S1 Families Research Articles

English

This study aimed to compare estimates of genetic gains using four indices of selection, based on the least squares method and the additive index through the multi-trait REML/BLUP (Best linear unbiased prediction/restricted maximum likelihood) to perform a selection early in S1 families. Eighty S1 testcross hybrids were proportionally separated into two groups: the CIMMYT-SH (CSH) and CIMMYT-8HS (C8HS) populations and assessed for main trait required by the market. The selection indices Smith & Hazel, Williams, Pesek & Baker, Mulamba & Mock and the additive multi-trait REML/BLUP were tested. The estimated gains from selection were assessed for each group (CSH and C8HS) separately, so as to maintain the identity of each population. Among the four selection indices based on the ANOVA (analysis of variance), the Mulamba & Mock was the most suitable for the selection of half-sib families in super sweet corn. The additive multi-trait REML/BLUP index showed even better predicted genetic gains than Mulamba & Mock, and was efficient to select half-sib families in super sweet corn. Based on the REML/BLUP were selected from each population, the 20 most promising progenies to continue the super sweet corn breeding program. The high level of coincidence between the multi-trait REML/BLUP and Mulamba & Mock indices indicates similar efficiency for selection purposes. However, REML/BLUP method showed better genetics gains, may be recommend the use of for future selection activities.

Inbreeding depression in cassava for productive traits

Understanding inbreeding in cassava can guide breeders to explore its effects. Therefore, the aim of this study was to evaluate the effects of inbreeding depression in cassava, as well as to select transgressive individuals. Five elite cassava varieties were self-pollinated (Cascuda, BRS Formosa, Fecula Branca, Mani-Branca, and BRS Mulatinha), and the S1 families were evaluated in an augmented block design with six repetitions. The traits evaluated were fresh root yield (RoYi), above ground yield (AGYi), starch yield (StYi), harvest index (HI), dry matter content (DMC), and plant height (PlHe). The inbreeding depression varied widely between families; it was high in BRS Formosa, with averages of 19.38 % (RoYi), 1.68 % (AGYi), 18.18 % (HI), 0.47 % (DMC), 17.54 % (StYi) and 3.5 % (PlHe). Except for the S1 family of BRS Formosa, the additive effects (μ + α) were the most important, ranging from 69.95 % (RoYi) to 98.20 % (AGYi). In contrast, the contribution of heterozygous loci (δ) was most relevant to RoYi, HI, and StYi, with averages of 30.05, 23.07, and 27.82 %, respectively, although these effects were more pronounced in S1 derived from BRS Formosa and Mani-Branca. Therefore, the exploitation of inbreeding effects in cassava can contribute to the selection of plants with better agronomic performance in order to obtain cassava inbred with high genetic and agronomic potential for use per se or as parents to produce new hybrids.

Eleven years of breeding efforts to combat cassava brown streak disease.

Cassava (Manihot esculenta Crantz) production is currently under threat from cassava brown streak disease (CBSD), a disease that is among the seven most serious obstacles to world’s food security. Three issues are of significance for CBSD. Firstly, the virus associated with CBSD, has co-evolved with cassava outside its center of origin for at least 90 years. Secondly, that for the last 74 years, CBSD was only limited to the low lands. Thirdly, that most research has largely focused on CBSD epidemiology and virus diversity. Accordingly, this paper focuses on CBSD genetics and/or breeding and hence, presents empirical data generated in the past 11 years of cassava breeding in Uganda. Specifically, this paper provides: 1) empirical data on CBSD resistance screening efforts to identify sources of resistance and/or tolerance; 2) an update on CBSD resistance population development comprising of full-sibs, half-sibs and S1 families and their respective field performances; and 3) insights into chromosomal regions and genes involved in CBSD resistance based on genome wide association analysis. It is expected that this information will provide a foundation for harmonizing on-going CBSD breeding efforts and consequently, inform the future breeding interventions aimed at combating CBSD.

Abundant Intergenic TAACTGA Direct Repeats and Putative Alternate RNA Polymerase β' Subunits in Marine Beggiatoaceae Genomes: Possible Regulatory Roles and Origins.

