Relationship between cane age and vegetative and reproductive traits of northern highbush blueberry in Chile and United States

Blueberry fruit yield increases with cane diameter. To optimize field management, it is necessary to understand the relationship between cane age, cane diameter, and the vegetative and reproductive expressions of the plant. Trials were conducted in two sites: 1) Linares, Maule, Chile (35°51′S, 71°36′W) in 'Duke' and 'Brigitta' (fourteen-year-old plants); and 2) Gobles, Michigan, USA (42°22′N, 85°54′W) in cv. 'Duke' (fifteen-year-old plants) and 'Brigitta' (nineteen-year-old plants). At each site, canes of different diameters (0.4 to 4 cm) were selected and measured for cane diameter and length, number of annual wood growth rings (cane age), number of flower buds per cane and of flowers per bud, and number and total length of the shoots. Cane diameter and cane age were positively and linearly associated for both cv. 'Brigitta' (r2=0.93 and 0.91 in Chile and USA, respectively; P<0.0001) and 'Duke' (r2=0.86 and 0.92 in Chile and USA, respectively; P<0.0001). For 'Duke', total shoot length was the vegetative variable most closely associated with both cane diameter (Chile, r2=0.74; USA, r2=0.80; P<0.001) and cane age (Chile, r2=0.68; USA, r2=0.72; P<0.0001). For 'Brigitta', the determination coefficients between total shoot length and cane diameter (Chile, r2=0.55; USA, r2=0.76; P≤0.001) and age (Chile, r2=0.50; USA, r2=0.47; P<0.05) were positive but lower. The number of flower buds per cane was linearly and positively associated with cane diameter and cane age for both cultivars and countries (r2=0.45-0.62; p<0.0001). The associations between cane age and diameter with the other vegetative and reproductive variables varied between both countries and cultivars (Chile, r2=0.69-0.01; USA, r2=0.84-0.02). Our results show that cane age and diameter are highly associated and can be used to assess various vegetative and reproductive traits in highbush blueberry plants. Consistently across cultivars and sites, the data shows that as canes aged and growth rings are added, they increased in diameter, total shoot length, number of shoots, number of flower buds and cane length. This information could be useful to estimate yield and define pruning practices in adult blueberries.