Abstract
Fourteen selections consisting of twelve new numbered hybrids, and two named rootstock cultivars were tested as rootstocks for 'Hamlin' orange trees (Citrus sinensis L. Osbeck) at the Whitmore Foundation Farm in Lake County, Florida. The test included four single-tree replications on each rootstock planted in randomized complete blocks on Astatula fine sand soil. Rootstock effects on five-year cumulative fruit production, fruit quality, tree growth, and tree health were compared. The standard rootstocks Carrizo citrange and Swingle citrumelo were intermediate to good in their effect on fruit productivity, while the new numbered hybrid selections ranged from high productivity to very low productivity. Cumulative production over the five year period (2001-2005) ranged from 817 kg of fruit per tree for US-1209 rootstock to 535 kg of fruit per tree for US-1211 rootstock. The rootstocks also differed significantly in their effect on tree size, as well as fruit brix and other fruit quality traits. The rootstocks Swingle citrumelo, US-1203, and US-1205 typically produced fruit with low brix values, while the rootstocks US-1213 and US-1210 produced fruit with higher soluble solids concentrations. Some of the new hybrid rootstocks appeared promising for more widespread commercial trials.
