Variety and temperature affect the production of multiple stems from peach seedling rootstocks

Seeds of different cultivars of peach rootstocks were assessed to determine the causes of several deleterious traits that affect the quality of the seedlings that result from them. The incidence of triple cotyledons was significantly influenced by variety. It was also found that that the production of multiple stems could be caused by either the production of multiple seeds or by multiple stems originating from cotyledonary axils. The incidence of both traits was heavily influenced by the genotype of the variety. The production of multiple shoots was also affected by temperature with low temperatures favouring their appearance. The incidence of double seeds also varied among cultivars with the average size of seeds from stones that contained double seeds being significantly smaller than for single seeds. The smaller size of double seeds was associated with poorer germination, reduced speed of germination and reduced growth rates. Although there was a strong relationship between seed size and stone (endocarp) size for stones that contained single seeds, no such relationship existed for those stones that contained double seeds. Therefore, selection on the basis of stone size cannot be used to select out stones containing double kernels. The elimination of multiple shoots and double seeds from peach seedlings would reduce the costs associated with rootstock production and could be achieved by removing plants that exhibit these traits from the production system and clonally propagating those trees that are free of such traits.