The triploid mandarin breeding program in Spain

Production of seedless citrus fruits is required for the fresh market because consumers do not acceptseedy fruits. Development of new seedless mandarin cultivars has a high priority for many citrus industriesworldwide. The recovery of triploid hybrids is the most promising approach to achieve this goal, since triploidshave a very low pollen and ovule fertility and usually are seedless or produce very low number of seeds, anddo not induce the formation of seeds in other cultivars by cross pollination. In Spain we are carrying a triploidbreeding program since 1996 based on 2x X 2x, 2x X 4x and 4x X 2x pollinations followed by embryo rescueand flow cytometry, and the use of different approaches to produce new tetraploid parents. The objectiveis to produce new high quality easy peeling and seedless mandarin cultivars. More than thirty spontaneousautotetraploid apomictic genotypes to be used as male parents have been selected from seedbeds by flowcytometry. Also nine autotetraploid non apomictic genotypes mainly to be used as female parents have beenobtained by chromosome duplication with treatments of micrografted shoot tips with colchicine. Symmetricprotoplast fusion is also being used to produce allotetraploid genotypes. So far, we have obtained morethan 5,500 triploid hybrids from 130 parental combinations by 2x X 2x pollinations, more than 4,300 triploidhybrids from 100 parental combinations by 2x X 4x pollinations, and more than 5,600 triploid hybrids from103 parental combinations by 4x X 2x pollinations. Recently we have released the first cultivars originated inthe program, the seedless late maturing mandarins ‘Garbí’ and ‘Safor’, obtained from 2x X 2x crosses. Morethan 400,000 trees of these varieties have been planted by growers during the last three years.