ABSTRACT. Heterosis has been one of the most studied phenomena since genetic studies were conceived. Knowledge of this phenomenon for the root distribution trait in beans (Phaseolus vulgaris L.) can favour the development of genotypes that are more tolerant to abiotic stresses. This study aimed to verify the occurrence of heterosis for the root distribution trait in hybrid F1 populations of common bean derived from crosses within and between gene groups. Thirty-six populations (six parents and 30 hybrids) were evaluated under field conditions in the agricultural years 2016/17 and 2017/18. The root distribution was assessed with the adapted Bohm method. The genotypes responded similarly to environmental changes (absence of an interaction). However, the root distribution differed significantly between the agricultural years. Comparisons between the mean of hybrids from crosses within each gene pool and the mean of parents did not reveal heterosis. The comparisons between gene groups showed significant differences only between BRS Embaixador x IPR Uirapuru, CBS 14 x IPR Uirapuru, and BAF 53 x IPR Uirapuru and the mean of parents. The absence of heterosis in the root trait can be explained by the degree of kinship between the gene groups, as well as some epistatic interactions.

RESUMO Quando combinados distintos grupos gênicos por meio de hibridações, é necessário o conhecimento do tipo de ação gênica preponderante na expressão de um caráter. O entendimento dessa informação ampara melhoristas para a tomada de decisões nas etapas de condução e seleção de populações segregantes no decorrer do programa de melhoramento genético. Assim, o objetivo do trabalho foi determinar os efeitos da capacidade de combinação e ação gênica para a característica distribuição radicular dos grupos de feijão Andino e Mesoamericano. Seis genitores de feijão dos grupos andino e mesoamericano foram hibridados em esquema de dialelo completo, resultando em 30 híbridos F1. Os genitores e híbridos foram conduzidos a campo em delineamento látice simples. A característica alvo foi a distribuição das raízes, calculada como a quantidade relativa de raízes no solo superior. O efeito da capacidade geral de combinação foi significativamente maior em relação aos efeitos de capacidade específica de combinação (58%) e efeito recíproco (41%). As estimativas de combinações foram modificadas em função da ordem dos grupos gênicos utilizados. As combinações IPR Uirapuru x BAF53 (mesoamericano x andino), BAF53 x CBS14 (andino x andino) e CBS14 x IPR Uirapuru (andino x mesoamericano) foram as principais responsáveis por incrementar a média da característica distribuição radicular. No entanto, mesmo que realizando combinações entre grupos gênicos, a maior fração da variância genética foi relacionada a componentes aditivos (60%). Consequentemente, a ação gênica aditiva foi predominante na expressão do caráter distribuição radicular em feijão independente do grupo gênico utilizado.

ABSTRACT When different gene groups are combined by hybridization, the expression of predominant genes for a trait must be known. This understanding is fundamental to the decisions made by breeders in the stages of cultivation and selection of segregating populations during the breeding program. Thus, the objective of this study was to determine the effects of combining ability and gene action for the root distribution traits of the Andean and Mesoamerican common bean gene groups. Six common bean parents from the Andean and Mesoamerican groups were hybridized in a complete diallel mating scheme, resulting in 30 F1 hybrids. The parents and hybrids were planted in the field in a simple lattice design. The target trait was root distribution, calculated as the relative number of roots in the topsoil. The effect of the general combining ability was significantly higher than that of the specific combining ability (58%) and the reciprocal effect (41%). Particularly, the combination estimates were modified according to the order of the gene groups used. The combinations IPR Uirapuru x BAF53 (Mesoamerican x Andean), BAF53 x CBS14 (Andean x Andean), and CBS14 x IPR Uirapuru (Andean x Mesoamerican) mainly exhibited an increase in the mean root distribution. However, the highest fraction of genetic variance correlated with additive components (60%), even in crosses involving different gene groups. Consequently, the additive gene action was predominant in the expression of root distribution trait in common bean, irrespective of the gene group used.

ABSTRACT Associations between root distribution and bean growth habit may contribute to the selection of genotypes adapted to restrictive environments. The present work aimed to relate and compare root distribution with the growth habit in beans. 10 bean genotypes of different growth habits (I, II and III) were evaluated for root distribution in two agricultural years (2014/15 and 2015/16). The genotypes responded similarly for the trait root distribution throughout the agricultural years, without any simple effect of the genotype x year interaction. The factors genotype and years were significant for the trait. The genotypes of a determinate habit showed significant differences compared to other genotypes (II and III), which were ascribed to their poor performance in the average of years. They include the Carioca Precoce, which showed a behavior similar to the other habits. It could be considered a “plastic” genotype under restrictive conditions. The contrasts revealed significant differences between the growth habits II vs I (2.87) and III vs I (3.64) for root distribution. The differences were also significant for grain yield. Thus, genotypes of indeterminate growth habit show greater root distribution than those of a determinate habit, regardless of the agricultural years. Therefore, they are promising for use in blocks of crosses, when the purpose is the selection of cultivars adapted to low input environments.

