Eucalyptus globulus and hybrids are important non-native tree species with a high production capacity. They also have a potential to grow on marginal lands and thereby provide an income for depressed rural areas in Southern Europe.
B4EST aims to identify and develop eucalypt trees well adapted to growing in rapidly changing environments, and those more tolerant to biological and climate threats. To do this it is first necessary to evaluate the amount of genetic variation amongst eucalypt trees for tolerance to cold (freezing temperatures) and to water stress. Tolerance to snout beetle (Gonipterus platensis), today’s eucalyptus pest with highest impact in Iberian Peninsula, is also being evaluated.
Trees’ growth and survival performances in these conditions will be assessed in a variety of circumstances:
- in a field trial with contrasted water availability,
- in controlled conditions for drought and cold tolerance,
- in breeding trials with contrasted drought and/or cold exposure, and
- in fields and laboratory for resistance to Gonipterus.
B4EST field trial with contrasted water availability
A field trial was established in June 2018 in central Portugal with thirty clones (genetically identical individuals) of Eucalyptus globulus and Eucalyptus spp. Hybrids are distributed in three blocks: 1) without irrigation, 2) with irrigation and additional fertilization, 3) without irrigation and on a soil with seasonal waterlogging.
The trial has a weather station on site to monitor daily climate variables (Figure 1a). It also has sensors monitoring the soil water and the amount of water supplied by irrigation (Figure 1b). The trees are also equipped with sensors to monitor daily micro-fluctuations in the trunks. This monitoring will provide measures of the extent to which the trees are adjusting in the short-term to site conditions, and of specific responses to drought by trees.
So far, the heights of the Eucalyptus clones have been assessed ten times. The results show that faster growth occurred as expected in the irrigated block and that clones which already have adult leaves show a faster early growth.
Assessing drought and cold resistance in controlled conditions
An experiment to test the tolerance of trees to cold (freezing) temperatures by 15 clones, including forest reproductive material being used in operational forestry, has been carried out and the damage to the foliage and survival rates of the trees are being evaluated from one week to one month after the stress.
Two eucalyptus clones with contrasting tolerance to drought were selected and used in a pilot study of drought tolerance carried out in the Toulouse Plant Microbe Phenotyping Platform in Toulouse (Figure 2). The results are being analysed to set up a larger experiment in the near future using the same trees as was used in the assessment of tolerance to cold.
Selecting clones with drought and cold resilience from field trials for further analysis
The breeding trials more exposed to cold and/or to drought were identified and split into four classes: 1) trials exposed to cold, 2) trials exposed to drought; 3) trials exposed to cold and drought; 4) trials less exposed to cold and drought.
An analysis was carried out ranking existing eucalyptus clones for growth and survival. This allowed the identification of 163 eucalyptus clones as a training population for genomic selection (a form of genetic selection using DNA markers). Leaves and wood samples from 160 clones have already been collected and have been sent for DNA extraction and micro-densitometry, respectively.
Assessing the susceptibility of eucalyptus to eucalyptus snout beetle
Laboratory tests are being carried out to assess the susceptibility of different eucalyptus trees to eucalyptus snout beetle (Gonipterus platensis). Twelve different trees of eucalyptus have already been tested – with the extent of foliage consumption by the Eucalyptus snout beetle and amount of egg laying in the leaves being evaluated. Field assessments have also been undertaken evaluating eucalyptus snout beetle attacks in eucalyptus breeding trials. Field work is still under way to evaluate the susceptibility to this beetle of more eucalyptus trees.
This work is carried out within the B4EST project as a collaboration between Altri Florestal (Portugal), CIRAD (France) and UPS (France) using the genetic material and field trials of Altri.