Scanning Electron Microscope Analysis of Drupelet Morphology of Red Raspberry and Related Rubus Genotypes

Abstract

Scanning electron microscopy was used to measure epidermal hairs and drupelet morphology of raspberry fruit. Significant differences were found among cultivars and selections in drupelet size, total contact area between drupelets, and contact area with hairs between drupelets, hair density index, and hair length. Drupelet numbers also differed. Fruit strength, as measured by cohesiveness, was related to contact area between drupelets, whether hair-covered or not, in conjunction with total drupelet number. Hair density contributed to cohesion in some years with certain cultivars. Resistance to compression was most consistently correlated with total drupelet area and contact area between drupelets alone and in conjunction with hair density.