An F2 population (Allium fistulosum x A. cepa) of 20plants, 10 BC1,[(A. fistulosum x A. cepa) x A. cepa], and 50 BC2 plants, [(A. fistulosum x A. cepa) x A. cepa] x A. cepa were studied cytogenetically and characterized for four isozyme alleles plus various morphological characteristics. All of the progenies were in A. fistulosum (the bunching onion) cytoplasm. In the F2 population we observed non-random chromosomal and allelic segregation, suppression of bulb onion allelic expression, and abnormalities in mitosis and meiosis. Most BC2 plants resembled A. cepa (the bulbing onion) morphologically, but anthers, filaments, pistils, and petals were abnormal. Only 3 plants, and these were most nearly like the F1 hybrid morphologically, produced any seeds.The data and observations support the hypothesis of nuclear-cytoplasmic incompatibility interactions between the bunching and bulb onion species.
Mitotic and meiotic studies were performed on Allium fistulosum, A. cepa, their F1 hybrid, and ten selected backcross (BC)1 plants [(A. fistulosum x A. cepa) x (A. cepa)]. Each BC1 plant had at least one A. cepa isozyme allele (Pgi, Idh, or Adh). Chromosome morphology and behavior differed among plants. Meiocytes were observed with one, two, or three bridges and/ or fragments, indicating at least three paracentric inversions between A. fistulosum and A. cepa. Unusual crossing over and multivalent associations suggest that the 5F subtelocentric chromosome of A. fistulosum is involved in at least one translocation. The number of bridges and fragments and multivalent associations varied between the F1 hybrid and BC1 progenies. The F1 hybrid and all BC1 progenies were either sterile or had very little seed set. Fertility was not restored in any of the selected BC1 plants.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.