Phenotypic and genotypic characterization and compatibility among genotypes to select elite clones of cupuassu

Abstract

The expansion of the genetic base of cultivated materials is an ongoing activity of the cupuassu (Theobroma grandiflorum) breeding program. However, the parents involved need to be genotypically and phenotypically characterized to ensure compatibility of crossings, as well as to assist in the selection of more promising individuals for hybridization. This study aimed to identify and select T. grandiflorum clones that are compatible and genetically divergent using tools such as the estimates of genotypic, phenotypic, and combined distances, as well as the compatibility rates among clones. The genetic distance analysis of the clones was performed with 14 heterologous microsatellite primers of cocoa (Theobroma cacao) that amplify the DNA of cupuassu. Phenotypic characterization was based on 14 variables related to fruit production. The joint dissimilarity matrix was obtained by means of the sum of the phenotypic and molecular dissimilarity matrices. The intra-and inter-clonal compatibility was estimated through controlled crossings. A low correlation was noted between the dissimilarity matrices based on the molecular and agronomic data. As for compatibility, all clones were self-incompatible, with different compatibility rates when crossed. The compatibility index was strongly influenced by the degree of relationship of the clones. It was possible to identify and select the most promising sets of cupuassu clones to be used in breeding programs, despite their genetic relationship. KEYWORDS: microsatellites, tropical fruit, diversity, plant breeding, Theobroma grandiflorum Caracterização fenotípica, genotípica e compatibilidade entre genótipos para seleção de clones elite de cupuaçuzeiro RESUMO A ampliação da base genética dos materiais de cultivo é trabalho contínuo do programa de melhoramento genético do cupuaçuzeiro (Theobroma grandiflorum). Há necessidade, entretanto, que os parentais envolvidos estejam caracterizados fenotípica e genotipicamente, para auxiliar na escolha dos indivíduos que serão hibridizados, bem como para garantir os mecanismos de rastreabilidade e proteção das cultivares. Este estudo teve como objetivo identificar e selecionar clones de cupuaçuzeiro inter-compatíveis e geneticamente divergentes, utilizando como ferramentas as distâncias genotípica, fenotípica e combinada mistas, assim como as taxas de compatibilidade entre os clones. Estimativas das distâncias genéticas entre os clones foram realizadas com base em 14 iniciadores microssatélites heterólogos de cacaueiro (Theobroma cacao) que amplificam o DNA do cupuaçuzeiro. Para a caracterização fenotípica foram empregadas 14 variáveis relacionadas à produção de frutos. A matriz de dissimilaridade conjunta foi obtida por meio da soma das matrizes de dissimilaridade fenotípica e molecular. A compatibilidade intra e inter-clonal foi estimada através de cruzamentos controlados. Houve uma baixa correlação entre as matrizes de dissimilaridade com base nos dados moleculares e agronômicos. Quanto à compatibilidade, todos os clones foram auto-...

Comparative assessment of genetic diversity matrices and clustering methods in white Guinea yam (Dioscorea rotundata) based on morphological and molecular markers

“…Superior accessions with desirable end-user attributes from these diverse genetic groups are a source of rare alleles for incorporation into elite breeding lines thereby maximizing heterosis in the progenies. The high and moderate correlations observed between the combined matrix and the genotypic and phenotypic dissimilarity matrices, respectively agree with the findings of Alves et al 19 , 22 who dissected genetic diversity in their studies using phenotypic, genotypic and combined distances. These correlations suggest that genetic diversity assessment employing the combined matrix could be an essential tool to capture phenotypic and genotypic information cumulatively.…”

“…As a result of the strong environmental influence on their expression, phenotypic markers may not precisely capture the available diversity in a population 7 , 17 . Molecular markers, particularly SSR and SNPs have been widely employed to study the diversity in many species with much success, however, very low or negligible correlations have been reported between the dissimilarity matrices from the genotypic and phenotypic data 18 , 19 . Hence, it suggests that the non-overlapping information is emanating from the phenotypic and genotypic dissimilarity matrices.…”

Genetic divergence of native palms of Oenocarpus distichus considering biometric fruit variables

“…Ex Spreng. 12 and Plukenetia volubilis L. 29 . However, they should be excluded from the analyses, because they may lead to false biological interpretations and errors in the genotype selection process, due to the lack of precision in parameter estimation.…”

Selection of triple-cross Theobroma grandiflorum genotypes, aiming at fruit production and resistance to Moniliophthora perniciosa

“…The experimental design was in randomized blocks with 25 treatments, having five replicates and three plants per plot. At first, clones selected from the Germoplasm Active Bank were hybridized (Alves et al, 2017) by using the cupuassu controlledpollination technique, as reported by Venturieri & Ribeiro Filho (1995). After evaluating and selecting the progenies, the most productive parents, who remained asymptomatic for M. perniciosa after 15 years of field exposure, were duly identified and selected.…”

“…In the following crosses, it is important that the used genotypes are genetically distant and compatible. The compatibility rate is found by the ratio between the number of pollinated flowers and the number of fruit, so that when the setting rate is above 30%, it is considered compatible (Alves et al, 2017). The triple-cross progenies used in the present study were obtained in this manner and were constituted by the genetic contributions of three distinct genotypes.…”