Topic
Heterosis
About: Heterosis is a research topic. Over the lifetime, 7094 publications have been published within this topic receiving 109091 citations. The topic is also known as: hybrid vigor.
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TL;DR: The objectives of this study were to determine the nature of the genetic improvement of maize hybrids over a period of about 40 years using a representative series of hybrids and to determine any associated changes in morphological and yield component traits.
Abstract: Improvement in the genetic worth of maize (Zea mays L.) hybrids over the years can be a consequence of increased heterosis and/or improved inbred parents. The objectives of this study were to determine the nature of the genetic improvement of maize hybrids over a period of about 40 years using a representative series of hybrids and to determine any associated changes in morphological and yield component traits. Non parental single crosses of double crosses from the 1930's and the 1950's and single crosses of the 1970's, their inbred parents, and their F, generations were grown at 31 500 and 58 800 plants/ha. The study was conducted at Urbana and Shabbona, 111. However, the inbreds were grown at Urbana only and, because of poor germination of the inbreds of the earlier decades, were grown at 31 500 and 48 800 plants/ha. The majority of the improvement in inbred and hybrid yielding ability occurred between the 1950's and the 1970's. Recent inbreds and hybrids stand better, stay green longer, and have smaller tassels than their earlier counterparts. Grain yield inbreeding depression (and heterosis) increased from the 1950's to the 1970's and a part of it is manifest at loci that condition the responsiveness of the hybrids of the 1970's to increased plant densities. Plant and ear height inbreeding depression seem to have decreased from the 1950's to the 1970's
2,533 citations
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02 Mar 2011
TL;DR: The first € price and the £ and $ price are net prices, subject to local VAT, and the €(D) includes 7% for Germany, the€(A) includes 10% for Austria.
1,945 citations
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TL;DR: The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades as mentioned in this paper, based on recent studies in many species, the authors argue that both phenomena are predominantly caused by the presence of recessive deleterious mutations in populations.
Abstract: The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Based on recent studies in many species, the authors argue that both phenomena are predominantly caused by the presence of recessive deleterious mutations in populations. Inbreeding depression — the reduced survival and fertility of offspring of related individuals — occurs in wild animal and plant populations as well as in humans, indicating that genetic variation in fitness traits exists in natural populations. Inbreeding depression is important in the evolution of outcrossing mating systems and, because intercrossing inbred strains improves yield (heterosis), which is important in crop breeding, the genetic basis of these effects has been debated since the early twentieth century. Classical genetic studies and modern molecular evolutionary approaches now suggest that inbreeding depression and heterosis are predominantly caused by the presence of recessive deleterious mutations in populations.
1,604 citations
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TL;DR: Whenever a QTL for grain yield was detected, the heterozygote had a higher phenotype than the respective homozygote suggesting not only overdominance (or pseudooverdominance) but also that these detected QTLs play a significant role in heterosis.
Abstract: The use of molecular markers to identify quantitative trait loci (QTLs) affecting agriculturally important traits has become a key approach in plant genetics-both for understanding the genetic basis of these traits and to help design novel plant improvement programs. In the study reported here, we mapped QTLs (and evaluated their phenotypic effects) associated with seven major traits (including grain yield) in a cross between two widely used elite maize inbred lines, B73 and Mo17, in order to explore two important phenomena in maize genetics-heterosis (hybrid vigor) and genotype-by-environment (G x E) interaction. We also compared two analytical approaches for identifying QTLs, the traditional single-marker method and the more recently described interval-mapping method. Phenotypic evaluations were made on 3168 plots (nearly 100,000 plants) grown in three states. Using 76 markers that represented 90-95% of the maize genome, both analytical methods showed virtually the same results in detecting QTLs affecting grain yield throughout the genome, except on chromosome 6. Fewer QTLs were detected for other quantitative traits measured. Whenever a QTL for grain yield was detected, the heterozygote had a higher phenotype than the respective homozygote (with only one exception) suggesting not only overdominance (or pseudooverdominance) but also that these detected QTLs play a significant role in heterosis. This conclusion was reinforced by a high correlation between grain yield and proportion of heterozygous markers. Although plant materials were grown and measured in six diverse environments (North Carolina, Iowa and Illinois) there was little evidence for G x E interaction for most QTLs.
847 citations
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TL;DR: A bimodal distribution of outCrossing rates was observed for natural plant populations, with more primarily selfing and primarily outcrossing species, and fewer species with intermediate outcrossed rate than expected by chance.
Abstract: A bimodal distribution of outcrossing rates was observed for natural plant populations, with more primarily selfing and primarily outcrossing species, and fewer species with intermediate outcrossing rate than expected by chance. We suggest that this distribution results from selection for the maintenance of outcrossing in historically large, outcrossing populations with substantial inbreeding depression, and from selection for selfing when increased inbreeding, due to pollinator failure or population bottlenecks, reduces the level of inbreeding depression. Few species or populations are fixed at complete selfing or complete outcrossing. A low level of selfing in primarily outcrossing species is unlikely to be selectively advantageous, but will not reduce inbreeding depression to the level where selfing is selectively favored, particularly if accompanied by reproductive compensation. Similarly, occasional outcrossing in primarily selfing species is unlikely to regularly provide sufficient heterosis to maintain selection for outcrossing through individual selection. Genetic, morphological and ecological constraints may limit the potential for outcrossing rates in selfers to be reduced below some minimum level.
818 citations