Diallel Scheme Research Articles

Herança da resistência ao enfezamento em milho

Os objetivos deste trabalho foram determinar a herança da resistência ao complexo de enfezamento em milho e determinar as melhores fontes de resistência entre as linhagens estudadas. Foram realizadas as análises dialélica e médias de gerações em linhagens de milho. Para a análise dialélica, foram cruzadas 12 linhagens de milho, em dialélico parcial. Para análises de médias de gerações, foram cruzadas três linhagens resistentes e quatro suscetíveis, para a obtenção das gerações F1, F2, RCP R e RCP S. Os trabalhos foram conduzidos em Jaboticabal, SP. A incidência de enfezamento foi avaliada no estádio fenológico R3. Efeitos significativos quanto à capacidade geral de combinação e capacidade específica de combinação foram obtidos, o que indicou que, no controle do caráter enfezamentos, estão envolvidos tanto os efeitos aditivos quanto os de dominância. Análises de médias de gerações mostraram a presença de poucos genes envolvidos com o controle da resistência, com predominância de efeitos aditivos, o que permite a seleção de genótipos resistentes. As linhagens L02, L03 e L05 poderão ser utilizadas como fontes de resistência, em futuras combinações híbridas.

The complex S-gene system for control of self-incompatibility in the buttercup genus Ranunculus

Continued research into the S-gene mechanisms in the genus Ranunculus, their genetic architecture and mode of cooperation, applied a backcross analysis in two steps to the three diploid, perennial, closely related, but reproductively perfectly isolated species R. acris. R. bulbosus. and R. polyanthemos. Parental plants were preferably taken from remote provenances, an F1 plant was selected to be crossed with pollen from the maternal parent, and the backcross offspring, altogether about 2300 plants in five backcross families, were tested individually with their pollen onto this parent. Backcross plants failing with their pollen on their backcrossed parent were selected and tested to one another in a diallel scheme of cross pollinations. The analyses based on these selected backcross plants showed 4 S-loci to be at work in all three species; in no case was it necessary to presume more than four. There were no indications that the higher levels of heterozygosity were favoured in any way. The main influence on the frequencies with which the different S-genotypes appeared among the selected backcross plants was seen to be associated with individual S-genes and not with specific S-gene constellations. The data are interpreted to testify to the ancient state of the complex S-gene system, to indicate that the 4 loci form the genuine number, at least for these three species, and to favour the view that they cooperate through a complex recognition molecule, at least a heterotetramer, where each of the four S-loci contribute by its specific polypeptide. The presumption of a restrictive supply of alleles in the team is supported by four of the five F1 plants showing S-gene identities between the crossed parental plants.

Genetic control on the performance of common bean differential cultivars to Colletotrichum lindemuthianum races

The aim of this work was to perform genetic control on differential cultivars Michelite, Michigan Dark Red Kidney, Perry Marrow, Cornell 49-242, PI 207262, AB 136 and G 2333 and its diallel hybrids by using Hayman's methodology. The entire F1s populations were evaluated in relation to race 89, whereas the race 31, the diallel scheme did not include the cultivar G 2333. The results showed that the additive effects were predominant for the 31 race, while non-additive effects were more important for race 89. The results demonstrated a high coefficient of genetic determination for the race 31. The G 2333, AB 136 and PI 207262 cultivars should be recommended obtaining cultivar resistant to anthracnose by backcross programs because theyshowed the highest proportion of resistant dominant alleles for the races 31 and 89.

Informações fenotípicas e marcadores microssatélites de QTL na escolha de populações segregantes de feijoeiro

O objetivo deste trabalho foi selecionar populações segregantes de feijoeiro promissoras para a produtividade de grãos e com polimorfismo para marcadores microssatélites ligados a QTL relacionados previamente à produtividade de grãos. Foram utilizadas 49 linhagens, avaliadas em dois experimentos em látice triplo. Sete linhagens foram selecionadas e intercruzadas no esquema dialélico e também genotipadas com 24 marcadores microssatélites ligados a QTL previamente identificados. As populações foram avaliadas em blocos completos casualizados, com três repetições. Foram observadas diferenças significativas entre as capacidades gerais (CGC) e específicas de combinação (CEC) e os efeitos não-aditivos foram mais pronunciados. As linhagens RC1-10 e Z-9 se destacaram em razão das elevadas estimativas de g i. Entre os microssatélites, 25% foram polimórficos. Foram selecionadas quatro populações para a seleção de famílias com base na avaliação das linhagens, na análise dialélica e no polimorfismo entre os marcadores microssatélites. Destacou-se a população RC1-10 x Z-9, formada por genitores de alta CGC, com alta média e CEC e ainda grãos do tipo Carioca. Considerando o baixo número de microssatélites polimórficos obtidos nas populações, pode-se concluir haver necessidade de utilização de maior número de microssatélites ligados a QTL da produção de grãos.