The genome sequences of several giant marine sulfur-oxidizing bacteria present evidence of a possible post-transcriptional regulatory network that may have been transmitted to or from two distantly related bacteria lineages. The draft genome of a Cand. “Maribeggiatoa” filament from the Guaymas Basin (Gulf of California, Mexico) seafloor contains 169 sets of TAACTGA direct repeats and one indirect repeat, with two to six copies per set. Related heptamers are rarely or never found as direct repeats. TAACTGA direct repeats are also found in some other Beggiatoaceae, Thiocystis violascens, a range of Cyanobacteria, and five Bacteroidetes. This phylogenetic distribution suggests they may have been transmitted horizontally, but no mechanism is evident. There is no correlation between total TAACTGA occurrences and repeats per genome. In most species the repeat units are relatively short, but longer arrays of up to 43 copies are found in several Bacteroidetes and Cyanobacteria. The majority of TAACTGA repeats in the Cand. “Maribeggiatoa” Orange Guaymas (BOGUAY) genome are within several nucleotides upstream of a putative start codon, suggesting they may be binding sites for a post-transcriptional regulator. Candidates include members of the ribosomal protein S1, Csp (cold shock protein), and Csr (carbon storage regulator) families. No pattern was evident in the predicted functions of the open reading frames (ORFs) downstream of repeats, but some encode presumably essential products such as ribosomal proteins. Among these is an ORF encoding a possible alternate or modified RNA polymerase beta prime subunit, predicted to have the expected subunit interaction domains but lacking most catalytic residues. A similar ORF was found in the Thioploca ingrica draft genome, but in no others. In both species they are immediately upstream of putative sensor kinase genes with nearly identical domain structures. In the marine Beggiatoaceae, a role for the TAACTGA repeats in translational regulation is suggested. More speculatively, the putative alternate RNA polymerase subunit could be a negative transcriptional regulator.

Diversity, Structures, and Collagen-Degrading Mechanisms of Bacterial Collagenolytic Proteases.

Bacterial collagenolytic proteases are important because of their essential role in global collagen degradation and because of their virulence in some human bacterial infections. Bacterial collagenolytic proteases include some metalloproteases of the M9 family from Clostridium or Vibrio strains, some serine proteases distributed in the S1, S8, and S53 families, and members of the U32 family. In recent years, there has been remarkable progress in discovering new bacterial collagenolytic proteases and in investigating the collagen-degrading mechanisms of bacterial collagenolytic proteases. This review provides comprehensive insight into bacterial collagenolytic proteases, especially focusing on the structures and collagen-degrading mechanisms of representative bacterial collagenolytic proteases in each family. The roles of bacterial collagenolytic proteases in human diseases and global nitrogen cycling, together with the biotechnological and medical applications for these proteases, are also briefly discussed.

Molecular changes in two maize (Zea mays L.) synthetics after reciprocal selection with two alternative methods

Agronomic evaluations demonstrated that a modification of the classical full-sib reciprocal recurrent selection (RRS-FS) which, in addition to crosses, uses S2 families evaluation (RRS-FS-S2) is more efficient than the classical method for developing high-yielding crosses between two varieties. The objective of this study was to investigate the changes in genetic diversity and structure after performing RRS-FS and RRS-FS-S2 selections. RRS-FS-S2 reduced more the variability, produced more differentiation between cycles of selection derived from the same materials but less between reciprocal populations, and produced a more clear change in the contribution of the parental lines than RRS-FS. On the other hand, the type of selection method did not have a considerable effect on the structure of the populations measured as departure of Hardy–Weinberg (HW) equilibrium at single markers and on linkage disequilibrium (LD) between pairs of markers. We identified some individual markers which were not in HW equilibrium in several populations probably due to genes favouring assortative mating. We also found pairs of markers which increased their LD with selection probably due to epistasis.

Variability and inbreeding in semiexotic maize populations.

Three semiexotic populations (CRE-01, CRE-02, CRE-03) obtained by incorporation of exotic germplasm (lines from CIMMYT, Colombia; selected for resistance to corn stunt complex) were evaluated in two cycles of recurrent selection with half-sib families. In cycle-I, samples comprising 50, 70, and 50 half-sib families were evaluated at Jataí (GO) and traits analyzed were ear yield, plant height, and ear height. For yield (t/ha), populations means were 5.86, 6.19, and 5.31, representing approximately 73% of hybrid check. Sets of parameters estimates representing the three populations were: [237, 485, and 608] for the additive genetic variance (σ(2)A: g/plant); [0.393, 0.584, 0.658] for the coefficient of heritability (h(2)m: progeny mean basis), and [0.464, 0.684, and 0.801] for the index of variation (θ). In cycle-II, materials analyzed included 60 non-inbred (half-sib) and 60 inbred (S1) families from each population, evaluated at Anhembi (SP) with two replications; traits analyzed included ear yield plus ear weight and grains weight of four ears, two plant traits (plant height and ear height), two ear traits (length and diameter), two tassel traits (branch number and length), and resistance to corn stunt complex. Means of half-sib families for ear yield (t/ha) were [10.614, 10.419, 10.842], representing 83 to 86% of the hybrid check. The same pattern of variation was observed for ear weight and grain weight of four ears. Means of S1 families were [6.465, 5.527, 5.925] and the inbreeding depression in percent of the non-inbred families were [39.1, 46.9, 45.3]. Estimates for other traits are also shown.

