Pests

Nematodes — hybrids between Citrus x aurantium L. x Citrus trifoliata L.

Hybrids between Citrus x aurantium L. x Citrus trifoliata L.

Hybrids of bitter orange and trifoliate orange are susceptible to the citrus nematode Tylenchulus semipenetrans, which causes 'slow decline'. The resistance of these forms is largely determined by the genetic contribution of Poncirus trifoliata and the Tyr1 locus.

In the reference 13 varieties crop Hybrids between Citrus x aurantium L. x Citrus trifoliata L., where this is mentioned in the description.

The primary pathogen for these hybrids is the sedentary semi-endoparasite Tylenchulus semipenetrans, which induces chlorosis, stunting, and dieback. The level of susceptibility depends on the presence of specific nematode biotypes in the soil, in particular the 'Poncirus biotype', which is capable of infesting Poncirus trifoliata, to which most other parasite populations are not adapted.

Genetic control of resistance includes the Tyr1 locus, used as a marker in rootstock breeding. To evaluate the degree of hybrid resistance, the reproduction factor (Rf) is applied: values below 1.0 indicate resistance, where the nematode cannot effectively reproduce within the plant root system.

General information about the subject — on the page Nematodes.

Sources8

Varieties of Hybrids between Citrus x aurantium L. x Citrus trifoliata L. mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.