Heterosis indicates the hybrid superiority over its parental lines and is often found for traits of agronomic importance. Heterosis is sizable for allogamous species, especially maize (Zea mays L.), and is crucial in crop sustainability through the optimization of grain yield physiology. Hybrid superiority has been extensively exploited, but its genetic basis is not completely understood. The objective of this three-step study was to gain information on agronomic and genetic aspects concerning heterosis in maize. We first conducted a study to detect Quantitative Trait Loci (QTL) affecting heterosis. A set of 142 Recombinant Inbred Lines (RILs), derived from the single cross B73 × H99, was crossed to the three testers B73, H99 and B73 × H99; then, testcrosses were evaluated, together with the RILs, in three environments. Several QTL for agronomic traits were detected and most of them were characterized by dominant or overdominant gene action. The most important QTL for grain yield overlapped with QTL for other traits (especially shoot weight at early stage, plant height and kernels/plant number), suggesting that QTL affected first these traits and then grain yield (pleiotropy). As a second step, we conducted a breeding program aimed at developing sets of Near Isogenic Lines (NILs), i.e., lines sharing the same genetic background but differing for the parental alleles at the QTL. In the final part of this work, an evaluation of the breeding material was made; results confirmed the importance of detected QTL, further indicating the importance of their dominance-overdominance effects. In the final step, NILs were crossed to related and unrelated testers with the objective to obtain a more thorough insight of QTL genetic effects. These testcrosses are now being evaluated in a research conducted across several environments, including stress vs. non-stress growing conditions and results obtained in the first year will be presented.

Genetic and agronomic aspects of heterosis in maize: QTL analysis, development and evaluation of near isogentic lines for heterotic QTL.

FRASCAROLI, ELISABETTA;CANE', MARIA ANGELA;LANDI, PIERANGELO;
2008

Abstract

Heterosis indicates the hybrid superiority over its parental lines and is often found for traits of agronomic importance. Heterosis is sizable for allogamous species, especially maize (Zea mays L.), and is crucial in crop sustainability through the optimization of grain yield physiology. Hybrid superiority has been extensively exploited, but its genetic basis is not completely understood. The objective of this three-step study was to gain information on agronomic and genetic aspects concerning heterosis in maize. We first conducted a study to detect Quantitative Trait Loci (QTL) affecting heterosis. A set of 142 Recombinant Inbred Lines (RILs), derived from the single cross B73 × H99, was crossed to the three testers B73, H99 and B73 × H99; then, testcrosses were evaluated, together with the RILs, in three environments. Several QTL for agronomic traits were detected and most of them were characterized by dominant or overdominant gene action. The most important QTL for grain yield overlapped with QTL for other traits (especially shoot weight at early stage, plant height and kernels/plant number), suggesting that QTL affected first these traits and then grain yield (pleiotropy). As a second step, we conducted a breeding program aimed at developing sets of Near Isogenic Lines (NILs), i.e., lines sharing the same genetic background but differing for the parental alleles at the QTL. In the final part of this work, an evaluation of the breeding material was made; results confirmed the importance of detected QTL, further indicating the importance of their dominance-overdominance effects. In the final step, NILs were crossed to related and unrelated testers with the objective to obtain a more thorough insight of QTL genetic effects. These testcrosses are now being evaluated in a research conducted across several environments, including stress vs. non-stress growing conditions and results obtained in the first year will be presented.
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E. Frascaroli; M. A. Canè; P. Landi; G. Pea; M. Morgante; M. E. Pè
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/66104
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