Assessment of genetic diversity on a sample of cocoa accessions resistant to witches' broom disease based on RAPD and pedigree data

Abstract

Genetic diversity in cocoa (Theobroma cacao L.) has been assessed based on morphological and molecular markers for germplasm management and breeding purposes. Pedigree data is available in cocoa but it has not been used for assessing genetic relatedness. The geneitic diversity of 30 clonal cocoa accessions resistant to witche´ broom disease, from the CEPEC series, were studied on the basis of RAPD data and pedigree information. Twenty of these accessions descend from the TSA-644 clone, originated from a cross between the Upper Amazon germplasm called Scavina-6, the main source of resistance to witches' broom disease, and IMC-67. The ten remaining clones come from different sources including Amazon and Trinitario germplasm. RAPD data was collected using 16 primers and pedigree information was obtained from the International Cocoa Germplasm Database. Genetic similarities, genetic distances and coefficient of parentage were calculated using available software. Relatively low genetic diversity was observed in this germplasm set, probably because of great genetic relatedness amongst accessions studied and the poor representation of the germplasm. The TSA-644 descendants were more diverse than the other accessions used in the study. This might be due to the origin of the TSA clone, which was derived from highly divergent genotypes. Association between genetic similarities based on RAPD data and coefficient of parentage, based on pedigree data, was very low, probably due to the homogeneity of the breeding stocks and poor pedigree information. These findings are useful to cocoa breeders in planning crosses for the development of hybrid and clonal cultivars.

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

“…Similarly, Maia et al (2011) obtained two groupings for 36 progenies of T. grandiflorum using the Tocher method (RAO, 1952) based only on phenotypic data. Santos et al (2005) found low genetic diversity among 30 cocoa clones based on the RAPD markers and genealogy information, which can also be attributed to the strong genetic relation among most of the studied materials. Studies of cupuassu diversity based on phenotypic data were performed by Araújo et al (2002), Maia et al (2011), andSantos et al (2015), among others, and obtained a reasonable phenotypic divergence, with the number of groups varying between two and seven, according to several grouping methods.…”

Diversidade genética entre acessos de cacau de fazendas e de banco de germoplasma na Bahia

“…Entre as 91 bandas RAPD obtidas no presente trabalho, 61 foram monomórficas e 30 polimórficas -estas representam 33%, o que corresponde a 2,3 bandas polimórficas por iniciador, o que é semelhante às 2,2 obtidas por Lerceteau et al (1997) e menor do que as 3,5 obtidas por Marita et al (2001), porém com qualidade satisfatória para as análises. Os 18 iniciadores selecionados por Lerceteau et al (1997) Santos et al (2005), entre clones da série CEPEC (mínimo de 0,18; máximo de 0,76). Entre as 102 seleções, foram observadas, em pelo menos três anos, 55 que possuem variação quanto à produção (Monteiro et al, 2003).…”

“…Comparações entre a distância genética de cada acesso de referência (Germoplasma) e as distâncias genéticas médias do grupo de acessos das fazendas (Seleções) e do grupo de acessos de referência. relatados como genitores utilizados na produção de híbridos pela Ceplac (Pinto & Pires, 1998;Santos et al, 2005).…”

“…Os marcadores genéticos RAPD (Williams et al, 1990), sozinhos ou em associação com outros marcadores moleculares, têm sido utilizados nos estudos da variabilidade genética entre acessos provenientes de bancos internacionais de germoplasma de cacau (Lerceteau et al, 1997;Marita et al, 2001;Faleiro et al, 2004c;Sounigo et al, 2005) e dos bancos de germoplasmas e cultivares brasileiros (Dias, 2001;Yamada et al, 2001Yamada et al, , 2003Santos et al, 2005). Algumas seleções das fazendas no Sul da Bahia foram caracterizadas com base em marcadores RAPD (Faleiro et al, 2004b;Yamada et al, 2005) e microssatélites (Faleiro et al, 2004a).…”

Molecular genetic diversity in a core of cocoa (Theobroma cacao L.) clones with potential for selection of disease resistance, plant height and fruit production

“…Several studies on the genetic diversity of cacao sought to characterize and define genetic groups (Santos et al, 2005;Sounigo et al, 2005;Faleiro et al, 2004a, b;Dias, 2001;Risterucci et al, 2000;Lanaud et al, 1999;Lerceteau, 1997a, b;Russel et al, 1993). Some studies made the assumption that it is possible to differentiate the Criollo of Forasteros by isoenzymes (Ronning and Schnell, 1994) or by means of DNA markers (Laurent et al, 1993a, b).…”