Dissecting drought‐ and cold‐tolerance traits in the Lolium–Festuca complex by introgression mapping

Abstract

Recent advances in the cytogenetics of the Lolium?Festuca complex provide new opportunities for understanding and manipulating complex physiological mechanisms such as drought and cold resistance. This paper describes breeding programmes involving hybrids between two species: L. multiflorum, which offers good early growth and high nutritive value, and F. arundinacea, which is more stress tolerant. The programmes are designed to allow a rapid recovery of the Lolium genome and to restrict numbers of recombinants derived from Festuca. Use of genomic in situ hybridization (GISH) and an isozyme marker demonstrates how gene complexes from any part of the Festuca genome can be introgressed into Lolium. This enables us to construct genotypes combining desirable traits of both Lolium and Festuca species. By introgressing different Festuca genes into Lolium, quantitative traits such as tolerance to drought and cold can be ?dissected? into their different components, to clarify their function. Festuca genes for stress tolerance can be located by genomic in situ hybridization (GISH) and assigned to regions of chromosome arms in Lolium. Two Lolium genotypes are described, in which genes for drought resistance transferred from the F. pratensis sub-genome of F. arundinacea onto chromosome 2 of Lolium. The two drought-resistant lines have the high water conductance of Festuca on their adaxial leaf surface and the low abaxial conductance of Lolium. The paper also describes how androgenesis of L. multiflorum?F. arundinacea hybrids has led to the selection and characterization of genotypes with coacclimation to drought and freezing stress, in some cases exceeding that in the Festuca parent.Peer reviewe

FISH Karyotype Analysis of Four Wild Cucurbitaceae Species Using 5S and 45S rDNA Probes and the Emergence of New Polyploids in Trichosanthes kirilowii Maxim.

“…This approach has been demonstrated in wheat, rice, rapeseed, and other crops (Anamthawat-Jónsson, 2001;Brar and Khush, 1997;Humphreys et al, 1997;Jiang et al, 1993;Lashermes et al, 2000;Snowdon et al, 1997). Some cucurbits have also benefitted from this breeding approach.…”

GISH/FISH mapping of genes for freezing tolerance transferred from Festuca pratensis to Lolium multiflorum

“…Conversely, although having relatively inferior seedling vigour and nutritive value, closely related Festuca pratensis (2n ¼ 2x ¼ 14; Fp), F. glaucescens (2n ¼ 4x ¼ 28; Fg), and F. arundinacea (2n ¼ 6x ¼ 42; Fa) can provide a greater tolerance to climatic stresses than Lolium. These Lolium and Festuca species hybridise readily and their homoeologous chromosomes pair and recombine at high frequency, enabling the assembly of their complementary characters within a single genotype (Humphreys et al, 1997). Intergeneric amphiploids that combine complementary characters of both genera have been generated (eg Lewis et al, 1973;Zwierzykowski et al, 1998;Casler et al, 2001), but homoeologous chromosome pairing has led often to aneuploidy, genetic imbalance, and sterility in the hybrids, limiting breeding progress.…”

“…Furthermore, a shift towards the Lolium parental genotype in amphiploid L. perenne or L. multiflorum  F. pratensis over several generations (up to F 8 ) has been observed by different research groups (Zwierzykowski et al, 1998(Zwierzykowski et al, , 2003Canter et al, 1999;Pašakinskienė and Jones, 2003). As recombination between homoeologous Lolium and Festuca chromosomes occurs frequently in hybrids, opportunities for gene introgression arise, enabling the transfer to Lolium of Festuca genes for improved persistency, through a backcross breeding programme (Thomas et al, 1994Humphreys et al, 1997Humphreys et al, , 2003Humphreys et al, , 2005King et al, 1998;Zwierzykowski et al, 1998Zwierzykowski et al, , 1999. The targeted inclusion of desirable Festuca gene combinations can be accompanied by the targeted exclusion of other Festuca genes considered detrimental to the high forage quality traits found in Lolium.…”

Designing Grass Cultivars for Droughts and Floods

“…A highly significant increase (P < 0.001) in WUE of 88 % in Bb2540 compared with the control Lolium cultivar Atalja demonstrates very well the possible impact and advantage such a cultivar might have in drought-prone grasslands. In its natural habitat, F. arundinacea var glaucescens undergoes a phase of summer quiescence (Humphreys et al 1997) which would be a highly unsuitable agronomic trait for livestock agriculture in European grasslands, where continued grassland growth and production in summer is considered an essential requirement. The high yields of Bb2540 both in irrigated and in droughted conditions are proof of its excellent agronomic performance.…”