Citrus rootstock are plants used asrootstock forcitrus plants. A rootstock plant must be compatible forscion grafting, and resistant to common threats, such as drought,frost, and commoncitrus diseases.
Sour orange: the only rootstock that truly is anorange (the Citrus ×aurantium or bitter orange). It is vigorous and highly drought-resistant.
Poncirus trifoliata: a close relative of the genusCitrus, sometimes classified asCitrus trifoliata. It is especially resistant to cold, thetristeza virus, and the oomycetePhytophthora parasitica (root rot), and grows well inloam soil. Among its disadvantages are its slow growth—it is the slowest growing rootstock—and its poor resistance to heat and drought. It is primarily used inChina,Japan, and areas ofCalifornia with heavy soils.[1]
Troyercitrange andCarrizo citrange: reasonably vigorous rootstocks, resistant toPhytophthora parasitica,nematodes, and tristeza virus and with good cold tolerance. They also are highlypolyembryonic, so growers can obtain multiple plants from a single seed. Citrange, however, does not do well in clay,calcareous or high-pH soils, and is sensitive to salinity. It is not feasible as rootstock formandarin scions, as it overgrows them by producing branches of its own in competition with the grafted budwood.[3] Citranges are hybrids of the Washington navel orange and thePoncirus trifoliata. The original crosses, made in the early 1900s by the U.S. Department of Agriculture with the intention of producing cold tolerant scion varieties, were later identified as suitable for use as rootstocks. The commercial use of these rootstocks began inAustralia in the 1960s. TheTroyer variety generally is found in California, while theCarrizo variety is used in Florida.
Cleopatra mandarin: tolerant of salinity and soilalkalinity and also suitable for shallow soils. It is used primarily inSpain,Australia, andFlorida.Dade County, for example, has 85%calcareous soil, a typical trait of land that has been under water.[4] The Cleopatra mandarin, originated inIndia and introduced into Florida fromJamaica in the mid-nineteenth century, has been distributed and tested as a rootstock throughout the world. Nowadays, however, it is considered an inferior rootstock because it is sensitive to many diseases, grows slowly, and is difficult to propagate.[5]
Bitters C-22citrange (X Citroncirus sp. Rutaceae): it was hybridized at theUSDA Date and Citrus Station inIndio, California, and developed further by theUniversity of California, Riverside. It is used primarily as rootstock for navel oranges in California. In 2009, a report suggested it also may be useful to replace sour orange rootstock for grapefruit in Texas because it is tolerant of calcareous soil.[7][8] Its name is not related to the bitter orange: it was named afterWillard Paul Bitters, emeritus professor of Horticulture and a curator of theCitrus Variety Collection.
