Micro-CT imaging of tomato seeds: Predictive potential of 3D morphometry on germination

The relationship between seed physical characteristics and seed quality is widely investigated by using X-ray based imaging techniques. Recently the use of X-ray micro-tomography (micro-CT) is increasingly used for more accurate characterisation of the internal seed morphology. In this work a germination test was carried out along with the morphometric characterisation of tomato seed internal structure by means of X-ray micro-CT and 3D image analysis. The aim was to accurately evaluate the predictive potential of internal seed 3D morphology for germination outcomes. The visual assessment allowed the relationship between specific internal seed abnormalities and the different germination outcomes to be demonstrated experimentally. Univariate analysis of morphometric seed traits allowed 3D free space % and Sauter diameter, among the most discriminant parameters, to be identified as the most effective for the prediction of germination outcomes. Discriminant Analysis (DA) of 3D morphometric dataset correctly classified 96.3% of normal seedlings, 83.3% of ungerminated seeds and 63.6% of abnormal seedlings, providing a high overall prediction potential of 91.9%. The above analyses have also been performed referring to the germination at 5 days after sowing. As a side effect of the applied technique, an increase of abnormal seedlings was observed at increasing X-ray exposure level. Overall, X-ray micro-CT coupled with DA of internal morphometric traits has proved to be an effective tool to investigate the relationship between tomato seed 3D morphology and seed physiology, although attention has to be paid to possible consequences of X-ray exposure.