Partial diallel to evaluate the combining ability for economically important traits of papaya

The dependence of Brazil on imported improved papaya seeds was the main motivation for this research that primarily intended to evaluate the combining ability of eight genotypes from the 'Solo' group, crossed with eight genotypes from the 'Formosa' group following a partial diallel scheme. The traits mean fruit weight, brix degree and flavor revealed prevalence of additive effects in both genetic groups, while plant height was preponderantly additive only for the 'Solo' genotypes. On the other hand, the yield trait expressed additive superiority for the 'Formosa' genotypes. For intrapopulation breeding for higher yield, the indicated genotypes are 'Maradol' and 'Cariflora' from the 'Formosa' group as well 'Sunrise Solo 783' and 'Sunrise Solo TJ' from the 'Solo' group; but, when the objective is to breed for better fruit quality, the genotypes 'JS 12' and 'JS 11' ('Formosa' group), and 'Sunrise Solo72/12' and 'Baixinho de Santa Amália' ('Solo' group) are indicated. Based on the set of evaluated traits, the best hybrid combinations were 'Sunrise Solo 72/12 × JS 12', 'Sunrise Solo TJ × JS 12', 'Baixinho de Santa Amália × JS 12', 'Sunrise Solo TJ X JS 11' and 'Sunrise Solo 72/12 × Costa Rica'.

Heterosis in papaya hybrids from partial diallel of ‘Solo’ and ‘Formosa’ parents

The high cost of imported papaya seed in Brazil has motivated the conduction of the present study, which aimed at estimating heterosis effects and the indication of superior papaya hybrids, by means of a partial diallel scheme of eight genotypes from the groups 'Solo' and 'Formosa'. Parents and hybrids were evaluated in a randomized complete block design with four replications and 80 treatments (64 hybrids and 16 parents). Nine traits were evaluated and heterobeltiosis was verified for all traits. It was concluded that the diallel is a suitable strategy for the generation of papaya hybrids that meet national and international market standards. Superior hybrids with a view to further evaluation and cultivar release are those formed by the parents 'JS11' and 'JS 12' with the parents: 'Sunrise Solo-TJ', 'Sunrise Solo-72/12-IS', 'Santa Barbara', 'Baixinho de Santa Amalia', 'Sao Mateus' and 'Sunrise Solo-783'.

Selection aiming at upright growth habit common bean with carioca type grains

Aiming at common bean lines with a high grain yield, upright growth habit and carioca type grains, ten common bean lines were crossed in a diallel scheme. The resulting populations were evaluated as to their capacity of generating superior lines. Eleven of the 42 evaluated populations were chosen to form the base population (S0) of the first cycle (C-0). The resultant families were evaluated up to the S0:5 generation for yield, plant architecture and grain type. In this generation, a total of 14 families was evaluated with two controls to estimate the genetic gain considering the three traits of interest together. The obtained genetic gain was 3.1% after one selection cycle, confirming the efficiency of the realized selection. The estimates of genetic and phenotypic parameters in the different generations associated to the mean family performance allow a prediction of the success of recurrent selection in future cycles.

