RESEARCH RESULTS ON BIENNAL BEARING VARIETAL FACTORS IN PRUNUS DOMESTICA

J. Couranjou
The object of our researches is to find the varietal causes of biennal bearing.

First hypothesis. A variety should be so much the more alternating as it should be more productive; the excess of produced fruits involve an important decrease of the flower bud number; the following year, the flower buds are formed in excess because of the high fertility of the variety; and so the biennal bearing is carried on. The regular varieties will be those which, because of a mean fertility, could form a standard number of flower buds. This hypothesis has been corroborated and this investigation allowed us to base on the modalities of the varietal fertility: the fertility level of a variety is determined by the ability of the inflorescence to give fruits; this two abilities are independent. The first one has been measured by the number of flower buds formed in absence of fruits (top rate). This top rate appeared like a constant about variety. The second one is not a constant for every variety. According to the case, it can increase or decrease the first one in its effect on biennal bearing. The union of the one and the other fix the fertility level of a variety which itself conditioned the alternate bearing intensity of a variety.

Second hypothesis. Another factor could interfer: some varieties should be less sensible than others at the presence of a fruit excess and could in these conditions form a good number of flower buds; they should be less alternating than varieties which are sensible at the fruit presence.

To corrobate this hypothesis, we compared the decrease graphs (the number of flower fuds in function of the number of the fruits). We obviously have determined the mathematic graph of this inverse relation. The first results showed sensibility differences between varieties without any relation with the fertility level.

The character of fertility and sensibility determined alternate tendency of each variety; four basic types have been like that pointed out.

Couranjou, J. (1975). RESEARCH RESULTS ON BIENNAL BEARING VARIETAL FACTORS IN PRUNUS DOMESTICA. Acta Hortic. 48, 35-50
DOI: 10.17660/ActaHortic.1975.48.5
https://doi.org/10.17660/ActaHortic.1975.48.5