Ricerche Sulla Biologia Fiorale Dell'olivo

Summary

In the researches illustrated by this publication, after pointing out the importance of knowing which varieties are self-fertile and which are self-sterile among orchard tres, the author considers our present knowledge on olive-tree's floral biology, regarding both self-sterility and ovary-abortion.

The results of the investigation are:

1.°) That systematical researches on self-sterility and self-fertility of okivetree varieties have not yet been carried out. The general belief is that autogamic fertilisation guarantees normal fructification of each variety.

2.°) That on the other hand numerous studies have been made on overy aborton of olive-trees and that great influence is attributed to it in determinating furit yield. The author then explains the results of his own researches carried out during the period 1936–1937–1938 on the principle Tuscan varieties and those of the province of Perugia, in order to determine the self-fertile and self-sterile varieties and also the pollinizing varieties.

The conclusions at which he arrives, based on numerous and laborious researches, are the followin:

1.°) The vaireities, moraiolo, leccino, pendolino, morchiaio, Madoma del. Ulmpruncla, olivo di seme, of the province of Florence and the varieties dolcc Agogia and Morella of the province of Perugia are practically self-sterile or in other words, that the single flowers of each variety are unable to bear fruit, niether with their own pollen nor with that of other flowers of the same olive-tree or of other olive-trees or the same variety.

For their fructification the presence of pollen of another variety in necessary. Consequently self-sterility of olive-tree varieities in the aforesaid localities is a rule rather than an exception.

2.°) On the contrary frantoio is a self-fertile variety because its flowers bear fruit also when they are fertilized by their own pollebn.

3.°) Each self-sterile variety owing to such biological behaviour during fertilization should be suitable mixed in the olive-orchards with other pollinizing varieties:

Good varietal cross-fertilization was obtained as follows:

moraiolo by morchiaio, frautoio and leccino;

pendolono by moraiolo and frantoio;

dolce agogia by morella;

morella by dolce agogia.

4.°) Among the self-sterile olive-tree varieties considered no inter-sterility was encountered, that is to say, each self-sterile variety may be fertilized by pollen of other self-sterile and self-fertile varieties and bear fruit.

This does not exclude that each variety may possess a special fertilizing affinity with the pollen of one or more of these varieites.

5.°) the olive-trees of the same variety in each locality all behaved in the same manner regarding self-fertility and self-sterility. such a behaviour gives ground to the belief that the population of olive-trees examined may belong to the same clonal strips with the exception of the frentoio variety, because the olive-trees of this variety seem to belong to a stirps different from the prevalent one which has proved to be self-sterile.

The investigations made so far on ovary-a bortion of olive trees have brought the author to the following conclusions:

1.°) Ovary-abortion is very seldom encountered in teh following varieties: frantoio, moraiolo, leccino, pendolino, Madonna dell'Im pruneta.

It occurs in very high percentages in the morchiaio and oliro di seme varieties cultivated in teh same ecological conditions as the aforesaid.

2.°) Partial ovary-abortion of olive-tree flowers when it is not a consequence of plant denutrition does not influence fruit yield to any great extent.

3.°) Self sterility in the olive-tree varieties examined cannot be caused by ovary-abortion which only partially aflects all varieties.

The same researches should be continued in order to ascertain the behaviour of the varieties cultivated in the other provinces of the country.