The transpiration rate (E) of ‘Colinmex’ avocado was evaluated over a year to determine its seasonal variation under two soil moisture (SM) regimes and its relationship to phenological phases. The following cultivar/interstock/rootstock (regional criollo originated from seed) and soil moisture regime combinations were evaluated: T1) ‘Colinmex’/’Colin-V101’/rootstock, irrigated; T2) ‘Colinmex’/’Colin-V101’/rootstock, rainfed; T3) ‘Colinmex’/’Colin-V33’/rootstock, irrigated; T4) ‘Colinmex’/’Colín-V33’/rootstock, rainfed. The transpiration rate varied from 1.38 to 4.55 mmol H2O·m-2·s-1 over the year; and during this time, available SM and ambient relative humidity (RH) were strongly correlated to E (r2 = 0.70 and 0.93, respectively). In the winter, T1 and T2 showed the highest E values, 3.32 and 3.3.18 mmol H2O·m-2·s-1, respectively. In the spring, E was similar from treatment to treatment with values ranging between 1.22 to 1.72 mmol H2O·m-2·s-1; this season also had the most severe SM deficit, the highest temperatures and the lowest RH. The highest E values occurred in the summer with averages from 4.45 to 4.65 mmol H2O·m-2·s-1. Similar E values were recorded during the fall for T1, T2 and T4 (4.10 to 4.90 mmol H2O·m-2·s-1). The highest averages of fruit weight, fruit number and fruit yield per tree corresponded to T3. Treatments with irrigation had the highest fruit production per tree.

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