Selfing confirmation in sugarcane by using simple sequence repeat markers: an individual reciprocal recurrent selection scheme.

Superior inbred clones selected in S1 families can integrate an individual reciprocal recurrent selection program in sugarcane by eliminating the genetic load of the population and exploring superior hybrid combinations. Molecular markers can be used for reliable identification of the true selfing-derived clones in these S1 populations. The objective of this study was to confirm true self-fertilized individuals in sugarcane families using microsatellite markers aimed at the use of self-fertilized plants in an individual reciprocal recurrent selection strategy. Self-fertilized individuals from five cultivars were genotyped with eight simple sequence repeat (SSR) markers. The markers generated 62 polymorphic markers, with an average of seven polymorphic alleles across the cultivars tested. Three loci revealed highly informative bands and were used to assess the level of selfing in five S1 families. Selfing in these families ranged from 71.7 to 97.6%. The SSR loci provide a reliable and accurate method to identify S1 progenies in sugarcane crosses and can be used as a tool to assist selection strategies in sugarcane breeding programs.

Avaliação da capacidade de combinação de famílias S2 de milho-pipoca por meio de diferentes testadores

The objective of this work was to compare three testers for discrimination and evaluation of the combining ability of 49 S2 families, derived from the topcross popcorn hybrid IAC 125. Families were evaluated by their per se performance and their crosses with the testers BRS ANGELA, IAC125 and Line 3.3. The experiment was conducted in lattice design, in Maringá, PR, Brazil, during 2007/2008 cropping season. Genetic and phenotypic parameters was estimated for grain yield and popping expansion, and compared using the topcrosses between families and testers and the families per se. General and specific combining ability were estimated according the partial diallel model. Topcrosses heterosis was also evaluated, and the capacity of discriminating the families was compared among testers using the differential index from Fasoulas (1983). The tester line 3.3 was the most suitable to evaluate the S2 families in respect to grain yield and popping expansion.

Genetic parameter and correlation estimates of processing traits in half-sib progenies of tropical-adapted carrot germplasm

The estimate of the genetic parameters associated with processing (fresh-cut) traits, including root length (RL), is crucial for carrot breeding programs in tropical areas. The cultivar Alvorada is an important germplasm due to its resistance to nematodes, leaf blight, heat-tolerance, and high carotenoid content. Seventy-four 'Alvorada' half-sib progenies were evaluated during the summer of 2005 in the Federal District, Brazil, in a randomized complete block design with three replications. Thirteen competitive plants in each block were randomly selected and evaluated and/or classified for RL and for number of leaves (NL), leaf length (LL), root tip type (RT), root mass (RW), crown shape (CS), root diameter (RD), and xylem diameter (XD). The Pearson's correlation coefficients and the heritability values were estimated for all traits. The path analysis was also used considering the RL trait as dependent variable. The heritability for RL ranged from 12 to 44%. For the other traits, the values ranged from 3% (RD) to 79% (LL). Phenotypic and genotypic correlations among all traits were low to intermediate. Path analysis indicated positive direct relationship between RL and RW, whereas RD and XD displayed negative direct effect on RL. Longer roots had narrow diameter and narrow XD. Recurrent selection based upon either half-sib or S1 families would be more effective than mass phenotypic recurrent selection in increasing RL and to develop populations expressing multiple desirable processing traits in tropical-adapted carrot germplasm.

Comparison of two methods of reciprocal recurrent selection in maize (Zea mays L.)

