Polyploidy of Pollen and Fruit Tissue, and Utilization for Triploid Breeding in 2x-4x-4x Ploidy Chimera Obtained by Colchicine Treatment of Citrus

Abstract

We investigated the characteristics and polyploidy of pollen and fruit tissue in 2x-4x-4x ploidy chimeras induced by colchicine treatment of citrus. The pollen size of 2x-4x-4x ploidy chimeras and tetraploids was larger than that of diploids in all cultivars and strains that we investigated. The peel of the tetraploid fruit was thicker than that of diploids in all cultivars and strains, but a constant tendency was not seen in 2x-4x-4x ploidy chimera fruits. The flavedo, segment membranes, and juice sac showed diploidy and tetraploidy, the albedo showed tetraploidy only, and the pollen showed diploidy and tetraploidy in all 2x-4x-4x ploidy chimeras cultivars and strains. All plants raised from a seed, which we crossbred with diploid pollens in these individuals, showed triploidy. These results indicate that the 2x-4x-4x ploidy chimeras would be useful parents for triploid breeding by crossing with diploids like tetraploids.