Functional stacking of three resistance genes against Phytophthora infestans in potato

Abstract

Functional stacking of broad spectrum resistance (R) genes could potentially be an effective strategy for more durable disease resistance, for example, to potato late blight caused by Phytophthora infestans (Pi). For this reason, three broad spectrum potato R genes (Rpi), Rpi-sto1 (Solanum stoloniferum), Rpi-vnt1.1 (S. venturii) and Rpi-blb3 (S. bulbocastanum) were selected, combined into a single binary vector pBINPLUS and transformed into the susceptible cultivar Desiree. Among the 550 kanamycin resistant regenerants, 28 were further investigated by gene specific PCRs. All regenerants were positive for the nptII gene and 23 of them contained the three Rpi genes, referred to as triple Rpi gene transformants. Detached leaf assay and agro-infiltration of avirulence (Avr) genes showed that the 23 triple Rpi gene transformants were resistant to the selected isolates and showed HR with the three Avr effectors indicating functional stacking of all the three Rpi genes. It is concluded that Avr genes, corresponding to the R genes to be stacked, must be available in order to assay for functionality of each stack component. No indications were found for silencing or any other negative effects affecting the function of the inserted Rpi genes. The resistance spectrum of these 23 triple Rpi gene transformants was, as expected, a sum of the spectra from the three individual Rpi genes. This is the first example of a one-step approach for the simultaneous domestication of three natural R genes against a single disease by genetic transformation.Electronic supplementary materialThe online version of this article (doi:10.1007/s11248-011-9510-1) contains supplementary material, which is available to authorized users.

Evidence for intragenic recombination and selective sweep in an effector gene of Phytophthora infestans

“…It is likely that potato cultivars with R3a gene have been intentionally or unintentionally used across many regions of the world, selecting for Avr3a isoforms able to circumvent the resistance. Indeed, the resistance gene has been detected in many potato cultivars recently (Nowicki, Foolad, Nowakowska, & Kozik, 2012; Zhu, Li, Vossen, Visser, & Jacobsen, 2012). In addition, environmental factors such as temperature may interact with host resistance influencing the fitness of Avr3a in P. infestans .…”

Resistance-Gene-Mediated Defense Responses against Biotic Stresses in the Crop Model Plant Tomato

“…With the recent advances in molecular biology and genetic approaches, several R-genes have been cloned (as discussed above). A broad-spectrum application for crop improvement and managing resistance that has gained great attention is non-host resistance [151]. Other alternatives include functional stacking of R-genes that has been successfully used in potato and tomato [152][153][154] and targeting the susceptible genes can result in a more broad-spectrum and durable type of resistance [155].…”

Application of Genetic Engineering in Plant Breeding for Biotic Stress Resistance

“…Previously, breeders were unable to prioritize Rpi genes that recognized the pathogen's most indispensable effectors; now they can. Moreover, if one can combine multiple Rpi genes on one DNA construct ('stacking'), then each gene can be expected to reduce the selection pressure against the other genes on the construct (Zhu et al, 2012). BASF developed a potato variety, Fortuna, which carries Rpi-blb1 and Rpi-blb2, and showed excellent field resistance .…”