Breeding Progress in Seedling Resistance against Various Races of Stripe and Leaf Rust in European Bread Wheat

Abstract

Background: Stripe and leaf rust are major constraints of wheat production with substantial impacts on grain yield. Population dynamics of both pathogens and the emergence of new virulent races have resulted in relentless efforts related to wheat breeding to improve resistance during the last decades.Methods: To evaluate the breeding progress achieved with respect to racespecific resistance, a set of nine isolates of the two rust pathogens have been tested in seedling assays on a panel of 191 elite winter wheat cultivars representing wheat breeding in Europe between 1966 and 2013.Results: Significant differences in the resistance of wheat cultivars concerning both pathogens have been detected by means of two-way ANOVA. Isolates as well as genotype × isolate interaction had a significant effect for both pathogens. Breeding progress, resulting in an increased seedling resistance, has been achieved against all nine isolates over the past five decades. The slope of progress was steeper for leaf rust than for stripe rust isolates. Progress against the highly common leaf rust isolate "4171" and" the stripe rust isolate "Warrior(-)" was strongest. Conclusions:The study reveals that a steady increase in seedling resistance was achieved during the past five decades. An additive contribution of these isolate specific R genes after breakdown has been hypothesised.

Efficiency of a Seedling Phenotyping Strategy to Support European Wheat Breeding Focusing on Leaf Rust Resistance

“…The susceptible standard variety Borenos was used as control. Inoculation was implemented in an air-blowing inoculation tower using uredospores of the aggressive leaf rust isolate 77 WxR [27]. After an incubation of 8 days under controlled temperature conditions (16 • C), visibly differentiable leaf rust symptoms appeared on the leaf segments.…”

“…Although the highly aggressive leaf rust isolate 77 WxR was applied, which exhibits virulence in juvenile plant stages against several resistance genes, viz. Lr1, Lr2a, Lr2b, Lr2c, Lr3a, Lr3bg, Lr3ka, Lr4, Lr11, Lr12, Lr13, Lr14a, Lr14b, Lr15, Lr17, Lr17b, Lr18, Lr20, Lr22a, Lr22b, Lr23, Lr26, Lr33, Lr35, Lr36, Lr37, Lr38, and Lr49 [27], natural selection pressure leads to divergent isolate populations resulting in differences between greenhouse and field trials. However, there are also differences between field trials.…”

“…It is known that the majority of discovered leaf rust resistance genes cause seedling resistance, while Lr1, Lr3, Lr10, Lr11, Lr12, Lr13, Lr14a, and Lr24 are frequently used within the European wheat germplasm [9]. The importance of detecting seedling resistance was underlined by their reduced, but continuous participation on leaf rust resistance, even after their break down [27]. Therefore, greenhouse observations of juvenile plants could support breeding for leaf rust resistance in European wheat.…”

Resistance Breeding Increases Winter Wheat Gross Margins–An Economic Assessment for Germany

“…This group contains the year of release and resistance variables. The variable, year of release shows how the gross margin changed over time with increased breeding progress (Cormier et al, 2016;Voss-Fels et al, 2019;Zetzsche et al, 2019Zetzsche et al, , 2020). An important aspect of winter wheat breeding is the increasing resistance of the varieties to fungal pathogens.…”

“…It is well-understood that a large determinant in the rise of yield levels in Germany was genetic gains by plant breeding and that this breeding-induced yield increase is not stagnating (Ahlemeyer and Friedt, 2010;Laidig et al, 2014;Voss-Fels et al, 2019). New varieties have accumulated genetic variants with beneficial effects on the important yield enhancing traits, such as nutrient use and photosynthetic efficiency as well as disease resistance (Voss-Fels et al, 2019;Zetzsche et al, 2019Zetzsche et al, , 2020. Over time, variety aging decreases the yield ability of varieties and is mainly induced by a steady breakdown of resistances due to pathogen evolution (Mackay et al, 2011;Fischer et al, 2014;Laidig et al, 2014;Piepho et al, 2014).…”