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Breeders have two non-exclusive strategic investment options for increasing smallholder farmers’ and consumers’ livelihoods through genetic improvement of crop varieties: (i) enhancing productivity; and (ii) enhancing value and market access. New Rice for Africa (NERICA) varieties with superior agronomic characteristics were bred and introduced in various African countries in the early 2000s. Two decades later, drought tolerant NERICA4 is among the popular upland rice varieties grown across Africa. We analyze market evidence for NERICA4 from Uganda in 2011, i.e. well before it massively reached urban markets, where it is currently commingled with standard rice. We then compare the breeding priorities that would have ensued from the 2011 market evidence with the reality a decade later. Non-hypothetical auction experiments with consumers were conducted in urban Uganda in 2011 to predict potential market share and value of non-fragrant NERICA4 and fragrant NERICA1, relative to two market standards, i.e. non-fragrant Kaiso, and Supa, the most popular fragrant rice variety in the region. Average consumer bids positioned the two NERICAs between both market standards. Whereas NERICA1 easily outcompeted NERICA4 and Kaiso in the non-fragrant rice category, it failed to compete with Supa in the fragrant category. The 2011 market evidence would have suggested breeders prioritize investment in breeding programs for fragrant NERICAs to help smallholders gain access to high-value markets and expand consumers’ choice with cheaper fragrant rice alternatives. However, the popularity of NERICA4 relative to NERICA1 in farmers’ fields seems to suggest that agronomic genetic gains may have outweighed market traits such as fragrance.

Maintaining low levels of rust incidence (caused by Puccinia novopanici) in switchgrass (Panicum virgatum L.) breeding populations is a priority for the USDA-ARS program engaged in improving cultivars for high biomass yield and quality. Essential to this goal is the unbiased and accurate estimation of genetic parameters to predict the merits of parents and progeny. Spores of the fungus were inoculated in greenhouse-grown seedling progeny of 31 half-sib families in generation 2 (Gen 2) of a composite Summer × Kanlow population for evaluation of rust incidence on the leaves with a 0–9 rating scale. Two parents were later chosen to cross and develop a linkage mapping population as Gen 3. The Gen 2, 3, and Kanlow seedlings were transplanted into the field located near Mead, NE, in early June 2020 and laid out as a replicated row–column design with six blocks of single-row plots of five plants each. The field trial was rated in September 2021 and 2022 with a 0–4 scale. Lab and field data were subjected to univariate linear mixed models via the restricted maximum likelihood to extract the variance components needed to predict the breeding values. The additive genetic variation was substantial (p < 0.01), enough to result in high heritability estimates ranging from 0.42 ± 14 to 0.73 ± 0.09 at the individual and family mean levels. This result implies that rust resistance is under strong genetic control to use mass selection for obtaining satisfactory gains. A possible rust incidence x year interaction was detected with a Spearman correlation of breeding values of −0.38, caused by significant rank changes of the Gen 3 genotypes in 2022 (a high heat and drought year). Genetic gains were predicted to reduce rust incidence scores by at least two points on the rating scale when selecting backwards, and by one point when selecting individual candidates as parents of the next generation. Faster gains (31 and 59%) were realized relative to the second generation by respectively selecting the top 10% of the families in Gen 3 or the top 10% of genotypes within this group. Based on these results, strategies for controlling the incidence of rust will be developed to optimize gains in the other traits of economic importance.

Pedigree-based best linear unbiased prediction (pBLUP) is an effective method for genetic evaluation. The objective of this study was to assess the efficacy of pBLUP to develop superior inbred lines, using field and simulated data. This study was based on the data of 30,986 plants from six S0 generations and eight inbred progeny trials (S1–S4), performed over eight years. We measured the grain yield and the expansion volume (EV). We also simulated the EV and grain yield of 5000 plants (S0–S4) in two in silico populations, assuming 300 and 400 genes distributed across 10 chromosomes of 200 cM, respectively, and 10% of pleiotropic genes. We selected selfed plants based on the predicted additive value for EV by fitting the individual model in inbred population. The use of pBLUP provided total genetic gains in EV in the range of 1 to 45%, inversely proportional to the level of improvement of the population, and indirect changes in grain yield in the range of −17 to 3%. Only from the analysis of the in silico populations, assuming selection based on the true additive value and genetic gain computed from the genotypic values, there was evidence that pBLUP is superior to phenotypic mass selection.

