If mphcorrelated genes contribute significantly to heterosis, this role should be interpretable in terms of quantitative genetics. Diallel analysis and estimation of heterosis in single cross maize hybrids. Pdf estimation of heterosis for quantitative characters. Pdf estimation of heterosis for quantitative characters in. Genomic dosage effects on heterosis in triploid maize pnas. Heterosis is used to increase yields, uniformity, and vigor. To dissect the genetic basis of yieldrelated traits and heterosis in maize, 301 recombinant. Under this premise it would be reasonable to define hybrids shull. Speculations as to the underlying causes began to appear early in this observational period. This hybrid vigor, or heterosis, occurs when crossing two genetically unrelated inbred parents to create a hybrid. E falconer and vigour is a key feature underlying the expression of grain yield in mackay, 1996. Maize is a highly cross pollinated crop and the scope for exploitation of hybrid vigour will depend on the direction and magnitude of heterosis, biological feasibility. Various models have been posited to explain heterosis, including dominance, overdominance, and pseudooverdominance.
Moll rh, clark cockerham c, stuber cw, williams wp 1978 selection responses, geneticenvironmental interactions and heterosis with recurrent selection for yield in maize. In this perspective, we consider that it might be useful to the field to abandon these. To quantify heterosis in diploid and triploid hybrids, field experiments were conducted in the summers of 2008 and 2009 to measure nine traits in eight maize lines fig. International journal of of combining ability and heterosis for yield and yield traits in pure and applied science and technology, 21 1. Heterotic loci identified for maize kernel traits in two. Shull 1952 coined the term heterosis and defined it as. Gibberellins, amylase, and the onset of heterosis in maize. Heterotic qtl for grain yield mapped near low r pericentromeric regions i. In maize crops, however, the use of heterosis developed in such a unique way that hybridization was recommended as a valuable breeding method. Growth rate rather than growth duration drives growth. Heterosis refers to the superior phenotypes observed in hybrids relative to their inbred parents with respect to traits such as growth rate, reproductive success, and yield. Pdf combining ability for growth parameter and yield components were evaluated in a 7. Farmers are always on the lookout for better maize hybrids in the competitive seed market.
Hybrid breeding methods are used in maize, sorghum, rice, sugar beet, onion, spinach, sunflowers, broccoli and to create a more psychoactive cannabis. Heterosis is prevalent for multiple traits in diverse maize. Heterosis was discovered in maize about a century ago and has subsequently been found to occur in many crop species. Heterosis or hybrid vigour is a phenomenon in which hybrid progeny exhibit superior yield and biomass to parental lines and has been used to breed f1 hybrid cultivars in many crops.
Gibberellins, amylase, and the onset of heterosis in maize seedlings. Heterosis it is defined as the superiority of f 1 hybrid over both the parents in terms of yield or some other characters. Determination of combining abilities and heterosis of parental lines is very important in selecting the mutant lines and in deciding breeding strategies for maize hybrid production. This suggests that expression differences of sequences in recombinationsuppressed regions are important in the establishment of heterosis for gy in f1 hybrids and also in the conservation of heterosis for gy across genotypes. Heterosis and combining ability in diallel crosses involving maize. Gowen and published by iowa state university press. Genomewide metaanalysis of maize heterosis reveals the. Rohman plant breeding division, bangladesh agricultural research institute joydebpur, gazipur, bangladesh abstract. Identification of genetic factors contributing to heterosis. Pdf standard heterosis for grain yield in maize hybrids. The hybrid vigor is one of the greatest practical contribution of genetics to the agricultural world and had its most significant expression in maize crops, being.
Heterosis and the nature and combining ability was studied in 7. S1 and materials and methods including the reciprocal triploid and diploid hybrids, mo17. Up to now the phenomenon of heterosis in corn has been explained mainly by one of two alternatives. The environment can influence heterosis, the phenomena in which the offspring of two inbred parents exhibits phenotypic performance beyond the inbred parents for specific traits. Pdf combining ability and heterosis in maize zea mays l. Genotypebyenvironment interactions affecting heterosis in maize. Standard heterosis of maize hybrids tested at rampur under observation nursery obn, top cross and coordinated varietal trialhybrid cvth in 200607. Heterosis is prevalent for multiple traits in diverse. When growing hybrid maize, the farmer generally obtains fresh f1 hybrid seed each year from growers who specialize in its production.
Classical genetic and quantitative trait loci analyses of. The contribution 76 of various potential molecular mechanisms to heterosis remains one of the most intriguing and. When two homozygous inbreeds a true breeding line obtained by continuous inbreeding of genetically unlike constituents are crossed together, the resulting hybrids obtained from. Heterosis estimates showed that heterosis was more important in grain yield, yield components, plant height, number of leaves per plant and, leaf area index than. In this study we measured 25 traits in a set of 47 maize hybrids and their inbred parents grown in 16 different environments with varying levels of average productivity. Maize is an important staple food for most kenyans. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the traits measured. The first has been largely descriptive and concerned with the frequency and magnitude of the observed effects.
Heterosis or hybrid vigor is the principal reason for the success of the commer cial maize industry. The experiment was conducted at institute for agricultural research farms, located at samaru. In this article we will discuss about heterosis or hybrid vigour. The mechanism by which heterosis enhances yield is not fully understood, but a comprehensive analysis of its effects has been provided by blum 20. Physiological mechanisms underlying heterosis for shade. Heterosis is prevalent for multiple traits in diverse maize germplasm sherry a. In this study, the genetic basis of heterosis for four maize kernel traits was. Estimation of heterosis and combining ability in maize zea mays l.
