Nathalie Moutier

The use of molecular markers for germplasm management in a French olive collection.

Abstract.With more than 100 accessions, the CBNMP olive collection includes a major part of the French germplasm. We used molecular markers to characterise all accessions and to study genetic relationships between cultivars. Firstly, 497 olive trees were genotyped using 32 RAPD markers. We identified 114 RAPD profiles and detected several cases of mislabelling, synonymy and homonymy. Secondly, for each RAPD profile, one tree was analysed using mtDNA RFLPs to determine the cytoplasmic lineage of each cultivar and using five nuclear SSR loci. French germplasm displayed ME1, MOM and MCK mitotypes with ME1 prevailing (84%). Based on SSR markers, we revealed a slight differentiation between French cultivars growing in the West and the East side of the Rhône Valley. This study allowed us to construct a molecular data-base for the reference collection and to analyse genetic diversity for further prospecting, and for introducing new olive accessions.

Plasticity in Vegetative Growth over Contrasted Growing Sites of an F1 Olive Tree Progeny during Its Juvenile Phase

Climatic changes impact fruit tree growth and severely limit their production. Investigating the tree ability to cope with environmental variations is thus necessary to adapt breeding and management strategies in order to ensure sustainable production. In this study, we assessed the genetic parameters and genotype by environment interaction (GxE) during the early tree growth. One hundred and twenty olive seedlings derived from the cross ‘Olivière’ x ‘Arbequina’ were examined across two sites with contrasted environments, accounting for ontogenetic trends over three years. Models including the year of growth, branching order, environment, genotype effects, and their interactions were built with variance function and covariance structure of residuals when necessary. After selection of a model, broad sense heritabilities were estimated. Despite strong environmental effect on most traits, no GxE was found. Moreover, the internal structure of traits co-variation was similar in both sites. Ontogenetic growth variation, related to (i) the overall tree form and (ii) the growth and branching habit at growth unit scale, was not altered by the environment. Finally, a moderate to strong genetic control was identified for traits at the whole tree scale and at internode scale. Among all studied traits, the maximal internode length exhibited the highest heritability (H2 = 0.74). Considering the determinant role of this trait in tree architecture and its stability across environments, this study consolidates its relevance for breeding.

Agronomical and genetical approaches developed in France for new olive planting systems.

French olive production is currently limited by its very high cost mainly due to labour expenses. A new olive planting system based on hedgerows and harvesting machines could be a solution to decrease olive oil production costs while maintaining good quality. In France various methods have been investigated to improve the management of such training system, based on architectural studies, improvement of tree training and search of low vigour material (existing genotypes, dwarfing rootstocks, offspring progeny) for the new orchards. The initial results for each approach and the research prospects are presented in this paper for better knowledge of tree development, influence of tree manipulations on tree architecture and productivity, and exploration of genetic solutions.

STUDYING THE GENETIC DETERMINISM OF OLIVE TREE ARCHITECTURE IN A F1 PROGENY 'OLIVIÈRE' × 'ARBEQUINA'

Tree architecture is of major importance for the agronomic performance of fruit tree orchards. It influences tree adaptability to cultivations systems, but also yields and fruit quality. In the present study, we aim at investigating the genetic determinism of architectural traits in the olive tree. A F1 hybrid population was created between two genotypes with contrasted architectures, ‘Oliviere’ and ‘Arbequina’. A phenotyping methodology was applied to analyze traits related to growth, branching and fruiting behaviour, that were measured during the first 4 years of tree growth. Taking into account the influence of tree ontogeny, the phenotypic variability was decomposed into genotypic and residual effects in order to identify the most heritable characters. Topological and geometrical variables showed relatively low to medium broad sense heritability values. The highest heritability values were found for the number of internodes and short laterals per growth unit, and the mean internodes length with H2 value greater than 0.5. Flowering variables showed high heritability values exceeding 0.6. A first QTL (quantitative trait loci) was detected for the number of lateral inflorescences, on the basis of a framework genetic map constructed with 44 SSR loci and 494 AFLP markers.