Herança da resistência à mancha-bacteriana em tomateiro

A herança da resistência do tomateiro (Lycopersicon esculentum) à mancha-bacteriana (Xanthomonas campestris pv. vesicatoria, raça T2) foi estudada, em condições de campo, cruzando-se os genótipos resistentes 'Ohio 8245' e 'Hawaii 7998' com os genótipos suscetíveis 'CNPH 401-08' e 'CNPH 416.81.01.02', em um esquema dialélico desconsiderando-se os recíprocos. Foram obtidas cinco famílias, cada uma constituída por seis gerações: Genitor1, Genitor2, F1, F2 e os retrocruzamentos (RC1 e RC2). A família 'Ohio 8245 <FONT FACE=Symbol>'</FONT> Hawaii 7998' apresentou menor média para severidade da doença, seguida por 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02' e 'Ohio 8245 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02', as quais, apresentaram maiores estimativas de herdabilidade e de predição de ganho por seleção. Em todas combinações, a herança da resistência genética à mancha-bacteriana foi do tipo quantitativa, com estimativa do número de genes variando de quatro a oito genes, conforme a família analisada. Foi observada segregação transgressiva nas famílias 'Ohio 8245 <FONT FACE=Symbol>'</FONT> CNPH 401-08', 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 401-08' e 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02'. Os efeitos gênicos foram do tipo aditivo para todas as famílias e os dados ajustados ao modelo aditivo-dominante, com o componente aditivo apresentando maior magnitude.

Estimates of genetic variance components in asparagus hybrids in two cultivation systems

In order to determine the genetic variance components and heritability of six pistillate and six asparagus elite plants, 18 hybrids were evaluated for yield traits in two cultivation systems (blanched and green asparagus) in two harvest periods. The circular partial diallel scheme was replicated twice in 20-plant plots in a randomized block design. The differences between the GCA and SCA effects varied depending on plant age and cultivation systems. The relative importance of the ratio of the combining ability variance showed that the additive components of variance were more important than the non-additive components. The GCA effects of three pistillate and two staminate plants as well as the SCA effects of three crosses were favorable for yield traits.

Avaliação de sete famílias S2 prolíficas de minimilho para a produção de híbridos

Sete famílias S2 de minimilho foram cruzadas entre si em esquema dialélico completo. Os híbridos simples obtidos foram avaliados na Estação Experimental de São Manuel, da Faculdade de Ciências Agrárias da Universidade de São Paulo (UNESP-Botucatu). O experimento foi delineado em blocos casualizados com três repetições. As parcelas consistiram de fileiras de 5 m espaçadas entre si por 0,90 m, com 50 plantas cada uma. Avaliaram-se as seguintes características: número de espigas por parcela (NE), massa de espigas com palha (MECP) e sem palha (MESP), comprimento de espigas com palha (CECP) e sem palha (CESP), diâmetro de espigas com palha (DECP) e sem palha (DESP), altura da planta (AP) e da espiga (AE). Estimaram-se os efeitos da capacidade geral e específica de combinação das famílias pelo método 4, modelo estatístico 1, proposto por Griffing. Houve predominância dos efeitos gênicos aditivos para a massa de espigas com palha e sem palha. Entretanto, para o comprimento de espigas sem palha, diâmetro de espigas com palha e sem palha, altura de planta e altura de espigas, os efeitos gênicos aditivos e não aditivos foram equivalentes. Pelas estimativas das capacidades combinatórias para o número de espigas por parcela, massa de espigas com palha e sem palha, a família 27 é a indicada para obter genótipos superiores.

Desempenho de híbridos de linhagens parcialmente endogâmicas de milho em regiões dos estados de Roraima e Minas Gerais

