VIGOR OF GREENHOUSE TOMATO PLANTS (LYCOPERSICON-ESCULENTUM MILL.) - ANALYSIS OF THE CRITERIA USED BY GROWERS AND SEARCH FOR OBJECTIVE CRITERIA

In greenhouse tomato crops, growers examine the ''vigour'' of the plan ts to choose cultivation techniques, but their observations are subjec tive. We aimed to determine what growers mean by vigour and to identif y objective criteria for measuring it. Two trials were conducted, in 1 994 and 1996. For both, four growers were asked to give a vigour score to each plant in the trial, and this was compared with agronomic vari ables such as leaf area, plant dry weight, stem diameter and fruit yie ld. The main criteria growers observe are stem diameter and internode length, on the top of the plant, between the apex and the flowering tr uss. They also take into account foliage colour and habit. Vigour scor es and vegetative measurements were well correlated (r from 0.6 to 0.9 ). Therefore, although the growers' definition of vigour is subjective , it characterizes the vegetative plant state. In particular, the vigo ur score was correlated with the measurement of stem diameter. Vigour on one occasion was correlated with the mean weight of the fruits harv ested two and a half months later. This suggests that growers can use vigour to determine which cultivation techniques to apply to modify pl ant habit and fruit size.