Gibberella ear rot (GER) of maize (Zea mays L.) caused by Fusarium graminearum Schwabe leads to yield loss and contamination with deoxynivalenol (DON), the most commonly detected mycotoxin. To enhance the efficiency of marker-assisted selection (MAS), it is necessary to identify quantitative trait loci (QTL), which are effective across different genetic backgrounds. The objectives of the present study were to (i) map QTL for GER resistance and reduced DQN contamination, (ii) examine the congruency of QTL across four connected populations (three from this study and one from an earlier study), and (iii) draw conclusions about the prospects of MAS. The populations under study comprised doubled haploid (DH) lines derived from crosses of four flint inbreds. The traits were recorded under artificial inoculation. Estimates of genotypic variances (a,-) were significant and heritabilities were moderately high to high. We mapped QTL together explaining 21 to 49% of n," for GER severity and 19 to 30% for DON concentration. Colocalized QTL for GER resistance and reduced DON contamination were identified in each mapping population. Further, QTL located at similar positions were detected across three populations in two chromosomal regions and across two populations in additional two regions. The study indicated that a combination of classical phenotypic selection and MAS is a promising strategy to breed maize for GER resistance and reduced DON contamination.
We investigated associations between line per se and testcross performance in rye and suggested that selection for per se performance is valuable for several traits in multi-stage selection programs. Genotypic correlation between line per se and testcross performance is an important quantitative-genetic parameter for optimizing hybrid breeding programs. The main goal of this survey was to study the association of line per se and testcross performance at the phenotypic level. We used experimental data from the line per se and testcross performance of two segregating winter rye populations (A, B) with each of 220 progenies tested in six environments for eight agronomic and quality traits. Genotypic variances were considerably larger for per se than for testcross performance of all investigated traits resulting in higher heritabilities of the former in most instances. Genotypic correlations (r g) between testcross and line per se performance decreased with increasing complexity of the trait as shown by the respective heritabilities. They were highest (r g ≥ 0.7) for plant height and test weight in population B, and thousand-kernel weight, falling number and starch content in both populations. A selection of these traits for line per se performance in early generations will save field plots in further testing testcross performance and increase efficiency of hybrid breeding.
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