The rootstock breeding and evaluation program at CREA, Italy

The CREA rootstock breeding program started in the late 1960s and is based on the generation of diploid hybrids, mostly obtained using Poncirus trifoliata and its hybrids as male parents. Currently, one of the major aims is to combine adaptability to calcareous soils with drought resistance and CTV tolerance/resistance. The selection of the promising hybrids is mostly performed in the open field in calcareous soils (>10% active lime, pH ~8.0). Propagation by seeds is still the preferred method in the case of highly apomictic selections, however clonal propagation by tissue culture or cutting is also used to accelerate the establishment of field trials. So far, a series of Citrus latipes hybrids showing high productivity and good fruit quality in combination with sweet orange and 'Clementine' cultivars has been released. Over the last 10 years, 11 new hybrid populations have been generated, and some hybrids are currently tested in replicated field trials, together with rootstocks from other international breeding programs. A total of 105 rootstocks (53 from CREA and 52 from abroad) are now under field evaluation in combination with 5 sweet orange selections in trials established between 2017 and 2023 at the Palazzelli experimental farm (Siracusa, Sicily). Some preliminary results regarding these new rootstock experiments are discussed in this paper.