Screening of new citrus rootstock cybrids for resistance to Phytophthora citrophithora

Phytophthora gummosis is a severe disease that poses a significant threat to citrus cultivation worldwide, including in Morocco.
The use of resistant rootstocks is considered the most effective strategy to combat this challenge.
Somatic hybridization has emerged as a valuable tool for generating novel genotypes that could serve as potential candidates in citrus breeding programs.
To assess the inheritance of Phytophthora gummosis resistance, eight somatic hybrids derived from diverse parental combinations (‘Rangpur’ lime + ‘Willow Leaf’ mandarin; ‘Carrizo’ citrange + ‘Willow Leaf’ mandarin; Citrumelo 4475 + ‘Willow Leaf’ mandarin; Citrandarin + ‘Willow Leaf’ mandarin; ‘C35’ citrange + ‘Willow Leaf’ mandarin; Volkameriana + ‘Willow Leaf’ mandarin; Macrophylla + ‘Valencia’ orange; Macrophylla + ‘Kinnow’ mandarin) were subjected to a rapid screening test for tolerance to Phytophthora citrophthora. Inoculation was performed by placing an agar disc containing fungal mycelium onto the centre of wounded leaves using a sterile needle.
The percentage of diseased tissue was assessed for each leaf of the hybrid plants and compared to that of the parental lines.
All somatic hybrids exhibited susceptibility to the employed isolate, except for seven genotypes that demonstrated high resistance to P. citrophthora. These resistant genotypes included 960a (‘Carrizo’ citrange + ‘Willow Leaf’ mandarin), 985 and 983 (Macrophylla + ‘Kinnow’ mandarin), H and 5 (‘Rangpur’ lime + ‘Willow Leaf’ mandarin), and 970 (Citrumelo 4475 + ‘Willow Leaf’ mandarin).

XV International Citrus Congress

O. Chetto, H. Benyahia, P. Barantin, P. Ollitrault, D. Dambier

citrus, somatic hybridization, rootstocks, P. citrophthora, resistance

https://doi.org/10.17660/ActaHortic.2026.1448.36