Restoring depleted Tunisian drylands with native steppic species: where should we source the seeds?
2001
Visser, M. | Reheul, D.
In many of the world's drylands genetic and soil erosion are widespread. To enhance success of any large scale restoration effort in these hazardous conditions, it is essential to set up systematic seed production of key native plant species. The aim of the traditional outline is to gather local yet ample genetic variation to avoid the risks of non-adaptation. But for Stipa lagascae R. and Sch, a North-African perennial bunch grass, we carried out an outline inspired from conventional forage breeding practice, with the aim to select for vigour. Here, we assess its outcomes as for the risk of selecting non-local and/or non-ample genetic variation. We established a collection composed of 276 clonal lines out of individuals coming from 70 accessions, spread over 6 major ecogeographic origins within Presaharian Tunisia (100 mm < average annual rainfall < 200 mm), both source and target region. During 7 successive growing seasons with stark contrasts for rainfall and fertility, we observed the collection for vigour and phenology. Principal Components Analysis has been carried out on a data matrix of 276 lines and 11 variables. Both for vigour and for phenology, individuals differentiated strongly, but irrespective of accession or ecogeographic origin. Moreover, differences for vigour persisted throughout contrasting growing seasons. Both facts combined (1) do not indicate any local adaptation within the target region, (2) suggest instead intense genetic structuring due to isolation by distance, (3) make it easy to cull a limited number of lines to combine considerable genetic variation with consistently superior vigour.
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