Erect plant architecture is preferred by farmers but results in late and scarce flowering, which slows down breeding considerably. Inducing earlier and abundant flowering in crossing nurseries (involving erect genotypes) is a key objective for cassava and was the subject of this study. Five genotypes with contrasting flowering behavior were grown under dark night (DN) and extended photoperiod (EP) conditions for three seasons. EP was achieved with different red light emitting diodes (LEDs) with 625&ndash, 635 nm wavelength all night long or through night-breaks. EP reduced height and number of days to first branching, particularly in non- or late-flowering genotypes. A minimum of 0.02 &mu, mol m&minus, 2 s&minus, 1 was required to elicit earlier flowering in plants illuminated all night. Early results using five genotypes were validated across 116 genotypes planted in a crossing nursery. EP promoted earlier flowering in erect-plant genotypes but reduced the number of branching events in early flowering genotypes to some extent. 50W LED lamps, fixed at 3 m above ground in a 4.5 m grid, proved to be a practical approach to extend photoperiod in breeding nurseries. Night breaks also proved effective, thus opening the possibility of using solar panels where electricity is not available.

Summary Agricultural production faces a Herculean challenge to feed the increasing global population. Food production systems need to deliver more with finite land and water resources while exerting the least negative influence on the ecosystem. The unpredictability of climate change and consequent changes in pests/pathogens dynamics aggravate the enormity of the challenge. Crop improvement has made significant contributions towards food security, and breeding climate‐smart cultivars are considered the most sustainable way to accelerate food production. However, a fundamental change is needed in the conventional breeding framework in order to respond adequately to the growing food demands. Progress in genomics has provided new concepts and tools that hold promise to make plant breeding procedures more precise and efficient. For instance, reference genome assemblies in combination with germplasm sequencing delineate breeding targets that could contribute to securing future food supply. In this review, we highlight key breakthroughs in plant genome sequencing and explain how the presence of these genome resources in combination with gene editing techniques has revolutionized the procedures of trait discovery and manipulation. Adoption of new approaches such as speed breeding, genomic selection and haplotype‐based breeding could overcome several limitations of conventional breeding. We advocate that strengthening varietal release and seed distribution systems will play a more determining role in delivering genetic gains at farmer’s field. A holistic approach outlined here would be crucial to deliver steady stream of climate‐smart crop cultivars for sustainable agriculture.

The selection of superior Carica papaya (L) genotypes depends on the availability of genetic variability and on the favorable and simultaneous response of the genotypes to those traits of most interest. However, manual phenotyping (MP) demands intensive labor, is time-consuming and expensive. The aim of the current study is to access the efficiency of image-based phenotyping (IBP) in estimating genetic parameters and in selecting F4 recombinant inbred lines. The genetic parameters and values were estimated in accordance with the REML/BLUB procedure and combined selection using the selection index based on standardized genetic values. The majority of traits accessed through IBP showed experimental coefficients of variation similar to those found through MP. Both methodologies showed genetic parameters of similar magnitude, indicating expressive genetic variability between lines in the traits accessed in this study. The same superior lines were indicated in both methodologies and expressive genetic gains obtained through the lines were selected for all traits. IBP performance was similar to that of MP with respect to the estimates of breeding-relevant traits such as commercial fruits and yield. Thus, IBP showed efficient phenotypic assessment, as well as selective accuracy in accessing genetic variability and genetic gains, when it was compared to MP. Since IBP is far less dependent on labor, it is expected to be incorporated into the routine of papaya breeding programs as a way of increasing the number of accessed lines and, consequently, increasing genetic gains.

Striga hermonthica is a major maize production constraint in West and Central Africa (WCA). Fifty-four early maturing maize hybrids of three breeding periods: 2008&ndash, 2011, 2012&ndash, 2013, 2014&ndash, 2015, were evaluated under Striga-infested and non-infested environments in WCA. The study aimed at assessing genetic improvement in grain yield of the hybrids, identifying traits associated with yield gain during the breeding periods, and grain yield and stability of the hybrids in Striga infested and non-infested environments. Annual increase in grain yield of 101 kg ha&minus, 1 (4.82 %) and 61 kg ha&minus, 1 (1.24%) were recorded in Striga-infested and non-infested environments, respectively. The gains in grain yield from period 1 to period 3 under Striga-infested environments were associated with reduced anthesis-silking interval, reduced Striga damage, number of emerged Striga plants, improved ear aspect, and increased ears per plant. Ear aspect, ears per plant, and Striga damage at 8 and 10 weeks after planting (WAP) were significantly correlated with yield in Striga-infested environments, whereas ears per plant and plant and ear aspects had significant correlations with yield in non-infested environments. Hybrids TZdEI 352 &times, TZEI 355, TZdEI 378 &times, TZdEI 173, and TZdEI 173 &times, TZdEI 352 were outstanding in grain yield and stability in Striga-infested environments, whereas TZEI 326 &times, TZdEI 352, TZEI 495 &times, ENT 13, and TZdEI 268 &times, TZdEI 131 were superior in non-stress environments. These hybrids should be further tested extensively and commercialized. Significant genetic gains have been made in breeding for resistance to Striga hermonthica in early maturing maize hybrids.

