SHOOT AND BLOSSOM SUSCEPTIBILITY TO FIREBLIGHT OF APPLE CULTIVARS

The fireblight susceptibility of 75 named cv. of apple and of two Malus species has been evaluated through artificial inoculation, during 3 or 4 consecutive years for shoots inoculation and 2 consecutive years for flowers inoculation.

The results of shoot inoculations are assessed in 5 classes of a varietal index of susceptibility (V.I.S.) :

Formula available in full text only

which takes into account the proportion of blighted shoots, and the progression of the disease after inoculation (LE LEZEC and PAULIN, 1984).

The results of flower inoculations are assessed in 5 classes (same limits as above) which are the actual percentages of infected blossoms after inoculation (=Varietal Receptivity).

A table shows the rating of the cv. and sp. according to these two assessments.
The correlation between the two indexes is usually poor (0.48 ≤ r ≤ 0.25).

Nevertheless it appears that this classification fits with the rating of field susceptibility as previously assessed in the same conditions, with few exceptions.

The relations between different ratings are discussed.

IV International Workshop on Fire Blight

M. LE LEZEC, J.P. PAULIN, P. LECOMTE

https://doi.org/10.17660/ActaHortic.1987.217.54