Ines Hugalde,* Cecilia B. Aguero, M. Andrew Walker, Felipe Barrios Masias, Andrew J. McElrone, Nina Romero, Andy V. Nguyen, Summaira Riaz, and Hernán Vila  
*INTA EEA Mendoza, San Martin 3853, Mayor Drummond, Lujan de Cuyo, 5507, Argentina (hugalde.ines@inta.gob.ar)

Mechanistic modelling provides an interesting tool to unravel complex biological phenomena. Our study describes the construction of a dynamic model for vigor, considering vigor as the interaction between the environment (soil and atmosphere) and plant physiology. To validate the model, 50 genotypes from the F1 progeny of Ramsey and Riparia GM, were evaluated. Plants with contrasting vigor were grown in a greenhouse during summer 2014 and 2015, pruned to a single shoot, and watered daily. Shoot growth rate (b), leaf area (LA), dry biomass, plant and root specific hydraulic conductance (Kh and Lpr), stomatal conductance (gs), water potential (Ψ), and photosynthesis (A) were measured. Partitioning indices and specific leaf area (SLA) were calculated. The model includes an empirical fit of a hypothesized seasonal pattern of gibberellins (not measured in situ) based on published seasonal patterns and reference values. Validation regression resulted in R2 = 0.96 between predicted and observed data. MSPE = 0.0628, mean bias = 0.001, line bias = 0.0968, and random variation = 0.01. Simulating single-variable variation defined the individual effect of each variable on vigor determination and explained why “smaller genotypes have higher Lpr”. It remains necessary to measure hormones to further refine the model. However, we propose that by measuring Lpr and SLA in young plants and including the hormone fit, the model can predict, with acceptable accuracy, the vigor of an adult plant.

Funding Support: Instituto Nacional de Tecnologia Agropecuaria, INTA – Viticulture and Enology, UC Davis