Highlights • Linear and consistent grain yield genetic gains in the HRWYT has been observed. • Several best performing lines were common in both high and low rainfall environments. • The genetic gains were explained by paralleled increases in grain weight, day to maturity and grain filling period. • These results indicate continuous genetic progress and yield stability in the HRWYT germplasm developed by CIMMYT., The effects of climate change together with the projected future demand represents a huge challenge for wheat production systems worldwide. Wheat breeding can contribute to global food security through the creation of genotypes exhibiting stress tolerance and higher yield potential. The objectives of our study were to (i) estimate the annual grain yield (GY) genetic gain of High Rainfall Wheat Yield Trials (HRWYT) grown from 2007 (15th HRWYT) to 2016 (24th HRWYT) across international environments, and (ii) determine the changes in physiological traits associated with GY genetic improvement. The GY genetic gains were estimated as genetic progress per se (GYP) and in terms of local checks (GYLC). In total, 239 international locations were classified into two groups: high- and low-rainfall environments based on climate variables and trial management practices. In the high-rainfall environment, the annual genetic gains for GYP and GYLC were 3.8 and 1.17 % (160 and 65.1 kg ha−1 yr−1), respectively. In the low-rainfall environment, the genetic gains were 0.93 and 0.73 % (40 and 33.1 kg ha−1 yr−1), for GYP and GYLC respectively. The GY of the lines included in each nursery showed a significant phenotypic correlation between high- and low-rainfall environments in all the examined years and several of the five best performing lines were common in both environments. The GY progress was mainly associated with increased grain weight (R2 = 0.35 p < 0.001), days to maturity (R2 = 0.20, p < 0.001) and grain filling period (R2 = 0.06, p < 0.05). These results indicate continuous GY genetic progress and yield stability in the HRWYT germplasm developed and distributed by CIMMYT.

The aims of this study were to i) identify the influence of the GxE interaction in the selection of inbred lines of melon, and ii) test the efficiency of different indexes in the selection of inbred lines with a higher yield potential and better quality fruit. For these purposes, 98 inbred lines of yellow melon and two commercial controls, Vereda and AF-646, were evaluated in a randomized block design with two replications, at the conditions present in Mossoró and Baraúna. Analyses of the following traits were performed: fruit yield, mean fruit weight, pulp thickness, pulp firmness and soluble solids content. A complex portion of the GxE interaction was predominantly detected for all traits. The recommendation in this case is to promote selection in each environment. Alternatively, selection based on the average behavior of the inbred lines is the strategy that generates the greatest gains, approaching those obtained through direct selection in each specific environment. The selection indexes aimed at reducing the expression of all traits proved to be best for both locations. The index constructed for Baraúna allowed the selection of a greater number of inbred lines with a higher yield potential and better quality fruit and, thus, greater efficiency. RESUMO. Objetivou-se com esse estudo: i) identificar a interferência da interação GxE no processo de seleção de linhagens de melão e; ii) testar a eficiência de índices na seleção de linhagens com maior potencial produtivo e melhor qualidade de fruto. Para isto, avaliaram-se 98 linhagens de melão amarelo e duas testemunhas, Vereda e AF-646, em blocos casualizados com duas repetições, em Mossoró e Baraúna, localizadas no Agropolo produtor desta hortaliça. Avaliaram-se os caracteres produtividade de frutos, massa média de frutos, espessura de polpa, firmeza de polpa e sólidos solúveis. Detectou-se uma predominância da porção complexa na interação GxE em todos os caracteres. A recomendação, neste caso, é promover a seleção em cada ambiente. Alternativamente, a seleção baseada no comportamento médio das linhagens é a estratégia que gera ganhos mais próximos àqueles obtidos pela seleção direta em cada ambiente específico. Os índices de seleção, com o propósito de reduzir a expressão de todos os caracteres, se mostraram melhores para ambas as localidades. Àquele construído para Baraúna permitiu selecionar um maior número de linhagens com elevado potencial produtivo e com melhores qualidades de fruto, sendo assim, mais eficiente.

