Use of molecular markers associated with inbreeding depression in onion

Resumo

Crossbreeding among a small number of plants occurs naturally, mainly due to the limited dispersion of pollen, and reduces inbreeding depression at the population level. The goal of this study was to discuss the genetic basis of inbreeding in onions and test a hypothesis, based on available studies and SSR results, that sibs affect inbreeding depression.  To test this hypothesis, 12 onion populations from Bayer's onion breeding program were used (derived from four different backgrounds and bred through self-fertilization of one plant, crossbreeding of two plants and crossbreeding of three plants). Three individuals from each line were analyzed and amplifications were performed using a set of primers selected for their relatively high polymorphism (based on germplasm characterizations performed at CITA) and ability to represent the onion genome.  The results showed that these SSRs can be used to detect germplasm variability in onions. Generally, heterozygosity is reduced by self-fertilization and increased by crossbreeding additional plants. For the best results, crossbreeding should start in lines with low-levels of inbreeding.