PEAR YELLOWNESS; AN ATYPICAL FORM OF IRON CHLOROSIS?

A decrease in the pigment content of pear leaves, thought to be related to iron deficiency, occurs in northeastern Spain where is usually called "pear yellowness". A nutritional study has been carried out on a pear orchard affected by this disease and growing in the medium Jalón river Valley.
Total iron contents were high both in deficient and control leaves, in good agreement with results obtained for iron deficient crops in the same area.
However, potassium/calcium ratios were low, in sharp contrast with the high potassium/calcium ratios usually associated with iron chlorosis worldwide.
Manganese contents per unit area were significantly lower in the yellow leaves.
A new high performance liquid chromatography method confirmed that most pigments decrease concomitantly with chlorophyll a in agreement with previous reports on iron deficiency from this laboratory.
The new method allowed us to quantify the amounts of some pigments not fully separated before -violaxanthin, anteraxanthin, zeaxanthin-. Total amounts of these pigments showed slight increases -about 20%- when chlorophyll decreased by 60% (mild chlorosis), and only moderate decreases -25%- when chlorophyll decreased by 80% (fully developed chlorosis).

V International Symposium on Pear Growing

A. Abadía, M. Sanz, J. Rivas, J. Abadía

https://doi.org/10.17660/ActaHortic.1989.256.25