AGRE-0067 Upgrading the Genetic Quality of Hardwoods by Selection of Elite Germplasm and Conservation on Marginal & Abandoned Farmland

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ECLAIR Cluster II - Lignocellulose : Plant Genetics : Wood (Lignocellulose)

The picture shows the establishment in the field of selected oak trees (Quercus petraea) which had been micropropagated. It demonstrates that micropropagation and field establishment of valuable hardwoods such as oak is possible - in this case on a pilot scale in Germany.

SUMMARY

Afforestation of marginal and abandoned farm land with broad leaf trees requires suitable planting material. This project assessed the feasibility and economics of this from a wide range of European trees including Acer, Alnus, Betula, Camellia, Fagus, Fraxinus, Juglans, Prunus, Quercus, Syringa, Tilia, Ulmus. Sterile cultures have been successfully initiated for all species using material of different physiological ages from immature embryos, embryonic axes, seeds, buds excised from seedlings, adolescent trees, adult trees, adult scions on grafted plants, forced dormant twigs and root suckers. It has been established that such techniques increase the facility of initiating cultures and increase the rate of shoot production. Micropropagation rate in vitro is strongly affected by genotype for Quercus, Castanea, Tilia and Syringa whereas for other species such as Betula and Prunus the propagation rate can be experimentally increased by choosing appropriate media.

INTRODUCTION

To take advantage of the opportunities for afforestation of marginal and abandoned farm land requires suitable planting material. Mixed deciduous (hardwood) forests are preferable from the point of view of diversification, wildlife and the environment in general, when compared with monoculture plantations of firs, pines or Eucalyptus. In contrast to these plantations, species-mixed broad leaf forests have much longer average life spans, hence, due consideration has to be paid to the nature of the resource and habitat which is being established for future generations. However, less work has been done on such species than for fast growing broad-leaved types such as poplar and willow investigated for short rotation forestry or as coppice. This project aimed to overcome this deficiency by identifying and conserving elite hardwood tree species.

OBJECTIVES

The primary objective was to develop an efficient strategy to vegetatively propagate a wide range of hardwood trees en mass so as to provide cloned material to meet needs for future afforestation. To achieve this it was necessary to develop and understand the ways and means of manipulating the physiological responses and biochemical events in tree tissue cultures so as to facilitate initiation of cultures, micropropagation and weaning.

ACTIVITIES

Selection: The following of elite trees were identified and mapped by foresters Prunus170, Quercus 125, Castanea 90, Juglans 110, Fraxinus 80, Acer 300, Camellia 200,Alnus 40, Ulmus 20, Populus 20, Tilia l0. Scions were collected and grafted and other propagules where taken from elite trees/seed sources. Such elite germplasm was exchanged amongst participants.

Culture Initiation: Methods for sterilisation of buds and other explants were developed. With Prunus, Castanea and Populus, around 90% of the material initiated was viable. For the remaining species, between 30 and 50% of initiated material was established. Of these, approximately 50% were capable of shoot proliferation and rooting.

Rejuvenation: Aged tissues showed poor shoot proliferation and rooting ability. In some cases, strong clonal effects were observed on rooting. Among 5 mature clones of Castanea, rooting rates of 11 to 94% were reported. It appears that micropropagated plants are capable of giving higher rooting rates in cuttings, than those taken from other sources such as hedged plantations or seedlings. Two marker proteins characterised mature tissues of Castanea and the stem diameter and growth angle were indicators of maturity status in shoots of Quercus in vitro.

Micropropagation: This was achieved for all species using juvenile sources of buds. Propagation rates had mean ranges of: 2.8-4.2 Betula; 2-5 Prunus; 1.6-2.3 Juglans; 1.7-2.3 Camellia; 1.3-5.3 Castanea; 1.4-4.0 Quercus; 3-4 Fraxinus; 1.0-3.0 Acer. Somatic embryogenesis was achieved using anthers and zygotic embryos of Quercus; seeds of Castanea and Fagus; cotyledons of Prunus and Camellia; embryonic axes of Juglans; roots and leaf explants of Cancellia.

Biochemistry: Biochemical markers were found which characterised rooting capacity, propagation rate, maturity status and adverse physiological disorders such as vitrification. An increase in peroxidase activity occurred during the induction of roots in Prunus, Juglans and Camellia and could be used to predict their rooting capacity. In Juglans, auxin accumulated at the base of rootable shoots and the number of roots/shoot was correlated with their content of hydrojuglone glucoside. Cumulative results suggest that in most cases a set of biochemical markers had to be considered together. In general, a higher content of endogenous auxin, polyamine and antioxidant (reducers), together with lower activities of antioxidant enzymes, were associated with a high capacity for rooting in juvenile and mature tissues.

Plant Production: The total production was 130,000 plants ofPrunus, 67,000 of Camellia, 42,000 of Castanea and around 10,000 for each for the remaining species. From 29 clones of Prunus, 42,000 plants were obtained and 67% were successfully weaned, whereas, with Juglans weaning ranged from 5 to 85% among 8 clones. At the industrial scale the viability was 70-80% for Tilia, 50% for Quercus and 80% for Syringa with over 200 plants species. Field plantings were made of Castanea, Camellia, Prunus, Betula and Quercus.

Upscaling and Automation: Over 100 cultures per clone were actively propagated for Prunus, Tilia, Syringa, Quercus, Betula, Castanea and Camellia.

Economic Assessment: An analysis of production costs showed variation between countries, but in most cases labour accounted for over 50% of total costs. The cost of plants were generally (but not always) higher when produced by micropropagation, as compared to the market price for equivalent seedlings.

Germplasm Conservation: The locations of elite trees in forests was documented and many clones of each species were established and conserved in the nursery, mainly by grafting.

CONCLUSIONS

Elite trees of the following have been identified and data banks generated: Acer, Alnus, Betula, Camellia, Fagus, Fraxinus, Juglans, Prunus, Quercus, Syringa, Tilia, Ulmus. Sterile cultures have been successfully initiated for all species using material of different physiological ages from immature embryos, embryonic axes, seeds, buds excised from seedlings, adolescent trees, adult trees, adult scions on grafted plants, forced dormant twigs and root suckers. It has been established that such techniques increase the facility of initiating cultures and increase the rate of shoot production.

EXPLOITATION

Many clones of each species have been produced and are available either as grafted plants, self rooted cuttings or sterile cultures. These have been exchanged internationally among institutional and industrial partners.

PARTICIPANTS

Niedersächsische Forstliche Versuchsanstalt (Germany), Firma H.G. Rahte (Germany), Coillte Teoranta, The Irish Forestry Board (Ireland), University of Liège, Laboratory of Hormonology (Belgium), SA Fee Bioplant (Belgium), CSIC (Spain), Azienda Regionale dell Foreste dell'Emilia Romagna (Italy), Institute for Forestry & Urban Ecology (Netherlands), CNR (Italy), INRA - SAAF (France), Azienda Agricola Meristema SRL (Italy), Bonsai-Flora SAT (Spain) and Cultigar SL (Spain).