Several traits must be observed in the selection of sour passion fruit progenies. For such, selection indices could be used for gradually increasing the frequency of favorable genotypes for the set of the traits of interest. This study aimed to compare parametric and non-parametric selection indices to be used in the selection of passion fruit progenies and identify the best economic weights. Thus, 118 full-sib families and three controls were assessed for days regarding flowering, productivity in kg ha-1 year, fruit mass in g, number of fruits, average length of fruits in mm, average fruit diameter in mm, fruit shape, average shell thickness in mm, pulp yield, pulp color, total soluble solids, titratable acidity and SS/ATT ratio. The non-parametric selection indexes used to obtain genetic gains were Mulamba and Mock, genotype-ideotype distance, multiplicative and Elston. Smith and Hazel, Williams and Pesek and Baker parametric indexes were used, with different economic weights attributed. The Mulamba and Mock, genotype-ideotype distance nonparametric selection indexes and the Williams parametric index showed satisfactory and balanced gains. The genetic variation coefficient, genetic standard deviation and random weight economic weights provided higher gains for non-parametric selection indexes. Similar gains were obtained for parametric indexes, regardless of assigned weight, except for Pesek and Baker, whose genetic standard deviation provided the highest gain. Resumo Na seleção de progênies de maracujazeiro-azedo, várias características devem ser observadas. Uma alternativa é o uso de índices de seleção que visem a melhorar gradativamente as frequências de genótipos favoráveis para o conjunto de características de interesse. O objetivo deste trabalho foi comparar índices de seleção paramétricos e não paramétricos na seleção de progênies de maracujazeiro-azedo e identificar os melhores pesos econômicos. Desta forma, 118 famílias de irmãos completos e três testemunhas foram avaliadas para dias para o florescimento, produtividade em kg ha-1 ano, massa de frutos em g, número de frutos, comprimento médio dos frutos em mm, diâmetro médio de frutos em mm, formato de fruto, espessura média de casca em mm, rendimento de polpa, coloração da polpa, teor de sólidos solúveis totais, acidez total titulável e ratio. Os índices de seleção não paramétricos empregados para a obtenção dos ganhos genéticos foram Mulamba e Mock, distância genótipo ideótipo, multiplicativo e Elston, e os índices paramétricos foram de Smith e Hazel, Williams e Pesek e Baker, com a atribuição de diferentes pesos econômicos. Os índices de seleção não paramétricos de Mulamba e Mock, distância genótipo ideótipo e o índice paramétrico de Williams apresentaram ganhos satisfatórios e equilibrados. Os pesos econômicos coeficiente de variação genético, desvio-padrão genético e peso aleatório proporcionaram maiores ganhos para os índices de seleção não paramétricos; para os índices paramétricos, os ganhos foram semelhantes, independentemente do peso atribuído, exceto para o índice de Pesek e Baker, em que o desvio-padrão genético proporcionou o maior ganho.

The noble scallop, Chlamys nobilis is one of the most economically important fishery and aquaculture species in the southern coast of China. In the present study, we conducted a one generation mass selection for shell length in a cultured noble scallop stock with a selection intensity of 1.732, to examine their response to selection. The results show that the selected line grew faster than the control line in shell length (P

Selection indexes are useful tools for the simultaneous selection of several descriptors aiming to promote genetic gains and a reliable advancement of segregating populations. This study tested the use of selection index of distance from the genotype to the ideotype to assist in the search for superior progenies, based on agronomic variables obtained from early generation progeny of intraspecific progenies of peanuts (Arachis hypogaea L.) Four segregating populations were used, each consisting of 90 progenies, arranged in a randomized block design with three replicates, in which the best 30 progenies of each population were selected. The index of distance to the ideotype, used for the selection, was built from a non-real model cultivar that meets the requirements for traits main stem height (SH), early flowering (EF), number of pegs (NP), number of pods per plant (NPP), weight of 100 pods (WP100), number of seeds per plant, and weight 100 seed (WS100). It was observed that the selection index used was effective for differentiating progenies and promoting gains at a selection pressure of 33.33%. Gains were variable for the same traits in the different populations. The number of pods per plant, for example, ranged from 3.96% in the population 3 to 16.98% in the population 4. The analysis of diversity showed that progenies selected grouped differently, by principal coordinates analysis, which corroborates the ability of the index to form groups according to traits of interest. The groups formed revealed moderate variability by the diversity analysis by the Ward/MLM method.

