Recent genomic studies which show that large regions of the genome have limited recombination, providing a mechanism for the accumulation of deleterious mutations that can only be resolved and purged in rare recombinant gametes.
This research was complemented by a related study of near isogenic lines [ 4748 ]. The number of primary and secondary branches were also counted on ten plants and their means obtained by using SPSS software version 2.
For example, interspecific mammalian hybrids may display increased size, vigor, and other desirable fitness traits, but have are often highly sterile and therefore have reduced fecundity. The model proposes that allelic choice available in hybrids but not inbreds provides hybrids the opportunity to detect and Genetic analysis of heterosis preferentially the favorable allele.
A Case for the Dominance Hypothesis: Conclusion By this breeding program we have achieved the improvement of agronomical characters, and yield grain in chickpea in two ways by Desi x Kabuli and Kabuli x Kabuli crosses between complementary parents.
As the genetic distance becomes greater, and complexities of adaptation are introduced, the relationship between performance and genetic diversity is lost. Accumulation of mutations in centromeric regions with limited recombination results in quantitative genetic estimates of overdominance in variance analysis and QTL studies due to the high degree of persistent linkage disequilibrium in these regions.
A recent study in maize using Illumina sequencing and qPCR confirmation revealed that, as with gene transcription, small RNA levels are generally additive in the hybrid with amounts predictable based on the inbred [ 82 ]. In summary, extensive genomic studies provide insights but no direct answers regarding the basis of heterosis.
If overdominance was the primary basis of heterosis, the populations would diverge due to selection and increase homozygosity of alternative alleles within the populations to maximize heterozygosity and performance of the population cross. The role of epistasis in heterotic and nonheterotic trait performance remains intriguing and perplexing.
Proteomic analysis is another approach that has been used to characterize molecular components of heterosis. The more breeds that are used in a composite, the greater the proportion of the initial heterosis is retained in subsequent generations.
Generation means analysis provided some of the first compelling evidence for the role of epistasis in hybrid performance. To say that there is no missing unifying mechanism is not meant to diminish the importance of fundamental research.
The importance of dominance versus overdominance was further supported by recurrent selection studies in which populations were evaluated in crosses with each other, or with an inbred tester. Alleles with reduced or complete loss of function can be accumulated in random-mating Genetic analysis of heterosis heterozygous populations of individuals.
Furthermore, two inbred lines from the population exceeded the performance of the hybrid, consistent with the proposition that, under the dominance hypothesis, it is possible to produce a homozygous individual that contains all the favorable alleles that produced the observed hybrid performance.
It is also commensurate with allele- and locus-specific observations of paramutation [ 97 — 99 ] in which the allelic interaction results in a heritable change in expression state, an observation inconsistent with the tenets of quantitative genetic theory.
Research by Russell et al. It is notable that this type of epistatic interaction is rarely observed in genomewide transcriptome studies. Weight without seeds of twenty plants of parent cultivars and F2 of every cross Table 4. As a rule, can transitions between the single phenotypes of such features fluid be found.
They found that proteins enriched in stress response and protein and carbon metabolism were differentially expressed in heterotic hybrids.
The selection of high yielding and stable genotypes is possible in early generation F1 and F2 for B1K2 and B1D1 while further generations are necessarily for the selection of ND1. Initial QTL studies indicated many QTL with overdominant gene action in populations derived from heterotic maize hybrids for traits such as yield and plant height [ 3738 ].Heterosis, also known as ‘hybrid vigor’, is a well-known phenomenon whereby hybrid offspring resulting from cross pollination exhibit greater vigor than either parent.
Here, Hochholdinger and Baldauf provide an overview of this fascinating biological phenomenon and what is known about the underlying genetics and mechanisms. The Genetics Society of America (GSA), founded inis the professional membership organization for scientific researchers and educators in the field of genetics.
Our members work to advance knowledge in the basic mechanisms of inheritance, from the molecular to the population level. Request PDF on ResearchGate | Genetic analysis of heterosis for maize grain yield and its components in a set of SSSL testcross populations | The present study aimed to dissect the genetic basis of heterosis for grain yield and its components in maize (Zea mays L.).
The magic word is heterosis (G. SHULL, ). The genetic analysis shows that their genome is organized into two complexes, that were termed gaudens and velans by O. RENNER in (Universität Jena). The gaudens complex induces the formation of green buds, broad leaves and red spots on the rosette-forming leaves.
For quantitative genetic analysis, the deviation of the hybrid relative to the mid-parent is the relevant value. In a practical context, high-parent heterosis, which measures the superiority of the hybrid relative to the best parent, is the important metric.
M. Han et al., “MicroRNA transcriptomic analysis of heterosis during maize seed. These data were used to investigate the genetic diversity, population structure, and genomic characteristics of each population and the contribution of these loci to heterosis. Three subgroups were identified, in agreement with their known pedigrees, geographical distributions, and .Download