Measurement of grape root firmness and its application to the evaluation of cold hardiness

Background and Aims In this study, the cutting force and work to cut 12 grape cultivars with different cold hardiness were measured with a texture analyser to examine root firmness and its application to the evaluation of cold hardiness. Methods and Results The transverse cut method involved cutting in a direction perpendicular to vascular orientation, and the longitudinal cut method involved cutting in a direction perpendicular to the transverse cut. The transverse maximum cutting force (MCF) and cutting depth showed a linear relationship, while work of transverse cutting and cutting depth indicated a power function. Dornfelder, Merlot Noir, Tannat, Carmenère and Syrah required the least MCF, Vidal, SO4, 3309C and 101-14M a moderate MCF, and Chambourcin, Beta and Frontenac the highest MCF. Work classification of the 12 cultivars was consistent with MCF classification. Conclusions The correlation coefficients of cold hardiness and MCF at 2 mm cutting depth was the highest in the transverse cut, and the correlation coefficients of cold hardiness and phloem MCF of 1 mm cutting depth was highest in the longitudinal cut. The root phloem/radius ratio was correlated negatively with MCF and work, yet the correlation between xylem/radius and MCF and work was positive. The exodermis/radius ratio was significantly correlated with the MCF and the work of a transverse section and phloem longitudinal section. Significance of the Study The cross-sectional cut of 2 mm depth and longitudinal cut of 1 mm depth could distinguish the firmness of different cultivars, and could be considered as the determinant index of cold hardiness.