Diversity of scion development in a grafted Pyrus seedling rootstock population

The limited availability of a Pyrus-derived dwarfing rootstock, equivalent to apple’s ‘Malling 9’, limits the intensification of modern pear orchards. As part of the search for a Pyrus rootstock, this paper examines the diversity of key rootstock traits in a population of 420 P. communis seedlings from a cross between ‘Old Home’ and ‘Louise Bonne de Jersey’. The seedlings were used as rootstocks, budded with the scion ‘Doyenné du Comice’, and rootstock-induced changes in scion development were phenotyped for traits relating to tree architecture and flowering. The rootstocks induced a 2.7-fold range in tree size by year three. A range in tree form was also observed, originating from differences in sylleptic and proleptic branching. The rootstocks not only induced variation in length of the primary axis after year one, but also in the cross-sectional area of the main axis, with the segregation in cross-sectional area becoming greater as the trees aged. The trees began bearing flowers after season two, with considerable diversity in the flowering intensity; all trees flowered after season three. The wide diversity of scion growth, flowering, tree form and rootstock suckering suggest this cross might be suitable to identify a rootstock, for ‘Doyenné du Comice’ and other Pyrus cultivars, that has dwarfing ability as well as beneficial tree form and flowering characteristics.