DETERMINING PATERNITY IN POLYPLOIDS - HEXAPLOID SIMULATION STUDIES

The breeding of new sweetpotato varieties is a highly inefficient proc ess, confounded by incompatibility, poor fertility, open-pollination a nd hexaploidy. Upwards of 12-20 lines are combined in open pollinated nurseries based on horticulturally important characteristics. After se veral years of selection most progeny can be traced back to just 3 or 4 maternal lines. A method that would identify the paternal parent of superior progeny would enable breeders to combine parents that exhibit superior combining ability in more efficient, smaller nurseries. The objective of this work is to explore by means of computer simulation t he application of genealogy reconstruction techniques on hexaploid ind ividuals based on co-dominant marker data. The progeny obtained from e ach female parent is categorically assigned to each male with non-zero exclusion probability based on its paternity likelihood. Computer sim ulations show that even with polysomic segregation types, it is possib le to discriminate between putative parents with few errors or mis-ass ignments. The number of loci scored for a 10 parent population should not be less than 20 in the case of 3 alleles per locus, and no more th an 10 loci for a five allele model. An increment in the number of alle les or loci increases the discriminatory power with the number of alle les yielding a far more important effect than the number of loci. This study also demonstrates the feasibility of using simulations to deter mine the minimum requirements, i.e. number of loci to be genotyped, fo r unambiguous parentage allocation in polyploids.