Relationships between Degrees of Occurrence of “Yuzuhada” Disorder and Contents of Inorganic Elements of Fruit Pulp in Japanese Pear Cultivars

Abstract

The degree of occurrence of “Yuzuhada” disorder and its relation to the contents of inorganic elements in fruit pulp were compared among several Japsnese pear(P. serotina Rehd.) cultivars.
1) Japanese pear cultivars, Shinsui, Hosui, Kosui, Shinko, Chojuro and Nijisseiki were top-grafted on secondary scaffold branches of 12-year-old ‘Nijisseiki’ pear tree which was suffering from “Yuzuhada” disorder.
2) Three years after the grafting, the severe occurrence of “Yuzuhada” disorder was observed in ‘Shinko’, ‘Chojuro’ and ‘Nijisseiki’ fruits.
In ‘Shinsui’ and ‘Hosui’ fruits, a slight occurrence of the disorder was observed, while in ‘Kosui’ fruits, no symptom was observed.
3) Contents of soluble K, Ca and Mg in fruit pulp were compared at an early stage of fruit growth.
‘Shinko’, ‘Nijisseiki’ and ‘Chojuro’ were rich in soluble K and poor in soluble Ca. On the other hand, ‘Kosui’, ‘Shinsui’ and ‘Hosui’ fruit pulps were lowor in soluble K and higher in soluble Ca than those of the former three cultivars.
4) 0.2% ammonium oxalate soluble K contents in fruit pulp were high in ‘Shinko’, ‘Chojuro’ and ‘Nijisseiki’. These cultivars were suffering from severe “Yuzuhada” disorder.