Influence of Rootstock Cultivars on Firmness of Skin and Flesh of ‘Mizunasu’ Eggplant Fruit

Abstract

The influence of rootstock cultivars on the skin and flesh firmness of eggplant fruit was examined. ‘Mizunasu’ was grafted to three kinds of rootstock cultivars, ‘Torero’, ‘Hiranasu’ and ‘AE-RS01’. The samples 19 mm in diameter and 10 mm thickness including skin were prepared for puncture test using the universal testing machine, Instron 5540. A disc shaped plunger 1.5 mm in diameter punctured the samples at a speed of 20 mm per minute. The samples were punctured in both a centripetal direction (through the skin into the flesh) and a centrifugal direction (through the flesh against the skin). In both directions, the skin of the fruit was significantly firmer in ‘Mizunasu’ grafted to ‘Torero’ (M/T) than in ‘Mizunasu’ grafted to ‘Hiranasu’ (M/H) or in ‘Mizunasu’ grafted to ‘AE-RS01’ (M/A). The results of flesh firmness differed according to the puncture directions. The M/T plants showed more vigorous growth than the M/H or M/A plants. It was considered that ‘Mizunasu’ grafted to vigorous rootstock cultivar produced fruit with a firm skin.