Generations Of Inbreeding Research Articles

ОЦЕНКА САМОФЕРТИЛЬНОСТИ ПОДСОЛНЕЧНИКА В УСЛОВИЯХ КУЛУНДИНСКОЙ СТЕПИ

In the Kulunda steppe, sunflower yields are greatly in-fluenced by empty shells as a result of low self-fertility of plants under unfavorable conditions for pollination. There-fore, the development of sunflower varieties for high self-fertility is a topical issue. To determine self-fertility, it is necessary to take into account the number of tubiform flo-rets in the anthodium, and counting them is a rather labor-intensive task. Therefore,in order to facilitate the determi-nation of self-fertility, the possibility of its evaluation by direct counting of seeds in an anthodium was studied. The experiments were carried out from 2015 through 2018 in the fields of the Plant Breeding and Seed Production La-boratory of the Kulunda Agricultural Experimental Station of the Federal Altai Scientific Center of Agro-Biotechnologies. The research targets were self-pollinated offspring of the 1st-4th inbreeding generations obtained on the basis of large-fruited varieties Baloven, Altai and Kulundinsky 1 under the conditions of the Kulunda steppe of the Altai Region. The results of the experiment show that the self-fertility of the studied varieties is at a low level and averag-es 8.9% with a variation from 4.8% in the Altai variety to 16.4% in the Kulundinsky 1 variety. The study of the rela-tionship of self-fertility and the number of seeds in an an-thodium showed high dependence between these charactionship of self-fertility and the number of seeds in an an-thodium allows conducting primary evaluation of self-fertility on this basis.

Speed breeding and early panicle harvest accelerates oat (Avena sativa L.) breeding cycles

AbstractIncreasing the response to selection in plant breeding programs by reducing the time required to complete a generation of inbreeding can significantly shorten the time to release a cultivar. Recently, ‘speed breeding’ strategies that manage temperature, photoperiod, and micronutrients showed a significant reduction in time to inbreeding in several crops. The goal of this study was to determine if the speed breeding system can be effectively applied to oat (Avena sativa L.) for a single‐seed descent breeding scheme and to determine if seeds can be harvested early with acceptable germination for breeding purposes. Two systems were evaluated using eight genetically diverse oat genotypes under speed breeding (22‐h photoperiod) and normal growing conditions (16 h) in a randomized complete block design with a factorial arrangement of treatments and three replications. Our results indicated a significant reduction in time for all the phenological stages evaluated when speed breeding was used, compared with normal growing conditions. In particular, the reduction in time to flowering date was 11 d (62 vs. 51 d on average). Germination evaluations indicated that by 21 d after flowering, it was possible to obtain acceptable germination levels for all genotypes evaluated. This should be of great importance in breeding systems where single‐seed descent can be used.

Inbreeding Depression in Genotypically Matched Diploid and Tetraploid Maize.

The genetic and molecular basis of heterosis has long been studied but without a consensus about mechanism. The opposite effect, inbreeding depression, results from repeated self-pollination and leads to a reduction in vigor. A popular explanation for this reaction is the homozygosis of recessive, slightly deleterious alleles upon inbreeding. However, extensive studies in alfalfa indicated that inbreeding between diploids and autotetraploids was similar despite the fact that homozygosis of alleles would be dramatically different. The availability of tetraploid lines of maize generated directly from various inbred lines provided the opportunity to examine this issue in detail in perfectly matched diploid and tetraploid hybrids and their parallel inbreeding regimes. Identical hybrids at the diploid and tetraploid levels were inbred in triplicate for seven generations. At the conclusion of this regime, F1 hybrids and selected representative generations (S1, S3, S5, S7) were characterized phenotypically in randomized blocks during the same field conditions. Quantitative measures of the multiple generations of inbreeding provided little evidence for a distinction in the decline of vigor between the diploids and the tetraploids. The results suggest that the homozygosis of completely recessive, slightly deleterious alleles is an inadequate hypothesis to explain inbreeding depression in general.

