sunki

Sunki tangerine

Scientific name: Citrus sunki

Origen: China

Other names: Suenkat, Sunkat

Last update: August 2008

     Sunki belongs to the small tangerine group along with Cleopatra, Amblicarpa, Nasnaran, Pectinífera and others. Their fruit is small with 3-6 cm diameter, flat, with loose peel and yellow to orange in color. Sunki is originary from China where its use as a rootstock is common.

     The number of seeds in each Sunki fruit is typically large according to international references. However, the clone of Sunki present in São Paulo has fruit with very few seeds (average of less than 1 per fruit). In addition, our Sunki has seeds which are highly monoembryonic. This means that most of the Sunki seedlings used in citrus propagation as rootstocks in Sao Paulo are hybrids. Surprisingly, however, their uniformity is very high which may indicate a high degree of homozygosis. These characteristics indicate Sunki may be a primitive citrus plant established as a lineage throughout its development. Controlled crossings done by Citrolima in the last 15 years support these observations. Hybrids make up typically more than 95% of the seedlings from crossings with Sunki as the mother plant. Moreover, since obtained hybrids typically have the external characteristics of the male parent, we conclude that Sunki has a high level of recessive genes. Superior plants are commonly observed in Sunki stands in nurseries and several such hybrids have been selected recently at Citrolima and other places. Embrapa's experiment station in Bahia has release 2 open pollinated Sunki hybrids with more vigor and larger number of viable seeds than the traditional Sunki. Their performance in citrus groves, however, is yet to be evaluated.

      Trees budded on Sunki generally start bearing good crops somewhat earlier than trees on Cleopatra but later than those on Rangpur lime. In addition, Sunki seems to induce higher initial productivity and less alternate bearing than Cleopatra. Drought tolerance is higher than that of Cleopatra and fruit maturity occurs earlier. In general, we can think of Sunki as inducing intermediary characteristics to its scions between Cleopatra and Rangpur lime rootstocks. Therefore, fruit quality is better than on Rangpur but not as good as on Cleopatra, and fruit size not as large as on Rangpur but better than on Cleopatra.

Sunki's major drawback is its high susceptibility to foot and root rot. Healthy nursery trees and virgin soils, therefore, are very important in the establishment of citros orchards with Sunki as a rootstock. In relation to other diseases, however, Sunki shows significant commercial advantages. It is resistant to Exocortis, citrus blight, Tristeza, and Sudden Death. In addition, there are apparently no compatibility problems confirmed with commercial scions. Sunki utilization as a mother plant in breeding of new rootstocks seems very promising. A Sunki hybrid with Benecke trifoliata has been released in the United States and performs well in most trials. Citrolima has over 300 Sunki hybrids with trifoliata, Rangpur lime, Cleopatra, Volkameriana, Orlando tangelo, Carrizo citrange, and Swingle citrumelo. In addition, a great number of Sunki variants, originated from open pollination are also under field test.

Sunki tangerine today is basically used in Sao Paulo as a rootstock for Pera sweet orange in areas with high incidence of citrus blight or with citrus sudden death. It is also used as a second rootstock for Pera budded on Rangpur lime for the same reasons. Other varieties are also budded on Sunki but the numbers are typically inexpressive.

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