Entre as alternativas de tipos de híbridos de milho (Zea mays L.), os que envolvem linhagens parcialmente endogâmicas (LPE) S2 possuem a vantagem de maior rapidez na obtenção, se comparados com linhagens de endogamia completa. Essas LPE S2 podem ser obtidas a partir de qualquer tipo de população, porém, uma boa opção seria aquelas derivadas de híbridos simples comerciais, que associam produtividade e grande proporção de locos segregantes. Com esse intuito, o presente trabalho foi conduzido visando à avaliação de híbridos de LPE S2 derivados de três híbridos simples comerciais. Para obtenção dos híbridos, foram selecionados 30 LPE S2 de três populações distintas das cultivares híbridas comerciais: AG-9012, C-333B e Z-8392. Os cruzamentos foram realizados em esquema de dialelo circulante, em que cada LPE S2 de uma população foi cruzada com outras três LPE S2 de outra população. Para os cruzamentos, as LPE S2 foram semeadas em linha com dez metros cada uma. No aparecimento das primeiras espigas, as mesmas foram protegidas e, por ocasião da polinização, uma mistura de pólen de cada LPE S2 foi utilizada para polinizar pelo menos dez plantas de uma outra população LPE S2. Os híbridos obtidos foram avaliados em Boa Vista, Roraima e em Lavras, Minas Gerais, utilizando-se o delineamento látice simples 12x12, envolvendo os 135 híbridos LPE S2 obtidos e mais nove testemunhas, sendo elas as gerações F1 dos híbridos simples AG-9012, C-333B e Z-8392, um híbrido duplo (C 435) e cinco outros híbridos intervarietais. A parcela experimental foi constituída por uma linha de três metros de comprimento, espaçada de 90 cm entre linhas e permanecendo um total de cinco plantas por metro linear após o desbaste. As seguintes variáveis foram avaliadas: peso de espiga despalhada (PESP), altura de planta (ALTP) e altura de espiga (ALTE). Para a PESP, 81% dos híbridos S2 foram superiores às médias das testemunhas. Observou-se que 17% dos híbridos de LPE S2 tiveram desempenho superior ao híbrido simples C-333B C (10,76 t/ha) e 46% apresentaram desempenho superior à testemunha C-435 (9,56 t/ha), um híbrido duplo amplamente utilizado nos dois estados. Para ALTP e ALTE, os resultados foram semelhantes a PESP, salientado que o contraste H vs T foi não-significativo, inferindo-se que os híbridos S2 e as testemunhas apresentaram, em média, as mesmas ALTP e ALTE. Com esse fato, evidencia-se que os híbridos LPE S2 são semelhantes aos híbridos comerciais e mostra o potencial da utilização desse tipo de híbridos no Brasil, que pode substituir com vantagens alguns híbridos comerciais disponíveis no mercado.

Combining ability of inbred lines of maize and stability of their respective single-crosses

The utilization of diallel crosses for identification of superior combinations is a common practice in maize (Zea mays L.) breeding programs. This methodology allows the estimation of the combining ability of genotypes being evaluated. In this work, five inbred lines were evaluated as to their general (GCA) and specific (SCA) combining abilities, by using a complete diallel scheme. The single-crosses produced between these inbred lines were evaluated in seven environments, along with two checks, by using a randomized complete block design. Traits analized were: grain yield, plant height, ear height, ear placement, and prolificacy. A diallel analysis was carried out, following an adaptation of Griffing's method IV, in addition to hybrid stability and adaptability analyses. Significant differences were detected for entries and environments for all traits. The interaction genotype vs. environment was significant for all traits. GCA's were significant for all traits, while SCA's were non-significant only for ear placement. For grain yield, both additive (GCA) and non-additive (SCA) effects were important, while for the remaining traits additive effects were more important. The high yielding single-cross was obtained from the cross of lines L-08-05F and L-38-05D. Those inbred lines showed higher GCA's and their cross also had high SCA; also, it is responsive to environment improvements and reasonably stable. The second in rank high yielding single-cross, L-46-10D x L-08-05F, showed wide adaptability and stability.

Capacidade de combinação entre linhas tetraplóides e diplóides de melancia

A capacidade de combinação entre três genitores tetraplóides (LT7-48.1, LT9-24.1 e LTCC-24) e quatro diplóides de melancia ('Crimson Sweet', 'Pérola', 'New Hampshire Midget' e 'Charleston Gray') foi avaliada num esquema de cruzamentos dialélicos parciais. Utilizou-se delineamento de blocos casualizados, com três repetições, formadas por parcelas de sete plantas. Genitores e F1's foram avaliados quanto ao número de dias para o aparecimento da primeira flor masculina e feminina, número de frutos por planta, comprimento da rama principal, massa média dos frutos, teor médio de sólidos solúveis na polpa, diâmetros transversal e longitudinal do fruto, espessura da casca do fruto na região do pedúnculo e na região da cicatriz floral, cor da polpa e ocorrência de ocamento no fruto. Os genitores, tanto diplóides como tetraplóides, apresentaram-se bastante divergentes quanto às características estudadas. Os efeitos da capacidade geral de combinação (CGC) foram superiores aos efeitos da capacidade específica de combinação (CEC) para a maioria dos caracteres, especialmente daqueles relacionados com a produção da planta, indicando a maior importância dos efeitos gênicos aditivos. No entanto, algumas características, como precocidade e ocamento de frutos tiveram controle gênico não aditivo e, portanto, a avaliação e seleção de linhagens em combinações híbridas permitirão a síntese de híbridos triplóides superiores.

Combining ability in baby corn inbred lines (Zea mays L.)

