Efficient haploid production on ‘Wilking’ mandarin by induced gynogenesis

Seedlessness is a major criterion for the citrus fresh fruit market. Therefore, triploid breeding appears verypromising for the selection of new citrus cultivars. CIRAD has developed a method to produce triploid hybrids by somatic hybridization between diploid and haploid lines, and demonstrates the potential for haploidcitrus production by induced gynogenesis in clementine. In this work we analysed the efficiency of inducedgynogenesis by irradiated pollen in ‘Wilking’ mandarin (Citrus reticulata). Five doses of gamma irradiationof ‘Meyer’ lemon pollen were tested (0, 150, 200, 250, 300 Grays). Embryos were extracted from smallseeds, obtained in immature fruits, and cultivated in vitro. The ploidy level of plantlets was determined byflow cytometry analysis. Irradiated pollen appeared to be efficient for gynogenesis induction in ‘Wilking’. Arelatively high number of haploids (7 plantlets) were obtained, essentially after hybridisation with ‘Meyer’ lemon pollen irradiated at 250 Grays. The ploidy level of all haploid plantlets was confirmed by chromosomecounts, and molecular markers demonstrated their gynogenetic origin. These haploid lines should be usefulfor triploid breeding by somatic hybridisation, and also constitute interesting resources for genomic studies.