EVALUATION OF THE HORNER ROOTSTOCKS

Abstract

Five hundred and forty-five seedling rootstocks were created by Mr. Dave Horner. This was achieved by allowing open pollination of five 'Old Home' x 'Farmingdale' clonal rootstocks, in an isolated area of western Oregon. The rooting potential of 80 selections tested ranged from 0 to 100%. As an initial test of the potential of the series to produce smaller, more precocious trees, 13 of the selections were budded with the scion cultivar Beurre d'Anjou. All the selections exhibited reduced tree size by the 5th leaf but not in earlier years. Tree volumes of trees with Horner rootstocks ranged from 25 to 85% as compared with 'Beurre d'Anjou' trees on the control rootstock OHxF 97. Rootstock affected both tree height and spread. Trees on 12 of the 13 Horner rootstocks produced flowers in 1998 (4th leaf). Trees on H-4 and H-10 produced almost three times as many flowers as the control in 1998, and significantly more flowers in 1999. All selections produced flowers in the 5th leaf; however, only 12 of the 13 Horner selections carried fruit to maturity. Trees on H-4 and H-10 rootstocks out produced the trees on OHxF 97, and had higher yield efficiencies. Average fruit size on trees with three of the selections (H-1, H4, and H10) was larger than fruit on trees with OHxF 97 roots. The series offers the potential for producing smaller, more productive pear trees, which have larger fruit. In the future, the promising selections need to be more stringently tested with other scions, and in other locations, and the remainder of the series needs to be evaluated.