GENOTYPIC DIFFERENCES IN THE LENGTH DIAMETER RELATIONSHIP OF BRANCHESOF ONE-YEAR-OLD PEACH AND NECTARINE TREES

Genotypic variations in the length-diameter relationship of branches a mong peach and nectarine [Prunus persica (L.) Batsch.] cultivars were investigated. The length and basal diameter of all undamaged first-ord er shoots from 1-year-old trees of 14 cultivars and one accession were measured. Statistical analysis of the allometric relationship between length and basal diameter of shoots provided evidence of genotypic di fferences for that relationship, although the diameter of very short s hoots did not differ between genotypes. A gradient existed from 'Armki ng' with thin shoots (9 mm in diameter for 85.5-cm-long shoots) to 'Fl avorcrest' with thick shoots (16.4 mm in diameter for 85.5-cm-long sho ots). Early selection for shoot thickness should be possible in breedi ng programs. The likely consequences of observed shoot thickness varia tions on the mechanical and hydraulic properties of shoots are discuss ed.