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Richard C.,Makerere University | Richard C.,Seed Control and Certification Institute | Osiru D.S.,Makerere University | Mwala M.S.,University of Zambia | Lubberstedt T.,Iowa State University
Maydica | Year: 2016

The establishment of heterotic groups and heterotic patterns is crucial to a successful maize hybrid breeding programme. Molecular markers can be used for differentiating maize into heterotic groups which can be used for maximum exploitation of heterosis. A core set of 45 maize inbred lines was selected from 96 maize inbred lines that were obtained from major breeding programmes in Zambia, Zimbabwe, CIMMYT, IITA, and USA. The 45 inbred lines were assessed for their genetic diversity and assigned to different heterotic groups using 129SNPs. The genetic distance ranged from 0.03 to 0.99, with the highest distance observed between inbred lines B73 and Mo17 and the least between L3233 and N3. The inbred lines were clustered into four groups which corresponded to the N, SC, BSS, and Lancaster heterotic groups. The genetic divergence among temperate inbred lines was larger than that among tropical inbred lines. Temperate inbred lines with potential to improve the heterotic response of the N and SC heterotic groups were identified. The study has shown that including temperate inbred pairs from established and well-known heterotic groups is recommended for effective molecular characterisation of Southern African maize inbred lines. It is recommended that the genetic distance based grouping should be verified by combining ability studies. © 2016, Consiglio per la Ricercame la sperimentazione in Agrcoltura. All rights reserved. Source

Richard C.,Seed Control and Certification Institute | Richard C.,Makerere University | Munyinda K.,University of Zambia | Kinkese T.,University of Zambia | Osiru D.S.,Makerere University
Agronomy | Year: 2015

Maize (Zea mays L) is the most important food grain in sub-Saharan Africa and is mostly grown by small-scale farmers under rainfed conditions. Aluminum toxicity caused by low pH is one of the abiotic factors limiting maize production among smallholder farmers. Therefore, breeding maize hybrids that are tolerant to aluminum toxicity will sustain and increase maize production in these areas. Hence this study was undertaken to assess the genotypic variation for aluminum toxicity in maize inbred lines. Fourteen maize inbred lines of historical importance that are used in maize hybrid breeding in Zambia were studied for seedling root variation under different aluminum concentrations using hydroponic conditions. The aluminum tolerance membership index based on three traits (actual root length, relative root length and root length response) classified genotypes L3233 and L1214 as highly tolerant, L5527 and ZM421 as tolerant, and L12, L3234, and ZM521 as intermediate. The high PCV, GCV, and heritability observed for the root traits indicate that opportunities for selection and breeding for aluminum tolerance among Zambian inbred lines exist. Furthermore, the study indicated that a higher genetic gain would be expected from net root growth followed by shoot length response as selection traits, thus supporting the use of root traits for aluminum tolerance screening. © 2015 by the authors. Source

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