Seven baby corn inbreds were crossed in a complete diallel scheme. The single-cross hybrids obtained were assessed at the Sao Manuel Experimental Station, in Sao Paulo State, Brazil. The experiment was set up in a randomized complete block design with three replications, including one commercial control. The experimental plots consisted of a single row, 5 m long, with 25 plants. The traits assessed were: number of ears/plot, weight, length and diameter of husked and dehusked ears, plant height and ear height. General and specific combining ability effects (GCA and SCA) were determined. There was genetic variability among hybrids and the best hybrid (27Ax31B) was superior to the control for number of ears/plot and weight of ears dehusked. Inbreds 27 and 29 showed the best GCA effects for number of ears/plot, weight of husked and dehusked ears. The magnitude of GCA showed that the additive effects were dominant in most traits evaluated. The existence of dominance effects was also found.

Análise da capacidade combinatória em cruzamentos dialélicos de três cultivares de jiloeiro

As cultivares de jiloeiro (Solanum gilo) Tinguá, Comprido Verde Claro e Morro Redondo foram utilizadas em cruzamentos obedecendo a esquema dialélico, com os recíprocos. Os genitores e os respectivos híbridos F1 foram avaliados no campo, por 14 descritores fitotécnicos, dos quais sete foram estatisticamente analisados pelo Modelo de Griffing. Os genótipos demonstraram capacidade geral de combinação para comprimento, diâmetro e peso médio do fruto, número de dias até início da colheita e altura da planta. A capacidade específica de combinação, significativa para todas as características analisadas, indica efeitos de dominância e/ou epistáticos envolvidos no seu controle genético. Os híbridos ´Tinguá´ x ´Comprido Verde Claro´ e ´Comprido Verde Claro´ x ´Morro Redondo´ apresentaram resultados promissores para produção de frutos.

Analysis of Diallel Cross for the Evaluation of Maize Populations Across Environments

Eleven open-pollinated maize (Zea mays L.) populations were crossed in a diallel scheme and evaluated in five locations in the State of Parana: [1] Ponta Grossa, [2] Pato Branco, [3] Palotina, [4] Londrina and [5] Guarapuava. Two commercial hybrids (P 3230 and BR 201) were included as checks in the experiments, thus completing 68 entries (11 parents, 55 hybrids and 2 checks). Plots were represented by single rows 5 m long spaced 0.9m with 25 plants per plot after thinning. The following traits were analyzed: GY- total plot grain yield expressed in kg/ha after adjustment to 14.5% grain moisture; PH- plant height (cm); EH- ear height (cm); and FF- days for female flowering. Plant height and EH were not included in location [2]; FF was not include in locations [2] and [3]. The joint analysis of variance showed significance for all traits, only for the variation among location, entries, variety effects and average heterosis. For yield the total heterosis in mid-parent percentage varied from –0.96% (PMI 8403 x PMI 9304) to 32.4% (PMI 9302 x PMI 9307). Variety effects (v i ) and general combining ability (g i ) effects were in the range of –1483 to 772 kg/ha and from –847 to 448 kg/ha, respectively. Both g i (for yield) and v i (for the other traits) were used to select two populations to be used in a reciprocal recurrent selection program. BR 106 showed the highest estimates for both g i and v i for yield but also showed undesirable traits (tall plants and late flowering). Some outstanding populations for yield potential per se did not show a good performance in crosses. Other populations with outstanding performance in crosses exhibited lower variety effects for yield or high variety effects for the other traits. Some introduced populations who showed shorter plants and earliness should be submitted to selection for yield, adaptation and other agronomic traits before being indicated for crossing. However, they should be recommended as source populations for short architecture and early flowering. An overall analysis led to the decision of choosing the population IAPAR 26 to be used as contrasting parent of BR 106 in a reciprocal recurrent selection program at IAPAR (Londrina, State of Parana).

