Controlled pollination in root and tuber crops is challenging. Complex ploidy, cross-incompatibility, erratic flowering patterns, outcrossing, etc., limit the efficiency of breeding progress in these crops. Half-sib breeding that involves random pollination among parents is a viable method to harness genetic gain in outcrossing crops that are problematic for performing planned and controlled pollination. The authenticity of resulting progenies from the half-sib breeding is essential to monitor the selection gain in the breeding program. Parentage analysis facilitated by molecular markers is among the available handy tools for crop breeders to maximize genetic gain in a breeding program. It can help to resolve the identity of half-sib progenies and reconstruct the pedigree in the outcrossing crops. This paper reviews the potential benefits of parentage analysis in breeding selected outcrossing root and tuber crops. It assesses how paternity analysis facilitates breeding activities and the ways it improves genetic gain in the root and tuber breeding programs. Conscious use of complementary techniques in the root and tuber breeding programs can increase the selection gain by reducing the long breeding cycle and cost, as well as reliable exploitation of the heritable variation in the desired direction.

White Guinea yam (Dioscorea rotundata Poir.) is an important tuber crop grown extensively in tropical regions of West African yam belt. Tuber yield, dry matter content, and tolerance to yam mosaic virus are key traits used for identification and selection of superior varieties for commercial deployment. In this study, we estimated genetic parameters for fresh tuber yield, tuber dry matter content, and quantitative field tolerance to yam mosaic virus in 49 clones grown in multi-environment trials (METs). We conducted genomic prediction involving 6337 single nucleotide polymorphisms (SNPs) and phenotypic field evaluation of data collected on the three traits from four sites. Additive genetic and non-genetic factors contributed significantly to phenotypic variation of studied yam traits in METs but to varying degrees. The non-genetic effects were relatively high for most of the measured traits. Narrow-sense heritability values were low (<0.30) for all studied traits. Further analysis of the performance of the clones at test sites with additive main effects and multiplicative interaction (AMMI) analysis exhibited significant genotype by environment interactions (GEI) for the three traits. The AMMI identified TDr10/00412, TDr11/00055, and TDr09/00135 clones with lowest mean trait stability index and outstanding performance for fresh tuber yield (t ha −1), tuber dry matter, and mosaic virus resistance across sites. The elite clones identified could serve as useful source of alleles for the genetic improvement of the crop and possibly considered for release to farmers.

Despite the significance of cassava as food, feed and industrial root crop, little is known regarding the gene action determining root dry matter content (RDMC), fresh root yield, and tolerance to cassava mosaic disease (CMD), cassava green mite (CGM), and cassava mealy bug (CMB). Thus, a study was conducted to determine the general and specific combining abilities for disease, pest, RDMC, root yield and related traits by crossing 10 parents in a 6 × 4 line by tester design. The F 1 progenies and their parents were assessed in-field in a randomized complete block design (RCBD) with three replicates. Findings implied sufficient genetic variability for all traits studied. Family TMEB419×IBA030305 had the highest RDMC of 35.47%, whilst family TMEB7×IBA0000203 had the least RDMC (23.87%). Genotypes IBA020588, IBA916132 and TMEB419 were the best parents for improvement of harvest index (HI) and RDMC due to its high positive and significant GCA effects. Genotype IBA000203 contributed the highest to increased plant height, whereas TMEB1, TMEB47 and ZAR010116 had significant negative GCA effects. ZAR010116 was the best tester for HI. Families TMEB778×ZAR010116 (34.23) and IBA020588×ZAR010116 (32.78) were the best performing families for mean RDMC, with parent ZAR010116, exhibiting the highest GCA effect for RDMC. Families TMEB419×ZAR000156, IBA916132×ZAR000156 and IBA020588×IBA000156 had low mean CMD scores of 1.1, 1.2 and 1.2, respectively. The preponderance of non-additive gene actions indicated that selection of superior plants should be postponed to later generation.