HISTOLOGICAL AND POMOLOGICAL CHARACTERIZATION OF SCLEREID CELL CLUSTERS IN SOME IRANIAN LOCAL AND EUROPEAN PEAR CULTIVARS

Sclereid cell clusters are a significant character of pear fruits, both in Asian (Pyrus pyrifolia) and European cultivars (P. communis). The dispersal and form of sclereid clusters affects texture and fruit quality of pear cultivars. This research was carried out to evaluate histological and pomological characterization of 5 local, 19 exogenous (European) and 4 unknown pear cultivars from the Iranian National Pyrus Collection, established in Karaj. Histological evaluation of sclereids was performed microscopically by new-methylene blue staining of fruit tissue. The pomological evaluation of fruits was based on the UPOV descriptor and their correlations with sclereids characterizations were statistically determined. Among tested cultivars, two cultivars, ‘Felestini’ and ‘Red Bartlett’, showed the lowest and highest sclereid cluster per sample, while two cultivars, ‘Felestini’ and ‘Shahak’ demonstrated the lowest and highest sclereid cell per cluster, respectively. The fruit size and volume had high correlation with sclereid cluster density; accordingly genetically small fruit-bearing cultivars demonstrated higher sclereid density. The results also revealed that sclereid differentiation occurs in primary fruit development phase, before cell division termination that usually in pear fruits is not longer than 60 days. Therefore, more cell enlargement inducing condition result in a decrease in the sclereid density in pear fruits.