THE EFFECTS OF VIRUSES ON THE GROWTH, YIELD AND QUALITY OF THREE APPLE CULTIVARS ON HEALTHY AND INFECTED CLONES OF FOUR ROOTSTOCKS

A.I. Campbell
The growth of three apple cultivars (EMLA clones) on four clonal rootstocks with different virus infections was compared in a replicated experiment planted in 1967/68. Trees on EMLA clones of the rootstocks M9 and M7 free from all known viruses were compared with trees on clones M9A and M7A and with the original M9 and M7. Also included in this experiment was a comparison of trees on healthy clones of M26 and MM106 with similar clones inoculated with the viruses from M9, M9A, M7 and M7A.

Measurements showed that the latent virus infections significantly reduced the growth and yield of the trees and that some cultivars and rootstocks were more sensitive than others. Cox's Orange Pippin was more sensitive to infection than Egremont Russet and Worcester Pearmain particularly on the dwarfing rootstock M9. The three clones of M9 showed larger differences in yield than on M26, MM106 and M7 clones. The results also showed that the trees on M9A were weaker than trees on the original M9 although they carried similar virus infections.

When the crop weight to trunk area ratio was compared, the data showed that the differences between treatments was minimal. The smaller virus infected trees cropped as well as the healthy ones, in proportion to their size.

Grading showed that apples from the healthy trees were much larger than those from trees on infected rootstocks. With Cox on EMLA 9, 69% of the Class 1 fruit was over 60 mm whereas on the two infected clones of M9 only 53% were over 60 mm.

Campbell, A.I. (1981). THE EFFECTS OF VIRUSES ON THE GROWTH, YIELD AND QUALITY OF THREE APPLE CULTIVARS ON HEALTHY AND INFECTED CLONES OF FOUR ROOTSTOCKS. Acta Hortic. 114, 185-191
DOI: 10.17660/ActaHortic.1981.114.25
https://doi.org/10.17660/ActaHortic.1981.114.25

Acta Horticulturae