TransgenicPm3multilines of wheat show increased powdery mildew resistance in the field

Abstract

SummaryResistance (R) genes protect plants very effectively from disease, but many of them are rapidly overcome when present in widely grown cultivars. To overcome this lack of durability, strategies that increase host resistance diversity have been proposed. Among them is the use of multilines composed of near-isogenic lines (NILs) containing different disease resistance genes. In contrast to classical R-gene introgression by recurrent backcrossing, a transgenic approach allows the development of lines with identical genetic background, differing only in a single R gene. We have used alleles of the resistance locus Pm3 in wheat, conferring race-specific resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici), to develop transgenic wheat lines overexpressing Pm3a, Pm3c, Pm3d, Pm3f or Pm3g.In field experiments, all tested transgenic lines were significantly more resistant than their respective nontransformed sister lines. The resistance level of the transgenic Pm3 lines was determined mainly by the frequency of virulence to the particular Pm3 allele in the powdery mildew population, Pm3 expression levels and most likely also allele-specific properties. We created six two-way multilines by mixing seeds of the parental line Bobwhite and transgenic Pm3a, Pm3b and Pm3d lines. The Pm3 multilines were more resistant than their components when tested in the field. This demonstrates that the difference in a single R gene is sufficient to cause host-diversity effects and that multilines of transgenic Pm3 wheat lines represent a promising strategy for an effective and sustainable use of Pm3 alleles.

Oomycete Interactions with Plants: Infection Strategies and Resistance Principles

“…This has caused problems in agricultural contexts where R genes were employed to provide resistance to crop pathogens because the resistance has only been durable if the required Avr gene is essential to the pathogen's success. However, there have been various attempts to improve the chances of durability, namely, stacking multiple R genes within one variety (88) and/or using variety mixtures (89) or multilines (90), as well as engineered R genes with extended recognition spectra (91,92). The use of variety mixtures involves sowing several varieties containing different R genes and different parental backgrounds together in the same field.…”

Genetically modified crops in Switzerland: implications for agrosystem sustainability evidenced by multi-criteria model

“…There are multiple problems in agronomic systems that require locally adapted solutions: pest and disease control, salt and drought tolerance, heavy metal contaminations, crop quality and environmental impacts. The BR FR cis-genic apple described here or the wheat variety resistant to powdery mildew (Brunner et al 2012) is a good example of development answering a precise agronomic need. The new generation of genome editing technologies could empower local initiatives and responsive creation of varieties that may result in a more pragmatic way of using genetic technologies.…”

Modernization in plant breeding approaches for improvingbiotic stress resistance in crop plants

“…If any iso-line becomes susceptible, it can be removed from or replaced in the mixture (Keneni et al, 2012). Brunner et al (2012) followed a new procedure of introducing durable resistance that combines both the conventional breeding and modern transgenic approach to introduce powdery mildew resistant wheat. In their work, multilines were made by combining near-isogenic lines (NILs) containing different resistance genes.…”