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Genetic analysis of crown rust (Puccinia coronata f. sp. lolii) resistance in a perennial ryegrass (Lolium perenne) genotype

Schubiger, Franz Xaver, Boller, Beat
Euphytica 2017 v.213 no.8 pp. 167
Lolium perenne, Puccinia coronata, backcrossing, crown rust, cultivars, diploidy, dominant genes, genetic analysis, genotype, growth chambers, inheritance (genetics), plant breeding, progeny
In order to study the inheritance of resistance to crown rust (Puccinia coronata f. sp. lolii) in perennial ryegrass (Lolium perenne), we crossed a resistant, diploid genotype (A6128/05) with a susceptible genotype of the cultivar Aurora to generate a F₁ population. Individuals of the F₁ population were screened for their response to three single-pustule isolates (SPI) of crown rust in a detached-leaf segment test under growth chamber conditions. Out of the F₁ population, we selected two genotypes (I and II) based on the reaction to SPI of crown rust: genotype I was resistant to SPI A, D and F. Genotype II was resistant to SPI A, but susceptible to SPI D and F. Both genotypes were backcrossed with a second, susceptible Aurora genotype to generate two F₂ populations. A resistant genotype out of each of the two F₂ populations was used to generate a F₃ population by backcrossing with a susceptible Aurora genotype. In the F₂ and F₃ populations, derived from a cross with the genotype I, a good fit to a segregation ratio of 1R:1S (resistant:susceptible) was observed for the three SPI A, D and F. The frequency of resistant and susceptible plants within the F₂ and F₃ populations, derived from the genotype II, resulted in a ratio of 1R:1S for SPI A. In contrast, the F₂ and F₃ progeny was susceptible to SPI D and F. These results provide evidence that at least two different dominant genes for crown rust resistance occur in the resistance donor A6128/05.