Genetic characterization and divergence studies of maize (Zea maysL.) lines developed from landraces indigenous to North Eastern Hill Region (NEHR) of India

AbstractThe current study focused on characterization of the underlying genetic divergence in inbred lines developed from local landraces of North Eastern Hill Region of India – a designated Asiatic maize diversity centre – following six generations of inbreeding. Substantial genetic differentiation was indicated based on very high to moderateFstvalues for 22 of the 38 simple sequence repeat markers studied. STRUCTURE analysis partitioned the subset into two distinct and one admixture subgroup (Populations I, II and III respectively) accompanied by a significant reduction in heterozygosity. Population II was further subdivided into subpopulations Pop-M9 and Pop-T9. Nei's pairwise genetic distance and populationFstvalues indicated that Populations I and II were more divergent with neighbour joining clustering analysis clearly defining landraces originating from the states of Tripura (Population II) and Sikkim (Population I) as most divergent. Principal coordinates analysis could explain 31.26% of the variation present in the subgroups wherein Population I was more variable. Analysis of molecular variance andFstcoefficients (P< 0.001) indicated 17% population structuring with 55% variation detected for individuals within populations. These results combined with the presence of phenotypic variability in the subgroups for yield traits supported by results of a preliminary partial diallel analysis strongly suggest the existence of distinct heterotic groups. Divergence studies are crucial for exploiting heterosis, and the current study would go a long way to help establish a germplasm base for developing varieties with improved agronomic performance and surer commercial prospects no reports of which are available thus far.

Quantitative genetic analyses provide parameters for selection and conservation of captive Great-billed Seed-finches (Sporophila maximiliani).

The Great-billed Seed-finch (Sporophila maximiliani) is an endangered South American bird that has suffered from trafficking and the destruction of its natural habitat. In contrast, there are over 180,000 Great-billed Seed-finches legally raised in captivity in Brazil. The interest as a pet for Great-billed Seed-finches is due to their exceptional ability to sing. In the present research, the unknown genetic structure of the Great-billed Seed-finch captive population was investigated by quantitative analysis of 6,226 pedigree records. Additionally, 7,671 phenotypic records were available to estimate genetic parameters such as heritability and evolvability of a song-related trait of these birds for competitions. The captive Great-billed Seed-Finch population faces many of the problems commonly encountered in domestic animal populations such as a high level of inbreeding (average of 8.26%, 70.47% of birds were inbred), pedigree bottlenecks, unbalanced contribution of breeding animals and structuring (equivalent number of subpopulations of 2.91). Despite this, most genetic diversity remains preserved within aviaries. The high generation interval (5.74 years) found for this population should help to prevent a rapid increase in inbreeding and genetic drift. These results should serve as strong motivation and support for urgent actions to manage the genetic diversity of captive Great-billed Seed-Finches. From the viewpoint of genetic improvement for singing time in tournaments (STT), this trait presents sufficient variability to allow response to artificial selection given the heritability of 18.7% and evolvability of 2,447%. In contrast, inbreeding and high generation interval appear to be the most considerable barriers that may limit the genetic gain for STT. Widespread adoption of techniques such as optimal genetic contribution selection and implementation of routine genetic diversity monitoring via pedigree analysis and molecular tools can be crucial both in terms of breeding and conservation of genetic diversity of captive Great-billed Seed-Finches.

Partially inbred maize lines in topcrosses and hybrid performance

ABSTRACT In plant breeding programs, the selection of potential progenies in early generations of inbreeding is an essential step. Considering that, the adoption of topcrosses helps the breeder in the selection, this study aimed to verify the potential of S2 strains for synthesis of synthetic varieties and to obtain experimental information on yield and agronomic potential of topcross hybrids. As such, 75 topcross hybrids were generated from crossing 75 S2 lines with F2 generation of the commercial hybrid. The 75 hybrids were grown in a field, along with two commercial hybrids in a randomized complete block design with 4 replicates and in 4-meter plots. Flowering, plant height, height, diameter, length and weight in the ear, and grain yield traits were examined. Analysis of variance was performed, the combining ability was estimated, and, from the means, the Scott & Knott test was conducted. So, the topcross hybrids that distinguished themselves for grain yield were those composed by lines 67, 14, 44, and 69, presenting high CGA, therefore indicating good potential for producing synthetic or base population. For the other traits of agronomic interest that were assessed in maize, a potential for selection with different focuses was found: reduction of cycle and height and increase in length and diameter of the ear.

