Avr gene model and previous observations by Foster et al (2009) andPel (2010). The EC-1 strains may differ in their virulence due to several factors.…”

“…The EC-1 lineage was recently further characterized in Ecuador and found to present genetic and virulence variation (Delgado et al 2013). Therefore, it is plausible that the EC-1 strain used by Foster et al (2009) andPel (2010) differs in virulence from the EC-1 strains used in our study. The Avr-vnt1 gene expression was detected in the Peruvian EC-1 isolates POX067 and POX109 when inoculated on transgenic resistant plants and on the susceptible cultivar Yungay, contrasting with the observed absence of expression of Avr-vnt1 in the EC-1 strains used by Foster et al (2009) andPel (2010).…”

“…Experimental conditions to prepare the P. infestans inoculum could reset expression of Avr-vnt1 gene in the case of an epigenetic control. Foster et al (2009) andPel et al (2009) used Rye B agar and high inoculum concentrations (50,000 sporangia/mL) whereas we used potato tuber slices and less concentrated inoculum (3000 sporangia/mL). The EC-1 lineage was recently further characterized in Ecuador and found to present genetic and virulence variation (Delgado et al 2013).…”

Identification, Mapping and Pyramiding of Genes/Quantitative Trait Loci (QTLs) for Durable Resistance of Crops to Biotic Stresses

“…Thus, recently molecular markers and genetic engineering are widely used in crop improvement program to stack series of resistance genes into elite cultivar to develop durable and/or broad-spectrum resistance to biotic stress. Therefore, to minimize yield loss due to biotic stress, developing countries including Ethiopia shall include gene pyramiding in their Late blight R genes from wild relatives Foster et al [113] Late blight R gene from wild relative Bradeen et al [114] Late blight R gene from wild relative Halterman et al [115] Potato virus X Mammalian interferoninduced enzyme Truve et al [116] Rice Bacterial blight and bacterial streak Engineered E gene Hummel et al [30] Bacterial streak R gene from maize Zhao et al [117] Squash …”

Expresión de efectores RXLR en el linaje clonal EC-1 de Phytophthora infestans en Perú

“…Esto ha sido mostrado en el caso del silenciamiento de Avr-vnt1 que lleva al escape del reconocimiento por el gen R Rpi-vnt1 en el linaje clonal EC-1 (Pel 2010). El gen de resistencia Rpi-vnt1 fue clonado de las especies de Sudamérica S. venturii (Foster et al 2009) y luego fue mostrado que Rpi-phu1 originario de Solanum phureja (Zimnoch) es idéntico a Rpi-vnt1 (Pel 2010). El grupo de papa Phureja ha sido comúnmente cultivado en los Andes haciendo posible que el silenciamiento de Avr-vnt1 sea un resultado de la co-evolución.…”