FACTORS AFFECTING NUT WEIGHT IN WALNUT (Juglans regia L.) – AN ANALYSIS OF GENOTYPES WITH CONTRASTING BRANCHING PATTERNS

For walnut, Juglans regia L., nut weight is a cultivar characteristic which can vary according to climatic conditions, notably rainfall during nut growth, training, irrigation, fertilisation and fruit load. For a given genotype, the homogeneity between yields and the sustainability of nut quality over the years are also related to the branching and fruiting behaviour of the tree. With regard to this last point, two extreme types are usually described. Terminal bearing cultivars are known to produce nuts of regular weight from year to year, but have a low yield. On the other hand, for lateral bearing cultivars, yield is high but as the tree ages, the weight of nuts usually decreases together with an increase in nut weight heterogeneity. For these last cultivars, this phenomenon may be checked by appropriate training and the use of vigorous rootstocks. A study was carried out over two successive years, 1996 and 1997, in order to analyse nut weight variability for five genotypes, Lara and four others, including Fernor, released from the INRA breeding programme. Broadly speaking, these genotypes belong to the lateral fruiting type, but with various lateral branching densities and fruiting behaviours. Results show that at least two factors are involved in nut weight variability: length of preformed subtending axis and number of nuts developing from the inflorescence. Nut weight homogeneity was greater for genotypes with longer preformed subtending axes than for genotypes with short preformed subtending axes. For these last genotypes, short preformed subtending axes (of under 6 cm) or the presence of more than one nut per inflorescence were shown to significantly reduce nut weight and increase nut weight heterogeneity.

IV International Walnut Symposium

P.E. Lauri, F. Delort, E. Germain, P. Reynet

english walnut, Juglans regia L., weight nut, crop quality, branching patterns, fruiting types

https://doi.org/10.17660/ActaHortic.2001.544.35