Biased chloroplast and mitochondrial transmission in somatic hybrids of Allium ampeloprasum L. and Allium cepa L.

Abstract

Somatic hybrid plants, produced by symmetric protoplast fusion between leek ( Allium ampeloprasum) and cytoplasmic male sterile onion ( Allium cepa), were analyzed for their organelle composition. Mitochondrial DNA (mtDNA) analyses were performed using PCR amplification of the V7 region of the mitochondrial small ribosomal RNA (srRNA) gene in conjunction with restriction site analysis and Southern hybridization. Of the 55 hybrids analyzed with the PCR method only three hybrids had mtDNA restriction fragment patterns of both parents, while the remaining hybrids displayed a pattern identical to A. ampeloprasum. Detailed analysis of 18 of these hybrids with Southern hybridization using five mitochondrial probes revealed that 15 hybrids possessed a rearranged mitochondrial genome of both parents, but with a predominance of mtDNA fragments of A. ampeloprasum. The other three hybrids had the same hybridization pattern as A. ampeloprasum, indicating that these hybrids probably contain the unaltered parental A. ampeloprasum mitochondrial genome. The same 18 hybrids were analyzed for their cpDNA using the Petunia chloroplasts DNA pPCY64 probe. A total of 15 hybrids possessed chloroplasts identical to A. ampeloprasum and three had A. cepa chloroplasts. Therefore, it is suggested that the chloroplasts of the hybrids did not sort out randomly. Also a novel combination of chloroplasts and mtDNA was found in two hybrids.