Characterisation of the agroforestry performance of 12 walnut (Juglans sp.) genotypes grown in two locations of Catalonia

Abstract

The performance of 10 progenies of J. regia and two Juglans commercial hybrids (Ng23 x Ra and Mj209xRa) at two planting sites, Massanes (Girona) and Prades (Tarragona), which was monitored during 6 consecutive years starting in1995, is here described. Based on differences in height growth rate, three well-defined genotypic groups could be established: 1) genotypes with an average growth of up to 60 cm per year, which comprises the two commercial hybrids; 2) genotypes with an average growth of about 50 cm per year, which includes those J. regia flushing before April 20; and 3) genotypes with an average growth less than 40 cm per year, which corresponds to J. regia progenies flushing after April 20. Growth evolution over time for height and diameter was significantly affected by the location, while progeny ranking was similar for both traits at both sites. Trunk diameter at 2,50 m at the sixth growing season depended on planting site and genotype. Thus, the largest diameters at 2,50 m always appeared in Massanes, regardless of the genotype, whereas the hybrid progenies showed an advantage in diameter of about twice the value for the best J. regia at both Massanes and Prades. Apical dominance and stem form were mostly dependent on genotype. Accordingly, only two J. regia showed an acceptable forest aptitude, that is, two Italian provenances namely «Bleggiana» and «Boschi Maria Grazia». Overall, the commercial hybrids Ng23xRa and Mj209xRa exhibited a better agroforestry behaviour than the J. regia genotypes studied: less orchard mortality, better primary and secondary growth, and more suitable apical dominance and stem form.