The estimates of dominance variance were higher in magnitude than their corresponding additive genetic variance indicating preponderance of non-additive gene action except for days to 50% flowering. The 30 F 1 hybrids generated from a 6 × 6 diallel and two local checks were evaluated in 2009 at three sites in Uganda. Current Category » Effects and Use of Heterosis in Plant Breeding Manifestation Effects of Heterosis: 1 Increase Yield: Heterosis is generally expressed as an increase in the yield of hybrid and may be measured in terms of grain, fruit, seed, leaf, tubers, etc. It is commercially exploited in seed production of cross pollinated crops like Jawar, maize, bajara, onion, and cucurbit. Mixed group F1 hybrids were taller and more productive in seed yield than both European and Asiatic ones. Article shared by Heterosis hybrid vigour refers to the superiority of F 1 hybrids in one or more characters over its parents.
The bin map showed that, among all traits, dominance was more important to heterosis than other genetic effects. Development of numerous molecular tools stimulated efforts to determine the prognostic criteria for selection of best parental combinations. These results indicate that the direct effect of polyploidization in B. . An understanding of the extent, distribution and patterns of genetic variation is useful for estimation of any possible loss of genetic diversity and assessment of genetic variability and its potential use in breeding programs, including establishment of heterotic groups. It is indispensable in the design of hybridization strategies for the breeding of cultivars or hybrids, in the under- standing of gene segregation, and consequently of the resulting inbreeding and heterosis effects Birchler 2013;Washburn and Birchler 2014 in the establish- ment of the relation between cultivated plants and their ancestors Soltis et al.
The phenotype is known as a reflection of dynamic interaction between the genome, environmental conditions and the multiple plant responses that determines the plant performance. Such use was evaluated in 20 maize inbreds classified as first-cycle, second-cycle, good, and poor lines, and in diallel crosses within types. Alternative Title: hybrid vigour Heterosis, also called hybrid vigour, the increase in such characteristics as size, growth rate, fertility, and yield of a organism over those of its parents. An understanding of the extent, distribution, and patterns of genetic variation is useful for assessment of genetic variability and its potential use in breeding programs, including establishment of heterotic groups. The chapter presents data from several crops to illustrate the use of maps to reveal the features of crop genomes with implications for crop improvement. Because many types of regulatory processes exhibit dosage-dependent behavior, they would impact quantitative traits and contribute to their multigenic control in a semidominant fashion.
Unpollinated ears at the time of flowering ear shoots were selected for the studies because they are metabolically active, rich in mitochondria, and the sizes of the ears are diagnostic of yield heterosis. Greater uptake followed by better utilisation of nutrients by hybrids. Quantitative Effects: a Increase in size and genetic vigour: Hybrids are generally more vigorous I;e larger, healthier and faster growing than the parents e. Dominance Hypothesis has Assumptions: a Dominant genes are beneficial and recessive genes are deleterious. We conclude that hybrids as compared with their parent inbreds express heterosis in source components, including embryo size, as well as sink components, all contributing to higher biomass and grain yields of maize. According to this hypothesis there are contrasting alleles for example a 1 and a 2 , for a single locus.
It is shown here that this direct transposition is incorrect. The effects of different inbreeding levels were estimated for the following traits: number of inflorescences, number of flowers per inflorescence, fruit yield per plant, fruit number per plant, average fruit weight, weight of leaves per plant and pollen viability. Or Heterosis is a multigenic complex trait and can be extrapolated as the sum total of many physiological and phenotypic traits. It was concluded that heterozygotes were not necessarily advantageous for trait performance even among genotypes derived from such a highly heterotic hybrid. Smith and Ben Bowen, Genome-wide transcript analysis of maize hybrids: allelic additive gene expression and yield heterosis , Theoretical and Applied Genetics , 10. Thus we are faced with a striking discordance between our limited comprehension of the causal factors and mechanism of heter osis on the one hand, and the extensive agricultural practice of utiliza tion of hybrid vigor on the other.
In crops like, sugar cane, potato, sweet potato, banana, where vegetative propagation is a rule, hybrids can be easily developed. Results of this study could be used to i introgress varieties or populations, ii search for race collections with better agronomic type that belong to the racial heterotic pattern, iii improve gene pools based on racial heterotic patterns and geographical origins, iv establish reciprocal recurrent selection between two races that exhibited heterosis when crossed, or v develop hybrids based on lines derived from the collections studied in each environment The phenomenon of heterosis or hybrid vigor has long been recognized to have a genetic basis. The genetic and molecular approaches to heterosis usually do not rely on any model of the genotype—phenotype relationship. Such inbreds should be as vigorous as the F hybrids, but such inbreds have not been isolated. Such utilization is the result of the economic value of hybrid combinations displaying superior yields and qualities as well as stability of performance, of benefits derived in breeding programs, and of the enhanced varietal protection of proprietary rights. We also explore a biochemical model of gene dosage effects in macromolecular complexes in a similar context. The hybrid means were adjusted by removing environmental effects, using residuals as dependent variables in the regression analysis.
In most of the cases the utilisation of this heterosis phenomenon is not successful because of difficulty in production of large quantities of hybrid seeds. Maximum inter cluster distance of 578. These key proteins might be targets for improving metabolite contents of the fruit. The allotetraploids are genetically stable and tractable, which provides an excellent model system for mechanistic studies on polyploidy and hybrid vigor. Low frequency: The frequency of desirable heterotic combination is very low. It appears that, in analogy to what occurs in bureaucracy, increasing the number of protocols most often results in a stronger repression of productive activity, and better performance is an exception rather than the rule. Efficient uptake and assimilation of nutrients by heterotic hybrid seedlings confer the following advantages: 1.
Drought is one of the major environmental factors which threaten wheat production worldwide. Heterosis has been widely explored in Larix breeding for more than a century, but the molecular mechanisms underlying this phenomenon remain elusive. Information is presented in sections considering: a historical perspective; genetic theories of heterosis; physiological and biochemical basis of heterosis; heterosis in population crosses; hybrid predictions for maize, rapeseed, small grains and other crops groundnuts, tomatoes and rice ; and genetics and enhancement of heterosis using molecular markers. It is basically the result of the increased metabolic activity of the heterozygote Its effects are well established or manifested in the following tree ways: 1. In order to understand the genetic mechanism of heterosis that has been observed in hybrids between Brassica napus and partial new-type B. Publisher Summary On a worldwide basis, plant breeding has been one of the most successful technologies developed in modern agriculture: its methods are opportunistic and adaptable to myriad production schemes, they require relatively inexpensive input, and their products have pervasive social benefits. We suggest that such epigenetically generated differences in gene activity may contribute to hybrid vigor and that the epigenetic diversity between ecotypes provides increased allelic epi-allelic variability that could contribute to heterosis.