Xylem conductivity and vulnerability in cultivars and races of avocado

Anatomical vessel features of Guatemalan, Mexican and West Indian races and cultivars Col??n V-33, Fuerte and Hass of Persea americana Mill. were studied in 10-year-old trees grown in the field under similar environmental and management conditions with the main purpose to get insight on anatomical variation among genotypes. The cultivars differed anatomically from the races, showing an inverse relationship between races and cultivars with respect to vessel frequency and diameter, however, relative conductivity was similar among cultivars suggesting an adjustment between vessel diameter and frequency that maintains a similar relative conductivity among genotypes. The three races had the higher vessel frequency and the narrower vessel diameters as well as the lowest vulnerability index values compared to Hass and Fuerte cultivars. An important finding in this study was that cultivar Col??n V-33, a dwarf genotype, had intermediate anatomical characteristics between races and the other cultivars suggesting a better adapted hydraulic system to water deficits.