Effects of cell type used for fusion on chromosome elimination and chloroplast segregation in Brassica oleracea (+) Brassica napus hybrids

Abstract

To determine how the developmental and physiological characteristics of parental cells can influence the fate of chromosomes and chloroplasts in somatic hybrids, fusions were made between Brassica napus and B. oleracea using hypocotyl and/or mesophyll protoplasts in four different combinations. Chromosome number varied greatly among the hybrids obtained. Most hybrids (58%) had more chromosomes than the parental sum, 32% had a DNA-content corresponding to the sum, and only 10% had fewer chromosomes than the sum. The frequencies of symmetric hybrids and chromosome eliminating hybrids obtained in fusions performed by combining mesophyll and hypocotyl protoplasts did not differ significantly from those obtained by combining protoplasts from the same cell type. However, the frequency of hybrids with a DNA-content corresponding to one genome from one of the parental species and two from the other and the frequency of hybrids having the reciprocal combination of three genomes differed significantly between fusion categories. Of 128 hybrids examined, 36 (28%) had B. oleracea chloroplasts and 92 (72%) had B. napus chloroplasts. The pattern of chloroplast segregation did not differ significantly between fusion categories.