Introgression of crown rust (Puccinia coronata) resistance from meadow fescue (Festuca pratensis) into Italian ryegrass (Lolium multiflorum) and physical mapping of the locus

Abstract

Resistance was found in the meadow fescue (Festuca pratensis) to crown rust (Puccinia coronata), originating from ryegrasses (Lolium spp). A backcrossing programme successfully transferred this resistance into diploid Italian ryegrass (Lolium multiflorum) and genomic in situ hybridisation (GISH) was used to identify the introgressed fescue chromosome segment. The resistant (R) plants in two BC 3 lines all carried an introgressed segment on a single chromosome, which in one of the lines was confined to the short arm of the chromosome. Susceptible (S) plants either contained no introgressed chromosome segment or a segment which was physically smaller than the segments in resistant plants. Using GISH the resistance locus could be physically mapped to the midpoint of a short arm. Segregation ratios of the progeny of BC 3 plants, when crossed as R Â S and R Â R, were in agreement with the hypothesis that the resistance was controlled by a single gene or very closely linked genes. No R plants were produced by crossing S Â S plants.

Four QTLs determine crown rust (Puccinia coronata f. sp. lolii) resistance in a perennial ryegrass (Lolium perenne) population

“…Evidence for genefor-gene resistance towards crown rust in Lolium has been reported by several authors (Dumsday et al, 2003;Roderick et al, 2003;Aldaoud et al, 2004). In the case of QTL2 (LpPc2), it is likely that we detect a genomic region coding for gene-for-gene resistance as the mapped RGA marker (NBS-1) coincides with LpPc2.…”

Biology and Genetics of Crown Rust Disease in Ryegrasses

“…Wilkins (1978) demonstrated the ineff ectiveness of single major genes compared to multiple minor genes for maintainance of durable resistance, and proposed that durable disease control was positively correlated with the presence of numerous and diverse host resistance mechanisms. In addition, crown rust resistance genes have been introgressed into Italian ryegrass from the closelyrelated species meadow fescue, using a backcrossing program and genomic in situ hybridization (GISH) to identify the introgressed chromosomal segment (Roderick et al, 2003). In addition, crown rust resistance genes have been introgressed into Italian ryegrass from the closelyrelated species meadow fescue, using a backcrossing program and genomic in situ hybridization (GISH) to identify the introgressed chromosomal segment (Roderick et al, 2003).…”

Exploitation of interspecific diversity for monocot crop improvement

“…Examples of previous introgressions from alien species in the forage grasses includes genes that confer resistance to disease and tolerance to abiotic stress, etc. (for example, Roderick et al, 2003;Humphreys et al, 2005;Armstead et al, 2006b). In addition, hybrids between the world's major temperate forage grass Lolium perenne (high yielding, highly digestible) and Festuca species (low digestibility, but highly tolerant to abiotic and biotic stresses) such as Festuca pratensis are being directly exploited commercially.…”