Effects of Inbreeding on Genetic Characteristic, Growth, Survival Rates, and Immune Responses of a New Inbred Line of Exopalaemon carinicauda

The Exopalaemon carinicauda could be a useful crustacean laboratory animal in many research fields. We newly established an inbred line of Exopalaemon carinicauda named EC4 inbred line by brother×sister mating and keeping to F11 generation. Trends in heterozygosity in the process of producing EC4 inbred line were examined through the characterization of polymorphisms based on gene frequencies of SNP and EST-SSR loci. The results demonstrated that the number of alleles (N), observed heterozygosity (Ho), expected heterozygosity (He), and polymorphism information content (PIC) gradually decreased with the increase of inbreeding generations. The genetic detection results indicated that 9 (29.03%, 9/31) of the SNP loci and 15 (32.61%, 15/46) of the EST-SSR loci were homozygous in F11 generation of EC4 inbred line. The variation of the growth-related traits, the immune responses, and antioxidant status were described in experimental full-sibling inbred populations of E. carinicauda at five levels of inbreeding coefficient (F = 0.785, F = 0.816, F = 0.859, F = 0.886, F = 0.908) under controlled laboratory conditions. The body weight, body length, and survival rate in EC4 inbred line of all generations were less than the control population. Inbreeding affected the antibacterial activity, phenoloxidase (PO) activity, and superoxide dismutase (SOD) which decreased at the eleventh generation of EC4 inbred line. This study demonstrated that inbreeding had a negative effect on the economic traits and immune response, but our inbred line was established successfully until F11 and confirmed by genetic detection using SNP and EST-SSR loci.

Probabilities of Multilocus Genotypes in SIB Recombinant Inbred Lines.

Recombinant Inbred Lines (RILs) are obtained through successive generations of inbreeding. In 1931 Haldane and Waddington published a landmark paper where they provided the probabilities of achieving any combination of alleles in 2-way RILs for 2 and 3 loci. In the case of sibling RILs where sisters and brothers are crossed at each generation, there has been no progress in treating 4 or more loci, a limitation we overcome here without much increase in complexity. In the general situation of L loci, the task is to determine 2L probabilities, but we find that it is necessary to first calculate the 4L “identical by descent” (IBD) probabilities that a RIL inherits at each locus its DNA from one of the four originating chromosomes. We show that these 4L probabilities satisfy a system of linear equations that follow from self-consistency. In the absence of genetic interference—crossovers arising independently—the associated matrix can be written explicitly in terms of the recombination rates between the different loci. We provide the matrices for L up to 4 and also include a computer program to automatically generate the matrices for higher values of L. Furthermore, our framework can be generalized to recombination rates that are different in female and male meiosis which allows us to show that the Haldane and Waddington 2-locus formula is valid in that more subtle case if the meiotic recombination rate is taken as the average rate across female and male. Once the 4L IBD probabilities are determined, the 2L probabilities of RIL genotypes are obtained via summations of these quantities. In fine, our computer program allows to determine the probabilities of all the multilocus genotypes produced in such sibling-based RILs for L<=10, a huge leap beyond the L = 3 restriction of Haldane and Waddington.

