This work was performed to estimate pollen fertility and determinate the ploidy level of 11 to 12 years old progenies of crosses of 'Montenegrina' mandarin (Citrus deliciosa Ten.) with 'King' mandarin (C. nobilis Lour.) and with 'Caipira' sweet orange (C. sinensis (L.) Osb.) maintained at Estação Experimental Agronômica of UFRGS, in Eldorado do Sul, Brazil. The ploidy level was determined by chromosome countings in meiosis cells and pollen fertility evaluated by staining pollen grains with propionic carmine. All evaluated hybrids are diploid and pollen fertility varied from zero to 98%. C27, a hybrid 'Montenegrina' x 'Caipira', was found is sterile, and C21, from the same cross, showed 10 % fertility. The lowest observed fertility in the progeny 'Montenegrina' x 'King' was 42 %.
Citrus sp.; chromosome number; breeding; mandarin