RESUMO Dentre as doenças que afetam as lavouras de feijão está a antracnose, causada pelo fungo Colletotrichum lindemuthianum (Sacc. & Magnus), com ocorrência em todo o Brasil, acarretando perdas de até 100 % na produção de grãos. Cerca de 20 genes que conferem resistência a raças específicas do patógeno já foram descritos na literatura. Objetivou-se avaliar as variedades de feijoeiro dos estados de Santa Catarina e Paraná, no que diz respeito à resistência a antracnose, em duas safras. Além disso, duas cultivares comerciais foram utilizadas como controles: IPR Tangará, como suscetível; e BRS Campeiro, como moderadamente resistente. A maioria das variedades locais foi considerada resistente ou moderadamente resistente, sendo mais pronunciada a cultivar Amendoim, com grãos grandes e tegumento vermelho, evidenciando resistência em ambas as avaliações. A este respeito, a possibilidade de utilizá-las como fontes de resistência à antracnose pode ser considerada, pois, também, demonstram adaptabilidade às condições ambientais.

ABSTRACT Anthracnose is an important disease caused by the Colletotrichum lindemuthianum (Sacc. & Magnus) fungus in bean crops. It occurs throughout Brazil and may cause losses of up to 100 % in grain production. About 20 genes that confer resistance to specific races of the pathogen have already been described in the literature. This study aimed to evaluate bean varieties from the Brazilian states of Santa Catarina and Paraná, regarding the resistance to anthracnose, in two cropping seasons. In addition, two commercial cultivars were used as controls: IPR Tangará, as susceptible; and BRS Campeiro, as moderately resistant. The majority of the local varieties was considered resistant or moderately resistant, being more pronounced the Amendoim cultivar, with large grains and red tegument, evincing resistance in both evaluations. Regarding this, the possibility of using them as resistance sources to anthracnose may be considered, since they also show adaptability to the environmental conditions.

RESUMO: O objetivo deste trabalho foi estudar a herança de caracteres em trigo utilizando análise de variância multivariada. Foram avaliadas dezesseis constituições genéticas, entre cultivares comerciais e progênies F1 e F2. Os tratamentos foram dispostos em blocos completos casualizados, com três repetições. Cinco caracteres foram mensurados. Para testar as hipóteses foi realizada análise de variância multivariada, e posteriormente contrastes multivariados. As diferenças significativas obtidas para as comparações entre os genitores e as progênies F1, podem ser indícios da ocorrência de heterose. No entanto, somente as comparações entre as progênies P1_P3 (F1) vs. P1_P3 (F2) e P4_P2 (F1) vs. P4_P2 (F2) apresentaram diferenças significativas. A análise de variância multivariada revelou que a herança dos caracteres estudados é predominantemente do tipo aditiva. Isto ocorreu, possivelmente pelo grau de parentesco entre os genitores que reuniram alelos idênticos no mesmo loco por ascendência, como resultado dos efeitos da endogamia. O conhecimento da herança aditiva pode representar a incorporação mais rápida de resistência ou de características de qualidade em novas cultivares.

ABSTRACT: The objective of this study was to analize the inheritance of characters in wheat using multivariate analysis of variance. Sixteen genetic constitutions were evaluated between commercial cultivars and progenies F1 and F2. Treatments were arranged in completely randomized blocks, with three replicates. Five characters were evaluated. Multivariate analysis of variance and multivariate contrasts were then performed to test the hypotheses. The significant differences, obtained for comparison between parents and progenies F1, may be evidence of heterosis occurrence. However, only comparisons between progenies P1_P3 (F1) vs. P1_P3 (F2) and P4_P2 (F1) vs. P4_P2 (F2) showed significant differences. Multivariate analysis of variance revealed that inheritance of the characters studied is predominantly of the additive type. It is possible that, this occurred due to the degree of relationship between parents who reunited identical alleles at the same locus, by ancestry, as a result of inbreeding effects. The knowledge of additive inheritance may represent a faster incorporation of resistance or quality characteristics in new cultivars.