What five insects told us about how a native plant copes with real-world problems

What five insects told us about how a native plant copes with real-world problems

Polymorphism of genes controlling low level of linolenic acid in lines from VIR flax genetic collection

Background. Linseed solin varieties were created for nutrition, but the effect of oil fatty acid (FA) composition on other characters is not clear.&#x0D; Materials and methods. Using 6 inbreeding generations from 26 heterogeneous flax accessions were generated 19 high (HL), 7 medium (ML) and 14 low linolenic (LL) lines. For each lines contents of 5 basic FA: palmitic, stearic, oleic (OLE), linoleic (LIO) and linolenic (LIN); the ratio LIO/LIN, oil iodine number, vegetative period (VP) phases and plants size were evaluated. Development of CAPS marker for LuFAD3A gene was performed using idtdna.com. Sequencing of LIN genes sites was done in the Centre MCT SPBGU and Eurogen.&#x0D; Results. ANOVA showed significant differences HL, ML and LL groups for PAL, OLE, LIO, LIN, LIO/LIN, IOD. Considerable decrease of LIN, causes asymmetric changes in FA ratio and correlations between them and other traits. Factor analysis revealed the influence of two factors. The first one divided lines according to their LIN level and characters associated with it, the second one according to the VP and OLE. LIN synthesis is controlled by two complementary genes LuFAD3A and LuFAD3B. Sequencing of LuFAD3A gene 1 exon of 6 lines revealed a mutation (G255 A255), resulting in formation of stop codon. Developed developed CAPS-marker confirmed the homozygosity of hybrids between LL (gc-391) and HL lines (gc-65, 109, 121). Descendants of hybrid between gc-109 and gc-391 ripened 8-10 days earlier than gc-391. CAPS markers of LuFAD3B gene revealed differences between HL, ML, LL lines. Sequencing of this gene first exon and the beginning of the second one in 3 lines (1HL, 2LL) showed that this method reveals a mutation in the second restriction site, located in the 2 exon (C6 T6), and causing the replacement Hys Tyr.&#x0D; Conclusion. Lines from GC have wide variability of FA and other agronomic characters, combination of which will expand the cultivation of solin.

The Genome of C57BL/6J "Eve", the Mother of the Laboratory Mouse Genome Reference Strain.

Isogenic laboratory mouse strains enhance reproducibility because individual animals are genetically identical. For the most widely used isogenic strain, C57BL/6, there exists a wealth of genetic, phenotypic, and genomic data, including a high-quality reference genome (GRCm38.p6). Now 20 years after the first release of the mouse reference genome, C57BL/6J mice are at least 26 inbreeding generations removed from GRCm38 and the strain is now maintained with periodic reintroduction of cryorecovered mice derived from a single breeder pair, aptly named Adam and Eve. To provide an update to the mouse reference genome that more accurately represents the genome of today’s C57BL/6J mice, we took advantage of long read, short read, and optical mapping technologies to generate a de novo assembly of the C57BL/6J Eve genome (B6Eve). Using these data, we have addressed recurring variants observed in previous mouse genomic studies. We have also identified structural variations, closed gaps in the mouse reference assembly, and revealed previously unannotated coding sequences. This B6Eve assembly explains discrepant observations that have been associated with GRCm38-based analyses, and will inform a reference genome that is more representative of the C57BL/6J mice that are in use today.

Founder effects on trans-generational dynamics of closed inbreeding lineages of the predatory mite Phytoseiulus persimilis.

Both close inbreeding and distant outbreeding may reduce fitness below the level of individuals with intermediate parental relatedness. In the haplodiploid plant-inhabiting predatory mite Phytoseiulus persimilis, which is patchily distributed within and among host plants, fitness is indeed reduced in the short term, i.e. by a single generation of inbreeding. However, in the medium to long term (multiple generations), distant out-breeding should provide for favorable demographic founder effects in isolated populations. We tested this prediction in isolated experimental lineages founded by females mated to a sibling (close inbreeding), a male from the same population (intermediate relatedness) or a male from another population (distant outbreeding) and monitored lineage growth and persistence over four generations. Cross-generationally, lineages founded by distantly outbred females performed the best, i.e. produced the most descendants. However, this was solely due to superior performance from the F2 generation onwards, whereas in the F1 generation, lineages founded by females mated to males from their own population (intermediate relatedness) performed the best, as predicted from short-term in- and out-breeding depression effects. At the genetic level, this result was most likely due to distantly outbred founders introducing higher allelic variability and lower homozygosity levels, counterbalancing inbreeding depression, which inevitably occurs in isolated lineages, from the F2 generation onwards.

