The agronomic and pulping performance of transgenic trees with altered lignin has been evaluated in duplicated, long-term field trials. Poplars expressing cinnamyl alcohol dehydrogenase (CAD) or caffeate/5-hydroxy-ferulate O-methyltransferase (COMT) antisense transgenes were grown for four years at two sites, in France and England. The trees remained healthy throughout the trial. Growth indicators and interactions with insects were normal. No changes in soil microbial communities were detected beneath the transgenic trees. The expected modifications to lignin were maintained in the transgenics over four years, at both sites. Kraft pulping of tree trunks showed that the reduced-CAD lines had improved characteristics, allowing easier delignification, using smaller amounts of chemicals, while yielding more high-quality pulp. This work highlights the potential of engineering wood quality for more environmentally benign papermaking without interfering with tree growth or fitness.

Few experiments have yet been performed to explore the potential ecological impacts of genetic modification in long-lifespan species such as trees. In this paper, we review the available data on GM trees with modified lignin focussing on the results of the first long-term field trials of such trees. These trials evaluated poplars expressing antisense transgenes to reduce the expression of the lignin biosynthesis genes cinnamyl alcohol dehydrogenase (CAD) or caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) with the aim of producing trees with improved pulping characteristics. The trees were grown for 4 years at two sites in France and England, and their ecological impacts and agronomic performance were assessed. Modifications to lignin in the poplars were maintained over the 4 years of the trial. The trees remained healthy throughout and growth was normal. The lignin modifications had no unexpected biological or ecological impacts. Interactions with leaf-feeding insects, microbial pathogens and soil organisms were unaltered although the short-term decomposition of transgenic roots was slightly enhanced. Investigation of the ecological impacts of the GM trees was curtailed by the early termination of the field trial when it was attacked and largely destroyed by anti-GM protestors. To supplement our work on the decomposition of GM plant materials with modified lignin, we have therefore turned to the study of transgenic tobacco lines where we can perform more comprehensive and controlled analyses of the biological and ecological effects of ligningene suppression.

Byrne, S., Guiney, E., Barth, S., Donnison, I. S., Mur, L. A. J., Milbourne, D. (2009). Identification of coincident QTL for days to heading, spike length and spikelets per spike in Lolium perenne L. Euphytica, 166, (1), 61-70. S. Byrne was awarded a Teagasc Walsh Fellowship/Ireland to undertake this study IMPF: 01.40 Sponsorship: BBSRC RONO: BBS/E/W/00003134BFlowering time is a trait which has a major influence on the quality of forage. In addition, flowering and subsequent seed yields are important traits for seed production by grass breeders. In this study, we have identified quantitative trait loci (QTL) for flowering time and morphological traits of the flowering head in an F1 mapping population in Lolium perenne L (perennial ryegrass), a number of which have not previously been identified in L. perenne mapping studies. QTL for days to heading (DTH) were mapped in both outdoor and glasshouse experiments, revealing three and five QTL for DTH which explained 53% and 42% of the total phenotypic variation observed, respectively. Two QTL for DTH were detected in both environments, although they had contrasting relative magnitudes in each environment. One QTL for spike length and three QTL for spikelets per spike were also identified explaining, a total of 32 and 33% of the phenotypic variance, respectively. Furthermore, the QTL for spike length and spikelets per spike generally coincided with QTL for days to heading, implying co-ordinate regulation by underlying genes. Of particular interest was a region harbouring overlapping QTL for days to heading, spike length and spikelets per spike on the top of linkage group 4, containing the major QTL for spike length identified in this population.Peer reviewe

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Byrne, S. L., Guiney, E., Donnison, I. S., Mur, L. A. J., Milbourne, D., Barth, S. (2009). Identification of genes involved in the floral transition at the shoot apical meristem of Lolium perenne L. by use of suppression subtractive hybridisation. Plant Growth Regulation, 59, (3), 215-225. Electronic supplementary material. The online version of this article (doi:10.1007/s10725-009-9407-7) contains supplementary material, which is available to authorized users. IMPF: 01.53 RONO: 03134 Sponsorship: BBSRC, TEAGASC, Ireland RONO: BBS/E/W/00003134BGenerally, heading in Lolium perenne L. (perennial ryegrass) is associated with a reduction in the feed quality of the forage and therefore extending the period of vegetative growth during the growing season will contribute to an improvement in quality. The genetic control of floral transition has been well studied in model plant species but less research has been done in economically important crop species such as perennial ryegrass. A differential gene expression study was performed between two full sibling lines of L. perenne with contrasting flowering time. Suppression subtractive hybridization was used to identify 155 transcripts differentially expressed between the two sibling lines in the shoot apical meristem after primary and during secondary induction. Transcripts with a putative role in the floral transition were further characterized, through floral induction stages, by real time RT?PCR. This revealed five genes with greater than tenfold difference in expression between the lines during floral induction. Furthermore, a putative methyl binding domain protein and bHLH transcription factor were identified, which show clear differential expression patterns through floral induction and may act as potential enhancers of flowering in L. perennePeer reviewe