Reciprocal recurrent selection (RRS) was proposed for simultaneously improving two populations and their cross. A modification of the classical full-sib RRS (FS-RRS) was proposed in which the performance of full-sibs and S(2) families is combined in a selection index (FS-S(2)-RRS). The Mediterranean corn borer (MCB) is the main corn borer species in the Mediterranean and adjacent areas and produces important yield losses. We started two RRS programs (FS-RRS and FS-S(2)-RRS) from the same maize population in which the selection criterion was grain yield under artificial infestation with MCB eggs. Original populations, two cycles of selection derived from them by both RRS methods, and population crosses were evaluated under MCB attack and under insecticide treatment in three different environments. The objective was to compare the efficiency of the FS-RRS and the FS-S(2)-RRS methods for improving grain yield. We found that the FS-S(2)-RRS method was successful for improving the yield of the population cross under optimum conditions (the regression coefficient over cycles was b = 0.87** Mg ha(-1) cycle(-1)) without losing yield under high pressure of MCB attack (b = 0.07). On the contrary, FS-RRS failed to improve the yield of the population cross under optimum conditions (b = 0.65) and tended to decrease the yield under high levels of MCB attack (b = -0.26). We conclude that for developing high yielding and stable varieties, FS-S(2)-RRS is more efficient than the classical FS-RRS method.

Combined S1-TC-RRS with consideration of cms and dihaploids in maize

Herein, we present the combined S1-HS-RRS method using inbred testers (S1-TC-RRS) as a long-term maize breeding program, which increases the frequency of favorable alleles and maintains genetic variability in two genetically opposite populations. The method improves two different genetic sources simultaneously, where S1 families, developed by selfing phenotypically superior plants from both breeding populations are crossed with opposite inbred testers for specific combining ability selection, accompanied by selection of S1 families per se. A certain percentage of the evaluated S1 families is used for the next TC-RRS selection cycle. Maternal haploids from the selected S1 lines of each cycle of S1-TC-RRS can serve to produce elite 100% homozygous inbred lines (dihaploids) in a short time, which decreases the time and expenses of the selection cycle and influence the efficiency of seed production, as well as, variety protection rights. This elite lines than can be converted to CMS versions (paternal haploids), for the seed production, which lowers the costs of it.

Advances in Improving <i>Ukiriguru</i> Composite B Maize (<i>Zea mays</i> L.) Variety through S1 Recurrent Selection

S1 recurrent selection was carried out to improve grain yield, plant height, ear placement, resistance to lodging and other desirable agronomic traits in Ukiriguru composite B (UCB) maize variety. This paper presents the genetic gain and progress made in improving these traits through two cycles of selection. Three hundred and sixty, and 254 S1 families were evaluated in three environments and 36 and 25 families were selected following 10% selection intensity during the first (C1) and the second (C2) cycles, respectively. The selected families were recombined in isolated half-sib recombination blocks using remnant seeds. The progress made through selection was determined by evaluating the parent population (UCB C0), the first (UCB S1 C1) and the second (UCB S1 C2) selection cycles in six environments in a randomized complete block design in four replications. Commercial open-pollinated and hybrid varieties were included as checks. UCB S1 C2 produced mean grain yield of 8.7 t ha-1 and had a significant (P < 0.01) genetic gain of 30% (2.0 t ha-1) with mean gain of 15.0% (1.0 t ha-1) cycle-1. The selection also resulted in short plant height and low ear placement with significant (P < 0.01) genetic gain of 9.6% (30.8 cm) and 19.6% (39.6 cm), respectively, and superiority in tolerance to diseases and resistance to lodging. Still selection had significant (P < 0.01) grain yield benefit of 35.0% (3.1 t ha-1) and 29.3% (2.6 t ha-1) relative to Gibe Composite 1 and Kuleni, respectively, and showed comparable yield potential with commercial hybrids, BH660 and BH670. It was concluded that two cycles of S1 recurrent selection have brought significant genetic improvement in grain yield and major agronomic traits in UCB. Hence UCB S1 C2 was fully released and recommended for commercial production in the mid-altitude (1600-1800 masl) agro-ecologies of Jimma and Illu Ababora Zones, and similar areas in the south-western areas of Ethiopia. After release, it was named as ‘Morka’ meaning ‘competent’, to express its yield potential which is comparable to the yield potential of popular hybrid varieties in the zones.Keywords: Genetic Gain; Morka; Recurrent Selection; Response to Selection; Ukiriguru Composite B

Evaluation of broad spectrum sources of resistance to Fusarium verticillioides and advanced maize breeding lines