Jul 23, 2018 heterosis has been widely used to increase grain quality and yield, but its genetic mechanism remains unclear. The increased vigour, speed of development, resistance to disease and insect. Khaleque mian 2, nasrin akter ivy 2, jalal uddin ahmed 3. We have used expression profiling to determine whether the level, or types, of nonadditive gene expression vary in maize hybrids. Importantly functional analysis of heterosis associated genes from these genomic. Pdf combining ability, gene action and heterosis in maize. Heterotic grouping of selected inbred lines of maize zea. Combining ability and heterosis for yield and component. May 01, 2007 the exploitation of heterosis is one of the most outstanding advancements in plant breeding, although its genetic basis is not well understood yet. Heterosis, inbreeding depression, various theories of. Investigations of the phenomenon have followed two separate courses. Heterosis has been widely used to increase grain quality and yield, but its genetic mechanism remains unclear.
Journal of bioscience and agriculture research, 182, pp. This study was aimed at determining the level of nematode resistance among f1 hybrids, and to estimate grain yield, heterosis and yield losses. Heterosis, heterobeltiosis and standard heterosis for maize yield per plot and yield. Despite the importance of heterosis, the molecular basis of this phenomenon is unclear 67. Table m means of 55 single above diagonal specific combining ability effects estimates below diagonal and general combining ability effects estimates for grain yield qha evaluated at six locations. Sep 09, 2019 utilization of heterosis in maize could be critical in maize breeding for boosting grain yield.
Combining ability and heterosis for yield and component characters in maize m. Hybrid maize generates high yields, increased value and reduced production costs. Iranian maize inbred lines reported that the lines could be classified into four preliminary heterotic groups. Vancouver karim ms, ahmed s, akhi ah, amiruzzaman m and karim anma. The results are consistent with the theory that ga are one factor involved in the regulation of heterosis of shoot growth in maize, a theory that suggests that a partial deficiency in endogenous. Pdf combining ability, gene action and heterosis in.
Research article open access genomewide metaanalysis of. Average heterosis it is the heterosis where f 1 is superior to mid parent value. Dec 10, 2019 heterosis for grain yield in maize was attributed to heterosis for leaf size, maximum lai, leaf staygreen traits, sustaining rate of photosynthesis during the grain filling period and larger. Pdf determination of heterosis in maize hybrids is necessary for their commercial exploitation. To this end, we analyzed the 1,999 mphcorrelated genes from thiemann et al. Heterosis for grain yield and its component traits in maize ijpab. Abstract today the concept of heterotic groups and patterns is fundamental to hybrid breeding theory and practice. However, the genetic architecture of heterosis is not fully understood. Schull and first proposed in 1914 see hayes 1952 and is usually described in terms of the. This research was conducted on the materials arising from the maize single cross b73. H99 to study heterosis by procedures of classical genetic and quantitative trait loci qtl analyses. Grain yield and heterosis of maize hybrids under nematode.
Edwards heterosis is the foundation of modern maize breeding programs. The increasing population trend in the face of declining yields in maize production has intensified food insecurity countrywide. Heterosis is the superior performance of f1 hybrid progeny relative to the parental phenotypes. Heterosis dominated the thinking of plant and animal geneticists in the 1940s and 1950s as evidenced by the now classic book entitled heterosis edited by john w. Combining ability and heterosis in maize zea mays l. Concept of heterotic groups and pattern the phenomenon of heterosis was first detected in maize. Heterosis in maize has been known since the early 1900s concept of heterotic patterns developed in the 1960s and 1970s breeding for heterotic patterns has resulted in increased divergence between groups tracy and chandler 2006 pp 219233. The possible involvement of gibberellins and amylase in heterosis of maize seedlings was investigated in two parental inbreds, cm7 and cm49, and their single cross f 1 hybrid, cm7. Concept of heterotic group and its exploitation in hybrid. Genetic dissection of yieldrelated traits and midparent. The low grain yield can be attributed to foliar diseases mainly gray leaf spot and maize streak virus and expensive hybrid seeds. Materials were the basic generations, the derived 142. Heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of development, and fertility than both parents.
Estimation of heterosis and combining ability in maize zea. Jbar diallel analysis heterosis single cross maize hybrids. Heterosis for grain yield in maize was attributed to heterosis for leaf size, maximum lai, leaf staygreen traits, sustaining rate of photosynthesis during the grain filling period and larger. Despite its importance in maize production, we know surprisingly little about the genetic basis of heterosis. Combining ability, gene action and heterosis for grain yield and yield contributing traits were studied under drought stress at flowering in maize. Springer3 1usdaars, plant genetics research unit, and division of plant sciences, university of missouri, columbia, missouri, united states of america, 2usdaars, u. Corn maize nearly all field corn grown in most developed nations exhibits heterosis. Physiological basis of heterosis for nitrogen use efficiency. The heterosis concept, defined over a century ago, continues to be applied in the production of several hybrids from different vegetable species. Small rnas and heterosis in maize plant physiology. Plantparasitic nematodes are present on maize but resistant genotypes have not been identified in uganda.
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