Raspberry canes frequently have several buds at a node, but it was found that the ability of more than one to develop into a fruiting lateral was influenced by several genetic and non-genetic factors. Cane diameter was important: a high diameter favoured the production of multiple laterals at a node but reduced the percentage of lateral-bearing nodes. Consequently, overall lateral production remained nearly constant over a range of cane diameters. Cultivar Glen Clova and other genotypes with a high incidence of multiple laterals were used as donor parents of multiple lateral production in a breeding programme and were shown to transmit the character through genes acting in an essentially additive way. Genes affecting cane diameter contributed to these genetic differences but genotypes differed in their response to cane diameter variation. Gene L2] reduced the incidence of multiple laterals. Frost injuries checked the primary laterals and induced a very high incidence of multiple laterals; performance in a frost year may not be related to performance in other years.
It is concluded that multiple laterals are a yield component of only limited value. Their potential for increasing yield is rarely fully realized because reduction in other yield components tends to be associated with their development except when cane diameters are very large.