Measurement of Starch Index in Radish Roots and Its Application to Evaluate Inheritance of Tissue Firmness

As one of the major storage carbohydrates, starch correlates with the tissue firmness and cell wall contents as well as contributes to the textural quality of radish (Raphanus sativus L.) root. In this study we developed a simple method to evaluate starch content and tissue firmness by measuring the color (Hunter 'b') of iodized radish slice as a starch index. The gelatinization of radish slice was optimized by swelling at 60℃ for 20 min, and the Hunter 'b' value and the concentration of iodized potato starch were highly correlated (r²=0.948). This relationship was also effective to the analyses of inheritable texture traits of three F₁ hybrids and their breeding lines. The heritability of tissue firmness of radish root, based on starch index and compressibility, turned out to be fairly high, ranging from 0.47 to 0.93. However, heterosis was relatively low. This method is simple and rapid, and, therein, could be employed as a quick evaluation for qualifying radish texture since the correlation between Hunter 'b' value and starch content was consistent among different cultivars. The present study also revealed that either parental line which exhibits a relatively less firm in texture of the root was dominant.