Frutos no estádio vermelho maduro de trinta e três acessos de tomate do banco de germoplasma do CCA-UFES, sendo 15 do "tipo Cereja" e 18 do "tipo Salada", foram caracterizados com base nos seguintes descritores morfoagronômicos: peso médio do fruto; comprimento médio do fruto; diâmetro médio do fruto; diâmetro da cicatriz peduncular; espessura do mesocarpo do fruto; teor de sólidos solúveis e pH do fruto. Com base nas variáveis teor de sólidos solúveis (TSS) e pH do fruto, calculou-se a variável sabor, por meio da relação TSS/pH². Foram realizadas análises de variâncias e análises de correlações simples e parciais, determinando a distribuição dos acessos quanto às classes de sabor. Com base nas distribuições de frequências, formaram-se quatro classes para essa variável, sendo que, a maior parcela (33%) dos acessos "tipo Salada" alocaram-se na classe mais baixa (0,05-0,12 ºBrix.pH-2), correspondendo a frutos de sabor menos desejável, enquanto a maior parcela (30%) dos acessos "tipo Cereja", alocaram-se em classe imediatamente superior (0,13-0,20 ºBrix.pH-2). Os dados demonstram a possibilidade de se obter ganhos genéticos para sabor concomitantemente ao peso, comprimento e espessura do mesocarpo dos frutos. Fruits in the ripe red stage of thirty three tomato (Lycopersicon esculentum Mill.) accessions from CCA-UFES germplasm collection, being 15 "Cherry type" and 18 "Salad type", were characterized based on the following morphooagronomic descriptors: average fruit weight; average fruit length; average fruit diameter; peduncle scar diameter; fruit mesocarp thickness; soluble solids and fruit pH. Based on the data from the soluble solids and fruit pH, the flavor variable was calculated by the ratio TSS/pH². Variance analysis and simple and partial correlations were calculated, and the accessions were clustered in flavor classes. Based on the statistical model of distribution of frequencies, four classes were formed for flavor variable. The largest portion (33%) of the accessions of salad type were located in the lowest class (0.05-0.12 ºBrix.pH-2), corresponding to the accessions with not so desirable a flavor, while the largest portion (30%) of the accessions of the "cherry" type were clustered in the next class above (0.13-0.20 ºBrix.pH-2). The possibility of concomitantly obtaining genetic gains for flavor, weight, length and mesocarp thickness of the fruits was demonstrated.

O objetivo deste trabalho foi avaliar parâmetros genéticos e comparar os ganhos preditos por meio de diferentes métodos de seleção em famílias de meios-irmãos de Eucalyptus urophylla. Foi utilizada seleção entre e dentro, seleção combinada e seleção com base em modelos mistos (REML/BLUP) para os caracteres diâmetro à altura do peito, altura total e volume total com casca. Foi utilizado o teste de progênie constituído de 100 famílias de meios-irmãos com 55 meses de idade, em espaçamento de 3x2 m, em delineamento de blocos ao acaso, com cinco repetições. As progênies apresentaram variabilidade genética significativa e elevada magnitude de herdabilidade para os caracteres estudados, o que evidencia alto controle genético e condições favoráveis para seleção. Todos os métodos avaliados foram eficientes para aplicação no melhoramento de eucalipto. No entanto, a seleção combinada e a seleção por modelos mistos (BLUP) proporcionam estimativas de ganhos significativamente maiores às obtidas com a seleção entre e dentro, e maior eficiência na escolha dos melhores indivíduos dentro da população. The objective of this work was to evaluate genetic parameters and to compare predicted gains using different selection methods in half-sib families of Eucalyptus urophylla. Within and between selection, combined selection and selection based on mixed model equations (REML/BLUP) were used for the traits diameter at breast height, total height and total volume with bark. The progeny test used consisted of 100 55-month-old half-sib families distributed in a 3x2-m spacing, in randomized complete block design with five replicates. The progenies showed significant genetic variability and high heritability for the studied traits, which indicates high genetic control and favorable conditions for selection. All the methods tested were efficient in eucalyptus breeding. However, the combined selection and the selection based on mixed models (BLUP) provided gains significantly larger than those obtained with within and between selections, and were more efficient in the selection of the best individuals in the population.