Multigenerational prediction of genetic values using genome-enabled prediction.

The identification of elite individuals is a critical component of most breeding programs. However, the achievement of this goal is limited by the high cost of phenotyping and experimental research. A significant benefit of genomic selection (GS) to plant breeding is the identification of elite individuals without the need for phenotyping. This study aimed to propose different calibration strategies using combinations between generations from different genetic backgrounds to improve the reliability of GS and to investigate the effects of LD in different types of mating systems: outcrossing (An) self-pollination (Sn) and hybridization (Hn). For this purpose, we simulated a genome with 10 linkage groups. In each group, two QTL were simulated. Subsequently, an F2 population was created, followed by four generations of inbreeding (S1 to S4, H1 to H 4, A1, to A4,). Quantitative traits were simulated in three scenarios considering three degrees of dominance (d/a = 0, 0.5 and 1) and two broad sense heritabilities (h2 = 0.30 and 0.70), totaling six genetic architectures. To evaluate prediction reliability, a model (RR-BLUP) was trained in one generation and used to predict the following generations of mating systems. For example, the marker effects estimated in the F2 population were used to estimate the expected genomic breeding value (GEBV) in populations S1 through A4. The squared correlation between the GEBV and the true genetic value were used to measure the reliability of the predictions. Independently of the population used to estimate the marker effect, reliability showed the lowest values in the scenario where d = 1. For any scenario, the use of the multigenerational prediction methodology improved the reliability of GS.

Potential of soybean crosses in early inbreeding generations for grain yield

Abstract The present study aimed to evaluate the combining ability of 16 soybean genotypes using a partial diallel. Two experiments were carried out to estimate the general (GCA) and specific (SCA) combining ability, one with 64 crosses and the other with 16 parents. At the R8 stage, F2 plants and the parents were evaluated for the following traits: number of days to flowering (NDF), number of days to maturity (NDM), plant height at maturity (PHM), and grain yield (GY). Results indicated genetic variability between the parents and between the crosses. For GY, six (37.5%) parents stood out with high yield. The GCA and SCA estimates were significant for all traits, revealing additive and non-additive effects. The parent USP 04-17.027 (4) was superior for presenting the highest means, heritability, and GCA. The cross (4x13 = USP 04-17.027 x USP 231-2224-12) stood out owing to the highest SCA for GY.

Maternal components of RNA-directed DNA methylation are required for seed development in Brassica rapa.

Small RNAs trigger repressive DNA methylation at thousands of transposable elements in a process called RNA-directed DNA methylation (RdDM). The molecular mechanism of RdDM is well characterized in Arabidopsis, yet the biological function remains unclear, as loss of RdDM in Arabidopsis causes no overt defects, even after generations of inbreeding. It is known that 24 nucleotide Pol IV-dependent siRNAs, the hallmark of RdDM, are abundant in flowers and developing seeds, indicating that RdDM might be important during reproduction. Here we show that, unlike Arabidopsis, mutations in the Pol IV-dependent small RNA pathway cause severe and specific reproductive defects in Brassica rapa. High rates of abortion occur when seeds have RdDM mutant mothers, but not when they have mutant fathers. Although abortion occurs after fertilization, RdDM function is required in maternal somatic tissue, not in the female gametophyte or the developing zygote, suggesting that siRNAs from the maternal soma might function in filial tissues. We propose that recently outbreeding species such as B.rapa are key to understanding the role of RdDM during plant reproduction.

