Genome constitution and evolution in Lolium x Festuca hybrid cultivars (Festulolium).

Festulolium hybrids are being increasingly used worldwide as forage grasses. This is due to their superior agronomic characteristics, which combine yield performance of ryegrasses (Lolium multiflorum and L. perenne) and tolerance against abiotic stress of fescues (Festuca pratensis, F. arundinacea and F. arundinacea var. glaucescens). Despite the widespread use, only fragmentary information exists on their genomic constitution. We used genomic in situ hybridization (GISH) to analyze genomic constitution of over 600 plants from almost all commercially available cultivars of Festulolium. Our results revealed a surprisingly large range of variation in the proportions of parental genomes and in the extent of intergenomic recombination. Using fluorescence in situ hybridization (FISH) with probes for ribosomal DNA, we assessed the frequency of recombination and elimination of particular chromosomes and chromosome groups in three contrasting Festulolium cultivars. This study provides novel information that will aid in understanding the relationship between a genetic make-up and the phenotype of Festulolium hybrids. Our results indicate that GISH might be a useful tool to aid in Festulolium breeding and provide data for a more detailed description of registered cultivars.

Influence of consumption of endophyte-infested tall fescue hay on performance of heifers and lambs.

Two experiments were conducted to evaluate performance and physiological responses of heifers and lambs to Neotyphodium coenophialum-infested tall fescue hay fed under European rearing conditions. Endophyte-free (E-) or 100% endophyte-infested (E+) hay was derived from the same cultivar (cv. Clarine) so that the effect of the endophytic fungus could be clearly separated from a possible cultivar effect. In Exp. 1, starting in June 1996, 20 age- and body weight-paired Holstein dairy heifers were assigned for 97 d to one of two treatments consisting of ad libitum access to either E- or E+ hay, corresponding to 0 and .41 mg/kg ergovaline, respectively. During the experimental period, no significant difference (P>.20) in forage consumption, rectal temperature, or behavioral status of the animals was observed between the two treatments. The E+ diet induced a 10% apparent decrease in ADG and a clear reduction in prolactin (PRL) plasma concentration compared to the E- diet. When animals were all reassigned to a common endophyte-free diet, the E+ group recovered body weight and PRL to levels similar to those in animals fed E- after 7 wk. In Exp. 2, 30 Texel ram lambs were assigned to two treatments consisting of dietary E- or E+ tall fescue hay. The E- and E+ hays were harvested from the same plots as used in Exp. 1 and contained 0 and .96 mg/kg ergovaline, respectively. No effect of the endophyte was found on intake or carcass or testicle weight (P>.20) after the 95-d feeding period. The E+ treatment resulted in a slight reduction in BW at slaughter, mainly explained by a lower ruminal fill (P<.01). In E+ treated animals, prolactin concentrations dropped significantly (P<.001) from d 27. Hay assessment in both experiments showed no difference in chemical composition and IVDMD. The endophytic fungus strongly lowered the palatability of the E+ hay, although there was no effect on intake with heifers (Exp. 1) or with lambs (Exp. 2). The potential of severe heat stress, as expressed by the temperature humidity index, was not high in our experimental conditions, although they were considered rather unusually stressful for the western part of northern Europe. Yet, no economic effect on cattle was observed, in disagreement with results obtained in many previous U.S. studies.