STONE MORPHOLOGY IN PRUNUS DOMESTICA. ELEMENTS OF VARIETAL AND CLONAL CHARACTERIZATION. CLIMATIC INFLUENCE.

Stone dimensions ratio (Kobel-Roeder index) and some characteristics permitted differenciation and characterization of French prune mutants. Study of these ratio during six consecutive years for 50 prospected French prune types facilitated the differenciation of 20 clones.

After three cycles of vegetative propagation in 20 years, it is demonstrated that three of the clones maintained well the differences in their ratios.

Annual climatic conditions modified, in the same way, the ratios of all clones. April low temperature lengthens stones; high temperature induces more globular stones.

The precise characteristics of cultivars has become of interest again not only because of problems of protection in newly obtained varieties but also to put repository collections in order. In the species Prunus domestica (hexaploid and of complex origin) most morphological characteristics of the different cultivars present a continuing spectrum of variation. Among other factors, the environment has an influence on the quantitative aspect of numerous characteristics. For example, the pilosity of reproductive organs (calice, ovaries) is more intense in dry years.

Fortunately, in this species, each organ displays, following its variety, a great morphological diversity. Thanks to the very different characteristics such as twigs, leaves, fruit and stone, the varieties can be differentiated, their synonymies discovered and even diverse clones of the same variety characterized.

The stone has proved to be an interesting organ, easy to observe and conserve. Numerous varieties can be distinguished by stone morphology. However, to differntiate the various clones of a variety, it is necessary to use biometric methods such as a study of the three dimensions: height (h), width (w), thickness (t). Figure 1, borrowed from the Pomology of H. Caillavet, indicates the different characteristic parts of the stone and the manner in which the three dimensions must be measured.

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