Uneven recombination rate and linkage disequilibrium across a reference SNP map for common bean (Phaseolus vulgaris L.).

Recombination (R) rate and linkage disequilibrium (LD) analyses are the basis for plant breeding. These vary by breeding system, by generation of inbreeding or outcrossing and by region in the chromosome. Common bean (Phaseolus vulgaris L.) is a favored food legume with a small sequenced genome (514 Mb) and n = 11 chromosomes. The goal of this study was to describe R and LD in the common bean genome using a 768-marker array of single nucleotide polymorphisms (SNP) based on Trans-legume Orthologous Group (TOG) genes along with an advanced-generation Recombinant Inbred Line reference mapping population (BAT93 x Jalo EEP558) and an internationally available diversity panel. A whole genome genetic map was created that covered all eleven linkage groups (LG). The LGs were linked to the physical map by sequence data of the TOGs compared to each chromosome sequence of common bean. The genetic map length in total was smaller than for previous maps reflecting the precision of allele calling and mapping with SNP technology as well as the use of gene-based markers. A total of 91.4% of TOG markers had singleton hits with annotated Pv genes and all mapped outside of regions of resistance gene clusters. LD levels were found to be stronger within the Mesoamerican genepool and decay more rapidly within the Andean genepool. The recombination rate across the genome was 2.13 cM / Mb but R was found to be highly repressed around centromeres and frequent outside peri-centromeric regions. These results have important implications for association and genetic mapping or crop improvement in common bean.

Detection of genetic purging and predictive value of purging parameters estimated in pedigreed populations.

The consequences of inbreeding for fitness are important in evolutionary and conservation biology, but can critically depend on genetic purging. However, estimating purging has proven elusive. Using PURGd software, we assess the performance of the Inbreeding-Purging (IP) model and of ancestral inbreeding (Fa) models to detect purging in simulated pedigreed populations, and to estimate parameters that allow reliably predicting the evolution of fitness under inbreeding. The power to detect purging in a single small population of size N is low for both models during the first few generations of inbreeding (t ≈ N/2), but increases for longer periods of slower inbreeding and is, on average, larger for the IP model. The ancestral inbreeding approach overestimates the rate of inbreeding depression during long inbreeding periods, and produces joint estimates of the effects of inbreeding and purging that lead to unreliable predictions for the evolution of fitness. The IP estimates of the rate of inbreeding depression become downwardly biased when obtained from long inbreeding processes. However, the effect of this bias is canceled out by a coupled downward bias in the estimate of the purging coefficient so that, unless the population is very small, the joint estimate of these two IP parameters yields good predictions of the evolution of mean fitness in populations of different sizes during periods of different lengths. Therefore, our results support the use of the IP model to detect inbreeding depression and purging, and to estimate reliable parameters for predictive purposes.

Analysis of embryonic mortality frequency in Drosophila melanogaster stocks with radius incompletus mutation under inbreeding conditions

