CMA Staining Analysis of Chromosomes in Citrus Relatives, Clymenia, Eremocitrus and Microcitrus

Abstract

Fluorochrome staining with chromomycin A3 (CMA) was used to characterize and compare the CMA banding patterns of chromosomes of Clymenia, Eremocitrus, and Microcitrus, which belong to true citrus fruit trees (Citrinae, Rutaceae). All species had 2n = 18 chromosomes. These chromosomes were classified into six types based on the number and position of CMA-positive bands; A: two telomeric and one proximal band, B: one telomeric and one proximal band, C: two telomeric bands, D: one telomeric band, E: without bands, and Dst: type D with a satellite chromosome. Each species possessed three or four types of chromosomes and unique CMA banding patterns. The CMA banding patterns were 2C + 8D + 8E in Cl. polyandra, 2C + 9D + 7E in E. glauca, 1C + 11D + 6E in M. australis, 1B + 2C + 10D + 5E in M. australasica, 8C + 7D + 2E + 1Dst in M. inodora, 2A + 14D + 2Dst in M. warburgiana, and 2C + 9D + 7E in Sydney hybrid. Chromosome configurations of Cl. polyandra, E. glauca, M. australis, and Sydney hybrid resembled each other. This may indicate a common ground of chromosome configuration in the true citrus fruit trees. On the other hand, variability in Microcitrus chromosomes was also demonstrated.