Multi‐trait selection in a diallel crossing scheme of cocoa

AbstractCocoa breeding seeks to increase the yield by area unit. In this context, one must consider the resistance to Phytophthora disease, the most serious one in cocoa culture. Thus, herein two traits were used: yield, i.e. number of healthy pods obtained in 7 years and Phytophthora resistance, estimated by pod rot rate. A combined individual‐family selection is proposed on the basis of the total genetic value in order to spread clonal material. This selection method was applied in a 6 × 6 diallel scheme in Cameroon. The heritability of Phytophthora resistance (near 0.2) was higher than for yield (0.13). A selection index was constructed to obtain good genetic gains on each of the two traits (yield and Phytophthora resistance). To improve prediction of genetic values, a third trait, potential yield, was used. With the chosen weight, the expected genetic gain was about 35% for resistance at 1% level of selection. This selection was applied and a confirmation trial is being established with the selected trees.

Heterotic groups based on yield-specific combining ability data and phylogenetic relationship determined by RAPD markers for 28 tropical maize open pollinated varieties

Twenty eight maize open pollinated varieties (OPVs) were crossed in a diallel scheme and the 378 F1's were evaluated in 10 environments in Brazil. Based on yield-specific combining ability data (SCA), these varieties were classified in four heterotic groups. The consistence of the proposed heterotic groups was confirmed comparing intra- and inter-group F1 values and midparent heterosis. Superior OPVs combinations for use as a source of inbreds in hybrid breeding programs were determined. RAPD markers were used to genotype these varieties. A UPGMA dendogram, based on marker data from 50 primers and 178 polymorphic bands, was obtained. Phylogeny obtained with RAPD markers agreed with known pedigree data. Dent germplasm tended to group separately from flint germplasm. Multidimensional Scaling Analysis on marker data and morphological data showed a higher degree of genetic divergence among the dent germplasm than among the flint germplasm used in this study. Correlation between RAPD marker estimated genetic distance and SCA for yield was low and positive (r = 0.16**).

Diallel crosses among maize lines with emphasis on resistance to foliar diseases

Ten elite maize (Zea mays L.) lines were crossed in a complete diallel scheme and the single-cross hybrids obtained were assessed at four experimental stations of the Agronomic Institute of Campinas, in São Paulo State, Brazil. The experiments were set up in a randomized complete block design with three replications, including four commercial checks. The experimental plots consisted of two 5-m rows spaced at 0.9 m, with a total of 50 plants. The traits assessed included: days to mid-tassel pollen shed (DPS), plant height (PH), ear height (EH), grain yield, corrected for a 50-plant stand and 14% moisture (GY corr.), and resistance to Phaeosphaeria maydis and Puccinia polysora. General and specific combining ability effects (GCA and SCA) were determined. There was extensive genetic variability among hybrids with the best hybrids (HS 04 x 10 and HS 10 x 11) not differing from the commercial checks. The lines with the greatest potential for hybrid synthesis included: L 10, L 11 and L 13, because they had higher GCA for yield, moderate resistance to P. maydis and reduced EH. The greatest contribution to reduction of the Phaeosphaeria stain was obtained with L 5. The magnitude of the GCA relative to the total variation indicated that additive effects predominated for resistance to P. maydis and P. polysora. Significant SCA (P < 0.01) was also found, indicating dominance effects as well.

Provenance hybridization in a diallel mating scheme of maritime pine (Pinus pinaster). II. Heterosis

Maritime pine (Pinus pinaster Ait.) is a species characterized by a discontinuous natural range with populations as a rule of small size and growing in heterogeneous environments. Ten provenances belonging to the three biosystematic groups of the species (Atlantic, Mediterranean, and North African) were crossed using a diallel scheme. Parental provenances and their hybrids were tested and measured for height growth at age 1, 2, 3, 8 and 13, as well as for insect resistance and stem crookedness in a trial in southwestern France. The results show a decrease in the variance of heterosis for height growth with age. Heterosis measured as the relative superiority of the hybrid to the midparent varies from -10% to 42% at age 1 and between 2 and 20% at age 13. There is no age effect on the mean value of heterosis, which amounts to 9.7% at age 1 and 8.4% at age 13. The value of heterosis was then compared with the genetic distance of parental provenances measured with various traits and markers (phenotypic traits, terpenes, isozymes, denaturated proteins). There was a weak but significant positive correlation between genetic divergence based on markers and heterosis for height at all ages. These relations were confirmed when the level of heterosis was compared for hybrids clustered according to the subdivision of the species in three major groups. The results are in agreement with theoretical analysis of heterosis and suggest that there is a disequilibrium between loci controlling height growth and neutral loci at the between population level. No significant relationship between levels of heterosis and stem crookedness or insect resistance was detected.