Gish analysis of advanced backcross plants from an interspecific hybrid between Allium cepa and A. fistulosum and genetics of seed yield in onion

Allium fistulosum possesses numerous traits useful in the genetic improvement of the bulb onion (A. cepa). There is little evidence of recombination between the genomes and no bulb-onion cultivars have been developed possessing a beneficial trait from A. fistulosum. In this study, restriction fragment length polymorphisms in the chloroplast genome established that three advanced backcross (BC) populations (AC94009, AC94010, and AC94011) derived from an A. fisltulosum x A. cepa hybrid possess the normal male-fertile cytoplasm of bulb onion. We used genomic in situ hybridization (GISH) to identify three recombination or translocation events among the chromosomes of A. cepa and A. fistulosum in these advanced BC populations. This research demonstrates that GISH analysis can reveal recombination events and chromosome substitutions between A. cepa and A. fistulosum.; Cytoplasmic-genic male-sterility (CMS) systems allow the production of hybrid onion. Bulb onion shows high inbreeding depression and the production of F1 seed is challenging. Selection of inbred parents for seed production has not been a priority since the final product of onion is the bulb and not the seed. Diallel analysis was carried out to determine the significance for general (GCA) and specific (SCA) combining ability over three environments. Correlation or regression analyses were performed for scape height, percent heterozygosity, and sugar concentration across four stages of flower development and the mean performance of inbreds (GCA) and the inbreds per se. A significant correlation was also found between height of scape and inbred seed production, but not for the mean performance of inbreds. High correlation was found between percent heterozygosity and seed yield of the mean performance of the inbred lines, but no effect was found for the seed yield of the inbreds per se. Little to no narrow-sense heritability was found when a parent-offspring regression was performed for random bulbs selected from three open pollinated populations.