The prevalence of sour orange rootstock in the southern and eastern part of the Mediterranean Basin is presently threatened by the spread of Citrus Tristeza Virus (CTV) and its main vector Toxoptera citricida, combined with abiotic constraints such as drought, salinity and alkalinity. The search for alternative CTV-resistant rootstocks that also withstand the other constraints is now considered an urgent priority for a sustainable citrus industry in the area. Complementary progenitors can be found in citrus germplasm to combine the desired traits, particularly between Poncirus and Citrus genera. The production of somatic hybrids allows cumulating all dominant traits irrespective of their heterozygosity level, and would appear to be an effective way to solve the rootstock challenge facing the Mediterranean citrus industry. This paper presents the results obtained during a regional collaborative effort between five countries, to develop new rootstocks by somatic hybridization. New embryogenic callus lines to be used for somatic hybridization have been created. Protoplast fusions have been performed at CIRAD and IVIA laboratories, focusing on intergeneric combinations. Analysis of ploidy level by flow cytometry and molecular markers confirmed the acquisition of new interesting tetraploid somatic hybrids for six combinations. Diploid cybrids with intergeneric (Citrus × Poncirus) nucleus and C. reticulata or C. aurantifolia mitochondria were also identified for four combinations. The agronomical performance of a pre-existing somatic hybrid between Poncirus trifoliata and Citrus reticulata was validated in calcareous soils in Morocco. Somatic hybridization is now integrated into the breeding programs of the five Mediterranean countries.

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This work was carried out in collaboration between all authors. Author HN designed the study, performed the statistical analysis, wrote the protocol and wrote the first draft of the manuscript. Author Benyahia Hamid managed the analyses of the study. Author AN managed the laboratory technique.Author Benaouda Hassan managed the scientific searches. All authors read and approved the final manuscript.

20 clones of orange trees, identified at the level of the collection of nucellar citrus varieties, have been the subject of several tests of behavior at the level of different citrus fruit sites in Morocco. Indeed, the present work aims to evaluate these variants on a clay soil at the Gharb region (INRA/Kenitra). The variants grafted on Citrange troyer were divided into three groups. Each group contains variants, genetically similar, from seedlings of the same parent variety. Clonal selection is based on the synthesis of the results of the study of the variability of the criteria of fruit quality and production. The average yield varies from 44.25 kg / tree to 217.30 kg / tree. While the average weight of a fruit varies from 95 g to 360 g. The results showed a predominance of juicy and medium-sized fruits with an equatorial diameter greater than 56 mm, acceptable for the fresh fruit market or the juice industry. The maturity coefficient study of the variants within each group, or between the three groups, showed that the harvest period extends over four months, from December to March. The final selection was focused on six productive and good quality variants. These promising variants have been described according to UPOV, and then presented for registration in the official catalog.

Oranges are classified as the most traded fruit variety worldwide. The diversification of the varietal profile of this group is among the objectives of the Citrus breeding program. So, the creation of new triploid hybrids via immature embryos rescue, can lead to an increase in gene pool and produce seedless varieties. In addition, flow cytometry was successfully used for analyzing ploidy levels and genetic origin of triploid plants. The present study was aimed at optimizing immature embryos in vitro germination and plantlet development based on medium chemical composition of the two orange varieties, Pineapple and Parson Brown. When the fruit gets matured, they are harvested and the seeds extracted are classified according to their size. Only those which are small are cultured in a sterile Murashige and Tucker (MT) basal medium. The different concentrations of growth regulators are put to the test in order to gain the best medium for seeds development. M1 (MT + 1 mg/L gibberellic acid (GA3)), M2 (MT + 1 mg/L kenitin + 0.5 mg/L 6-benzylaminopurine (BAP) + 0.1 naphthalene acetic acid (NAA)), M3 (MT + 25 mg/L adenine sulfate (ADS)), M4 (MT + 0.5 mg/L kenitin + 0.5 mg/L BAP + 1 mg/L GA3). Percentage of germinated embryos (PGE) is the highest in M3 with 100% and 90% for both Pineapple and Parson Brown varieties, respectively. In addition, the germination interval average (GIA) is shorter in M1 for both varieties, which takes 6 d and 7 d, respectively. As regard to speed seedling growth (mm/week), both varieties undergo significant change in all four mediums. Similarly, the highest rate of acclimatization for the Pineapple and Parson Brown varieties is 80% and 90% in M1. In general, the smaller the embryos are, the more sensitive they are to culture medium composition. It is therefore essential to optimize the medium components in order to stimulate their in vitro development. Therefore, M1 (MT + 1 mg/L GA3) remains the best to promote short term good germination and produce a better rate of acclimatization.