In Africa, many smallholder farmers grow open‐pollinated maize (Zea mays L.) varieties (OPVs), which allow seed recycling and outyield traditional unimproved landraces. Seeds of productive OPVs are provided to farmers, often by nongovernmental organizations (NGOs) that help farmers access improved seeds, particularly following disasters in which original seed is lost. However, NGOs often rely on local seed suppliers to provide seed, and in some years the seeds provided to the farmers are suspected not to be of the promised variety. Here we present methodology to prove within a high level of confidence if two samples of seeds are the same genetic population or not, despite the difficulties involved in fingerprinting heterologous populations. In addition to heterogeneity within populations, difficulties can include sampling errors, differences in the fields or years in which the seeds were multiplied, and seed mixing. Despite these confounding sources of variation, we show the possibility to conclusively differentiate each of the populations used in this work. This methodology will allow breeders, seed companies, government agencies, and NGOs to ensure the purity and identity of high‐yielding, locally adapted OPVs reach farmers so they can generate the highest yields possible in their fields.
The introgression of exotic germplasm could increase the heterosis among maize (Zea mays L.) populations. Our objective was to assess heterotic relationships among BSSS (R) (‘Reid’ germplasm) and BS 26 (‘Lancaster’ germplasm) from the temperate USA; the southern African cultivars Salisbury White, Southern Cross, and Natal Potchefstroom Pearl Elite Selection (NPP ES); and the subtropical CIMMYT Populations 34, 42, 44, and 47. The nine cultivars and their diallel crosses were evaluated at five Mexico, Zimbabwe, and U.S. locations. Populations 34, 42, 44, and 47 and NPP ES demonstrated the highest per se grain yield with Population 44 ranking first (8.42 Mg ha−1). Low to moderate levels of high parent heterosis was observed for their crosses; nonetheless, they occurred frequently as parents of superior crosses at Mexico where Population 42 × Population 47 ranked first (8.42 Mg ha−1). BSSS (R) demonstrated the best general combining ability with variety heterosis effects averaging 1.34 Mg ha−1 Diversity among varieties was determined on the basis of “dominance‐associated” gene effects. When the diversity was resolved by principle coordinate analysis, BSSS (R) was separated from BS 26, and Salisbury White from Southern Cross along different dimensional axes, suggesting that the two pairs are sources of different genes for heterosis. The highest yielding cross (9.28 Mg ha−1) and best heterotic combination involved Population 44 and BSSS (R). BSSS (R), NPP ES, and Populations 44 and 42 performed well outside their target ecologic zones, indicating their potential benefit to breeding programs in new geographic areas.
Observed 30 selected lines were crossed to two testers: CML-320 (heterotic group “A”) and CML- 321 (heterotic group “B”). The 60 line x tester combinations were evaluated at four location in the subtropical region of Mexico. In the combined analysis across locations the variance componentsfor the GCA and SCA were significant for grain yield. Significant SCA values allowed the separation of the inbred lines into two opposite heterotic groups based on the performance of the test crosses. On the basis of this information, two synthetics were formed with 7 inbred lines each defined as heterotic groups “A” and “B”. Nine single crosses outyielded the commercial check hybrid. Across locations the top yielder hybrid produced 9.48 t/ha which was 15.6% higher than the check. Average yield by location was 7.1, 3.8, 11.1 and 9.0 t/ha at Tlaltizapán, Tlajomulco, Celaya y Pabellón, respectively. Positive and significant GCA values were observed in six inbred lines. The GCA effects ranged from 1.18 to -2.19. The inbred lines from this study can effectively be used in hybridization programs.
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