Classification of 'Tosa-Buntan' pummelo (Citrus grandis [L.] Osb.), 'Washington' navel orange (C-sinensis [L.] Osb.) and trifoliate orange (Poncirus trifoliata [L.] Raf.) chromosomes using young leaves

Chromosome samples of young leaves of 'Tosa-Buntan' pummelo (Citrus grandis [L.] Osb.), 'Washington' navel orange (C. sinensis [L.] Osb.) and trifolia te orange (Poncirus trifoliata [L.] Raf.) were prepared by the enzymatic ma ceration method. The preparations were sequentially stained with Giemsa, qu inacrine mustard (QM), chromomycin A(3) (CMA), and 4'-6-diamidino-2-phenyli ndole (DAPI). The chromosome lengths and banding patterns among 4 staining methods were compared. The discrimination of centromeres was easier by QM s taining than by Giemsa staining. By CMA staining, 5 characteristic banding patterns were observed. Therefore, 'Washington' chromosomes were divided in to 4 groups, trifoliate orange chromosomes into 3 groups, and 'Tosa-Buntan' chromosomes into 5 groups. CMA staining enabled the confirmation of chromo some number as 18 in cells in which chromosome lengths were relatively long . Chromosome number in 'Washington' and 'Tosa-Buntan' were difficult to cou nt by the Giemsa stain. We conclude that chromosome samples prepared by usi ng young leaves and QM and CMA stainings are effective means to reveal chro mosomes in citrus. Hence, a good possibility of karyotyping citrus in the f uture exists.