The fungus Fusarium verticillioides is commonly associated with maize production in temperate regions of the world, producing ear rot and grain contamination by fumonisins. Genetic resistance is the best preventive action against fumonisin contamination, although at present no commercial maize hybrids are completely resistant. Several studies of the relationship between Fusarium and other species producing ear rot suggest that these fungal species interact in similar ways with the host plant. Consequently, host plant resistance to one pathogen could be associated with resistance to another. The aim of this study was to introduce sources of resistance to Fusarium spp. into maize inbred lines and to evaluate ear rot severity and fumonisin B1 contamination in advanced breeding lines and hybrids after artificial and natural infection with F. verticillioides. Two inbred lines (CO430 and MP420) with resistance to kernel infection by Fusarium graminearum and Aspergillus flavus, respectively, were crossed and backcrossed to susceptible inbred 1203. The BC1S1 progenies were evaluated for plant morphology and silk date and the selected S1 plants were self-pollinated. The S2 families were evaluated under artificial and natural infection with F. verticillioides. Selected S2 progenies were grown ear-to-row until S5-derived inbreds were developed. The S5 lines were evaluated under artificial and natural infection and used as males to produce single crosses. In both crosses, the mean ear rot of the S5 lines with the lowest ear rot was not significantly different from the resistant parent means. Significant progress was observed in the hybrids regarding ear rot performance: on average, ear rot severity decreased significantly from 23% in check hybrids to 5.3% in CO430-derived hybrids. Our results suggest that inbred lines bred for resistance to A. flavus and F. graminearum ear rot could be used to select advanced breeding lines with increased resistances to F. verticillioides ear rot.

Erratum to: Hybrid maize breeding with doubled haploids: V. Selection strategies for testcross performance with variable sizes of crosses and S1 families

Erratum to: Hybrid maize breeding with doubled haploids: V. Selection strategies for testcross performance with variable sizes of crosses and S1 families

Effects of Recurrent Selection for Grain Yield and Striga Resistance in an Extra‐Early Maize Population

ABSTRACTStriga hermonthica (Del.) Benth threatens maize (Zea mays L.) production in sub‐Saharan Africa. In an extra‐early population, S1 families derived from four cycles of recurrent selection for grain yield and Striga resistance were evaluated with and without Striga infestation at three locations in Nigeria for 2 yr to determine relative changes in genetic variances, heritabilities, and genetic correlations for yield and other traits. Under infestation, yield was not correlated with other traits at C0 but was significantly correlated with ears per plant (EPP), Striga damage, and emerged Striga plants in advanced cycles. Genetic correlations between yield and most traits were significant in C0 when Striga‐free but was reduced in advanced cycles. Genetic variances and heritabilities for yield and ear aspect increased in advanced cycles. Genetic variances decreased with selection for emerged Striga counts and EPP under infestation. A response to selection for improved yield, Striga emergence and EPP is expected in subsequent cycles. Low genetic variances and heritabilities for Striga damage and low predicted gain cycle−1 for all traits except numbers of emerged Striga plants suggest a need to introgress novel resistance genes into the population for faster progress from selection for increased yield.

Recurrent selection for physiological resistance to white mould in dry bean

With 1 figure and 5 tables AbstractWhite mould (WM) [caused by Sclerotinia sclerotiorum (Lib.) de Bary] is a widespread disease of dry and green bean (Phaseolus vulgaris L.) in North America and elsewhere. Our objective was to determine the effectiveness of recurrent selection (RS) for pyramiding WM resistance from Andean, Middle American and inter‐specific breeding lines. Two double‐cross populations, Pop I = USPT‐WM‐1/CORNELL 601//USPT‐CBB‐1/92BG‐7 and Pop II = ‘Chase’/I 9365–25//ABL 15/A 195 were developed. Each double‐cross comprised 848 F1 plants for RS cycle one (C1). Twenty six WM‐resistant plants from each double‐cross were used to produce RS cycle two (C2). To measure the gain for WM resistance, 13 selected S2 families from each of C1 and C2 of each population and their four parents (C0) were tested in a randomized complete block design with three replicates in two greenhouse environments in 2008. Two separate inoculations on each plant one week apart using a cut‐stem method were made. The WM reaction was scored at 16, 23 and 33 days post inoculation (DPI) using a 1 (no disease symptoms) to 9 (severely diseased or dead plants) scale. The effects of environment were significant (P = 0.05), but replicate and population effects were not significant (P > 0.05). The RS was effective in changing the mean WM score of selected families from C0 to C1 and C2, but the gain between C1 and C2 was not significant in Pop I. The gain in WM resistance for Pop I was 12%. Selection gain in Pop II was 5%, but no significant differences in mean WM scores of C0, C1 and C2 were found. However, selected S2 families had WM scores similar to those of the best parent and selected families from Pop I. Thus, one cycle of RS applied to double‐cross populations was adequate for improving WM resistance in common bean.

