Legume Genomics and Genetics 2026, Vol.17, No.1, 1-13 http://cropscipublisher.com/index.php/lgg 2 2019), bean (Santos, et al., 2002), wheat (Agorastos and Goulas, 2005), and rice (Roy et al., 2016), reinforcing that “pure lines” may not be entirely genetically uniform. Several mechanisms can contribute to this variability, including residual heterozygosity, spontaneous mutations, activity of transposable elements, epigenetic modifications, occasional cross-pollination, and chromosomal alterations (Tokatlidis, 2015). These mechanisms introduce genomic changes that may lead to phenotypic divergence within cultivars, potentially affecting their stability but also providing novel sources of variation for breeding. Among these processes, residual heterozygosity (RH) is particularly relevant. Under continuous self-fertilization, the proportion of heterozygous loci is expected to decrease by half each generation. Thus, after seven selfing generations, approximately 99.2% of the loci should be homozygous. Even so, the persistence of low-frequency heterozygous loci can still result in segregation, giving rise to detectable phenotypic and physiological variation. The development of new soybean cultivars requires substantial investment and time. In this context, evaluating and selecting superior plants within existing cultivars has emerged as a cost-effective breeding strategy, enabling breeders to derive one or more purified lines that may outperform or replace the original cultivar. Such lines retain agronomically relevant traits already recognized by farmers while exhibiting greater predictability, uniformity, and a higher degree of homozygosity. Therefore, this study investigates the extent of intracultivar variability in six soybean cultivars using phenotypic and genotypic data to assess their genetic stability and potential impact on breeding. 2Results 2.1 Phenotypic data For individual analysis (data not shown), results were divided by cycle: early and late-maturity. In early-maturity cultivars, significant differences were observed for YIELD and FM in the 2018/19 season across tests, progenies, populations, and among early populations. In 2019/20, YIELD showed significant variation within tests, populations, and notably within SYN1359. Plant height differed significantly among NA5909 progenies, while DF differences were exclusive to NA5909. For late-maturity cultivars, in 2018/19, YIELD showed significant differences within tests, progenies, populations, and among late populations. In 2019/20, all traits differed significantly within the variety 97R73 and at the progeny level. Additionally, 98Y11 showed significant differences for YIELD and plant height. Progeny selection accuracy ranged from medium to high, with YIELD accuracy varying from 0.35 (EARLY 19/20) to 0.82 (LATE 18/19). Population selection accuracy ( rgg pop ) which measures the accuracy of selection at the population level, exhibited high magnitudes, with values ranging from 0.71 to 0.51 (data not shown). These estimates for the variables, in general, were higher for the late-maturity group in both years. The estimates of CVe ranged from 1.13 for FM, (LATE 19/20) to 17.91 for YIELD, (EARLY 18/19). The CVgprog is relatively low compared to CVgpop, suggesting more variation among populations than within for most of the traits. In the multi-environment analysis (Table 1), a significant variation was detected for progenies for the traits YIELD, PH, and FM. Variation was detected among populations for all traits, as well as between early and late maturity cultivars. The environmental variance (σe 2) was not significant for YIELD and PH, but was significant for FM and DF. In contrast, the interaction (σGxE 2 ) was significant for YIELD, FM and DF, whereas it was not significant for PH. The progeny heritability (hprog 2 ), ranged from low, FM (0.12) and YIELD (0.17), to medium, DF (0.45) to high, PH (0.86). Nonetheless the population heritability (hpop 2 ) ranged from low, YIELD (0.18) to high, PH (0.96), FM (0.86) and DF (0.96), in this regard at population level all the traits showed higher heritability. These results followed the same pattern for accuracy, where total accuracy (rgg Total) ranged from medium, YIELD (0.55) to high, PH (0.99), FM (0.94) and DF (0.99).
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