Micropropagation of walnut: a real opportunity
Since 2005, Vitroplant Italia s.r.l. has been producing micropropagated walnut plants, which have been planted in demonstrative orchards from 2007 with excellent results. Following this first experience, from 2013 there has been an increasing demand for micropropagated walnut plants. The micropropagated Chandler potted plants, 10 cm height (in 0.9-L pot) and 30 cm height (1.7-L pot), were compared with bare root 1-year-old Chandler grafted plants, on rootstock J. regia seedlings, 1.80 m height. The plantation was made for all the plants at the end of April in a demonstrative orchard in Emilia Romagna region (45°N, Italy). Micropropagated plants in 0.9-L pots got an equivalent or higher growth than grafted plants at the third year, while the micropropagated plants in1.7-L pots overtook growing performance of grafted plants already during the first year. The cumulative production per plant since now has been equivalent or higher in micropropagated Chandler orchards than in grafted ones. This result was obtained with less pruning and greater vegetative growth of micropropagated plants, which made easier the training of structured central axis. In the last few years, the most planted type of micropropagated plants was the dormant bare root type. These plants can be obtained in one growing season in the nursery, after early spring acclimation ex vitro. This type of plant was between 0.20 and 0.60 m height and easier to be managed during the first year of growth in the orchard compared to the pot plants. Therefore, in a second demonstrative field trial, Chandler dormant bare root plants from micropropagation were compared with 1-year-old grafted plants on J. regia seedlings 1.80 m height. Micropropagated plants showed better growth rate and more homogeneity with minimal pruning to train the structured central axis. While, a delay in production of female flowers was found in micropropagated Chandler trees during the first 3-4 years, the cumulative production per plant was higher than in grafted plants 8 years after planting.
Navacchi, O., Bastianelli, M., Neri, D. and Cozzolino, E. (2021). Micropropagation of walnut: a real opportunity. Acta Hortic. 1318, 63-70
bare root scions, potted scions, female flowers, type of propagation