It is known that inbreeding leads to homozygotization of alleles of the most genes. The rate of this process is determined by the degree of kinship between crossed individuals. In addition, inbred breeding is accompanied by a change in the structure and functioning of the genome of cells of females’ generative system: mutational level increases and oogenetic segregation may be violated. This leads to a decrease in the number of laid eggs and an increase in the level of embryonic mortality. This process, described as "the effect of resistance to selection," is aimed at adapting to external conditions and associated with the selection of viable offspring. The character of manifestations of mutational variability is determined to a large extent by the direction of selection. However, up to now our knowledge of the role of the genotype in controlling the level of embryonic mortality in Drosophila melanogaster stocks in conditions of inbred breeding is not deep enough. The purpose of our work was to analyze the frequency of dominant lethal mutations in Drosophila stocks from radiation-contaminated regions of Ukraine (Polesskoe and Ozero), carrying radius incompletus mutation, depending on the degree of inbreeding. It is shown that under conditions of severe inbreeding (without selection) changes in the total frequency of dominant lethal mutations have a cyclic character, which depends on the genotype of the stocks. So, in radius incompletus stock, the indicator studied increases after 10 generations of selection and remains at enough high level for 20 generations. For the stocks from radiation-contaminated territories of Ukraine with radius incompletus mutation, which are contrasting in the level of embryonic mortality, two decrease peaks are shown (for the stock ri(Oz) – after 5 and 65 generations of inbreeding) and an increase (for the line ri(Pol) – after 5 and 32 generations of inbreeding) of the total frequency of dominant lethal mutations. The main factor influencing the change in the mortality level at the stage of early embryogenesis in Drosophila carrying radius incompletus mutation is the genotype of the stocks that are used in the work. It’s contribution increases after 10 (h2gen=44.78), 15 (h2gen=45.86) and 100 (h2gen=46.36) generations of inbreeding. The effect of inbred breeding was observed after 32 (h2inbr=22.61) and 65 (h2inbr=11.89) generations. The combined effect of both factors on the total frequency of dominant lethal mutations is shown for each of the generations studied. The highest values were shown after the 5th (h2comb=53.86) and the 65th (h2comb =40.63) generations of inbred breeding.

H-383, híbrido de maíz blanco intermedio para grano y forraje para el norte centro y occidente de México

En México la demanda de grano de maíz para consumo humano y pecuario es de alrededor de 38 millones de toneladas; sin embargo, solo se producen entre 25 y 28 millones, el resto se importa de Estados Unidos. El déficit en la producción de maíz se debe principalmente al uso de variedades no apropiadas, manejo deficiente del cultivo y a problemas bióticos y abióticos que ocurren regularmente durante el ciclo del cultivo. Ante la necesidad de contar con híbridos más productivos, el Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP) en 2000, inició un programa de mejoramiento genético orientado a obtener híbridos de alto rendimiento de grano y forraje, del cual se derivó el híbrido de cruza simple H-383 de grano blanco formado por la combinación de las líneas PAB7 y PAB8. La línea PAB7 se derivó de la población PGB y su genealogía es PGB-2-1-3-1-1-N1-3-b-b-b. La línea PAB8, corresponde con la línea pública subtropical CML312 del Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT) con tres generaciones más de endogamia para selección de mayor sanidad de mazorca. El híbrido tiene un potencial de rendimiento superior a la 15 t ha-1 de grano en riego, y hasta 12 t ha-1 en áreas de buen temporal; produce entre 24.7 y 26 t ha-1 de materia seca, con valores entre 71 y 74% en digestibilidad y entre 40 y 48% en digestibilidad de la fibra. Tiene adaptación en áreas de riego de la región Norte Centro de México y El Bajío; así como, en áreas de buen temporal del Centro y Occidente de México, localizadas entre los 1 600 y 2 000 msnm. Es de ciclo intermedio, hojas color verde oscuro y altura entre 3 y 3.2 m. El híbrido se registró en el Servicio Nacional de Inspección y Certificación de Semillas (SNICS) con la clave: MAZ-1352-190712.&#x0D; &#x0D;

Inbreeding depression in maize populations and its effects on the obtention of promising inbred lines

Inbreeding can potentially be used for the development of inbred lines containing alleles of interest, but the genetic causes that control inbreeding depression are not completely known, and there are few studies found in the literature. The present study aimed to obtain estimates of inbreeding depression for eight traits in seven tropical maize populations, analyze the effects of inbreeding over generations and environments, and predict the behavior of inbred lines in future generation S? through linear regression methods. It was found that regardless of the base population used, prediction values could vary when the model was based on only 2 generations of inbreeding due to the environmental component. The influence of the environment in this type of study could be reduced when considering 3 generations of inbreeding, allowing greater precision in predicting the phenotypes of inbred lines. The use of linear regression was effective for inbred line prediction for the different agronomic traits evaluated. The use of 3 levels of inbreeding minimizes the effects of the environmental component in inbred line prediction for grain yield. GO-S was the most promising population for inbred line extraction.