Differences in root and shoot development of tomato (Lycopersicon esculentum L.) varieties across contrasting soil environments

The root and shoot growth of three tomato (Lycopersicon esculentum L.) varieties, VF-10, VF-1908 and Paste 56 were compared in either a river-washed sand or an alluvial silty loam, with or without added nutrients, to determine factors influencing root growth and development. VF-10 had consistently higher shoot weights than the other two varieties, particularly by 45 days from germination. Although the root-to-shoot ratio varied with soil treatment, no significant differences in this ratio occurred among varieties. The roots were characterised by a taproot, thickened in the uppermost 3 to 5 cm, with 86 to 190 secondary roots when harvested 30 days after germination. The variety VF-1908 had a higher proportion of fine roots than the other two varieties over all treatments. On the basis of root weight and length, VF-1908 was also more stable across the imposed environmental gradient than the varieties VF-10 or Paste 56. This arose from less variability across soil treatments in secondary branching in VF-1908; over the four soil treatments the number of secondary roots varied from 104 to 131 in VF-1908 compared to 86 to 139 in VF-10 and 95 to 190 in Paste 56. VF-1908 and Paste 56 also had less variation in tertiary branching than VF-10, which had a consistently greater number of major tertiary roots than the other two varieties over all soil treatments. With the exception of Paste 56 in the fertilized silt, shoot growth was correlated with root length.