Initial Time of Development of Hard End Disorder in ‘Bartlett’ Pear

YAMAMOTO Takanori, WATANABE Shunzo

doi:10.2503/jjshs.51.142

In order to clarify the relationship between water conditions and the occurrence of hard end disorder in ‘Bartlett’ pear fruit, it is necessary to know when the disorder begins to develop. In the present study, fruit characters seemed to be related to the occurrence of this disorder were investigated in relation to fruit growth and after ripening in comparison of a tree having every year a high percentage of hard end (affected tree) and normal, healthy tress (growing in the same orchard).<br>1. Between after-ripened fruits from normal and affected trees, significant differences were found in mean fruit weight, fruit length, degree of flatness of calyx end, and peel and flesh firmness. They were also found in the densities of pectic substance and tannin but not corky substance and starch determined by histochemical observations. However, it was pectic substance alone that showed a close correlation to flesh firmness in their distributions on the vertical section of each fruit.<br>2. Fruits from the affected tree were smaller in weight and size, and lower in Mg and higher in total polyphenol contents in calyx end than those from the normal trees throughout fruit growth. While, their cell size, Ca content and Ca/K ratio became inferior and K and HCl-soluble pectin contents became superior at calyx end to those of normal trees from 40 to 50 days after full-bloom. Further, from 55 to 60 days after full-bloom, peel firmness and contents of alcohol insoluble solids and holocellulose at calyx end of fruit, and from 60 to 65 days after full-bloom, the degree of flatness of fruit and flesh firmness, and α-cellulose content, at calyx end of fruit, became higher in the affected tree than normal trees.<br>3. At the time of ripening (about 120 days after full-bloom), there were found great differences only in peel and flesh firmness, contents of HCl-soluble and water-soluble pectins in calyx end of fruit between normal and affected trees.<br>4. From these results, it is concluded that hard end disorder begins to develop as early as 40 to 65 days after full-bloom, although, externally, it is characteristic of this disorder that the calyx end of fruit is kept hard even at after ripening stage perhaps due to insufficient degradation of pectic substances.

Initial Time of Development of Hard End Disorder in ‘Bartlett’ Pear

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