Hybrid maize breeding with doubled haploids: V. Selection strategies for testcross performance with variable sizes of crosses and S1 families

In hybrid maize (Zea mays L.) breeding, doubled haploids (DH) are increasingly replacing inbreds developed by recurrent selfing. Doubled haploids may be developed directly from S(0) plants in the parental cross or via S(1) families. In both these breeding schemes, we examined 2 two-stage selecting strategies, i.e., considering or ignoring cross and family structure while selection among and within parental crosses and S(1) families. We examined the optimum allocation of resources to maximize the selection gain DeltaG and the probability P(q) of identifying the q% best genotypes. Our specific objectives were to (1) determine the optimum number and size of crosses and S(1) families, as well as the optimum number of test environments and (2) identify the superior selection strategy. Selection was based on the evaluation of testcross progenies of (1) DH lines in both stages (DHTC) and (2) S(1) families in the first stage and of DH lines within S(1) families in the second stage (S(1)TC-DHTC) with uniform and variable sizes of crosses and S(1) families. We developed and employed simulation programs for selection with variable sizes of crosses and S(1) families within crosses. The breeding schemes and selection strategies showed similar relative efficiency for both optimization criteria DeltaG and P (0.1%). As compared with DHTC, S(1)TC-DHTC had larger DeltaG and P (0.1%), but a higher standard deviation of DeltaG. The superiority of S(1)TC-DHTC was increased when the selection was done among all DH lines ignoring their cross and family structure and using variable sizes of crosses and S(1) families. In DHTC, the best selection strategy was to ignore cross structures and use uniform size of crosses.

A classification of near-horizon geometries of extremal vacuum black holes

We consider the near-horizon geometries of extremal, rotating black hole solutions of the vacuum Einstein equations, including a negative cosmological constant, in four and five dimensions. We assume the existence of one rotational symmetry in four dimensions (4D), two commuting rotational symmetries in five dimensions (5D), and in both cases nontoroidal horizon topology. In 4D we determine the most general near-horizon geometry of such a black hole and prove it is the same as the near-horizon limit of the extremal Kerr-AdS4 black hole. In 5D, without a cosmological constant, we determine all possible near-horizon geometries of such black holes. We prove that the only possibilities are one family with a topologically S1×S2 horizon and two distinct families with topologically S3 horizons. The S1×S2 family contains the near-horizon limit of the boosted extremal Kerr string and the extremal vacuum black ring. The first topologically spherical case is identical to the near-horizon limit of two different black hole solutions: the extremal Myers–Perry black hole and the slowly rotating extremal Kaluza–Klein (KK) black hole. The second topologically spherical case contains the near-horizon limit of the fast rotating extremal KK black hole. Finally, in 5D with a negative cosmological constant, we reduce the problem to solving a sixth-order nonlinear ordinary differential equation of one function. This allows us to recover the near-horizon limit of the known, topologically S3, extremal rotating AdS5 black hole. Further, we construct an approximate solution corresponding to the near-horizon geometry of a small, extremal AdS5 black ring.

Variabilidade genética em famílias S1 de diferentes populações de milho

The objectives of the present work were directed towards the study of genetic variability in seven maize populations with a broad genetic base, as a guide for population improvement. The field evaluation was conducted in completely randomized blocks, at one location (Anhembi, Sao Paulo state) with different groups of S1 families obtained from seven populations (GO-D: dent type, GO-F: flint type, GO-L: long ear, GO-G: thick ear; and composites G3, G4 and GO-S). Estimates were obtained for genetic variance (progeny mean basis), phenotypic variance of families means, and coefficient of heritability (broad sense) for progeny means. Estimates of heritability were high for ear weight (0.89 to 0.94), ear length (0.77 to 0.88) and ear diameter (0.77 to 0.92); and lower for plant height (0.58 to 0.80) and ear height (0.54 to 0.84), thus showing the high potential of the populations for recurrent selection based on S1 families. Ear yield in the base populations used as controls varied from 11,200 kg ha-1 (GO-D) to 12,800 kg ha-1 (G3). The means of S1 families varied from 6,070 kg ha-1 (GO-F) to 7,380 kg ha-1 (G4); the inbreeding depression in S1 families varied from 37.5% (G4) to 48.0% (G3) relative to the non-inbred population.