The response of 52 citrus hybrid rootstocks to a Mediterranean biotype of Tylenchulus semipenetrans Cobb was determined in greenhouse tests. Seven selections of the cross ‘Cleopatra’ mandarin [Citrus reshni Hort. x Poncirus trifoliata (L.) Raf], and one
of Citrus volkameriana Pasq. x P. trifoliata did not support nematode reproduction and were considered as highly resistant to the citrus nematode. The nematode showed very low infectivity and reproductive potential on seven additional selections of ‘Cleopatra’ mandarin x P. trifoliata, one of ‘King’ mandarin x P. trifoliata, and two C. volkameriana x P. trifoliata. These selections were considered as nematode resistant. All the selections with ‘Troyer’ citrange [Citrus sinensis (L). Osbeck x P. trifoliata (L.) Raf] in their parentage supported nematode reproduction but showed different levels of susceptibility