Although Brazil has reduced its importation of popcorn grain in recent years, the availability of improved varieties is still rare. In order to improve a popcorn population and to estimate the prediction of genetic gains, the third cycle of intrapopulation recurrent selection was carried out. One hundred ninety two half-sib families were obtained from the second cycle of the UNB-2 U population and tested in a randomized complete block design with two replications within sets in two locations. The presence of statistical significance for sets for grain yield, poorly husked ear and broken plants proved the efficiency and the necessity for the use of the hierarchical statistical model by sets. Except for the poorly husked ear, there was significance for families within sets for the other evaluated traits, showing that there was sufficient genetic variability for exploitation in future cycles. Although the heritability for popping expansion was higher than for grain yield, the predicted genetic gain for the latter was superior to popping expansion because of the higher magnitude of the genetic standard deviation for grain yield. It is expected that in the fifth recurrent cycle, the first popcorn variety with yellow grains may be released for Rio de Janeiro State. Embora o Brasil tenha reduzido a importação de grãos de milho pipoca, a disponibilidade de variedade melhorada ainda é rara no país. Com o objetivo de melhorar a população UNB-2 U de milho pipoca e estimar a predição de ganhos genéticos, implementou-se o terceiro ciclo de seleção recorrente intrapopulacional. Cento e noventa e duas famílias de meios-irmãos foram obtidas e avaliadas em delineamento de blocos casualizados, com duas repetições, dentro de "sets" em dois locais. A presença de significância para "sets", para produção de grãos, espigas mal empalhadas e plantas quebradas, comprovou a eficiência do uso do modelo estatístico hierarquizado por "sets". Com exceção das espigas mal empalhadas, houve significância para famílias dentro de "sets" para as demais características, revelando que há suficiente variabilidade genética a ser explorada em ciclos futuros. Ainda que a herdabilidade para capacidade de expansão (PE) tenha sido superior à da produção de grãos (GY), o ganho predito para GY foi superior a PE, em decorrência da maior estimativa da magnitude do desvio-padrão genético para GY. Espera-se que, no quinto ciclo de seleção recorrente, seja possível a recomendação da primeira variedade de milho pipoca com grãos amarelos para o Estado do Rio de Janeiro.

Os objetivos deste trabalho foram analisar ganhos genéticos teóricos de milho como resultado da seleção entre famílias de irmãos completos e de meios-irmãos, obtidas pelos Delineamentos I, de Irmãos Completos e de Meios-Irmãos, e a variabilidade genotípica e perda de genes com seleção a longo prazo. Os delineamentos foram avaliados por simulação, com base nos ganhos médios estimados após dez ciclos de seleção. O processo de simulação considerou sete sistemas gênicos com dez genes (com distintos graus de dominância), três classes de populações (com diferentes freqüências gênicas), sob três condições de ambiente (valores de herdabilidade), e quatro estratégias de seleção. Cada combinação foi repetida dez vezes, totalizando 25.200 simulações. Seleção entre famílias de irmãos completos é geralmente mais eficiente do que seleção com base em progênies de meios-irmãos. Empregar famílias de irmãos completos obtidas pelo Delineamento I é geralmente mais eficiente que usar progênies derivadas do Delineamento de Irmãos Completos. O Delineamento I, com 50 machos e 200 fêmeas (tamanho efetivo de 160), não determinou população melhorada com variabilidade genotípica mínima. Nas populações melhoradas com menor tamanho efetivo (160 e 400), a perda de genes favoráveis é restrita àqueles recessivos em baixa freqüência. The objectives of this work were to analyze theoretical genetic gains of maize due to recurrent selection among full-sib and half-sib families, obtained by Design I, Full-Sib Design and Half-Sib Design, and genotypic variability and gene loss with long term selection. The designs were evaluated by simulation, based on average estimated gains after ten selection cycles. The simulation process was based on seven gene systems with ten genes (with distinct degrees of dominance), three population classes (with different gene frequencies), under three environmental conditions (heritability values), and four selection strategies. Each combination was repeated ten times, amounting to 25, 200 simulations. Full-sib selection is generally more efficient than half-sib selection, mainly with favorable dominant genes. The use of full-sib families derived by Design I is generally more efficient than using progenies obtained by Full-Sib Design. Using Design I with 50 males and 200 females (effective size of 160) did not result in improved populations with minimum genotypic variability. In the populations with lower effective size (160 and 400) the loss of favorable genes was restricted to recessive genes with reduced frequencies.